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#41
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
"Eeyore" wrote in message ... EADGBE wrote: (Scott Dorsey) wrote: Does an ohmmeter show them as open or not? SCOTT: The fuse resistor that didn't blow reads exactly 1.04 ohms (that's an in-circuit reading). The fuse resistor that blew reads open circuit....and that is with the resistor TAKEN OUT of circuit completely. I figured I could replace the fuse resistor with a regular 1-ohm resistor and get things working again, but I also realize that that is NOT safe, and so the deck will not be powered up again until it has a new 1-ohm fuse resistor in place...and I might even replace the other 1-ohm fuse resistor whilst I'm at it. I wouldn't excessively fret over not fitting a genuine fusible resistor. The only difference between them and normal resistors is that they are (a) designed to fail open and (b) are flameproof. There's still another one in circuit ! If one of those fusibles had failed (as it seems) that's why you have no display. Graham I completely concur. Two fusible R's in a single winding to single filament circuit such as this appears to be, is an overkill. At least as a temporary measure, I would have no qualms about subbing a standard 1 ohm resistor at all, and all the 'usual suspects' that know me on here, would readily confirm that I *never* advocate *any* practice that is in *any way* dangerous. By all means fit a genuine replacement in the end if that makes you feel better, but to try it, just put your pliers across the failed one .... Honestly, you can !! Arfa |
#42
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
First of all, I would like to extend a HUGE THANK YOU to everyone who helped me figure out the problem with my CR-7A cassette deck. I had made a couple of hasty assumptions, and you folks put me on the right track. Now if I could only find a couple of 1-ohm, 1/4-watt fusible resistors....these things are BLOODY HARD to find!!!!!!!!!!!! |
#43
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
Eeyore wrote:
The filament btw acts as a directly heated cathode in a VFD. The segments that illuminate are the anodes and the remaining connections are control grids. It's a big multipin triode. Umpteenode? -- One phrase that explains 99% of all idiot driving: "You can't block traffic if you're not in the way." |
#44
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
"EADGBE" wrote in message ups.com... First of all, I would like to extend a HUGE THANK YOU to everyone who helped me figure out the problem with my CR-7A cassette deck. I had made a couple of hasty assumptions, and you folks put me on the right track. Now if I could only find a couple of 1-ohm, 1/4-watt fusible resistors....these things are BLOODY HARD to find!!!!!!!!!!!! Where are you ? If it's really that hard in your locality, I'll bung a couple in a Jiffy bag for you ! I have a drawer full of 'em ... Arfa |
#45
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
EADGBE wrote:
Now if I could only find a couple of 1-ohm, 1/4-watt fusible resistors....these things are BLOODY HARD to find!!!!!!!!!!!! As I said earlier, MCM electronics stocks them. Other places that cater to the (rapidly dwindling) TV repair crowd like B+D Enterprises may help as well. Parts Express MIGHT have them, but they don't carry too many TV set parts any more. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#46
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
On Sep 29, 7:51 am, (Scott Dorsey) wrote:
As I said earlier, MCM electronics stocks them. Other places that cater to the (rapidly dwindling) TV repair crowd like B+D Enterprises may help as well. Parts Express MIGHT have them, but they don't carry too many TV set parts any more. SCOTT: Thanks, but I have already checked all of those sites, including MCM. Nobody seems to stock a 1/4-watt, 1-ohm fusing resistor. I may have overlooked the part in my search results, but I have tried all of those sites (and others) multiple times. I can't believe that this part would be this hard to find. |
#47
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
On Sep 29, 7:32 am, "Arfa Daily" wrote:
Where are you ? If it's really that hard in your locality, I'll bung a couple in a Jiffy bag for you ! I have a drawer full of 'em ... ARFA: I may have to get you to send some to me. They are rare as hen's teeth around here. Thanks! |
#48
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
On Sat, 29 Sep 2007 06:46:28 -0700, EADGBE
wrote: On Sep 29, 7:51 am, (Scott Dorsey) wrote: As I said earlier, MCM electronics stocks them. Other places that cater to the (rapidly dwindling) TV repair crowd like B+D Enterprises may help as well. Parts Express MIGHT have them, but they don't carry too many TV set parts any more. SCOTT: Thanks, but I have already checked all of those sites, including MCM. Nobody seems to stock a 1/4-watt, 1-ohm fusing resistor. I may have overlooked the part in my search results, but I have tried all of those sites (and others) multiple times. I can't believe that this part would be this hard to find. Radiospares have them. Part No 267-1569 d -- Pearce Consulting http://www.pearce.uk.com |
#49
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
"EADGBE" wrote in message oups.com... On Sep 29, 7:32 am, "Arfa Daily" wrote: Where are you ? If it's really that hard in your locality, I'll bung a couple in a Jiffy bag for you ! I have a drawer full of 'em ... ARFA: I may have to get you to send some to me. They are rare as hen's teeth around here. Thanks! Well, if you need me to, just contact me off-group using the same e-mail address as I use to post. Even if you are the other side of the world to me, it's only gonna set me back the cost of a coupla stamps to get you out of trouble, and I guess that I can stand that without going bankrupt ... Arfa |
#50
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
Don Pearce wrote: EADGBE wrote: (Scott Dorsey) wrote: As I said earlier, MCM electronics stocks them. Other places that cater to the (rapidly dwindling) TV repair crowd like B+D Enterprises may help as well. Parts Express MIGHT have them, but they don't carry too many TV set parts any more. SCOTT: Thanks, but I have already checked all of those sites, including MCM. Nobody seems to stock a 1/4-watt, 1-ohm fusing resistor. I may have overlooked the part in my search results, but I have tried all of those sites (and others) multiple times. I can't believe that this part would be this hard to find. Radiospares have them. Part No 267-1569 They have an absurd minimum order charge. Graham |
#51
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
On Sat, 29 Sep 2007 21:10:22 +0100, Eeyore
wrote: Don Pearce wrote: EADGBE wrote: (Scott Dorsey) wrote: As I said earlier, MCM electronics stocks them. Other places that cater to the (rapidly dwindling) TV repair crowd like B+D Enterprises may help as well. Parts Express MIGHT have them, but they don't carry too many TV set parts any more. SCOTT: Thanks, but I have already checked all of those sites, including MCM. Nobody seems to stock a 1/4-watt, 1-ohm fusing resistor. I may have overlooked the part in my search results, but I have tried all of those sites (and others) multiple times. I can't believe that this part would be this hard to find. Radiospares have them. Part No 267-1569 They have an absurd minimum order charge. Graham You can always top up with useful stuff - they have plenty. d -- Pearce Consulting http://www.pearce.uk.com |
#52
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
Don Pearce wrote:
On Sat, 29 Sep 2007 21:10:22 +0100, Eeyore wrote: Don Pearce wrote: EADGBE wrote: (Scott Dorsey) wrote: As I said earlier, MCM electronics stocks them. Other places that cater to the (rapidly dwindling) TV repair crowd like B+D Enterprises may help as well. Parts Express MIGHT have them, but they don't carry too many TV set parts any more. SCOTT: Thanks, but I have already checked all of those sites, including MCM. Nobody seems to stock a 1/4-watt, 1-ohm fusing resistor. I may have overlooked the part in my search results, but I have tried all of those sites (and others) multiple times. I can't believe that this part would be this hard to find. Radiospares have them. Part No 267-1569 They have an absurd minimum order charge. Graham You can always top up with useful stuff - they have plenty. d NAh if you do that, you`ll end up with all the crap you ordered to make up the value, and the resistors will be out of stock! Ron(UK) |
#53
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
"Ron(UK)" wrote in message ... Don Pearce wrote: On Sat, 29 Sep 2007 21:10:22 +0100, Eeyore wrote: Don Pearce wrote: EADGBE wrote: (Scott Dorsey) wrote: As I said earlier, MCM electronics stocks them. Other places that cater to the (rapidly dwindling) TV repair crowd like B+D Enterprises may help as well. Parts Express MIGHT have them, but they don't carry too many TV set parts any more. SCOTT: Thanks, but I have already checked all of those sites, including MCM. Nobody seems to stock a 1/4-watt, 1-ohm fusing resistor. I may have overlooked the part in my search results, but I have tried all of those sites (and others) multiple times. I can't believe that this part would be this hard to find. Radiospares have them. Part No 267-1569 They have an absurd minimum order charge. Graham You can always top up with useful stuff - they have plenty. d NAh if you do that, you`ll end up with all the crap you ordered to make up the value, and the resistors will be out of stock! Ron(UK) Oh Ron, and haven't we all been *there* !! Last time for me just two weeks ago ... Arfa |
#54
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
Don Pearce wrote: Eeyore wrote: Don Pearce wrote: EADGBE wrote: (Scott Dorsey) wrote: As I said earlier, MCM electronics stocks them. Other places that cater to the (rapidly dwindling) TV repair crowd like B+D Enterprises may help as well. Parts Express MIGHT have them, but they don't carry too many TV set parts any more. SCOTT: Thanks, but I have already checked all of those sites, including MCM. Nobody seems to stock a 1/4-watt, 1-ohm fusing resistor. I may have overlooked the part in my search results, but I have tried all of those sites (and others) multiple times. I can't believe that this part would be this hard to find. Radiospares have them. Part No 267-1569 They have an absurd minimum order charge. You can always top up with useful stuff - they have plenty. What exactly would the OP want to 'top up' with ? He's not a repairman. Graham |
#55
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
In article .com,
EADGBE wrote: On Sep 29, 7:32 am, "Arfa Daily" wrote: Where are you ? If it's really that hard in your locality, I'll bung a couple in a Jiffy bag for you ! I have a drawer full of 'em ... ARFA: I may have to get you to send some to me. They are rare as hen's teeth around here. Digi-Key part PPC1.0ATR-ND. That's a 1/3 watt and not a 1/4 watt but should be fine. MCM only has half-watt ones, part number 370-1. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#56
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
Thanks for all the help, folks!
I finally found 1/4-watt, 1-ohm fusible resistors from a supplier in Europe. They should be in my mailbox in about a week, hopefully. It's weird that a part that I would have assumed to be fairly common is so hard to find in the U.S. Have fusible resistors "gone out of style" in place of something else? I was pretty sure I could have used a regular flameproof 1-ohm resistor for this particular circuit, but I was just paranoid enough to want to be able to use exactly the right part. Why? Well, the unit in question had undoubtedly been hit with some sort of voltage surge, causing several other power supply components to fry. Those other components have been replaced, and the deck's power supply has been stable so far. However, this latest component failure, in a very low-voltage circuit that is completely unrelated to the previously-repaired circuits, shows me that there could be other weakened components hiding just about anywhere--so I might as well re- install ALL of the original protective elements and keep a watchful eye until I am convinced the deck is completely rehabilitated. |
#57
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
"EADGBE" wrote in message oups.com... Thanks for all the help, folks! I finally found 1/4-watt, 1-ohm fusible resistors from a supplier in Europe. They should be in my mailbox in about a week, hopefully. It's weird that a part that I would have assumed to be fairly common is so hard to find in the U.S. Have fusible resistors "gone out of style" in place of something else? I was pretty sure I could have used a regular flameproof 1-ohm resistor for this particular circuit, but I was just paranoid enough to want to be able to use exactly the right part. Why? Well, the unit in question had undoubtedly been hit with some sort of voltage surge, causing several other power supply components to fry. Those other components have been replaced, and the deck's power supply has been stable so far. However, this latest component failure, in a very low-voltage circuit that is completely unrelated to the previously-repaired circuits, shows me that there could be other weakened components hiding just about anywhere--so I might as well re- install ALL of the original protective elements and keep a watchful eye until I am convinced the deck is completely rehabilitated. Not a bad philosophy at the end of the day. Arfa |
#58
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
On Oct 2, 7:32 am, Meat Plow wrote:
I just realized your nickname is the standard tuning of a guitar. Yep! That's it! :-) |
#59
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
On Oct 2, 2:32 pm, Meat Plow wrote:
So i take it you play? Oh, yes. My love of playing comes from the same spot as my love of fine stereo/audio equipment, both analogue and digital. |
#60
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
EADGBE wrote: Meat Plow wrote: So i take it you play? Oh, yes. My love of playing comes from the same spot as my love of fine stereo/audio equipment, both analogue and digital. On the subject of the original post, have you tried powering the VFD display and is it working now ? Graham |
#61
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
On Oct 2, 6:22 pm, Eeyore
wrote: On the subject of the original post, have you tried powering the VFD display and is it working now ? Graham GRAHAM: No, I haven't powered it on yet. I'm still waiting for the replacement fusible resistors to arrive from my parts source. I didn't want to use just a regular flameproof resistor, partly because of my own paranoia and partly because the fusible resistors are marked as "critical components" in the Nakamichi service manual. |
#62
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
EADGBE wrote: Eeyore wrote: On the subject of the original post, have you tried powering the VFD display and is it working now ? GRAHAM: No, I haven't powered it on yet. I'm still waiting for the replacement fusible resistors to arrive from my parts source. I didn't want to use just a regular flameproof resistor, partly because of my own paranoia and partly because the fusible resistors are marked as "critical components" in the Nakamichi service manual. They're simply 'covering themselves' when they say that but I won't argue with your caution. Graham |
#63
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
Nice guitars! I like the Les Paul Studio flametop.
I could see the small versions of the photos but I couldn't supersize them. Must be a glitch. |
#64
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
Eeyore wrote:
EADGBE wrote: Eeyore wrote: On the subject of the original post, have you tried powering the VFD display and is it working now ? GRAHAM: No, I haven't powered it on yet. I'm still waiting for the replacement fusible resistors to arrive from my parts source. I didn't want to use just a regular flameproof resistor, partly because of my own paranoia and partly because the fusible resistors are marked as "critical components" in the Nakamichi service manual. They're simply 'covering themselves' when they say that but I won't argue with your caution. Graham If you were to be supercautious, you should order the absolutely correct part direct from Naki Ron(UK) |
#65
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
On Oct 3, 8:58 am, "Ron(UK)" wrote:
If you were to be supercautious, you should order the absolutely correct part direct from Naki Ron(UK) I had always heard that Nak would not sell parts directly to consumers (a common policy among manufacturers). And since Nakamichi's decline, I would have been very surprised to hear that anyone could order anything at all from them. Do you have ordering information? I would really appreciate it. Thanks! |
#66
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
EADGBE wrote:
On Oct 3, 8:58 am, "Ron(UK)" wrote: If you were to be supercautious, you should order the absolutely correct part direct from Naki Ron(UK) I had always heard that Nak would not sell parts directly to consumers (a common policy among manufacturers). And since Nakamichi's decline, I would have been very surprised to hear that anyone could order anything at all from them. Do you have ordering information? I would really appreciate it. Thanks! Well it was meant to be a joke actually, if you read the manual it generally says that only the manufacturers specified part number should be used where a crucial safety component is marked. I`m surprised you had trouble finding 1R fusibles, they are a pretty common component in a great many items. I find Rapid Electronics are pretty good for small orders in the UK Ron(UK) -- Lune Valley Audio Public Address Systems Hire Sales Maintenance www.lunevalleyaudio.com |
#67
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
On Oct 3, 10:02 am, "Ron(UK)" wrote:
I`m surprised you had trouble finding 1R fusibles, they are a pretty common component in a great many items. I find Rapid Electronics are pretty good for small orders in the UK Ron(UK) RON: Whoops! I should have known it was a joke. Sorry about that. Yes, I did indeed have lots of trouble finding 1R fusibles. But perseverance paid off! Thanks for the tip about Rapid Electronics. I'll try to remember them! |
#68
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
"Arfa Daily" wrote in message ... "Eeyore" wrote in message ... EADGBE wrote: (Scott Dorsey) wrote: Does an ohmmeter show them as open or not? SCOTT: The fuse resistor that didn't blow reads exactly 1.04 ohms (that's an in-circuit reading). The fuse resistor that blew reads open circuit....and that is with the resistor TAKEN OUT of circuit completely. I figured I could replace the fuse resistor with a regular 1-ohm resistor and get things working again, but I also realize that that is NOT safe, and so the deck will not be powered up again until it has a new 1-ohm fuse resistor in place...and I might even replace the other 1-ohm fuse resistor whilst I'm at it. I wouldn't excessively fret over not fitting a genuine fusible resistor. The only difference between them and normal resistors is that they are (a) designed to fail open and (b) are flameproof. There's still another one in circuit ! If one of those fusibles had failed (as it seems) that's why you have no display. Graham I completely concur. Two fusible R's in a single winding to single filament circuit such as this appears to be, is an overkill. At least as a temporary measure, I would have no qualms about subbing a standard 1 ohm resistor at all, and all the 'usual suspects' that know me on here, would readily confirm that I *never* advocate *any* practice that is in *any way* dangerous. By all means fit a genuine replacement in the end if that makes you feel better, but to try it, just put your pliers across the failed one ... Honestly, you can !! Arfa I'll agree that Arfa never advocates anything that is dangerous. If he says it is ok you can take his word. I also see no problem doing this either.. You still have one fuse in the line. In your house's wiring there is only one fuse or circuit breaker in the supply. Using 2 is overkill. Mike |
#69
Posted to rec.audio.tech,sci.electronics.repair,rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
"Michael Kennedy" wrote in message . .. "Arfa Daily" wrote in message ... "Eeyore" wrote in message ... EADGBE wrote: (Scott Dorsey) wrote: Does an ohmmeter show them as open or not? SCOTT: The fuse resistor that didn't blow reads exactly 1.04 ohms (that's an in-circuit reading). The fuse resistor that blew reads open circuit....and that is with the resistor TAKEN OUT of circuit completely. I figured I could replace the fuse resistor with a regular 1-ohm resistor and get things working again, but I also realize that that is NOT safe, and so the deck will not be powered up again until it has a new 1-ohm fuse resistor in place...and I might even replace the other 1-ohm fuse resistor whilst I'm at it. I wouldn't excessively fret over not fitting a genuine fusible resistor. The only difference between them and normal resistors is that they are (a) designed to fail open and (b) are flameproof. There's still another one in circuit ! If one of those fusibles had failed (as it seems) that's why you have no display. Graham I completely concur. Two fusible R's in a single winding to single filament circuit such as this appears to be, is an overkill. At least as a temporary measure, I would have no qualms about subbing a standard 1 ohm resistor at all, and all the 'usual suspects' that know me on here, would readily confirm that I *never* advocate *any* practice that is in *any way* dangerous. By all means fit a genuine replacement in the end if that makes you feel better, but to try it, just put your pliers across the failed one ... Honestly, you can !! Arfa I'll agree that Arfa never advocates anything that is dangerous. If he says it is ok you can take his word. I also see no problem doing this either.. You still have one fuse in the line. In your house's wiring there is only one fuse or circuit breaker in the supply. Using 2 is overkill. Mike Thanks Michael. Support appreciated, as always. Arfa |
#70
Posted to rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
On Friday, 28 September 2007 04:46:58 UTC+1, EADGBE wrote:
Thanks for the link - I have already downloaded the service manual. That's how I know the voltages for the secondary outputs. I should have made that more clear in my original post (sorry). Hi, I came across this thread as I just had my display on my CR7 cut out, and some mild burning smell. After investigation my 4r7 fusible resistors are both blown so I need to investigate further. The service manual I DLed has no mention of transformer voltages and so I wondered if you could hint me the link that was deleted, or tell me the voltages expected on the red wires from the transformer. cheers |
#71
Posted to rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
wrote:
On Friday, 28 September 2007 04:46:58 UTC+1, EADGBE wrote: Thanks for the link - I have already downloaded the service manual. That's how I know the voltages for the secondary outputs. I should have made that more clear in my original post (sorry). Hi, I came across this thread as I just had my display on my CR7 cut out, and some mild burning smell. After investigation my 4r7 fusible resistors are both blown so I need to investigate further. There are four of them. Which ones are blown? The service manual I DLed has no mention of transformer voltages and so I wondered if you could hint me the link that was deleted, or tell me the voltages expected on the red wires from the transformer. The paper one from the manufacturer lists them. T1 has 36VCT, 30VCT, then some 3.5V and 5V windings. But replace the fuses, check the pass transistors, the filter caps, and the bridge rectifiers, and then disconnect the logic board from the power supply board and see if the unloaded voltages are good. You may have an issue on the power supply board causing it to pull too much current (such as a shorted filter cap), or you might have something on the logic board causing it to pull too much current (such as bad decoupling caps on the logic board). cheers I haven't worked one of of these things for more than twenty years and I recall them being a real pain. I really hate consumer electronics. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#72
Posted to rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
On 1/29/2015 10:29 AM, Scott Dorsey wrote:
wrote: On Friday, 28 September 2007 04:46:58 UTC+1, EADGBE wrote: Thanks for the link - I have already downloaded the service manual. That's how I know the voltages for the secondary outputs. I should have made that more clear in my original post (sorry). Hi, I came across this thread as I just had my display on my CR7 cut out, and some mild burning smell. After investigation my 4r7 fusible resistors are both blown so I need to investigate further. There are four of them. Which ones are blown? The service manual I DLed has no mention of transformer voltages and so I wondered if you could hint me the link that was deleted, or tell me the voltages expected on the red wires from the transformer. The paper one from the manufacturer lists them. T1 has 36VCT, 30VCT, then some 3.5V and 5V windings. But replace the fuses, check the pass transistors, the filter caps, and the bridge rectifiers, and then disconnect the logic board from the power supply board and see if the unloaded voltages are good. You may have an issue on the power supply board causing it to pull too much current (such as a shorted filter cap), or you might have something on the logic board causing it to pull too much current (such as bad decoupling caps on the logic board). cheers I haven't worked one of of these things for more than twenty years and I recall them being a real pain. I really hate consumer electronics. --scott Gotta love USENET, a followup question to a post posted in 2007 being answered in 2015. Speaks to the long term integral use of this newsgroup. Tim Sprout |
#73
Posted to rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
On Thursday, September 27, 2007 at 9:24:01 PM UTC-4, EADGBE wrote:
I have a Nakamichi CR-7A that works and sounds great, but it has developed a problem, and I am wondering how difficult it will be to repair. The flourescent meter window has stopped working. I know a little about electronics, so I opened up the deck and checked the voltages coming off of the transformer. As expected, there were various different outputs of AC voltage, including an output of 3.5v AC. This 3.5v AC output feeds the flourescent meter window AND NOTHING ELSE. But this output has stopped working. No smoke, no fire, everything else on the deck works perfectly fine. There is just no more 3.5v AC output from the transformer. QUESTION 1: What happened? Did the transformer have a meltdown or is it as simple as some kind of internal fuse? (I should point out that this deck's power supply circuit had been damaged at some point, possibly by a power surge, but it was professionally repaired by an authorized Nak repair center). QUESTION 2: Can this be fixed - and if so, how difficult is it? QUESTION 3: Will it be possible to find a replacement transformer? For the record, this transformer has the following PAIRS of outputs: 3.5v AC (two of them) 5v AC (two of them) 15v AC (two of them) 18v AC (two of them) Any help would be much appreciated. Strange that one winding would open. Check continuity of that winding. If open, tear off coil wrapper to see if a cold solder joint (lead wire to magnet wire) is the problem. I think this has the schematic, too.... http://www.ant-audio.co.uk/Tape_Reco...AMICHI_CR7.pdf |
#74
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PROBLEM: Nakamichi CR-7A Power Transformer
On Thursday, January 29, 2015 at 3:38:00 PM UTC-5, Tim Sprout wrote:
On 1/29/2015 10:29 AM, Scott Dorsey wrote: wrote: On Friday, 28 September 2007 04:46:58 UTC+1, EADGBE wrote: Thanks for the link - I have already downloaded the service manual. That's how I know the voltages for the secondary outputs. I should have made that more clear in my original post (sorry). Hi, I came across this thread as I just had my display on my CR7 cut out, and some mild burning smell. After investigation my 4r7 fusible resistors are both blown so I need to investigate further. There are four of them. Which ones are blown? The service manual I DLed has no mention of transformer voltages and so I wondered if you could hint me the link that was deleted, or tell me the voltages expected on the red wires from the transformer. The paper one from the manufacturer lists them. T1 has 36VCT, 30VCT, then some 3.5V and 5V windings. But replace the fuses, check the pass transistors, the filter caps, and the bridge rectifiers, and then disconnect the logic board from the power supply board and see if the unloaded voltages are good. You may have an issue on the power supply board causing it to pull too much current (such as a shorted filter cap), or you might have something on the logic board causing it to pull too much current (such as bad decoupling caps on the logic board). cheers I haven't worked one of of these things for more than twenty years and I recall them being a real pain. I really hate consumer electronics. --scott Gotta love USENET, a followup question to a post posted in 2007 being answered in 2015. Speaks to the long term integral use of this newsgroup. Tim Sprout Did he ever get it fixed? :-) |
#75
Posted to rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
On Thursday, 29 January 2015 19:29:17 UTC, Scott Dorsey wrote:
wrote: On Friday, 28 September 2007 04:46:58 UTC+1, EADGBE wrote: Thanks for the link - I have already downloaded the service manual. That's how I know the voltages for the secondary outputs. I should have made that more clear in my original post (sorry). Hi, I came across this thread as I just had my display on my CR7 cut out, and some mild burning smell. After investigation my 4r7 fusible resistors are both blown so I need to investigate further. There are four of them. Which ones are blown? The service manual I DLed has no mention of transformer voltages and so I wondered if you could hint me the link that was deleted, or tell me the voltages expected on the red wires from the transformer. The paper one from the manufacturer lists them. T1 has 36VCT, 30VCT, then some 3.5V and 5V windings. But replace the fuses, check the pass transistors, the filter caps, and the bridge rectifiers, and then disconnect the logic board from the power supply board and see if the unloaded voltages are good. You may have an issue on the power supply board causing it to pull too much current (such as a shorted filter cap), or you might have something on the logic board causing it to pull too much current (such as bad decoupling caps on the logic board). cheers I haven't worked one of of these things for more than twenty years and I recall them being a real pain. I really hate consumer electronics. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." I already disconnected the logic board. Voltages seemed good from the other windings, and made sense after the bridge rectifiers, apart from the reds which were 40v in and 1v out. I expect the 1v was from a cap or some other backwards flow as the 4r7's were both blown. You say 4 of them, are you including the 1 ohm ones on the display circuit? These seem ok (haven't lifted a leg to double check but no reason to think they are an issue) Voltages seem high but this is with no load so is probably fine (41v, 7.9v etc) I'll just have to try the 4r7's and see if it all works ok. thanks for the info |
#76
Posted to rec.audio.pro
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PROBLEM: Nakamichi CR-7A Power Transformer
wrote:
I already disconnected the logic board. Voltages seemed good from the other= windings, and made sense after the bridge rectifiers, apart from the reds = which were 40v in and 1v out. I expect the 1v was from a cap or some other = backwards flow as the 4r7's were both blown. You say 4 of them, are you inc= luding the 1 ohm ones on the display circuit? These seem ok (haven't lifted= a leg to double check but no reason to think they are an issue) No. There are four of them for the two supplies that go to connectors six and seven. R423, R424, R425, and R426. Which ones are blown? Tack fusible resistors in parallel with the open ones. Apply AC power with the connector to the logic board removed. Do they blow? Do the voltages on the (CH-7 or CH-6) connector match the numbers in the manual? What do you mean "the reds?" Do you mean D407, D404, D401, or one of the other bridges? If you see 40V going into a bridge rectifier and 1V coming out, the bridge is bad. If the bridge were good and the output shorted, it would pull the input down. (Make sure you're using the DC setting to measure the output and the AC setting to measure the input of course.) Voltages seem high but this is with no load so is probably fine (41v, 7.9v = etc) Except for the ones that are zero, presumably. Also, the manual may be old enough that it expects voltages to be measured with a low-Z meter. Because Japanese line voltages are often lower than US voltages, you will sometimes see higher than normal unregulated voltages in Japanese gear. Don't worry about that unless it's a Dokorder (in which case throw it away). Once you get past the regulator stage, though, they should match the ones on the schematic. I'll just have to try the 4r7's and see if it all works ok. thanks for the = info Fuses don't just blow for no reason, find out what is blowing them. Your first job is to find out if it's on the logic board or the supply board. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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