Amp Fix

Kalamazoo Model 1 Tube Amp

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Kalamazoo Model 1 (B) Outside: Front After repair and cleaningKalamazoo Model 1 (B) Outside: Front After repair and cleaning This could be the cleanest (electronically) Kalamazoo amp that you'll ever see. The chassis is completely clean with not a spot of rust and the lettering is perfect. I'm afraid the knobs may not be original, as they are different than the other ones I've seen and the little blue indicator line on the knob seems out of place.  read more »

Gregory Apollo 800

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Tube guitar amp from the 60's. Tube lineup: 6CA4, 2x 12AX7 and 2x 6BQ5, 12" speaker combo. The speaker is a 12 inch Quam-Nichols ceramic speaker. All the Gregory amps came with this make of speaker. Actually sounds pretty good with a nice breakup when pushed. Some of this is probably due to the cathode biased class A output stage. Gregory Apollo 800 frontGregory Apollo 800 front Decent output at 10.5 Watts at 5% distortion. 12" speaker gives you good low end, but it's not very efficient, so it won't get super loud.  read more »

Hughes & Kettner Vortex Guitar Amp Head, 80 Watts

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Vortex Front: Hughes & Kettner VortexVortex Front: Hughes & Kettner Vortex Made in Germany, but so what? Pretty cheap bare bones construction: particle board cabinet that was cracked, needed glue and clamping, dowels that held the joints together had come apart due to lack of glue. The Korean spring reverb inside had fallen off due to cheap springs that held it to the chassis. The chassis itself was just a piece of rolled metal, not a box like the nice Fender chassis. Anyway, the amp came to me non functional and blowing fuses.  read more »

Peavey JSX Mini Colossal

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Peavey JSX MiniPeavey JSX Mini This amp came to me with a very low output problem from a music store. All the power supply voltages were fine, but the output was low and it seemed like the amp was loaded down because the output transformer was fine. Since the amp was a "Power Soak" feature, I disconnect that to see it it was the issue. It was not. Upon futher disassembling the amp, it was apparent that the output wire from the output transformer was pinched. The power soak PCB was pinching the wire against the chassis. It was probably fine at the factory, but over a period of time and jostling around, it ended up a partial short. A little heat shrink tubing and re-routing the wire fixed things right away.

Then I went on to some mods...  read more »

Fender Champ 600

Fender Champ - Front: Wrong resistor installed at the factory!Fender Champ - Front: Wrong resistor installed at the factory!

New amp from the store, someone returned it saying there was little of no output. Well, they were right, very low volume and distorted. I checked the supplies, they were fine, so I checked the bias voltages. The voltage on the cathode of the 6V6 was 30 or 40 volts and all over the place. The resistor that was installed at the factory was some oddball value 7 or 8 times the normal and on top of that, it had failed and become intermittent early in life.  read more »

Cheap Orange Bass Practice Amp

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Orange Crush 20B Amp Front: Loose speaker connection.Orange Crush 20B Amp Front: Loose speaker connection.

This is a cheap bass amp. The original owner said there was no sound. Easy enough, once disassembled, it was obvious that the speaker connection came off the PCB. These quick connects are often loose and a quick clamp with a wrench can tighten them down. These quick connects are used in the Valve Juniors and Champs too.

Fender Super Champ XD

Fender Super Champ XDFender Super Champ XD This was also a music store amp, no output. This is a hybrid amp with 1 12AX7 and push-pull 6V6 output and a DSP/opamp signal conditioning preamp. Power supply and bias voltages checked out OK. I shorted out the DSP and the amp worked perfect, actually sounded pretty nice without all that digital stuff dulling the sound. I also noticed that the LEDs which were driven by the DSP were also not responding to the controls (specifically the channel switching).  read more »

Univox U65RN Fix

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Univox U65RN Front: No speaker, scratchy pots, intermittent jack.Univox U65RN Front: No speaker, scratchy pots, intermittent jack.

Made in Japan, this is actually a decent sounding solid state amp with decent reverb. The reverb tank is pretty small and it's located inside the chassis, so you won't see it from the outside. Amp didn't need much besides a good cleaning and a "new" speaker. I put an old Stromberg Carlson ceramic speaker (similar to a Jensen C12R) in there and that did the job nicely. The input jack was corroded and the connection to the chassis wasn't solid.  read more »

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