Lafayette LR-200A
- Thread starter TopperCat
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Surely the presumptive culprit has to be the tape monitor switch. Have you tried cleaning it?
Oh, and may I say "Welcome to AK!"? I see you've been a member for a while, but first posts are always noteworthy.
The tape monitor switch plays perfectly, the problems is when switched to aux/ Fm radio and phono is when I have distortion in right channel, I recapped the right channel but still have distortion, I don't have a schmatic so I am just trying to find problem blindly. I tested some transistors and they are OK. Checked all resistors and compared them the to working Left channel all are working voltage are a little different, All Output transistors are all working and read same voltage, No shorts anywhere, I not sure what to do next.
Thanks.
What you might be missing is that the FM and other sources also pass through that switch.
peteCWA
Active Member
As indicated by other posters, all signals from other sources pass through the preamp section and thru the MONITOR switch. Oxidation of the switch contacts is not uncommon and can result in distortion. A dab of contact cleaner and exercise of the push button a number of times can clean away the oxidation and crud off the contacts.
Having repaired a number of LR-200's and 200A's when doing service at Lafayette Radio, and reviewing the schematic and my service notes, the preamp section of each channel used either two 2SC644 or 2SC900 transistors. My notes indicate that the 2SC900 was prone to noise, distortion, or total failure.
Obviously, having an audio generator and a scope for test instruments and you could probably find the problem in a few minutes. Also, the shotgun approach of replacing all the caps before identifying the problem component(s), is really never a great idea. Further, resistors age and can change value,or if passing some current, can fail or cause noise or distortion in a circuit.
Having repaired a number of LR-200's and 200A's when doing service at Lafayette Radio, and reviewing the schematic and my service notes, the preamp section of each channel used either two 2SC644 or 2SC900 transistors. My notes indicate that the 2SC900 was prone to noise, distortion, or total failure.
Obviously, having an audio generator and a scope for test instruments and you could probably find the problem in a few minutes. Also, the shotgun approach of replacing all the caps before identifying the problem component(s), is really never a great idea. Further, resistors age and can change value,or if passing some current, can fail or cause noise or distortion in a circuit.
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