Hi I had this amp working for years but recently one of the channels is substantially subdued.
I tried Servisol 10, twisting volume control and selector switch repeatedly but to no avail.
I can't even find out where to test for voltages to see where the problem lies-the channel isn't completely dead, just substantially muted.
Any help will be very welcome.
I tried Servisol 10, twisting volume control and selector switch repeatedly but to no avail.
I can't even find out where to test for voltages to see where the problem lies-the channel isn't completely dead, just substantially muted.
Any help will be very welcome.
Set it on the bench with an oscillator and an AC voltmeter -OR- a listening probe (headphone amp with gator-clip leads). Run mid-band mid-level tone through and note signal voltage/loudness at maybe 3 key points per channel. Possible levels may be 0.1V or pretty-soft at volume control wiper(s), 3V or very-loud at chip output. Keep checking hour to hour day to day until a level drops. The problem is before that spot. Quick backtracking may find the exact "leak/clog" spot, or you may have to set intermediate checkpoints and be patient some more.
It may help to put 100 Ohms in series with a speaker and leave it on the speaker terminals that you think go bad. Then go about other business. If you can stand the drone, any change in drone will wake you right up. (Obviously your family could hate you...)
It may help to put 100 Ohms in series with a speaker and leave it on the speaker terminals that you think go bad. Then go about other business. If you can stand the drone, any change in drone will wake you right up. (Obviously your family could hate you...)
As first-poster, you could have edited the Subject (I think)?
If the amp's output is low all the time (i.e., this isn't a sporadic issue) I'd measure the gain of the amp. I give some tips on how to do that with a multimeter and a smartphone here:
You'll probably find that the gain of one channel is quite a bit lower than that of the other. To sort out why, I would eliminate anything at the input of the amp. So bypass volume pots, tone controls, etc. and connect the signal generator directly to the input of the amp. You don't need to add a load on the amp, though testing with a load is always better. Then remeasure the gain. If the low gain is still present, the issue is with the power amp. If it isn't, the issue is with all the stuff you bypassed.
If the issue is with the power amp, it's probably a bad connection somewhere. I'd wiggle the wires to the amp while watching the output of the amp on a scope or DMM. It's unlikely to be a bad component in the power amp, though that is possible.
Tom
You'll probably find that the gain of one channel is quite a bit lower than that of the other. To sort out why, I would eliminate anything at the input of the amp. So bypass volume pots, tone controls, etc. and connect the signal generator directly to the input of the amp. You don't need to add a load on the amp, though testing with a load is always better. Then remeasure the gain. If the low gain is still present, the issue is with the power amp. If it isn't, the issue is with all the stuff you bypassed.
If the issue is with the power amp, it's probably a bad connection somewhere. I'd wiggle the wires to the amp while watching the output of the amp on a scope or DMM. It's unlikely to be a bad component in the power amp, though that is possible.
Tom
Remove all the connections from the amp and speakers. Put a little drop of sewing machine oil on each of them and re-connect,
I had this happen at a friends house instant cure.
Cheers -J
I had this happen at a friends house instant cure.
Cheers -J
Oil is bad idea.
DeoxiIt is way to go.
https://www.google.com/search?q=deo...-verizon-sscr&sourceid=chrome-mobile&ie=UTF-8
DeoxiIt is way to go.
https://www.google.com/search?q=deo...-verizon-sscr&sourceid=chrome-mobile&ie=UTF-8
Other issue may be poor soldering, which over time made dead contact. I would retouch the soldering on bad channel.
Rust is oxidized metal, various forms. Oil has no effect on ferrum oxide.
Deoxit reacts with oxide, reducing it, and removing it from the surface.
Oil does nothing, on the contrary, lubricates surface, preventing proper conductive connection.
Do whatever you want.
What do i care.
Deoxit reacts with oxide, reducing it, and removing it from the surface.
Oil does nothing, on the contrary, lubricates surface, preventing proper conductive connection.
Do whatever you want.
What do i care.