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.
James Horrocks is the bass player in the Lol Goodman Band a top class blues band that can be seen at blues venues and festivals around the UK. He called in with a Trace Elliot Boneville C50 1×12 lead combo. It was sounding rubbish, kept cutting out and the reverb was weak and had a hiss. It needed a new pair of EL34 output tubes and some fresh resistors in the reverb circuit. I have never encountered one of these before. It is unusual in that it has two foot switchable channels but volume level is the only parameter you can set independently. The GAIN control and PREAMP STYLE are common to both. Also, it has an FX loop switch on the front panel that cuts off the guitar signal completely when the rear FX LOOP switch is set to SERIES. I thought this was a fault at first but when I looked at the circuit, it was designed this way. The FX OFF switch works as expected when the rear switch is in PARALLEL mode. Despite it’s quirks, it sounds and looks good, especially if you’re into motorbikes. Like the green tolex too.
James said: “Amp sound great Dan …. good job well done :)”
I had a Fender Rhodes 54 key electric piano in for repair last month. They use guitar type magnetic pickups wired together. If one pickup fails, every key goes silent. It is still easy to get spare parts for these so they can be brought back to top condition. The 73 or 88 key versions are more popular than this 1980 vintage 54 key instrument. I repaired or replaced 17 pickups on this one, re-adjusted the hammer action and individual note volume and re-tuned. Call me if you have one needs some attention.
One of my regulars brought this in. He bought it for partly nostalgic reasons. It was in pretty good nick. All I did was PAT test, clean heads and change tape. The original send/return jack on this model is a 3 pole stereo TRS jack like an insert jack on a mixer channel. The extra, non standard jack next to it had been wired to the playback head mix. From here you got the echoes without the original. Presumably the owner wanted a tape delay for some reason. There was a bit of flutter from the direct drive induction motor but it kind of adds to the character of the effect. For a circuit that uses all 741 op-amps it had very little background hiss. Nice bit of vintage gear.
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.
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!
Tony from Oldham’s ‘A Band Of Gypsies’ (ABOG Reverb Nation and on North west bands) had some work done on his Marshall DSL 50. He didn’t like the fist pair of EL34’s I put in so I changed them for a pair of pricey but highly praised Svetlana Winged C’s. They were Hot running high gain selected tubes for that bluesy compressed late break up.
I also fixed a couple of Marshall 4×12 cabs for Tony. The jack socket switch contacts always go on them so I replace them with Neutrik gold plated jobbies that should last a bit longer.
In July I had a visit from local prog rock artist John Graham of the band Ontofield (see www.ontofield.com). His Blackstar needed a couple of new tubes.