ksdaddy Posted July 8, 2022 Share Posted July 8, 2022 I'm not an amp mechanic. I couple months ago I picked up a half dozen amps in a bulk purchase. Sold some, kept the Ampeg B-15 for myself, and there was also a newer Chinese Randall with 2-12's that sounded great. I knew it wasn't worth much so I opted to just keep it around until I had some compelling reason not to. Once in a while, when I turned the amp on "cold" (after not being used for a day, let's say), the amp would have almost no output and it would be distorted. Maybe if I slapped the amp, picked it up an inch and dropped it, rocked it to and fro, you know, much like we slapped the tv in the 60s to get it to work. 100% of the time it would snap out of it and not do it again until the next day... or week even. I pulled the chassis and looked for dumb stuff, obvious arcing soot, cold solder joints. Nothing. I then saw one of the speaker terminals was very rusty. I mean tailpipe rusty. I cleaned it up with a Dremel and of course it didn't falter after that. I thought I had nailed it. But a few days ago it did it again and doesn't seem to want to come out of it. It's not contingent on which channel I use. I also plugged in an extension speaker and it did the same, thus eliminating the speaker and wires from the mix. My cleaning of the speaker terminals, while a positive thing, wasn't the fix. I hope it's some physical problem, i.e. a bad solder joint. I can surely find that, even if it means dabbing each one with a soldering pencil until it's gone. Hopefully it's not some type of component failure because I won't have a clue how to assess. I'm thinking of going on ebay and picking up an old audio signal generator just so I don't have to keep hitting the strings. I have no idea what I'm doing. And yes, I'm aware of death voltage. If anyone has any cheat hints, please let me know. Quote Link to comment Share on other sites More sharing options...
jdgm Posted July 8, 2022 Share Posted July 8, 2022 (edited) Unfortunately it is far more likely to be a failing component than a dry solder joint. I'm no expert though, it could be something shorting out. Look for signs of leakage/heat damage/discoloration where the components are soldered to the board. Post a good pic of the chassis and there is a fair chance that if it's obvious, @BBP may be able to spot it. Edited July 8, 2022 by jdgm Quote Link to comment Share on other sites More sharing options...
saturn Posted July 10, 2022 Share Posted July 10, 2022 Surprised Bad Blues Player hasn't chimed in. Isn't he an amp repair guy? Quote Link to comment Share on other sites More sharing options...
Sgt. Pepper Posted July 10, 2022 Share Posted July 10, 2022 I think guys that work on amps are more electricians than mechanics. Not to many moving parts in an amp except the potentiometer, which is also electrical, and just a variable resistor. Quote Link to comment Share on other sites More sharing options...
ksdaddy Posted July 10, 2022 Author Share Posted July 10, 2022 I fired it up today and it was the same, almost zero output, but when I switched from the clean channel to the overdriven channel, I could hear a slight change in volume and the driven side sounded it (fuzz). Exactly what you'd expect to hear if you were switching channels and the driven side's gain were cranked..... just all at almost nonexistent volume. Because I'm an idiot that doesn't know any better, I rocked the amp forward and backwards... let's just say it could now be suffering from Shaken Amplifier Syndrome. But it popped out of it's funk and sounded great again! Whatever is wrong with it definitely responds to getting the sh slapped out of it. Next rainy weekend I'll pull the chassis and once again look for something stupid. But I will look closer this time. Quote Link to comment Share on other sites More sharing options...
Sgt. Pepper Posted July 10, 2022 Share Posted July 10, 2022 (edited) 53 minutes ago, ksdaddy said: I fired it up today and it was the same, almost zero output, but when I switched from the clean channel to the overdriven channel, I could hear a slight change in volume and the driven side sounded it (fuzz). Exactly what you'd expect to hear if you were switching channels and the driven side's gain were cranked..... just all at almost nonexistent volume. Because I'm an idiot that doesn't know any better, I rocked the amp forward and backwards... let's just say it could now be suffering from Shaken Amplifier Syndrome. But it popped out of it's funk and sounded great again! Whatever is wrong with it definitely responds to getting the sh slapped out of it. Next rainy weekend I'll pull the chassis and once again look for something stupid. But I will look closer this time. Its the same as when a gage doesn't read what you want it to, so you tap on it till it does. I saw guys in the military all the time not think the pressure or temperature gage was reading correctly so they would tap on it. If its a tube amp you may have knocked the tube back in its socket. Something was not making good contact before you man handled it. Edited July 10, 2022 by Sgt. Pepper Quote Link to comment Share on other sites More sharing options...
Murph Posted July 10, 2022 Share Posted July 10, 2022 If a hammer doesn't fix it, it's an electrical problem. 1 1 Quote Link to comment Share on other sites More sharing options...
merciful-evans Posted July 10, 2022 Share Posted July 10, 2022 1 hour ago, Murph said: If a hammer doesn't fix it, it's an electrical problem. That expresses my feelings on the matter. Thanks Murph. I must remember that quote. Quote Link to comment Share on other sites More sharing options...
badbluesplayer Posted July 10, 2022 Share Posted July 10, 2022 Sounds like most likely a bad tube or socket or a bad connection somewhere. Wiggle the power tubes to see if it's a power tube or socket. Replace the power tubes if you have some and see if anything changes. If you don't have any other power tubes, you could pull one power tube and see if it's the same. Then pull the other power tube, replace the first, and see if it's the same. That might tell you whether one of the power tubes is bad. Then try removing the preamp tubes one at a time, starting back at the last one before the power tubes and proceeding to the input tube, and see if the same thing happens. If it stops happening with one of the tubes pulled then the prob is before the tube that was just removed. Then remove the next tube toward the input and see if it's still happening. That'll tell you where the problem is. You can "stick" the thing. Power the amp on and get a plain stick, like a pencil, but with no lead - lead is conductive. And take the stick and poke and prod the wires and components with the amp on to see if you can make it cut out to find a bad connection or component. Quote Link to comment Share on other sites More sharing options...
Sgt. Pepper Posted July 10, 2022 Share Posted July 10, 2022 5 hours ago, Murph said: If a hammer doesn't fix it, it's an electrical problem. Duct Tape too. Quote Link to comment Share on other sites More sharing options...
badbluesplayer Posted July 10, 2022 Share Posted July 10, 2022 For the input - if you have a low-z mic you could try using it and play the radio or TV thru it. Or wire a radio/stereo speaker output to an input jack? Quote Link to comment Share on other sites More sharing options...
MissouriPicker Posted July 10, 2022 Share Posted July 10, 2022 If an amp has a problem that plugging it in won’t solve, I’m out-of-luck. Quote Link to comment Share on other sites More sharing options...
gearbasher Posted July 10, 2022 Share Posted July 10, 2022 Does it go to 11? Quote Link to comment Share on other sites More sharing options...
ksdaddy Posted July 11, 2022 Author Share Posted July 11, 2022 19 hours ago, badbluesplayer said: For the input - if you have a low-z mic you could try using it and play the radio or TV thru it. Or wire a radio/stereo speaker output to an input jack? I bought an old audio signal generator off ebay for $25 last night. Good idea about the mic though. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.