Interesting repair work followup

I decided not to trace the Locobox delay after all. Seeing how the circuit most probably resembles other Japanese BBD (MN3005) delays from the era, for which schematics abound. I expect some 'delay-aficionados' will want to know exactly what makes a certain box tick and how it differs from others. In this case there seems to be a lot of rebranded releases of the same PCB..
I'm not one of those guys. I do love delays, just not the hype surrounding certain models. It's just not very interesting from a circuit design standpoint either, considering how noisy it is. Some of the noise can probably be attributed to ageing components and damaged semiconductors, but that isn't likely to be the only source. I'm guessing the effect is inherently noisy, and fixing that would require quite invasive modifications, lowering second hand price for the afficionados who want their vintage stuff original..
So this one goes back to the customer mostly unchanged and untraced.

The TS9DX DC jack was intermittent, fixed by having the joints re-soldered, so it was an easy repair. It's interesting to see how boardmounted hardware in theory shouldn't be any more susceptible to mechanical stress and damage than 'off board'-wired, but in theory this just doesn't seem to be the case. I guess tolerances explain most of it, but it makes me wonder.
Also, interesting to see the "Stinkfoot" mods, performed in 2004-09-11? Hej Andreas!

Repaired ('Stinkfoot'-modded) TS9DX


Interesting repair work

A friend of mine asked me to fix his '"Locobox" Analog Delay' and a 'Ibanez TS9DX Turbo Tube Screamer'. I rarely come across pedals I haven't already heard of but the "Locobox" brand is all new to me. It's apparently a somewhat obscure Japanese brand. This particular model is probably 1970's vintage. I just might trace the circuit but I'm already pretty sure it'll be very close, if not identical to other Japanese brands from the era. We'll see.

Arty Locobox Analog Delay gutshot
Locobox Analog Delay and TS9DX


Circuit testing and debugging

Everything fired up first go. The channel boards contain the PLL, VCO, waveshaper, ringmod, VCA, lock indicator and various related electronics. There are two identical channel boards, capable of operating independently from each other, but really designed with cross-modulation in mind. Each board is controlled from a 8-bit parallel data bus. Many features are jumperable the board is laid out for easy experimentation with features. There are so many possible configurations! Testing everything as a complete unit is difficult due to the sheer complexity of the PCB interconnect wiring and front panel control stuff. So I've been breaking it down into smaller parts, "divide and conquer".

One of the two 'channels' near completion.

Digital control board, PIC goes in the empty socket.

Two identical 'channel' boards.

Analog Harmonizer/Octaver PCBs

Lots of progress has been made during the last 6 months.
Design finalized, circuit prototyped, PCBs designed and manufactured,
components fitted, circuit tested and debugged (partly still in progress) ..
Some of the pre amp and fundamental extraction circuitry is built by hand on perfboard or breadboards. The remaining boards, 3 double-sided and 1 single-sided, are all done. 
Making your own boards like this is hardly worth it considering how relatively easy it is to have a board house make the PCBs for you. However, buying this many boards from a fab house would be pretty expensive, especially when I probably won't bother with more than one unit. So in this case, a single run, prototype through hole. 
Some photos of the etching process;

Sample of the PCB designs.

Developed PCB.

Etching in a etching tank.

Preview of the result.

All PCBs etched.


Next Distortion X

Got one of these in for repairs. CMOS inverter overdrive made in the early 80's.
Seems somewhat rare, can't find any schematics or such. So I traced it out.

Some values are missing but I'm fairly sure it's correct. Interesting circuit design.
That weird 5-terminal potentiometer is crazy
worn down, good luck finding a replacement..

Kitty cameo
Distortion X

Distortion X PCB top

Distortion X PCB bottom
Distortion X schematic



A project of mine wouldn't 'hardware compile'.. That is, I didn't manage to squeeze all the (tiny SMD) components onto a PCB small enough to fit the enclosure. The "brains" made up of a bunch of discrete logic gate IC's could be replaced by just a single 8-pin microcontroller.. 
Coding assembler is a pain.

PICkit 2 programmer/debugger


State of Guitar-Synthy-Monstrosity -affairs

Input stage, compressor, filtering & fundamental extractor.
Overview: Input stage bottom left.
Input/output -thingy top left.
Channel #1 top right. Channel #2 bottom right.


Guitar 'synth' Update

Debugged the new waveshaper circuitry. Works very well using a technique rarely (if ever) seen in audio stuff. Also added a simple ring modulator a'la Korg MS-20 which works very well with the oscillators footswitchable 'note hold'-function.
Some of the 'typical' synth waveforms didn't sound interesting enough and got replaced by  my own weirdo concoctions..