Peavey Studiopro 110

[laurie]

Picked one of these up today for free - not working. Tested and it does actually pass signal, it just needs regular maintenance.

[Pepe]

Looks interesting, I just read the manual. The "SuperSat®/Pull Gain" knob seems to be a predecessor of the Peavey TransTube technology.

[laurie]

The copyright notice on the manual is 1994, so this amp is about 30 years old so that sounds right.

It is pretty dirty. All the potentiometers and jacks are intermittent (as is normal). At that age the electrolytic caps will all need to be checked. The only thing I didn't test was the reverb tank, but they rarely fail and can usually be repaired.

A few hours work and it should be up-and-running, rescued from the landfill. Pics to follow.

[laurie]

Internals are quite clean.

There was one burned out resistor. See the arrow showing the location (burned one is removed in the pic). This is a design fault. A one Watt resistor installed where there needed to be a Higher wattage resistor. It was part of a high-frequency rejection circuit on the speaker output, so it didn't affect the operation of the amp.

Looks like it is a common problem, which supports the "design fault" diagnosis:
https://www.reddit.com/r/diyaudio/comme ... trans_amp/

The board had been burned under the failed resistor so I cleaned it up and used some acrylic paint to seal it (leaving it unsealed would allow moisture into the board substrate). Not an issue in the next few years, but one that will eventually cause issues.

Interestingly for a 30 year old amp all the electrolytic capacitors tested OK. So I'll leave them (for now).

The reverb tank had some surface corrosion that I sanded off then sealed the outside of the tank with clear-coat.

I should have it all back together tomorrow after I get a replacement resistor at the store in the morning.

It sounded OK on the initial test. This one might be a keeper for the price
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peavey_studiopro_internal.jpg (395.24 KiB) Viewed 5696 times

[The_Doc]

Nice job Laurie. I’ve always enjoyed playing through Peavey amps.

[laurie]

I decided to change the main filter caps. 30 years is too old... whether I keep it or not, the caps are going to fail.

[bigtone23]

This is a pretty cool era of Peavey.
The clean channel is pretty classic, Fender with a Vox hint. The dirt channel is pretty hard hitting, the EQ is very effective. They used this platform across all of their amps of the time. My '91 Bravo was the all tube, 20W 1x12" version of this amp. Same controls, etc...

[laurie]

Thanks for the info!

FYI - I found out the definitive reason the amp had been junked. It had been dropped "on its head" and the weight of the transformer had deformed the chassis to the point that one of the connectors on the PCB had momentarily(?) made contact with the chassis. This particular connector is the incoming 110V hot connection from the power cord, prior to the fuse. This would have shorted to ground on the chassis and taken out the house breaker - because the connector is before the fuse. Would have made a bang and a flash!

This shows the vital importance of always using a grounded power cord. Without a grounded cord, the chassis (and any instrument plugged into the amp) would have been live with 110V.

Fixed now. Straightened the chassis. Plus installed some insulation between the PCB and chassis in case it ever happens again.

Pics prior to doing any work on the amp:
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Bent chassis.jpg (306.2 KiB) Viewed 5665 times

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Pin.jpg (258.05 KiB) Viewed 5665 times

[laurie]

Burned out 1W resistor replaced with 2W resistor with plenty of clearance in case of future heat.

I also cut half an inch off the ribbon cable and reterminated it - the insulation had been burned by the old resistor.
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Resistor.jpg (350.44 KiB) Viewed 5647 times

[laurie]

Giving the hardware a lick-o-paint. Rustoleum black, with a coat of clear satin.
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Hardware.jpg (244.45 KiB) Viewed 5647 times