Hi everyone. I have a neat little guitar amp that needs a little TLC. I have limited knowledge in electronics, however, so your help will be appreciated.
The amp in question is an ampeg ss70c guitar combo amp. I think it was made in the 80's by SLM electronics. It is a 70 watt solid state amp w/ built in chorus and an accutronics reverb tank.
When I play through it,initially, everything works as it should. After an undetermined amount of time, the output goes from a full, well rounded sound, to a thin echoey one. At this point, only channel B can be heard with all values at 10. Even then, it still has less than half output. Sometimes, fiddling with knobs will bring it back for a short time.
I have inspected the board and connections, and it "looks" good. I have cleaned the potentiometers and they seem fine. It seems to me to be a heat issue. Is there a component that keeps failing? I would love to hear a techs point of view.
Thanks in advance for any input that puts me closer to solving this problem. It is appreciated
The amp in question is an ampeg ss70c guitar combo amp. I think it was made in the 80's by SLM electronics. It is a 70 watt solid state amp w/ built in chorus and an accutronics reverb tank.
When I play through it,initially, everything works as it should. After an undetermined amount of time, the output goes from a full, well rounded sound, to a thin echoey one. At this point, only channel B can be heard with all values at 10. Even then, it still has less than half output. Sometimes, fiddling with knobs will bring it back for a short time.
I have inspected the board and connections, and it "looks" good. I have cleaned the potentiometers and they seem fine. It seems to me to be a heat issue. Is there a component that keeps failing? I would love to hear a techs point of view.
Thanks in advance for any input that puts me closer to solving this problem. It is appreciated
Sounds like it may be a bad solder joint in the power amp. Check all the big rectangular resistors for looseness.
From a June 2008 post on Activity Stream - Music Electronics Forum with requests to post SS-70CA schematics:
"
well, I just got an answer from SLM tech support, they denied me the possibility to redistribute the schematic by posting it here, anyway, kind and cooperative as always, they allowed me to post a link to their e-mail address together with the instructions to get the schematics :
Please submit all requests to:
techmail@loudtechinc.com, enter “SCHEMATIC REQUEST” into the subject field and the model and serial number of the unit in question in the main email field.
You will be sent a short disclaimer that you must agree to, and then we will email the schematic (or access to) in the order received.
"
Thanks to Bob.
If you need the schematics.
🙂
"
well, I just got an answer from SLM tech support, they denied me the possibility to redistribute the schematic by posting it here, anyway, kind and cooperative as always, they allowed me to post a link to their e-mail address together with the instructions to get the schematics :
Please submit all requests to:
techmail@loudtechinc.com, enter “SCHEMATIC REQUEST” into the subject field and the model and serial number of the unit in question in the main email field.
You will be sent a short disclaimer that you must agree to, and then we will email the schematic (or access to) in the order received.
"
Thanks to Bob.
If you need the schematics.
🙂
What Jon said^^^
If ther is an FX loop, plug a spare cord from send to return, any help?
Likewise, if there is a pair of jacks preamp out and power amp in, try a cord from one to the other.
And one more subtle test. When the sound goes away, ball up your fist and whack the top of the amp hard. Does that try to bring the sound back? This is to expose loose connections inside. A 100% amp will not react to a whack on the top.
If ther is an FX loop, plug a spare cord from send to return, any help?
Likewise, if there is a pair of jacks preamp out and power amp in, try a cord from one to the other.
And one more subtle test. When the sound goes away, ball up your fist and whack the top of the amp hard. Does that try to bring the sound back? This is to expose loose connections inside. A 100% amp will not react to a whack on the top.
Thanks all ,for your speedy replies and helpful input.
I am currently in the garage right now trying to make it act up. She's proving to be a stubborn beast ,in that she is working fine! So, I haven't been able to try the effects loop trick yet. I did put a spare cord in there anyway ,as well as the foot switch and headphone jacks. The one jack that sounded scratchy was the footswitch.
So, pound I did on the top of the amp. It sounded like a DJ battle down at the Y!
So it looks like I've got some soldering to do first.
Thanks again guys
I am currently in the garage right now trying to make it act up. She's proving to be a stubborn beast ,in that she is working fine! So, I haven't been able to try the effects loop trick yet. I did put a spare cord in there anyway ,as well as the foot switch and headphone jacks. The one jack that sounded scratchy was the footswitch.
So, pound I did on the top of the amp. It sounded like a DJ battle down at the Y!
So it looks like I've got some soldering to do first.
Thanks again guys
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