I'm having trouble with my latest project, it's pedalpcb super fuzz clone called the uber fuzz.
https://www.pedalpcb.com/docs/Uberfuzz.pdf
With the pedal engaged I get absolute silence, other than the amps usual noise floor.
I did the dumb checks first, but I figured the signal was grounding, so I moved onto using a audio probe pretty quickly. I get sound up until the input side of R1 (22K) after that the signal seems to go to ground. I get nothing on the output side of R1. I've poked around and checked for bridges.
I assume I get sound on the input side of R1 because the other side is grounded an I effectively have 22k of resistance between ground when the probes on the input side, correct?
The so is a short to ground at R2 the only explanation?
Although the 2SC828 is "just another NPN", it has a different pinout than a great many other similar-gain NPNs, being ECB rather than EBC. Possible you've used a transistor type that requires twisting the leads around to work with that board?
The other thing to note is that the orientation of the 10uf electros keeps changing in the Superfuzz. I'm reminded here of a street in Montreal that is one-way, but changes direction about 5 times in 5 blocks; you have to stay on top of which way things are going on this block and that, and in this part of the circuit versus that one.
Really? That was one of my dumb checks... I used 2n2222's.
I googled the pinouts for both... I'm going to google them again.
Right so 828's have ECB pinout and 2n2222's have EBC pinout.
You know that was actually not that easy to find out. Google images brings up plenty of 828's with regular pinout and some of those specs sheets with the ambiguous top down view, or is it bottom up? I don't know because I can't read Russian.
Anyway, I guess I've fried those transistors. But I'm relieved the mystery has been solved.
Thanks for the help.
Quote from: replaceablehead on August 31, 2019, 09:16:56 AM
Anyway, I guess I've fried those transistors....
Fairly unlikely, BJTs can be pretty robust in this sort of pinout mix-up.
Agreed. There's actually more risk to the transistor from overheating during unsoldering than there is by being installed the wrong way around.
Carefully unsolder (and fresh, or flux-enhanced, solder wick would be best for that job) the first transistor, slip a piece of insulation you stripped off some wire over the relevant transistor pins, so you can bend them around to conform to the board's pinout without shorting out against each other, and do the same signal tracing you did before. The odds are good you'll see the signal proceed through more of the circuit.
can we see photos of your build?
look for the 3d diagram of the part in question. draw it on all your diagrams, until you know it.
(https://c1.staticflickr.com/9/8288/29174639861_a1c1a224d2_o.jpg)
and the thing with the 2d diagrams - if you view the transistor from the top, you can't see the pins. this renders the diagram somewhat useless. you can only see the pins looking onto the pins.
(https://www.atariarchives.org/ecp/figure8-1.gif)
Alright, it's working.
I ended up looking up the 2n2222a pinout again, because these ones were marked ctp2n2222a and I was feeling a little paranoid. Anyway next thing I'm looking at the diagram of a p2n2222a telling me the pinout is different to a pn2222a and at that point I was like "eh, I've used these a million times". And sure enough the ctp2n2222a's were just plain old 2n2222a's, but damn if it ain't hard to be sure of this stuff.