Adventures in amp repair.

This past weekend I spent a great deal of time working on a few of the amps we have in the studio. Three of them have issues severe enough that I thought I’d have to take them in to Al’s Diner for proper repair, but after doing some reading I decided to at least attempt to simply clean them up. To do so, I purchased a can of DeoxIT and a can of compressed air.

The first amp on the bench was a Gallien-Krueger 800RB that has been in the basement for several years. It was essentially abandoned by it’s owner and has been sitting unused since the last repair I had done. It worked for about a week before becoming a noisy inconsistent wreck. Taking the top off was a breeze. Getting the front panel off and pulling the preamp, which had all the pots and jacks on it, was less fun.

Once I got it apart I blew out as much dust as I could including blowing out each pot individually. I then sprayed the DeoxIT into each pot and switch. I was afraid that three of the pots would need to be replaced because they were a bit loose, although none of the solder joints were cracked. I worked each pot and switch for a bit then left it over night to dry out.

The next morning I put it back together and plugged it in. The difference was amazing! No glitching, no static, no sudden bursts of volume; just gloriously even sounding solid state tone. With this first amp working I was emboldened to start on the next two: a Fender Deluxe 85 and a Peavey TKP 65.

The Fender was another amp that was given to me by Steve Toth. He told me at the time that it didn’t work and if I could fix it I could have it. I left it alone for quite awhile but got curious one day and plugged it in. The reverb pot was broken and it was somewhat scratchy sounding on about half the other pots, but it worked. Anthea has used it occasionally, but never really liked fussing with it tonally because of the static bursts from the EQ pots.

I ripped into this amp and cleaned it up in the same manner. This was much easier to work on. I found that the speaker was not secured in place. There were only two screws, both on the same side of the speaker from and they were about an 1/8 of an inch unscrewed. I moved one of the screws to the opposite side of the other screw and tightened them both down. Issue number one solved.

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Cleaning this amp up took quite some time. Steve’s a smoker and I had to scrape a bit of cigarette tar off the knobs and face plate. I also sprayed the pots three separate times to loosen them up. I found a spider nest under two of the input jacks as well.

I was going to put it back together and plug it on, but decided to look for the replacement pot for the reverb. It had been sheared off prior to my receiving it. I was able to find the parts list for the amp and ordered the pot and knob from Darren Riley’s Guitar & Amp Shop. Darren Riley was a blind Google search find, but was super awesome to work with and had exactly what I needed in stock. He even emailed me to let me know they shipped. On a Sunday. He was awesome and I highly recommend using him.

Since the parts were on order for the Fender I turned to the Peavey. I bought this from Eric Brown sometime in the 90’s and used it on stage a couple times, but mostly used it for occasional band practice since it was much smaller than my stage rig, which consists of a the second Fender Bassman 135 (Blackface) on top of a Fender Spectrum two 10″ by one 18″ cabinet that I bought in 1989 for my first Bassman head (Silverface). It’s been pretty good in the studio as well both direct and mic’d, but over the years it’s gotten more and more nasty sounding.

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I’ve pulled this amp apart a few times so no surprises here. I followed suit with the pots and jacks as I did before, but on this amp the attached power cable needed to be replaced. It was frayed at the plug and the amp. This was more difficult than I had wished for. There is a  protective clip that surrounds the power cable so the metal backing doesn’t cut into it. I ended up having to cut the cable off to figure out how to get it out. It’s a squeeze clip that cute into the cable a bit. This proved more difficult to get back in later than it was almost worth, but I got it on the end.

The parts for the Fender arrived on Thursday. I pulled the preamp board out with little difficulty and propped it up. Since I had no solder sucker I had to use braid to pull the old solder out. Not ideal but after some time and with a little patience I got the broken pot off. Putting the new one in wasn’t that difficult, but my soldering skills are a bit rusty. I’m hoping I didn’t do any damage.

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Once together the amp sounds much better but the reverb is still not working. I banged on the reverb pan and got it to make some sound but nothing being driven from the amp. It seems to need more work. For now I’ll leave it alone.

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