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#1
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TFM-35 Problem
Hi All,
I've had my Carver TFM-35 for 10 years or so, with never a problem. Recently the speaker protection relay began cycling now and then. Now it cycles almost constantly. Does not matter which set of speakers are coupled up. Also, the front panel lights for the VU meters are out. Any ideas? Thanks, Ernst |
#2
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TFM-35 Problem
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#4
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TFM-35 Problem
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#5
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TFM-35 Problem
wrote:
Tim, I appreciate the reply; however, I'd like to fix the problem rather than patch it up. in making a recommendation one must make quite a few assumptions based upon incomplete data. my first assumption is that if you are qualified to troubleshoot and repair electronic equipment or you were inclined to take it to qualified personnel you would have already done so. my second assumption based on your post was aside from the 2 issues mentioned al else was fine. conclusion: problem in the protection circuit. possibly a weak or magnetized relay. maybe worn, pitted, intermittent contacts. finding exact parts or even reasonably close these days can be a real challenge. if on the other hand the prot circuit is just doing its job by all means fix the real problem. i must confess that i did not look up the TFM-35 and assumed it was a low power consumer stereo. at 350 WPC you can get into serious trouble with this thing. please refer servicing to qualified personel. I got inside the cabinet and the only thing obvious I found was a swollen filter cap. These caps seem to have four terminals instead of the customary two. you can read about 4 pole capacitors here http://www.jensencapacitors.com/audi...ctrolytic.html Seems like the first thing to do is replace both of the filter caps (the other can't be far behind). maybe, as a service tech i never felt it was in the customers best interest to change out parts that test good. in commercial/industrial equipment there is more budget for repair, however for example one box with 50 to 100 v-mos output FETs at $60 each means you either be ready to swear every one was bad or be real persuasive as to why you needed to change all of them. in the case of old caps its a judgment call. much audio gear from the 60's and earlier often needs to be recapped to achieve spec performance. 70's and newer, evaluate on an individual bases. Regards, Ernst TimPerry wrote: wrote: Hi All, I've had my Carver TFM-35 for 10 years or so, with never a problem. Recently the speaker protection relay began cycling now and then. Now it cycles almost constantly. Does not matter which set of speakers are coupled up. Also, the front panel lights for the VU meters are out. Any ideas? Thanks, Ernst add a capacitor across the relay coil to act as a time delay. this will preserve the function of the circuit, just slow it down a little. size is dependand on relay coil current. i might start off with a 100 uF / 35V. this is assuming that the relay itself is ok. replace VU lights as desired. no problem with leaving them dark. |
#6
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TFM-35 Problem
TimPerry wrote:
my first assumption is that if you are qualified to troubleshoot and repair electronic equipment or you were inclined to take it to qualified personnel you would have already done so. Well, sort of. I'm actually a jet mech by training; although I completed a Cleaveland Institute of Electronics course and have been tinkering with electronics for 30 years or so. I actually was employed as an "Electro-Mechanical Technician" in a manufacturing environment (PLC's, mechanical fab and repair) for a while between contracts. my second assumption based on your post was aside from the 2 issues mentioned al else was fine. That's correct. conclusion: problem in the protection circuit. I agree. Truth is, I don't have alot of experience with protection circuits, and no servicing data to follow. It seems to me that there exists some sort of imbalance that is causing the protection to trip (or more acurately, to cycle); and the only obvious defect is the filter cap. At least if it is not the cause, I know it has to be replaced anyway. Keep in mind that I have owned the unit since it was new, so I at least have the full history. It's very rarely pushed hard, has never overheated, or tripped protection as a result of a shorted (or really low impedance) output load. It has been subjected to vibration at least during a fairly recent move (MS to TX). I say this because one of the panel lamps has a detached filament. Not popped like a burnt-out lamp, just detached. I checked really close for cracked solder joints, loose components and such. maybe, as a service tech i never felt it was in the customers best interest to change out parts that test good. in commercial/industrial equipment there is more budget for repair, however for example one box with 50 to 100 v-mos output FETs at $60 each means you either be ready to swear every one was bad or be real persuasive as to why you needed to change all of them. With that sort of expense, I would concur. But since I have two of the same part, of the same age, operating in the same environment.... I'm willing to fork over the extra $25.00 to change the second cap just for the sake of preventative maintenance. I'm not too proud to send the amp in for service. I'm just too cheap. There's only one place I know of that works on this gear. They are very, very good, and their prices reflect it. Before I spend that kind of bucks on this amp, I'll sell it for parts and look for a replacement. Ernst |
#7
Posted to rec.audio.tech
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TFM-35 Problem
TimPerry wrote:
my first assumption is that if you are qualified to troubleshoot and repair electronic equipment or you were inclined to take it to qualified personnel you would have already done so. Well, sort of. I'm actually a jet mech by training; although I completed a Cleaveland Institute of Electronics course and have been tinkering with electronics for 30 years or so. I actually was employed as an "Electro-Mechanical Technician" in a manufacturing environment (PLC's, mechanical fab and repair) for a while between contracts. my second assumption based on your post was aside from the 2 issues mentioned al else was fine. That's correct. conclusion: problem in the protection circuit. I agree. Truth is, I don't have alot of experience with protection circuits, and no servicing data to follow. It seems to me that there exists some sort of imbalance that is causing the protection to trip (or more acurately, to cycle); and the only obvious defect is the filter cap. At least if it is not the cause, I know it has to be replaced anyway. Keep in mind that I have owned the unit since it was new, so I at least have the full history. It's very rarely pushed hard, has never overheated, or tripped protection as a result of a shorted (or really low impedance) output load. It has been subjected to vibration at least during a fairly recent move (MS to TX). I say this because one of the panel lamps has a detached filament. Not popped like a burnt-out lamp, just detached. I checked really close for cracked solder joints, loose components and such. maybe, as a service tech i never felt it was in the customers best interest to change out parts that test good. in commercial/industrial equipment there is more budget for repair, however for example one box with 50 to 100 v-mos output FETs at $60 each means you either be ready to swear every one was bad or be real persuasive as to why you needed to change all of them. With that sort of expense, I would concur. But since I have two of the same part, of the same age, operating in the same environment.... I'm willing to fork over the extra $25.00 to change the second cap just for the sake of preventative maintenance. I'm not too proud to send the amp in for service. I'm just too cheap. There's only one place I know of that works on this gear. They are very, very good, and their prices reflect it. Before I spend that kind of bucks on this amp, I'll sell it for parts and look for a replacement. Ernst |
#8
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TFM-35 Problem
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#9
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TFM-35 Problem
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