repairing 1970s DIY on-board distortion unit

[TheresanLinSolder]

dmeek - That photo is strikingly familiar! Brilliant detective work!

I've also found Google images of Univoxes that have the same labelling on the knobs. I've found a chap who discusses troubleshooting them: it's clearly beyond my abilities, but fascinating to find out that this puzzling and usually broken thing stuck in the back of my guitar is actually (a DIY version of) quite a famous effect. Thank you so much all.

Anyone know a repairer in south or central London?

[dmeek]

The board in your guitar doesn't look diy. It looks like it came from the original pedal and installed in the guitar

[TheresanLinSolder]

Wow. I'm definitely going to get it repaired then. I've found a place over here that sells them in kit form, I might ask if they can help. One of the qs for me was, will it sound as awful now I can play properly as it did when I was a kid? Given what it is, probably not! This has been such an interesting journey ... thank you all again.

[J M Fahey]

definitely the same: 6 transistors, 2 germanium diodes, same layout ... what else?

But you forgot an important part: you treated us to two top pictures ... but none of the bottom, copper tracks side.

[pdf64]

Try JPF Amps https://jpfamps.com/ at Regent Sounds in Denmark St. They’re members here, probably been too busy to visit for a while.
Fixed fee of Ł22 plus parts for pedals, though not sure how current that is or whether it could be strictly classified as a pedal 😀

[Mark Hammer]

If it can't be fixed by someone on Denmark St., then I imagine nobody can fix it!

My own personal view is that things that can be done better and more effectively off the guitar should be done off the guitar. In this case, a vintage FY-6 circuit board, rehoused to an enclosure with a suitable stompswitch, and tone-selector switch, could be worth a fair amount. Not retirement-sized, but certainly enough to more than cover the cost of the repair.

[TheresanLinSolder]

pdf64 - many thanks! I actually bought the guitar all those years ago in Macari's, which was in a different lot than it is now. They said it had a box in the back, but they couldn't charge me for it as it was broken. Dad fixed it for a short while by sticking back the black wire (5th one along) which was self-evidently not attached at the time. I'll contact Regent Sounds and see what they can do - that's a reasonable price.

Mark Hammer - agreed about nobody else having a better chance of fixing it. My instinct is to leave it in the guitar, just for nostalgia, but I'll see what the repairer thinks - there is a chance that being housed this way is making it more prone to damage (eg, I have to wiggle it to get the battery in/out). I aint sellin' unless it really is retirement-worthy!

JM Fahey - germanium? Even cooler! I do have a photo of the underneath, but my "upload" box is full. I was hoping to post a pic of the battery clip, in case that is shot, because I reckon even I could replace that.

If I get it going, I may post an update. I love a good anecdote, and you've all been so helpful ...

[52 Bill]

Here are the wire connections for the pc board.

Red- Battery Positive
Orange- Expander control Wiper
White- Expander control CW
Blue- Input to foot switch
Black- Circuit Ground (Earth)
Brown- Output to foot switch
Yellow- Balance control wiper
Red- Tone switch
Green- Tone switch

Hope that this helps.

[TheresanLinSolder]

52 Bill, that's incredibly kind ... thank you for taking the trouble. Since nothing at all is coming out, I'm sort of wondering if my re-attaching of the battery clip was bad.

[TheresanLinSolder]

For anyone still following ... I now realise from 52 Bill's helpful list, that the wire I attached to the battery clip was the brown one that's supposed to go to the footswitch.

I've had my share of help, but two last questions: this leaves my battery with just one wire - the red positive one. Is this OK? And, if the brown is, as it looks, too short to reach without being taut, is it OK to buy a new piece of wire and replace it? It doesn't have to be special wire, just the right gauge?

[The Dude]

Just about any old piece of wire will work (within reason). That circuit won't draw much current. Generally, on an active guitar, which this basically is, the battery ground will go to a stereo input jack ring. The ground is then completed when a standard 1/4" jack is plugged in shorting ring to sleeve. This keeps the battery from draining when the guitar is unplugged.

[g1]

Have you inspected the clip itself? Often stuff that sits for a while gets bad corrosion on the clip contacts.

[52 Bill]

The battery clip should have a red wire and a black wire. The black wire usually goes to the ring contact of the input jack. This way the battery is turned off when the input plug is pulled out of the jack.

I would assume that the guitar has a stereo output jack installed. The black battery lead should go the ring contact of the guitar jack.

[J M Fahey]

plus:

52 Bill

Here are the wire connections for the pc board.

Red- Battery Positive
Orange- Expander control Wiper
White- Expander control CW
Blue- Input to foot switch
Black- Circuit Ground (Earth)
Brown- Output to foot switch
Yellow- Balance control wiper
Red- Tone switch
Green- Tone switch

In principle, and just for testing, connect battery clip Red to Red on PCB, and battery clip Black to Black/Ground/Earth on PCB.

This will put Fuzz ON , not depending on external switching jacks or wiring and it will either work or not, period.

IF it works, pull battery after testing and weŽll wire the switching jack

IF not, eitherv repair PCB or build a new one and replace it.

But thereŽs high probability it works, simply not getting power yet.

[TheresanLinSolder]

Great ... I'm going near a hardware shop later, so I will look for suitable wire there. I think the clip contacts are OK, I guess I could buy a new one in case, I doubt they cost much. I'll do the test using the PCB earth, and if it works, then I'll go ahead and put things together properly as suggested. If the test doesn't work, it's off to Denmark St for a professional repair.

I'm very grateful.

Paul