This is one of the more interesting jobs I’ve had. The Q-Chord Omnichord which is actually made by the Suzuki Corporation. The current owner of this one took a gamble on buying it in a broken state. It looked as if a previous owner had not noticed all the screws that hold the covers together and had tried to prise it apart with a screwdriver. The PCB inside had a big crack in it and the DC power input jack was mashed. I did manage to get it all working in the end though you had to press quite hard on some of the chord buttons on one row to get them to sound. They use a conductive rubber pad under the button sheet to make contact. I cleaned the pads as best I could and guessed that with use they might improve. This model has a rhythm section. The plinky plonky tune (in a key to match the chord button currently playing) that is created by touching the touch sensitive strip to the right is quite delightful.
Here is a photo of another one I have just been working on: The Omnichord OM-84.
I use a thermionic valve (or vacuum tube) tester based on the excellent uTracer 3 circuit board designed and supplied as a kit by the Dutch wife and husband partnership Marie-José den Brok and Ronald Dekker. See https://www.dos4ever.com/uTracer3/uTracer3_pag0.html
Trace Elliot manufacturing, what were you thinking?! Expensive looking collet knobs on splined potentiometer shafts. They didn’t even put little shims in the slots as I have seen some manufacturers do so the slot closes up. The knobs just go on wonky and come loose so you would be paying for this lazy solution when the warranty claims start rolling in.
By the way folks. Don’t ever try to prise the slot apart, the metal breaks so easily and you end up paying for a new potentiometer. The only technique I found to get them to stay on was to give them a really good tighten with a good driver and hope for the best.
Model: Quad 65 DFX
Power output: 65 Watts RMS
Channels: Rhythm Neutral/Brilliant, Lead UK/USA
Effects: 8 x preset
Impedance: 8 Ω
Internal speaker: Celestion Seventy 80. 80 Watt RMS 8 Ω
Dimensions: 46 x 53 x 29.5 cm
XLR DI output
CD/AUX input summing stereo jack
FX Loop send/Return
Footswitch Jack (footswitch not included)
Amp is very tidy and has just been recovered with leather effect vinyl.
The laney TT100 service manual does not give a simple layout diagram to show which valve is which and what it does so I have posted one here. Click image for bigger picture. For the schematics see here: laney_tt100_sch
I had to repair a Gibson Les Paul boost circuit and drew out the diagram which does not seem to be available on the net so I thought I’d share. The 47k trimmer sets the boost gain. The 4.7pF caps are an educated guess. I think they are just there to avoid RF interference. It was odd but the source terminal of the J202 FET was connected to the 22k load resistor R3. I guess they are interchangeable.
Gibson Les Paul Boost Circuit
I think this is the most powerful tube bass amp on the market at the moment with eight Svetlana Winged C 6550 power tubes. This one belongs to Den Davis owner of MCC Global Entertainments studio in Mottram.
Most modern small venue mixers are constructed onto a single printed circuit board (PCB). To do any work on them I have to remove every knob and nut (Too many knobs and nuts, like a gay night club). That’s an hours labour before I even get to find the fault and fix it.
Kam mixer dissassembled
I used to burn the midnight hours coding computer programs. This bracken fern style picture is generated by a fractal generator I wrote from scratch. I think the program got deleted (probably on a non-readable floppy disk somewhere!). The fractal was generated in monochrome at a very high resolution then each pixels intensity was set by the number of hits within its bounds. I then gave it a green tinge.
Fuck all to do with amp repairs though!