Ampeg SS-150H cutting out

[Pepe]

Hey guys, I'm nee here and I'm not entirely sure if this is the correct section to post a repair question, if so I apologize.

I recently purchased an ampeg ss150 head off of reverb. When it arrived, it seemed like it had been sitting for a very long time, dust was really caked on this thing. The previous owner said he cleaned out the pots, it plays well but cuts out after 10 or so minutes. It happens in both channel A and B, once it cuts out I will play with the volume to try and get it to produce sound again. Sometimes that method works, sometimes it doesn't. I tried the cable jump method and it seems to work okay, channel a is good and channel b seems a little off but is doable. What causes this issue?

[DrGonz78]

I tried the cable jump method and it seems to work okay, channel a is good and channel b seems a little off but is doable. What causes this issue?

I assume this means you are placing a cable connecting the effects loop in and outs. Dirt, corrosion and worn out metal switching contacts are all possible reasons for the cutting out. But I don't see effects loop on the schematic so I am not sure if this is what you meant.

If the audio cuts out like clock work then it is always possible there is a cold solder joint. I would then input a test signal into the amp and when it cuts out I would scope or trace the signal in the amp. I would confirm preamp and power amp voltage while it is working and after it cuts out.

[Enzo]

There should be an FX loop on the rear.  Lower right corner.  Just below the FS jack.

If patching a cord across the FX loop restores the sound, then your return jack needs service.

[Pepe]

There should be an FX loop on the rear.  Lower right corner.  Just below the FS jack.

If patching a cord across the FX loop restores the sound, then your return jack needs service.

Considering how dusty and unused it seems to be, I would assume it just needs a thorough cleaning. Since this is my first ampeg, Im not sure how these amps behave when they become dirty (if that would have any effect at all on these amps).

[Pepe]

I tried the cable jump method and it seems to work okay, channel a is good and channel b seems a little off but is doable. What causes this issue?

I assume this means you are placing a cable connecting the effects loop in and outs. Dirt, corrosion and worn out metal switching contacts are all possible reasons for the cutting out. But I don't see effects loop on the schematic so I am not sure if this is what you meant.

Yeah that's pretty much what I did

If the audio cuts out like clock work then it is always possible there is a cold solder joint. I would then input a test signal into the amp and when it cuts out I would scope or trace the signal in the amp. I would confirm preamp and power amp voltage while it is working and after it cuts out.

It's not always on time, but it happens within that time frame. I'll try that out and see what pops up.

[Enzo]

"Dirt" in the jacks does not refer to visual grunge, it refers to electrical dirt.  Contact surfaces oxidize or build up a film of foreign matter.  This happens to ANY amp of ANY brand that has FX loop jacks.

You need to clean the cutout contacts, not just the parts a plug touches.

[Pepe]

"Dirt" in the jacks does not refer to visual grunge, it refers to electrical dirt.  Contact surfaces oxidize or build up a film of foreign matter.  This happens to ANY amp of ANY brand that has FX loop jacks.

You need to clean the cutout contacts, not just the parts a plug touches.

You were right, I cleaned out every jack with a touch of de-oxit and a q tip. Works without issue. Thanks man.