This Peavey Artist combo amp was WAY too distorted to suit even the most extreme metal head. Could the Unbrokenstring Crew look into this and put this unit back into service?
First, a tour. You can have two channels, or a mix of the two ‘Automix’ inputs. This was a ‘thing’ back in the day.
The other controls are straight-forward.
The standby switch is in the front, whereas the AC power on is in the back. Actually, I like this because if both power switches are in the back, half the time I switch the wrong one.
The AC line duties are all squared away on this side. The City Of Los Angeles has their own version of UL. That’s the yellow and red sticker.
The right hand side of the rear chassis has the ins and outs for this amp.
These are all Peavey-branded tubes. They are all in good shape and will stay in this amp for now.
So we put a clean sine wave in, and this is what we get out. The positive power supply is weak.
An overall gut shot shows power on the left, preamp on the right, and power amp on the bottom.
These capacitors have begun to swell and push the seals outwards.
We have signs of overheating. These resistors handle power distribution and are somehow related to our problems.
The other power supply has a cooked resistor as well.
Here I am just documenting all the plugs and wires so I can get them back in the same place.
These capacitors are also bulging and will be replaced.
Time to remove the power supply board and work it over.
This circuit board holds the tube sockets. We have an intermittent short to ground under this assembly.
At first I thought that the short was under the tip terminals of these jacks, but that was not the case.
I am going to pull this assembly out and look it over as well. The blue, red, and brown wires are high voltage.
The blue capacitor in the upper right is the ‘death cap.’ If it shorts, 115vac is connected to the chassis. Not good if you ever touch the amplifier. Fatal if you touch the amplifier with one hand and grab a microphone with the other hand.
This circuit board is supported by the tube sockets. All four sockets will be unsoldered.
Out this guy comes.
Here is our short circuit. These are component leads from parts installed on top of the circuit board and soldered from the top. I guess if the excess length is out of sight, then it is out of mind.
Here are some of the parts on the top side. I don’t think these were replaced in the field, but rather it came from the factory with the untrimmed leads. Sloppy.
However, wires that are too long are easier to deal with than wires that are too short.
I am cleaning up the bits of crap in the bottom of the chassis, using some sticky tape as a way to capture the crap.
I have installed new bleeder resistors and new capacitors on this assembly. That big blue resistor is a high voltage dropping resistor. This part is fine and will not be replaced. However, those are not made anymore, and I have some of the last remaining stock of the OEM resistor. You’re welcome.
Everything gets trimmed and cleaned up before reassembly.
The power supply board has new caps everywhere.
The Ty-Wrap was my idea. These big parts need some mechanical support, but I’m not big on lots of hot glue.
The original power resistors were way out of spec, so these new parts are higher wattage to take the abuse.
These caps on the preamp board were replaced.
As was this guy.
These were the overheated resistors that we saw earlier.
These new resistors are actually more robust than the parts they replaced. And they are flame-proof.
We are back on the air!
Thanks for reading all the way to the end!
CONTACT – David Latchaw EE
281-636-8626