Ampeg B15 (Circa 1961) Bad hum w/chnl 1 hum w/no instrument

[Mars Amp Repair]

Hello Folks,
I have to think numerous folks have run into this issue and I haven't worked on a B15 for quite a few years to recall:
With no instrument...

[Mars Amp Repair]

Hey Enzo,
Yes, of course I just replaced it. Just curious if anyone encountered this before as most techs have worked on hundreds of these amps. As...

[Mars Amp Repair]

Hey folks,
This is a Hot Rod Deluxe that appears to be the 2nd version of the amp and is not labelled as the Deluxe III on the back. This version was...

[Mars Amp Repair]

Here is Service Manual and also a clearer copy of the power output/Pwr Supply circuit....

[Mars Amp Repair]

Hello folks,
I'm posting this for the benefit of others that might encounter this issue.
This Beta Lead had a nasty buzzing and square type pulse...

[Mars Amp Repair]

Thanx Tom...will help a lot as I don't think issue is with power stage & if so that will be easier to ferret out on the board now that I have preamp ...

[Mars Amp Repair]

Hello folks,
Does anyone have a schemo for the Crate KBA60 Keyboard amp? I can't seem to find one anywhere. Interestingly there is a Peavey Keyboard...

[Mars Amp Repair]

Thanx all. Mesa Boogie suggested just having cust send this to them. They apparently don't even have parts for this amp right now given the shipping issues....

[Mars Amp Repair]

Hello folks,
Has anyone have any experience with this D-Class Bass amp? I kinda figure these are just board replacement level type items. This one...

[Mars Amp Repair]

Hello folks,
I repaired many issues with this Ampeg SVT-AR head and am left with one more issue to solve. With all volumes down there is a low but...

[Mars Amp Repair]

Yo folks,
I've searched all over & cannot find the SVT-AR version schematic. Some are similar but none just like it. My issue is in the preamp...

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I actually think this guy just happened to notice the issue and was wondering if it was 'Normal' given the special price he paid for it ....

[Mars Amp Repair]

Not sure if I was clear: The ckt I added worked like a charm. As soon as the power is turned off the output is muted. Worked like a charm. Thanx again,...

[Mars Amp Repair]

Well, i hear what you're saying about that final drive ic should still have issues with the supplies going down unevenly. Perhaps there's more to it but given...

[Mars Amp Repair]

Addendum to previous post:
I just realized I didn't elaborate on the power on muting ckt.
The TC components are: C-44 & R59 near U3A.
...

[Mars Amp Repair]

Hey folks,
I apologize ahead of time for the long - windedness!
I have experienced this Ampeg model as well as some others that upon power down,...

[Mars Amp Repair]

Another great troubleshooting technique which we all need on tough issues like ground loops! Years ago I cobbled together a computer monitor & a magnetic...

[Mars Amp Repair]

Hello folks,
Just entering an issue I had with one of these limited edition Vox AC30HW60's that are British made from a few years ago that were probably...

[Mars Amp Repair]

Thanx Delta...

[Mars Amp Repair]

Hello folks,
Does anyone know of a suitable sub for the MosFets in the bias ckt STK830 that are more common? I saw a post on re: the HT Club 40 that...

[Mars Amp Repair]

I believe this is the G-6160 model but the preamp schematic which seems to match the unit is 6141 which I don't see anywhere.
This unit has a standby...