Ampeg BA115HPT in trouble

[Artspoke]

I've got my friend's amp here - it hums loudly no matter how you have it set. Ii will amplify the bass some, but the tone starts to crackle and pop badly when you try to turn it up at all. The humming resonates in tune when I play a Bb - so it's around 60 or 120 Hz. When it's shut off, it bumps the speaker very loudly. I have disconnected the speaker, and am about to start measuring, but don't have the correct schematic.

I found the BA115HP schematic posted here by Enzo, but when I compared it to the circuits within the amp, I noticed quite a few changes - part values, names, etc. Is there any chance someone has a BA115HPT schematic? I want to put together a mouser order - new mosfets, diodes, electrolytics, etc., and want to be sure I'm ordering the right parts!

Thanks,
-James

P.S., Elsewhere on the net, someone pointed out that BA115 looks like BALLS - hilarious! Now that I read that, I can't see anything other than the word BALLS when I look at it!!

[doctor]

I've got my friend's amp here - it hums loudly no matter how you have it set. Ii will amplify the bass some, but the tone starts to crackle and pop badly when you try to turn it up at all. The humming resonates in tune when I play a Bb - so it's around 60 or 120 Hz. When it's shut off, it bumps the speaker very loudly. I have disconnected the speaker, and am about to start measuring, but don't have the correct schematic.

I found the BA115HP schematic posted here by Enzo, but when I compared it to the circuits within the amp, I noticed quite a few changes - part values, names, etc. Is there any chance someone has a BA115HPT schematic? I want to put together a mouser order - new mosfets, diodes, electrolytics, etc., and want to be sure I'm ordering the right parts!

Thanks,
-James

P.S., Elsewhere on the net, someone pointed out that BA115 looks like BALLS - hilarious! Now that I read that, I can't see anything other than the word BALLS when I look at it!!

Ampeg BA115HPT schematics

[Artspoke]

Thank you!

That helps soooo much - thanks!
-James

[SWEINC]

Have you checked to see if the main filter caps have cracked solder joints. Your description of your problem points pretty strongly to this. Hum because a cap is not hooked up and crackling when you play because the vibration from the speaker is causing the loose terminal of the cap to intermittently connect and disconnect from its solder pad

[Artspoke]

Checking filter caps

The solder joints look like brand new throughout the amp - including the ones on the main filter caps (C51, C54 = 5600uF x 80V). I'm going to replace them as part of the rebuild anyway. I typically replace all electrolytics, diodes, transistors (and MOSFET's like these), bridges, and anything burnt at once. This way, everything's like new again. Components are so inexpensive, and getting this chassis in and out of the cabinet is such a pain! I must remember to cover the back of the net retaining clips before trying to get this thing back together - they really grab and tear at the upholstery.

I'll start with the main filter caps, and let you know if that was it.

Thanks again,
-James

[Artspoke]

Silicone window caulk

It's everywhere!

Is this standard?

Is there a product that will help get this removed/cleaned up?

Should I add it to the components I replace?

I saw hot glue used like this in an amp once - heat gun made getting that out "easy", but it has no effect on the clear, rubbery, caulk everywhere.

I just went and found several posts about this stuff here, but no real recommendations for removing it. I don't think I'll be adding it back afterward - but I am excited to add a hot glue gun to my bench!

[J M Fahey]

You can cut it with a very sharp box cutter, but it stands more temperature than anything in your amp and is impervious to most (all?) chemicals.
It sticks perfectly to bare glass, I think that says a lot.
Use it on components which may crack their legs by vibration.