Peavey original Backstage schematics

[Sbyrax]

Hi to all,

I tried to clean the pots of my old Peavey Backstage amp (original model) with a KONTAKT PR spray and made a mess of it. After I thoroughly sprayed and let it dry, I tried to power it up. Started humming, no volume control was possible, and in a few seconds it blew the fuse.

I will have a go at fixing it, however I can not find the PCB schematics anywhere on line.

Can anyone help? Any tips welcome!

Thanks

ps The PCB of this model is an artwork in itself!

[Enzo]

You call customer service at peavey and ask for it. I have it on paper at the shop, but not scanned here on my computer.

When you powered it up, had you installed it back into the chassis?

I have no idea what you may have done to it, but when they blow fuses, first thing is to check the output transistors for E-C shorts, and also the main rectifier diodes.

[DrGonz78]

Welcome to the place! Sorry about the amp

You will need to build a Light Bulb Limiter, if you don't have one already. The light bulb limiter will allow the amp to power up without blowing the fuse. Perhaps something got shorted out on something when you put it back together? Inspect the amp to make sure there is not something amiss. Do you have a multimeter for measuring voltages and resistance etc? Since you were working on the amp recently there is a good chance something may have caused this problem after you put the amp back together. Let us know what you find.

[Mick Bailey]

I have an old teal-stripe backstage 110 too. I also use Kontakt PR (from TME, Poland) and never had any problems with it, either on my own amps or on customer's amps.

I don't think your problem is related to the product and have used it pretty much every day for years. My feeling also is you've accidentally shorted something, though there is also the unlikely outside possibility that the next time you switched it on was its time to die. First thing to do is make certain everything is wired correctly. Are the speaker leads good where they exit the chassis?

[Sbyrax]

Hey guys,

thanks so much for the tips and schematic. I built a light bulb limiter (thanks @DrGonz78), opened up the amp and checked all the wiring. See some photos from the reverb unit here



I re-soldered some points (just did not look right to me), measured the pots (no problems there), put it all back together with caution, powered it up using the bulb limiter and unfortunately the result is the same , see video below

https://youtu.be/4IyvCbhBDbs

The humming is the same, no control by the pots, less louder due to the bulb limiter (the bulb is 40W, letting through about 1.5A at 220V).

My guess is that the spray contaminated some caps, I will try to replace them all and see where it goes.

Thanks for the help!

ps I scanned the original Peavey Backstage User Manual and Troubleshooter to share with you guys

Peavey Backstage Troubleshooter.pdf
Peavey Backstage User Manual.pdf

[Tom Phillips]

...My guess is that the spray contaminated some caps, I will try to replace them all and see where it goes...

I strongly suggest that you don't do that. Let's follow a logical series of troubleshooting tests and then fix the specific problem found. Please let us know more about your experience and what test equipment you have.

Meanwhile consider the following:
1) Your first post doesn't specifically say but i take it that the amp worked before you sprayed the pots. Correct?
2) Did you remove the board from the front panel when you sprayed the pots? If so, then maybe you disturbed something in the process. Maybe a ground connection is disconnected.
3) Capacitors would not normally be damaged by pot cleaner.
4) The photos of the reverb pan look normal. I.e. stock factory wiring.
5) Spray and let it dry is not a usual description of using pot cleaner.

You came to the right place for assistance. We can help but we don't favor shotgun parts replacement and the more work you do based on guessing the more additional problems you can cause.

[Mick Bailey]

Does the bulb limiter light up with the speaker disconnected? Double-check there's no short on the speaker leads.

Kontakt PR is dry isopropyl alcohol with various lubricants. It evaporates and leaves an oily, non-conductive film and is safe around commonly found amp components. I doubt it has anything to do with your fault.

[Sbyrax]

Hi Tom,

Thanks for the feedback. I am an electronics guy (degrees'n'all with good hands-on experience back in the early 90's - most of it digital I am afraid), I only have a portable multimeter (does not do diodes / transistors) and have some basic soldering equipment.

Replying to your questions:
1. Yes it did work, with terrible cracking noise in all pots.
2. Yes, I removed it. I double checked about ground connections, I did not observe anything missing/disconnected.
3. I understand, so I will not go this way
4. Yes, first time that the reverb pan saw the light after manufacturing
5. I sprayed thoroughly through the pot openings (bottom and front - that's why i removed it from the chassis), turned them clock-anticlock several times till I felt that they were easier to turn. After that, I sprayed with a board cleaner (Kontakt PRF 6-68) to remove the residues from the pot cleaner. Placed it back in the chassis, everything connected, fired it up and then all the humming started and eventually blew the fuse.

I did try what Mick said about a potential short in the speaker leads, no problem there. The bulb limiter lights up with speaker disconnected. (Thanks Mick)

So what do you suggest? Attack the transistors?

[DrGonz78]

Real quick... Do not hook up the speaker until you know that the hum is not the sound of substantial DC voltage burning down on the speaker. While you have the speaker disconnected measure to test if there is DC voltages across the speaker output wires.

[DrGonz78]

5. I sprayed thoroughly through the pot openings (bottom and front - that's why i removed it from the chassis), turned them clock-anticlock several times till I felt that they were easier to turn. After that, I sprayed with a board cleaner (Kontakt PRF 6-68) to remove the residues from the pot cleaner. Placed it back in the chassis, everything connected, fired it up and then all the humming started and eventually blew the fuse.

Just re-read this comment here... It depends on how much contact cleaner you used and how long you gave it dry out. The pot cleaner is not a worry but to me the contact spray could have caused a short circuit. How long did you wait after spraying the board with contact cleaner and then installing it back up?

[JudgeShredd]

I have an old teal-stripe backstage 110 too. I also use Kontakt PR (from TME, Poland) and never had any problems with it, either on my own amps or on customer's amps.

I don't think your problem is related to the product and have used it pretty much every day for years. My feeling also is you've accidentally shorted something, though there is also the unlikely outside possibility that the next time you switched it on was its time to die. First thing to do is make certain everything is wired correctly. Are the speaker leads good where they exit the chassis?

Mick Bailey, et al, renewing to see if Sbyrax will share what he found with his Backstage issue. I also have a Backstage 110 teal-stripe with overheating issue. Peavey has been UNRESPONSIVE to my requests for schematics for the amp. Can anyone share a 110 pdf or screenshot? Peavey has not even acknowledged receipt of my e-mails and I have asked them to at least confirm they've received them. At Peavey.com and also on the Peaveyforums page. That's another rant, but here I just ask for anyone's help with a schematic for the 110, which appears they sold only a few 100 of them. I have found 1@ 5w? (bigger) resistor, of only 2 on the board, that is scorched enough to obscure the value stripes. I would like to at least replace it as a starting point. TIA and Rock On Brothers!

[dmeek]

Backstage.pdf

Backstage 110.pdf