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#41
Posted to rec.audio.tubes
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what is causing this problem?
Phil Allison wrote:
"Ian Bell" I am not sure that choice is actually involved. The source material is inevitably coloured. If it is an old recording it was recorded using tubes or old transistor and transformer technology all of which adds its own colour. If it is a modern recording it is certain to have been 'processed' digitally which also adds its own particular colour. Having a totally transparent replay chain therefore has little effect. ** So Ian simply does not believe in " hi-fi " - the basic idea of which is that the equipment should not degrade or otherwise alter the audio signals presented to it. No, I don't believe it is often achieved in a normal domestic situation. When I was at Neve in 70s I had the opportunity to visit many studios and hear first hand the original recordings on professional speakers in properly treated rooms. The sound quality is stunning. My own hi-fi was so poor by comparison it put me off playing music at home for many years. Maybe when he goes to visit an art gallery or watch movie, he wears his favourite rose tinted glasses ?? So you think the lighting in art galleries is exactly as the artist intended - you fool. You think the quality of a picture several hundred years old is as good as when it was first painted - you fool. I don't very often go to the movies - the sound quality is so poor. Perhaps he has a whole bunch of different coloured tints and perspective altering lenses too. Wot a ******. Cheers Ian ...... Phil |
#42
Posted to rec.audio.tubes
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what is causing this problem?
On Dec 3, 5:16 pm, cipher wrote:
fryzz wrote : On Dec 3, 3:56 pm, cipher wrote: ok.. my mastersound amp.. love the sound of it. got it for a great price. BUT... every month or two, a channel would go out. id look inside and one of the resistor legs would be desoldered or one of the resitors would be completely desoldered and rattling around in the case. one time, the resistors were completely heat destroyed, totally crumbling heaps of powder. this happens about once a month. i love the amp, but damn. who can make this thing work for me? at a loss here. http://s99.photobucket.com/albums/l292/thebullards/? action=view¤t=dueventischematic.jpg http://www.yousendit.com/download/TT...YStTSURIRGc9PQ Do you have a schematic, a multimeter, and some technician skills? Is it always the same resistor? Do the output tubes ever run too hot, with the plates are glowing cherry red? The first thing to look at is what the output tubes' idle current is. You can measure the resistance of the plate windings on the output transformers, and with the amp on and the inputs shorted, measure the voltage between plate and V+. Then use that, with the resistance, and Ohm's law, to calculate the plate current. Multiply that current by the plate voltage to get the plate dissipation. You can look up the tube characteristics, and then determine if they are being run within ratings. If that all looks good, maybe the resistors used by the manufacturer are under rated. You can also use the drop across the cathode resistor (assuming it's cathode biased), remembering that this value will also include the screen current. I have that crude schematic. I do have a nice multimeter, yes. The tubes do actually run hot, yes with them glowing like close encounters or something......that has happened several times. I cant see why the ones used by the manufacturers woould be underrated?? they are a company of pretty good reputation, but..I am not a tech guy. www.mastersoundsas.it Oh, the chances are that they chose the right ratings for the parts and the fact that they are burning up means something else is amiss. There is often an electrolytic bypass capacitor connected across the cathode resistor. If this resistor is electrically leaky, then it will have the effect of lowering the effective resistance of the cathode resistor, causing the output tubes to be under-biased, which would in turn cause the output tubes to draw excess current. It is not at all unusual for a capacitor to become intermittent. I can only speculate without knowing more specifics. If you want to send me a copy of your schematic and if you can mark on it which parts are frying, I will tell you what I can. Unless you're keen on learning how to do this work yourself, you might be better off taking it to a qualified technician. |
#43
Posted to rec.audio.tubes
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what is causing this problem?
"Ian Bell the ****wit " Phil Allison wrote: "Ian Bell" I am not sure that choice is actually involved. The source material is inevitably coloured. If it is an old recording it was recorded using tubes or old transistor and transformer technology all of which adds its own colour. If it is a modern recording it is certain to have been 'processed' digitally which also adds its own particular colour. Having a totally transparent replay chain therefore has little effect. ** So Ian simply does not believe in " hi-fi " - the basic idea of which is that the equipment should not degrade or otherwise alter the audio signals presented to it. No, I don't believe it is often achieved ...... ** Not relevant to the point - ****WIT !! Maybe when he goes to visit an art gallery or watch movie, he wears his favourite rose tinted glasses ?? So you think the lighting in art galleries... ** Not relevant to the point - ****WIT !! I don't very often go to the movies .. ** Not relevant to the point - ****WIT !! Wot a ****ing useless ******. ...... Phil |
#44
Posted to rec.audio.tubes
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what is causing this problem?
"flipper" Arny Krueger Sonically transparent tubed amps can and have been built and sold. However, they tend to be far larger, heavier, more wasteful of natural resources, less reliable, more expensive to mainatin, and far, far more expensive than a SS amp that sounds the same. That is a matter of opinion and it should be obvious, by now, that not everyone agrees. ** Massive logical fallacy. Facts are not determined by taking a popular vote. IOW, the half baked opinions of the ill informed masses have no bearing on matters of fact. If transparent tube amps were the kinds of amps that tube hobbiest were building, then so be it, it is their time and money. However, SE and anti-inverse-feedback have become stylish. Still no problem, as it is still the tubies time and money. But then they get all weird and tell the rest of the world that this is the holy grail and the only way to obtain good sound. Foul! The only 'foul' I see are SS (appropriate coincidence) fascists ** Yawnnnnnn..... More half baked opinion presented in lieu of any kind of case. The pre-historic reptile brain is still alive an well inside any " tube head ". ....... Phil |
#45
Posted to rec.audio.tubes
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what is causing this problem?
"Phil Allison" wrote in
: "cipher" r68.. the problem children ** Jeez - it took a while to squeeze THAT simple fact out of you. What a ****head you are. The " problem children " are not the resistors but the EL34s, you colossal JERK. Get some good new ones (Russian not Chinese) and set the bias to 5 volts on each 68 ohm cathode resistor. ..... Phil you know what (and my apologies to Mr. Wieck and Mr. Flipper), **** you. I mentioned before that I am not a goddamned technician, and depend on the graces of POLITE GENTLEMEN like Mr. Wieck for what ****ing advice I can get from this mother****ing cynic circle jerk dick wagging site. and as I said before, you ****ing dick.. were you missing the point where I said that the resistor legs seemed to have been desoldered somehow, after replacing them at least 3 times?(the resistors, guh yup!!!) Ive gone through 5 sets of mother****ing tubes. 3 sets of mother****ing resistors and about 10 bottles of xanax with this mother****er and goddamnit I come here to ask for advice nicely giving my proper sirs and thanks yous and providing what information I had BECAUSE GUESS WHAT???? PROVIDE INFORMATION HELPS WHO??? Well goddamn!!! ME!!! replace resistors multiple times, replace tubes multiple times, and just meebbee it sounds like its neither one of those ****ing causes. my holding back on information was because guess what!!! YEP AGAIN!! THATS ALL THE INFORMATION I HAD!! IT is not part of some black op ts-3a classified s2 mission to keep some ****ing information from you or anybody else. I spent a good bit of my goddamned life in the us army infantry, 3 years in iraq and i know how to render courtesy when it is called for, but hell , man, or sir , or maam or it or whatever the ****... I can be a confrontational asshole too, but id rather not, so either be nice or shut the **** up already! if it is such a pain to help out, do me a favor and keep your chest puffing depakote mainlining sociopath kneejerk bull**** out of my ****ing AO! Mr. Wieck, and Mr. Flipper, and whoever is interested in helping...I thank you for your help, I am requesting a "real" schematic. |
#46
Posted to rec.audio.tubes
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what is causing this problem?
flipper wrote in
: On Thu, 04 Dec 2008 12:09:27 -0600, cipher wrote: flipper wrote in m: On Wed, 03 Dec 2008 14:56:46 -0600, cipher wrote: ok.. my mastersound amp.. love the sound of it. got it for a great price. BUT... every month or two, a channel would go out. id look inside and one of the resistor legs would be desoldered or one of the resitors would be completely desoldered and rattling around in the case. one time, the resistors were completely heat destroyed, totally crumbling heaps of powder. this happens about once a month. i love the amp, but damn. who can make this thing work for me? at a loss here. http://s99.photobucket.com/albums/l292/thebullards/? action=view¤t=dueventischematic.jpg http://www.yousendit.com/download/TT...YStTSURIRGc9PQ Which 'resistors'? If I were to guess I'd imagine it's the EL34 cathode resistors but you really need to be more detailed. Just looking at the schematic the first thing that pops out is whether it's biased properly. I.E. Those two pots down on the 20V winding. The second thing is those adjustment pots are not reliable, as designed. The wiper is all 'alone', meaning if it breaks contact, which can happen, bias goes bonkers. And that would be consistent with seeming to work fine for a while and then, all of a sudden, run away. Out of curiosity, why didn't you just post the schematic pic itself instead of a 'screen shot'? I posted what I had, bud. All I did was ask, 'bud', because it's hard to read. I sure as hell wouldnt hold anything back... Maybe not intentionally but it has the appearance. When you say "a channel," is it always the same channel or either or random? When was the 'first time' and who repaired it? What was diagnosed and what was replaced, and with what? And who repaired it the subsequent times? How diagnosed and replaced with what? Is it always the same channel *and* the same tube? Have you tested the tubes? Have they ever been replaced or moved to different sockets? When was the last time bias was checked? Are you able to read component values? If so, then trace it out and put some values on that schematic. And some meter readings would be nice. Are all the cathodes at 6V like the schematic says they should? But don't try if you're not skilled with high voltage circuits. r68.. the problem children I cant tell, for sure, from the picture which one is 'r68'. The sharpened 'blur' looks like it might be the cathode resistor under the left EL34. Just one? Because your description said "resistors:" plural. for the life of me, I cannot figure out why one seeking help would hold back information?? I called you bud as a friendly term.. apparently slurring each other is more appropo.. as for the technical stuff...working on it. |
#47
Posted to rec.audio.tubes
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what is causing this problem?
"Ian Bell" wrote in message
So why have a completely transparent amp when the speakers and room are so relatively poor. The reality of the situation is that a good listener can in some real world situations hear a +/- 0.5 dB difference in amp response, in a room/speaker situation where overall response is +/- 5 dB. However, you can't hear a +/- 0.1 dB difference in the amp, no matter how good the room+speakers are. Similarly, in some real-world situations nonlinear distortion that creates 0.1 % THD in the 15-20 KHz range can be heard, even though the room+speakers have equal or greater distortion. To obtain high fidelity you need to address all aspects of the system not just the amp. Agreed, but that doesn't mean that you intentionally make the strongest link into the weakest link. |
#48
Posted to rec.audio.tubes
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We have ourselves a red hot **** HEAD folks
"cipher" ** Christ alive, we have ourselves a red hot **** HEAD folks !!! r68.. the problem children ** Jeez - it took a while to squeeze THAT simple fact out of you. What a ****head you are. The " problem children " are not the resistors but the EL34s, you colossal JERK. Get some good new ones (Russian not Chinese) and set the bias to 5 volts on each 68 ohm cathode resistor. you know what (and my apologies to Mr. Wieck and Mr. Flipper), **** you. ** You are so * totally ****ed * already that insult has no value. I mentioned before that I am not a goddamned technician, ** But what you ARE is a 100% GODDAMED ****WIT !!!!! were you missing the point where I said that the resistor legs seemed to have been desoldered somehow, after replacing them at least 3 times? ** Hey, you ****ing ASSHOLE !! You never posted WHICH ONES THEY WERE !!!!!!!!! Ive gone through 5 sets of mother****ing tubes. ** You never posted that info before - either. Now how about you post what brand EL34s they were and where you got them ? YOU COLOSSAL ****ING MORON !!!!! 3 sets of mother****ing resistors and about 10 bottles of xanax with this mother****er and goddamnit I come here to ask for advice nicely giving my proper sirs and thanks yous and providing what information I had BECAUSE GUESS WHAT???? PROVIDE INFORMATION HELPS WHO??? Well goddamn!!! ME!!! replace resistors multiple times, replace tubes multiple times, and just meebbee it sounds like its neither one of those ****ing causes. ** Wot a complete lunatic !!!!! Too far gone for any shrink or medication to help. my holding back on information was because guess what!!! YEP AGAIN!! THATS ALL THE INFORMATION I HAD!! IT is not part of some black op ts-3a classified s2 mission to keep some ****ing information from you or anybody else. ** Wot a complete lunatic !!!!! Too far gone for any shrink or medication to help. I spent a good bit of my goddamned life in the us army infantry, 3 years in iraq and i know how to render courtesy when it is called for, but hell , man, or sir , or maam or it or whatever the ****... I can be a confrontational asshole too, but id rather not, so either be nice or shut the **** up already! ** Wot a complete lunatic !!!!! Too far gone for any shrink or medication to help. Bet he was discharged for gross metal instability. Mr. Wieck, and Mr. Flipper, and whoever is interested in helping...I thank you for your help, I am requesting a "real" schematic. ** There is a chance the demented cretin will electrocute himself. We can only hope. ..... Phil |
#49
Posted to rec.audio.tubes
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what is causing this problem?
"flipper the ****head " ** Massive logical fallacy. Nice try, but no. Facts are not determined by taking a popular vote. You are correct. 'facts' aren't. Unfortunately for your argument we're talking 'opinion'. ** You have ZERO comprehension of the topic. So **** the HELL OFF - you PATHETIC, hee hawing ASS !!! ... Phil |
#50
Posted to rec.audio.tubes
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We have ourselves a red hot **** HEAD folks
"Phil Allison" wrote in
: "cipher" ** Christ alive, we have ourselves a red hot **** HEAD folks !!! r68.. the problem children ** Jeez - it took a while to squeeze THAT simple fact out of you. What a ****head you are. The " problem children " are not the resistors but the EL34s, you colossal JERK. Get some good new ones (Russian not Chinese) and set the bias to 5 volts on each 68 ohm cathode resistor. you know what (and my apologies to Mr. Wieck and Mr. Flipper), **** you. ** You are so * totally ****ed * already that insult has no value. I mentioned before that I am not a goddamned technician, ** But what you ARE is a 100% GODDAMED ****WIT !!!!! were you missing the point where I said that the resistor legs seemed to have been desoldered somehow, after replacing them at least 3 times? ** Hey, you ****ing ASSHOLE !! You never posted WHICH ONES THEY WERE !!!!!!!!! Ive gone through 5 sets of mother****ing tubes. ** You never posted that info before - either. Now how about you post what brand EL34s they were and where you got them ? YOU COLOSSAL ****ING MORON !!!!! 3 sets of mother****ing resistors and about 10 bottles of xanax with this mother****er and goddamnit I come here to ask for advice nicely giving my proper sirs and thanks yous and providing what information I had BECAUSE GUESS WHAT???? PROVIDE INFORMATION HELPS WHO??? Well goddamn!!! ME!!! replace resistors multiple times, replace tubes multiple times, and just meebbee it sounds like its neither one of those ****ing causes. ** Wot a complete lunatic !!!!! Too far gone for any shrink or medication to help. my holding back on information was because guess what!!! YEP AGAIN!! THATS ALL THE INFORMATION I HAD!! IT is not part of some black op ts-3a classified s2 mission to keep some ****ing information from you or anybody else. ** Wot a complete lunatic !!!!! Too far gone for any shrink or medication to help. I spent a good bit of my goddamned life in the us army infantry, 3 years in iraq and i know how to render courtesy when it is called for, but hell , man, or sir , or maam or it or whatever the ****... I can be a confrontational asshole too, but id rather not, so either be nice or shut the **** up already! ** Wot a complete lunatic !!!!! Too far gone for any shrink or medication to help. Bet he was discharged for gross metal instability. Mr. Wieck, and Mr. Flipper, and whoever is interested in helping...I thank you for your help, I am requesting a "real" schematic. ** There is a chance the demented cretin will electrocute himself. We can only hope. .... Phil \ nah, I am fine really. I was just engaging in your native tounge. As for the tube types?? came from the dealer with EH tubes which I dont like at all for various reasons, biggest being they have a bad reputation. I called the dealer infuriated and asked for replacements (thinking it was just bad tubes) so he sent me JJs. Those worked fine for a while, until one day while doing a freq sweep cd I heard a pop and a dead channel...opened it up(the amp) saw a blown fuse and a resistor out of place, so I took it to my neighbor(who restores antique radios on the side) to see if he could put it back together. He soldererd the resistor back and it worked for a couple months..then one day...pop, channel goes out again...so I take it to another guy who takes it apart in front of me and discovers that the resistors had turned to dust, basically...he said from heat, but I dunno....anyway, he orders new ones of the same type and value from mouser and solders it.....I assumed I hadf the problem licked so I ordered some sed winged c el34 from thetubedepot.com was in bliss for a couple months then pop channel goes out(last week)... so the manufacturer has agreed to ship it over to italy for extensive repairs....but putting the resistors , soldering them back fixes it for a while., then they become desoldered.... |
#51
Posted to rec.audio.tubes
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We have ourselves a red hot **** HEAD folks
On Dec 5, 9:15*pm, cipher wrote:
so the manufacturer has agreed to ship it over to italy for extensive repairs....but putting the resistors , soldering them back fixes it for a while., then they become desoldered. 8 gets you 20 you don't get the same amp back. Perhaps the same sheet-metal, but I suspect it will be otherwise gutted almost entirely. And as for shipping it back to Italy - that is mind-boggling. Their local reps must be entirely clueless and/or know that something is radically wrong or both and don't quite want to admit it. Peter Wieck Melrose Park, PA |
#52
Posted to rec.audio.tubes
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what is causing this problem?
Phil Allison wrote:
"Ian Bell" So why have a completely transparent amp when the speakers and room are so relatively poor. ** Very accurate, low distortion speakers are readily available - but not necessarily cheap. Indeed, and there's the rub for most people. Treating a listening room so it does very little harm to the sound MORON. The whole point is that an untreated roo does a lot of harm to the room. is a quite straightforward exercise and can be done fairly cheaply. You clearly have little knowledge of practical acoustics. It is certainly not straightforward and is definitely not cheap. Transparent amplifiers are virtually a dime a dozen - choosing to NOT use one is kinda insane. Indeed, but that is not the point. Choosing a transparent amp in an already seriously flawed system is pointless. Except, of course, if you simply do not believe in "hi-if" at all Believe? Is this a matter of faith now!!!! Cheers Ian - like this demented clown. ..... Phil |
#53
Posted to rec.audio.tubes
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what is causing this problem?
On Fri, 05 Dec 2008 22:43:23 -0600, flipper wrote:
snip (about time someone did!) OK. As you probably saw in my other posts, first time around I missed the PDF but have it now. Have you asked Mastersound, themselves, why the amp does this? And what's their explanation for it? It looks as if the "68" is the value, not the resistor number, doesn't it? I was confused too... (I frequently am nowadays... :-( ) cipher: I hope we are talking about the same amp here. Is your amp the big black one in the pics? If so, I assume that you have rectifier tubes (GZ34 or something?) instead of the bridge recs shown in the pdf? If so, we can't read too much into the B+ voltage as we don't know what your mains transformer is really like. Personally, I'm not happy about trusting the production schematic (pdf) for a demo amp. Too many things may have changed. If that pdf is right then the 2 output cathode resistors should probably be about 2W rating for comfort. Any idea what's fitted, cipher? The standing dissipation is just over 0.5W (if you use the recommended 6v across the resistors) so I wouldn't like to risk 1W types if the chassis is at all cramped. Phil's suggestion of reducing the voltage to 5v looks good if you want a longer tube (and resistor!) life. Everything will run a bit cooler. You could comfortably fit 1W resistors in this case. -- Mick (Working in a M$-free zone!) Web: http://www.nascom.info Filtering everything posted from googlegroups to kill spam. |
#54
Posted to rec.audio.tubes
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what is causing this problem?
Phil Allison wrote:
"flipper the ****head " ** Massive logical fallacy. Nice try, but no. Facts are not determined by taking a popular vote. You are correct. 'facts' aren't. Unfortunately for your argument we're talking 'opinion'. ** You have ZERO comprehension of the topic. So **** the HELL OFF - you PATHETIC, hee hawing ASS !!! You can always tell when Phil is losing an argument! LOL Cheers IAn |
#55
Posted to rec.audio.tubes
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what is causing this problem?
Arny Krueger wrote:
"Ian Bell" wrote in message So why have a completely transparent amp when the speakers and room are so relatively poor. The reality of the situation is that a good listener can in some real world situations hear a +/- 0.5 dB difference in amp response, in a room/speaker situation where overall response is +/- 5 dB. However, you can't hear a +/- 0.1 dB difference in the amp, no matter how good the room+speakers are. Similarly, in some real-world situations nonlinear distortion that creates 0.1 % THD in the 15-20 KHz range can be heard, even though the room+speakers have equal or greater distortion. Is this simply your opinion or can you cite research that demonstrates these? |Cheers Ian To obtain high fidelity you need to address all aspects of the system not just the amp. Agreed, but that doesn't mean that you intentionally make the strongest link into the weakest link. Indeed, but that was not the point I was making originally. And I am so tired of reiterating it I am not going to bother doing so again. Cheers Ian |
#56
Posted to rec.audio.tubes
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what is causing this problem?
"Ian Bell" wrote in message
Phil Allison wrote: "Ian Bell" So why have a completely transparent amp when the speakers and room are so relatively poor. ** Very accurate, low distortion speakers are readily available - but not necessarily cheap. The prices are coming down, and they are not prohibitive. Indeed, and there's the rub for most people. Treating a listening room so it does very little harm to the sound MORON. The whole point is that an untreated room does a lot of harm to the room. So resolved, if you have rotten speakers and a very poor, untreated room, then tubed audio is for you! |
#57
Posted to rec.audio.tubes
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what is causing this problem?
"Ian Bell" wrote in message
Arny Krueger wrote: "Ian Bell" wrote in message So why have a completely transparent amp when the speakers and room are so relatively poor. The reality of the situation is that a good listener can in some real world situations hear a +/- 0.5 dB difference in amp response, in a room/speaker situation where overall response is +/- 5 dB. However, you can't hear a +/- 0.1 dB difference in the amp, no matter how good the room+speakers are. Similarly, in some real-world situations nonlinear distortion that creates 0.1 % THD in the 15-20 KHz range can be heard, even though the room+speakers have equal or greater distortion. Is this simply your opinion or can you cite research that demonstrates these? I could, but you seem to be so biased that you wouldn't be able to comprehend it. You might also have to pay some money to buy copies of the papers. |
#58
Posted to rec.audio.tubes
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what is causing this problem?
"Ian Bell is Full of **** " ** Very accurate, low distortion speakers are readily available - but not necessarily cheap. Indeed, and there's the rub for most people. ** ********. Treating a listening room so it does very little harm to the sound is a quite straightforward exercise and can be done fairly cheaply. You clearly have little knowledge of practical acoustics. ** Yawnnnnnnnnnnnnnn. No facts, no logic = no case to answer. Transparent amplifiers are virtually a dime a dozen - choosing to NOT use one is kinda insane. Indeed, but that is not the point. ** Yes it is - you boring as bat ****, autistic PITA ****head. Except, of course, if you simply do not believe in "hi-if" at all Believe? ** Yep. The basic concept of " hi-fi " is an inherently desirable goal. Non believers merely need to say so. Like non believers in democracy, science, fairness or the search for truth. Then we know exactly WHO to totally ****ing ignore. So go drop dead - you asinine, psychotic pommy ****. ...... Phil |
#59
Posted to rec.audio.tubes
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what is causing this problem?
Arny Krueger wrote:
"Ian Bell" wrote in message Arny Krueger wrote: "Ian Bell" wrote in message So why have a completely transparent amp when the speakers and room are so relatively poor. The reality of the situation is that a good listener can in some real world situations hear a +/- 0.5 dB difference in amp response, in a room/speaker situation where overall response is +/- 5 dB. However, you can't hear a +/- 0.1 dB difference in the amp, no matter how good the room+speakers are. Similarly, in some real-world situations nonlinear distortion that creates 0.1 % THD in the 15-20 KHz range can be heard, even though the room+speakers have equal or greater distortion. Is this simply your opinion or can you cite research that demonstrates these? I could, but you seem to be so biased that you wouldn't be able to comprehend it. You might also have to pay some money to buy copies of the papers. LOL. So name the articles then and let me decide whether or not to pay for them.. Cheers Ian |
#60
Posted to rec.audio.tubes
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what is causing this problem?
Arny Krueger wrote:
"Ian Bell" wrote in message Phil Allison wrote: "Ian Bell" So why have a completely transparent amp when the speakers and room are so relatively poor. ** Very accurate, low distortion speakers are readily available - but not necessarily cheap. The prices are coming down, and they are not prohibitive. Indeed, and there's the rub for most people. Treating a listening room so it does very little harm to the sound MORON. The whole point is that an untreated room does a lot of harm to the room. So resolved, if you have rotten speakers and a very poor, untreated room, then tubed audio is for you! No, all I said was a transparent amp in an already seriously flawed system is pointless. Cheers Ian |
#61
Posted to rec.audio.tubes
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what is causing this problem?
On Dec 3, 3:56 pm, cipher wrote:
ok.. my mastersound amp.. love the sound of it. got it for a great price. BUT... every month or two, a channel would go out. id look inside and one of the resistor legs would be desoldered or one of the resitors would be completely desoldered and rattling around in the case. one time, the resistors were completely heat destroyed, totally crumbling heaps of powder. this happens about once a month. i love the amp, but damn. who can make this thing work for me? at a loss here. http://s99.photobucket.com/albums/l292/thebullards/? action=view¤t=dueventischematic.jpg http://www.yousendit.com/download/TT...YStTSURIRGc9PQ I just spotted your schematic, duh. Sorry if this is redundant, I just didn't feel like wading through all the vituperative infantile bull**** that collects around here in order to be sure I wasn't repeating what someone else may have already said. I'm guessing you have an intermittent bias problem. Your amp has a separate bias supply, so the 68 ohm resistors are mostly just a convenient way of adjusting the idle current. If those bypass capacitors on the 68 ohm jobs are leaky, it would actually have the effect of increasing the negative voltage on the grid, which reduces the idle current, so that's not why the tubes would draw too much current. The first thing I would look at is the bias potentiometers, pots do tend to be trouble prone due to the moving parts. You could try cleaning them with something like Caig Deoxit. You might also try feeling those two filter caps in the bias supply after the amp has been on for a while. They'll pick up some heat just from being in a tubeamp, but if one is warmer than the other it's a sign that cap is leaking. Another thing you might try is touching up all of the solder joints in the bias supply. You might also just leave your multimeter hooked up, to see if the output of the bias supply is dropping when the amp gets that "close encounters" look. When you measure the output of the bias supply, it should be stable and noise free. Hope this helps |
#62
Posted to rec.audio.tubes
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what is causing this problem?
Phil Allison wrote:
"Ian Bell is Full of **** " ** Very accurate, low distortion speakers are readily available - but not necessarily cheap. Indeed, and there's the rub for most people. ** ********. You want to rub your ******** that's fine with me. Cheers Ian |
#63
Posted to rec.audio.tubes
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what is causing this problem?
"Ian Bell" wrote in message
Arny Krueger wrote: "Ian Bell" wrote in message Phil Allison wrote: "Ian Bell" So why have a completely transparent amp when the speakers and room are so relatively poor. ** Very accurate, low distortion speakers are readily available - but not necessarily cheap. The prices are coming down, and they are not prohibitive. Indeed, and there's the rub for most people. Treating a listening room so it does very little harm to the sound MORON. The whole point is that an untreated room does a lot of harm to the room. So resolved, if you have rotten speakers and a very poor, untreated room, then tubed audio is for you! No, all I said was a transparent amp in an already seriously flawed system is pointless. Right, but since when is our pursuit of the audio hobby about intentionally using a seriously flawed system? |
#64
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what is causing this problem?
On Sat, 06 Dec 2008 06:33:27 -0600, flipper wrote:
snip Those pics are of a different amp. I was wondering. If you reckon on two of the GT bottles being individual rectifiers for each channel then it could possibly be a dual mono amp on a single chassis. Mind you, that doesn't explain the, possibly EZ81-type thingy and there is one too many small B9A bottle. That may just be enough changes between a prototype and a production version though. It *could* have a valve rectifier for bias and an extra amplification stage. Come on, cipher, let us into the secret! ;-) -- Mick (Working in a M$-free zone!) Web: http://www.nascom.info Filtering everything posted from googlegroups to kill spam. |
#65
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what is causing this problem?
mick wrote in news:Mds_k.3938$fw1.2824
@newsfe25.ams2: On Fri, 05 Dec 2008 22:43:23 -0600, flipper wrote: snip (about time someone did!) OK. As you probably saw in my other posts, first time around I missed the PDF but have it now. Have you asked Mastersound, themselves, why the amp does this? And what's their explanation for it? It looks as if the "68" is the value, not the resistor number, doesn't it? I was confused too... (I frequently am nowadays... :-( ) cipher: I hope we are talking about the same amp here. Is your amp the big black one in the pics? If so, I assume that you have rectifier tubes (GZ34 or something?) instead of the bridge recs shown in the pdf? If so, we can't read too much into the B+ voltage as we don't know what your mains transformer is really like. Personally, I'm not happy about trusting the production schematic (pdf) for a demo amp. Too many things may have changed. If that pdf is right then the 2 output cathode resistors should probably be about 2W rating for comfort. Any idea what's fitted, cipher? The standing dissipation is just over 0.5W (if you use the recommended 6v across the resistors) so I wouldn't like to risk 1W types if the chassis is at all cramped. Phil's suggestion of reducing the voltage to 5v looks good if you want a longer tube (and resistor!) life. Everything will run a bit cooler. You could comfortably fit 1W resistors in this case. Hey Sir, it appears as though the pictures from that PDF are from the newer Due Venti(my amp model) with Auto-Bias. Mine does not have auto bias. I just figured out that the models with the green led are the newer ones, and mine (red LED) are older. |
#66
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what is causing this problem?
mick wrote in news:Mds_k.3938$fw1.2824
@newsfe25.ams2: On Fri, 05 Dec 2008 22:43:23 -0600, flipper wrote: snip (about time someone did!) OK. As you probably saw in my other posts, first time around I missed the PDF but have it now. Have you asked Mastersound, themselves, why the amp does this? And what's their explanation for it? It looks as if the "68" is the value, not the resistor number, doesn't it? I was confused too... (I frequently am nowadays... :-( ) cipher: I hope we are talking about the same amp here. Is your amp the big black one in the pics? If so, I assume that you have rectifier tubes (GZ34 or something?) instead of the bridge recs shown in the pdf? If so, we can't read too much into the B+ voltage as we don't know what your mains transformer is really like. Personally, I'm not happy about trusting the production schematic (pdf) for a demo amp. Too many things may have changed. If that pdf is right then the 2 output cathode resistors should probably be about 2W rating for comfort. Any idea what's fitted, cipher? The standing dissipation is just over 0.5W (if you use the recommended 6v across the resistors) so I wouldn't like to risk 1W types if the chassis is at all cramped. Phil's suggestion of reducing the voltage to 5v looks good if you want a longer tube (and resistor!) life. Everything will run a bit cooler. You could comfortably fit 1W resistors in this case. Hey Sir, my amp has 4 EL 34 components for the power amp section and 2 x ecc 82. the preamp tubes have never given me a problem, but the power amp section (specifically, the EL-34 in the back right slot (if looking at it from the front) always flare up....... it happens like this.. the tube grows bright red, the channel goes out completely.. I open it up and find desoldered resistors(or in one instance, "rotted" ones) what could be causing this much heat to desolder the connection??? the solder joints are nice, doesnt look shoddy or anything.. i am just going to open it up and take a picture. |
#67
Posted to rec.audio.tubes
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what is causing this problem?
mick wrote in news:LCx_k.17960$uy1.13602
@newsfe23.ams2: On Sat, 06 Dec 2008 06:33:27 -0600, flipper wrote: snip Those pics are of a different amp. I was wondering. If you reckon on two of the GT bottles being individual rectifiers for each channel then it could possibly be a dual mono amp on a single chassis. Mind you, that doesn't explain the, possibly EZ81-type thingy and there is one too many small B9A bottle. That may just be enough changes between a prototype and a production version though. It *could* have a valve rectifier for bias and an extra amplification stage. Come on, cipher, let us into the secret! ;-) http://www.mastersoundsas.it/NEW%20S...20Due%20Venti% 20manuale%20ingleseA.pdf yes, this PDF is not of my amp..mine is an older model without autobias. |
#68
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what is causing this problem?
mick wrote in news:LCx_k.17960$uy1.13602
@newsfe23.ams2: On Sat, 06 Dec 2008 06:33:27 -0600, flipper wrote: snip Those pics are of a different amp. I was wondering. If you reckon on two of the GT bottles being individual rectifiers for each channel then it could possibly be a dual mono amp on a single chassis. Mind you, that doesn't explain the, possibly EZ81-type thingy and there is one too many small B9A bottle. That may just be enough changes between a prototype and a production version though. It *could* have a valve rectifier for bias and an extra amplification stage. Come on, cipher, let us into the secret! ;-) nd Sir, I wish I knew what the secret was. it has been very frustrating , this whole thing.. what was once excstasy , hearing the sound of that amp, has been replaced by anger and bitterness at dealing with the mechanical/electrical issues. aint no free lunch i guess. http://s99.photobucket.com/albums/l292/thebullards/? action=view¤t=dueventischematic.jpg that one is mine. |
#69
Posted to rec.audio.tubes
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what is causing this problem?
Arny Krueger wrote:
"Ian Bell" wrote in message Arny Krueger wrote: "Ian Bell" wrote in message Phil Allison wrote: "Ian Bell" So why have a completely transparent amp when the speakers and room are so relatively poor. ** Very accurate, low distortion speakers are readily available - but not necessarily cheap. The prices are coming down, and they are not prohibitive. Indeed, and there's the rub for most people. Treating a listening room so it does very little harm to the sound MORON. The whole point is that an untreated room does a lot of harm to the room. So resolved, if you have rotten speakers and a very poor, untreated room, then tubed audio is for you! No, all I said was a transparent amp in an already seriously flawed system is pointless. Right, but since when is our pursuit of the audio hobby about intentionally using a seriously flawed system? Who said intentionally? The average hi-fi person does not have a clue about acoustics. Cheers Ian |
#70
Posted to rec.audio.tubes
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what is causing this problem?
On Sat, 06 Dec 2008 18:33:22 +0000, Ian Bell wrote:
snip Who said intentionally? The average hi-fi person does not have a clue about acoustics. ....and often doesn't care! The idea is to listen to the music. It must be awfully difficult for audio "professionals" to realise that this is the ultimate objective for your average couch potato with any *affordable* music reproduction gear. ;-) -- Mick (Working in a M$-free zone!) Web: http://www.nascom.info Filtering everything posted from googlegroups to kill spam. |
#71
Posted to rec.audio.tubes
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what is causing this problem?
On Sat, 06 Dec 2008 11:51:26 -0600, cipher wrote:
snip my amp has 4 EL 34 components for the power amp section and 2 x ecc 82. the preamp tubes have never given me a problem, but the power amp section (specifically, the EL-34 in the back right slot (if looking at it from the front) always flare up....... it happens like this.. the tube grows bright red, the channel goes out completely.. I open it up and find desoldered resistors(or in one instance, "rotted" ones) what could be causing this much heat to desolder the connection??? the solder joints are nice, doesnt look shoddy or anything.. i am just going to open it up and take a picture. Is it *always* the same socket position that fails? Please do take more pics! Are the problem resistors the 4 rectangular ones each side of the 4 electrolytics at the rear of the pcb? If so, they should be mounted well clear of the board, preferably by putting a kink or loop in their leads. That way less heat is conducted back to the connection. Keep them at least 10mm away for comfort... The heat comes from the current that you are asking the resistor to pass. More current = higher temperature. There can be several reasons for this overheating to happen, e.g. the (fixed) bias may be out or there could be another reason such as one or more leaky coupling capacitors - or just a duff bottle if it's always the same one. Would you be comfortable working on it "live"? You really need to know the voltages at each output valve cathode (i.e. across the 68R resistors). If this is more than +6v (to ground/chassis) on any of them then you have started to find the problem! Your description of the tube flaring up bright red then the resistor (or connection) failing makes me think that your bias controls may well be the problem. The circuit really needs to be changed, so that an open- circuit control won't cause this (the present arrangement is not good at all). It would be a case of adding a couple more resistors then setting up the bias again. Could you handle that, given a circuit diagram to work from? Incidentally, it's a good job that the cathode resistors do fail if there *is* a bias problem - they are protecting your tubes and output transformers! -- Mick (Working in a M$-free zone!) Web: http://www.nascom.info Filtering everything posted from googlegroups to kill spam. |
#72
Posted to rec.audio.tubes
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what is causing this problem?
On Dec 6, 12:47*pm, cipher wrote:
mick wrote in news:Mds_k.3938$fw1.2824 @newsfe25.ams2: On Fri, 05 Dec 2008 22:43:23 -0600, flipper wrote: snip *(about time someone did!) OK. As you probably saw in my other posts, first time around I missed the PDF but have it now. Have you asked Mastersound, themselves, why the amp does this? And what's their explanation for it? It looks as if the "68" is the value, not the resistor number, doesn't it? I was confused too... *(I frequently am nowadays... :-( *) cipher: I hope we are talking about the same amp here. Is your amp the big black one in the pics? If so, I assume that you have rectifier tubes (GZ34 or something?) instead of the bridge recs shown in the pdf? If so, we can't read too much into the B+ voltage as we don't know what your mains transformer is really like. Personally, I'm not happy about trusting the production schematic (pdf) for a demo amp. Too many things may have changed. If that pdf is right then the 2 output cathode resistors should probably be about 2W rating for comfort. Any idea what's fitted, cipher? The standing dissipation is just over 0.5W (if you use the recommended 6v across the resistors) so I wouldn't like to risk 1W types if the chassis is at all cramped. Phil's suggestion of reducing the voltage to 5v looks good if you want a longer tube (and resistor!) life. Everything will run a bit cooler. You could comfortably fit 1W resistors in this case. Hey Sir, it appears as though the pictures from that PDF are from the newer Due Venti(my amp model) with Auto-Bias. Mine does not have auto bias. I just figured out that the models with the green led are the newer ones, and mine (red LED) are older.- Hide quoted text - - Show quoted text - It would be no real trick to rebuild what you have to the "new" configuration. Betcha that is what will happen when it gets back to Italy. The question is how much you are willing to take on to do this, or how much you must farm out. If you farm it out - have the amp sent to Italy as long as you are not paying the freight. Let them figure it out and let them do it. Peter Wieck Melrose Park, PA |
#73
Posted to rec.audio.tubes
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what is causing this problem?
mick wrote in
: On Sat, 06 Dec 2008 11:51:26 -0600, cipher wrote: snip my amp has 4 EL 34 components for the power amp section and 2 x ecc 82. the preamp tubes have never given me a problem, but the power amp section (specifically, the EL-34 in the back right slot (if looking at it from the front) always flare up....... it happens like this.. the tube grows bright red, the channel goes out completely.. I open it up and find desoldered resistors(or in one instance, "rotted" ones) what could be causing this much heat to desolder the connection??? the solder joints are nice, doesnt look shoddy or anything.. i am just going to open it up and take a picture. Is it *always* the same socket position that fails? Please do take more pics! Are the problem resistors the 4 rectangular ones each side of the 4 electrolytics at the rear of the pcb? If so, they should be mounted well clear of the board, preferably by putting a kink or loop in their leads. That way less heat is conducted back to the connection. Keep them at least 10mm away for comfort... The heat comes from the current that you are asking the resistor to pass. More current = higher temperature. There can be several reasons for this overheating to happen, e.g. the (fixed) bias may be out or there could be another reason such as one or more leaky coupling capacitors - or just a duff bottle if it's always the same one. Would you be comfortable working on it "live"? You really need to know the voltages at each output valve cathode (i.e. across the 68R resistors). If this is more than +6v (to ground/chassis) on any of them then you have started to find the problem! Your description of the tube flaring up bright red then the resistor (or connection) failing makes me think that your bias controls may well be the problem. The circuit really needs to be changed, so that an open- circuit control won't cause this (the present arrangement is not good at all). It would be a case of adding a couple more resistors then setting up the bias again. Could you handle that, given a circuit diagram to work from? Incidentally, it's a good job that the cathode resistors do fail if there *is* a bias problem - they are protecting your tubes and output transformers! Sir, I will take good detailed pictures and post them up. who around these parts would be able to work on my amp? im sure most of you could, but who would?? I suck at soldering, so id rather send it so someone that wont look like a monkey ****ing a football. |
#74
Posted to rec.audio.tubes
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what is causing this problem?
On Sat, 06 Dec 2008 15:18:51 -0600, cipher wrote:
snip Sir, I will take good detailed pictures and post them up. who around these parts would be able to work on my amp? Around Mordor? Saruman Electronics, I suppose... Give him a *Ring*! im sure most of you could, but who would?? Difficult to guess when no-one knows where you are, isn't it? I suck at soldering, so id rather send it so someone that wont look like a monkey ****ing a football. Have you got, perhaps, a local guitar amp repair place or, maybe, a radio amateur or someone like that who might do it? There's a valid email address on my web site (Feedback and Links page) if you want to take this off-group. -- Mick (Working in a M$-free zone!) Web: http://www.nascom.info Filtering everything posted from googlegroups to kill spam. |
#75
Posted to rec.audio.tubes
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what is causing this problem?
mick wrote in
: On Sat, 06 Dec 2008 15:18:51 -0600, cipher wrote: snip Sir, I will take good detailed pictures and post them up. who around these parts would be able to work on my amp? Around Mordor? Saruman Electronics, I suppose... Give him a *Ring*! im sure most of you could, but who would?? Difficult to guess when no-one knows where you are, isn't it? I suck at soldering, so id rather send it so someone that wont look like a monkey ****ing a football. Have you got, perhaps, a local guitar amp repair place or, maybe, a radio amateur or someone like that who might do it? There's a valid email address on my web site (Feedback and Links page) if you want to take this off-group. sent you an email Sir. the guy that builds my mic amps is a Mick, too... Mick Hinton (dav electronics in Twickenham) |
#76
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what is causing this problem?
mick wrote:
On Sat, 06 Dec 2008 18:33:22 +0000, Ian Bell wrote: snip Who said intentionally? The average hi-fi person does not have a clue about acoustics. ...and often doesn't care! The idea is to listen to the music. It must be awfully difficult for audio "professionals" to realise that this is the ultimate objective for your average couch potato with any *affordable* music reproduction gear. ;-) I fully agree, as I was trying to point out to Phil when he suggested I might wear rose tinted specs. at an art gallery. Beauty is in the eye or ear of the beholder. That makes it even more pointless to have a transparent amp. Cheers Ian |
#77
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what is causing this problem?
On Dec 6, 4:35*pm, mick wrote:
On Sat, 06 Dec 2008 15:18:51 -0600, cipher wrote: snip Sir, I will take good detailed pictures and post them up. who around these parts would be able to work on my amp? Around Mordor? Saruman Electronics, I suppose... Give him a *Ring*! im sure most of you could, but who would?? Difficult to guess when no-one knows where you are, isn't it? I suck at soldering, so id rather send it so someone that wont look like a monkey ****ing a football. Have you got, perhaps, a local guitar amp repair place or, maybe, a radio amateur or someone like that who might do it? There's a valid email address on my web site (Feedback and Links page) if you want to take this off-group. -- Mick * * * * * * * * * * *(Working in a M$-free zone!) Web:http://www.nascom.info Filtering everything posted from googlegroups to kill spam. * * He is in Florida - and he would have to ship the amp anyway. So, as far as practicalities are concerned, the Continental US is all the same to him. I would be glad to do it, if he didn't mind waiting 30 - 90 days, as that is about how long it takes me to get to any fresh project these days. Peter Wieck Melrose Park, PA |
#78
Posted to rec.audio.tubes
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what is causing this problem?
On 6 Dec, 23:24, Peter Wieck wrote:
On Dec 6, 4:35*pm, mick wrote: On Sat, 06 Dec 2008 15:18:51 -0600, cipher wrote: snip Sir, I will take good detailed pictures and post them up. who around these parts would be able to work on my amp? Around Mordor? Saruman Electronics, I suppose... Give him a *Ring*! im sure most of you could, but who would?? Difficult to guess when no-one knows where you are, isn't it? I suck at soldering, so id rather send it so someone that wont look like a monkey ****ing a football. Have you got, perhaps, a local guitar amp repair place or, maybe, a radio amateur or someone like that who might do it? There's a valid email address on my web site (Feedback and Links page) if you want to take this off-group. -- Mick * * * * * * * * * * *(Working in a M$-free zone!) Web:http://www.nascom.info Filtering everything posted from googlegroups to kill spam. * * He is in Florida - and he would have to ship the amp anyway. So, as far as practicalities are concerned, the Continental US is all the same to him. I would be glad to do it, if he didn't mind waiting 30 - 90 days, as that is about how long it takes me to get to any fresh project these days. Peter Wieck Melrose Park, PA- Hide quoted text - - Show quoted text - Cipher, If you mean Twickenham UK. Then try John at http://www.chambonino.com/ He is the guy. Your amp really does look rough. What is the switch on the back panel in the middle of the warning label?. The fault is clearly a bias problem but looking at the state of the thing it has more wrong than that, its a mess. Dont be disheartened by this the transformers and all major components should be fine. You could just go mad and strip it right down. You then have no option but to learn. A great way to get into valve gear!. This is what I would do. Matt. |
#79
Posted to rec.audio.tubes
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what is causing this problem?
On 7 Dec, 01:31, flipper wrote:
On Sat, 06 Dec 2008 11:59:49 -0600, cipher wrote: mick wrote in news:LCx_k.17960$uy1.13602 : On Sat, 06 Dec 2008 06:33:27 -0600, flipper wrote: snip Those pics are of a different amp. I was wondering. If you reckon on two of the GT bottles being individual rectifiers for each channel then it could possibly be a dual mono amp on a single chassis. Mind you, that doesn't explain the, possibly EZ81-type thingy and there is one too many small B9A bottle. That may just be enough changes between a prototype and a production version though. It *could* have a valve rectifier for bias and an extra amplification stage. Come on, cipher, let us into the secret! *;-) nd Sir, I wish I knew what the secret was. it has been very frustrating , this whole thing.. He's asking if those amp pics *in your album are of the Mastersound. what was once excstasy , hearing the sound of that amp, has been replaced by anger and bitterness at dealing with the mechanical/electrical issues.. aint no free lunch i guess. http://s99.photobucket.com/albums/l292/thebullards/? action=view¤t=dueventischematic.jpg *that one is mine.- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text - Eactly Flipper, Its a bad bias design and just asking for a problem. My Tek scope went absolutely haywire because of a failed wiper. It took me 6 weeks to find it. I re-capped the power supply, totally modified the feedback in one stage of the supply. I thought I had cured it but I was only treating the symptoms. To my absolute delight and embarresment it was a very high quality Bournes pot. Sorry about the spelling. Any way can you stick up a link to your site I had to rebuild my laptop and lost all the good ****. Matt. |
#80
Posted to rec.audio.tubes
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what is causing this problem?
On Sat, 6 Dec 2008 05:18:46 -0800 (PST), fryzz
wrote: .....snip!..... I'm guessing you have an intermittent bias problem. Your amp has a separate bias supply, so the 68 ohm resistors are mostly just a convenient way of adjusting the idle current. If those bypass capacitors on the 68 ohm jobs are leaky, it would actually have the effect of increasing the negative voltage on the grid, which reduces the idle current, so that's not why the tubes would draw too much current. The first thing I would look at is the bias potentiometers, pots do tend to be trouble prone due to the moving parts. You could try cleaning them with something like Caig Deoxit. You might also try feeling those two filter caps in the bias supply after the amp has been on for a while. They'll pick up some heat just from being in a tubeamp, but if one is warmer than the other it's a sign that cap is leaking. Another thing you might try is touching up all of the solder joints in the bias supply. You might also just leave your multimeter hooked up, to see if the output of the bias supply is dropping when the amp gets that "close encounters" look. When you measure the output of the bias supply, it should be stable and noise free. The fact that just ONE tube goes red, and not the pair, suggests that the bias supply & adjustment is not a problem, since both tubes on each channel run off the same connection. If it is just the one tube that goes, and it's always the same socket (even if you switch tubes around), then I'd zero in on the socket, or the traces on the circuit board. That will require very careful inspection, resoldering, or possibly checking the springiness of the socket contacts. Since the socket gets alternately hot and cold with the accompanying expansion/contraction, it is very common for the socket contacts to break away from the circuit board. This is one of those applications where point-to-point wiring can be more reliable than circuit boards. I worked at RCA when they made tube sets..... there was no end of troubles with printed circuits and tube sockets that were soldered into them. I would also solder over the solder traces in case there was a crack in the board. That might not be practical, since most mfr.'s put stuff over the traces so when the boards are soldered, it won't adhere and waste solder. Very carefully inspect all the connections and traces between grid (pin 5) of the EL34's and the bias control. Make sure nothing is loose. If the caps in parallel with the 68 ohms were to get real leaky and short, the tube might get red, but the resistors would not cook (the caps would shunt all the current). My guess is your problem is in the grid circuit of the tube that cooks. If the 0.68 uF caps were to fail and break down, you would see symptoms similiar to what you're experiencing. Also if "R1K" and "R220K" in the grid circuits were to open up, you would get similiar behaviour. That's not very common for resistors, unless they have been mechanically abused. "Opening up" by a poor solder connection, thermal expansion, or bad trace would do the same (and more common). I also assume that this unit unit used common solder with tin/lead, and not the lead free (ROHS) kind. The lead free solder is not as reliable (critical equipment can duck out of the lead-free requirements!). How old is this unit? Did the manuals make any remark about being lead-free? A possible problem (but not likely, since the mfr. should have run into this) is that the system could be oscillating at some very high frequency. There are already grid stoppers, I'd be paranoid and put stoppers (100 ohms) in the screen circuit. If it did oscillate, probably both tubes would run red, and from your symptoms, that hasn't ocurred. I don't think you need this, but I would solder a resistor (100K) from the wiper of the bias pot to the (-) end where the cap is. If the wiper failed to make contact (as they do when dirty), you will still maintain a bias that won't destroy anything. Once you got mad in a previous post, and put down all the symptoms, it became a lot easier to troubleshoot. Just to make sure, is it just ONE tube that goes at a time? Does the same resistor cook each time? If so, it's probably a circuit issue. If the problem moves around, it MIGHT be a tube problem. Usually when I have a customer bringing in a naughty piece of equipment, it takes a few minutes of careful questioning to pin down the problem. Just a list of symptoms from the customer aren't enough..... I usually run them through what is for me a "troubleshooting tree". Knowing the history of the unit, what it does when naughty, what it does when you wack it (that's inevitable) helps enormously. The fact that it misbehaves intermittently makes it very difficult to service, and even more dependent on knowing the unit. Chances are, that on a bench, this thing could run properly for years! -Paul G. |
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