2 in 1 Build help needed

[jwyles90]

Hey all!
I just finished putting together a 2 in 1 build and have hit a wall troubleshooting wise. I've got the Greengage Overdrive on the left side and a Green Russian Big muff on the right (both from Pedal PCB). The Greengage side works great and sounds killer, however the Big Muff side doesn't work at all (aside from the LED). I've gone through some troubleshooting already (which I'll list below) and am still stumped as to what's causing it to not work, so any and all help is greatly appreciated.Here are the build docs as well: https://www.pedalpcb.com/docs/MuffinFuzz.pdf

Things I've tried (and maybe ruled out?):
--Checking 3PDT continuity
--Isolating the Big Muff PCB. Still doesn't work.
--Reflowing any and all solder joints that look like they could use a little help
--Took an audio probe to it. I was able to get a signal in R1, but one half of it sounded clear the other half sounded pretty quiet. Tried reflowing that joint. No signal past R1, so I reflowed and even replaced R2, reflowed Q1 socket joints, still nothing.
--Took the readings for all 4 2N5088s. Q1-Q3 are at 4.5v, Q4 is around 3.8v.
Is there anything else that I'm missing that I could try? I'm at a loss for what else to do since as far as I can tell everything is the right value and installed/wired correctly. Thanks in advance!!

[idy]

You should be able to measure R2 in circuit (power off) , is it the value it's supposed to be, 100k?
When you test you will be checking to make sure there is not a short to ground at the node where  R2 C1 and the base of Q1 meet.

You gave us one voltage for each Q, but we are greedy and want to see all three for each.... if for example the base of Q1 was 0....

[jwyles90]

You should be able to measure R2 in circuit (power off) , is it the value it's supposed to be, 100k?
When you test you will be checking to make sure there is not a short to ground at the node where  R2 C1 and the base of Q1 meet.

You gave us one voltage for each Q, but we are greedy and want to see all three for each.... if for example the base of Q1 was 0....

So it's not super consistent but every time I'm checking R2 it ends up right around 84k (or at least I think that's what I'm reading. I've got my multimeter on the 200k mode for measuring ohms).

Q1 has 4.5 for emitter and about .6 for Base. Same for q2 and q3. Q4 has similar base readings but 3.6 for emitter

[idy]

Something wrong at base of Q2.

power off, does B to E look like a diode to multi meter? It should.
Why is Base at .6v?

What about value of R 3?

Make sure that Q is snug in socket.

[antonis]

Q1 has 4.5 for emitter and about .6 for Base.

Considering you mean "Collector" instead of "Emitter", Q1 voltages are quite OK..

There should be some AC ground either between R1 & C1 or between C1 & Q1 Base..
(all red circled points)

Also, check for shorted C2 (470pF feedback cap) or   
(yellow circled points)

[iainpunk]

hey,

have you taken a look at this page:
debug guide

i recommend bookmarking it. ive been building for 8 years and still look at it sometimes.

cheers

[jwyles90]

Thanks for all the replies! And apologies for any mixed up terminology or things of that nature, I'm still getting the hang of measuring transistors with a multimeter and get which leg is which mixed up sometimes. I'll triple-check that everything is snug in their sockets. Q1 feels like it has some wiggle room, so I'll really try to jam it in there and see if it makes a difference.

I'll for sure bookmark that debugging page too! It's crazy how small my go-to back of troubleshooting tricks are when compared to that haha.

[duck_arse]

just for fun and practise, pull all the transistors out of the sockets. apply power to the circuit, and measure the voltages at each empty socket pin. then write down in
c - xx.xV
b - xx.xV
e - xx.xV
notation the corresponding voltage, for each transistor, and put the long string of results here. please.

[jwyles90]

just for fun and practise, pull all the transistors out of the sockets. apply power to the circuit, and measure the voltages at each empty socket pin. then write down in
c - xx.xV
b - xx.xV
e - xx.xV
notation the corresponding voltage, for each transistor, and put the long string of results here. please.

You got it! I'll give that a shot when I'm home from work.

[jwyles90]

just for fun and practise, pull all the transistors out of the sockets. apply power to the circuit, and measure the voltages at each empty socket pin. then write down in
c - xx.xV
b - xx.xV
e - xx.xV
notation the corresponding voltage, for each transistor, and put the long string of results here. please.

Ok so, assuming I measured them correctly here's what I got:
Q1
C - 0.00
B - 1.64
E - 9.44

Q2
C - 0.00
B -1.63
E - 9.44

Q3
C - 0.00
B - 1.52
E - 8.72

Q4
C - 0.00
B - 1.68
E - 9.64

[idy]

pretty sure that's upside down. The collectors on these should be towards power and the emitters towards ground.
2n5088 is EBC, viewed facing the flat side.

But with E and C reversed, those voltages are what you would expect with the transistors removed.

[jwyles90]

pretty sure that's upside down. The collectors on these should be towards power and the emitters towards ground.
2n5088 is EBC, viewed facing the flat side.

But with E and C reversed, those voltages are what you would expect with the transistors removed.

Dammit, sorry about that. I can't seem to keep track of which order that pin out is in for the life of me. But yes, you are correct it should be reversed. I briefly got a signal from the collector leg on q1 when I took the audioprobe to it again, but it was super faint and I had a hard time getting it consistently. I'm basically not getting anything from R2, 3 or 5 probe wise. C1 and c2 have signal though

[idy]

OK. So

it was super faint and I had a hard time getting it consistently. I'm basically not getting anything from R2, 3 or 5 probe wise. C1 and c2 have signal though

R2 goes from c1 to ground. Is there a signal on the side attached to c1? If not they are not connected.
R3 is connected to R2 and C1. If there is signal on C1... should be there on that end of R3 also. The other side of R3 is attached to Collector, where there should be louder signal. It is a feedback path.

No signal on Base of transistor? But yes on C1? those two things should be attached.

[jwyles90]

OK. So

it was super faint and I had a hard time getting it consistently. I'm basically not getting anything from R2, 3 or 5 probe wise. C1 and c2 have signal though

R2 goes from c1 to ground. Is there a signal on the side attached to c1? If not they are not connected.
R3 is connected to R2 and C1. If there is signal on C1... should be there on that end of R3 also. The other side of R3 is attached to Collector, where there should be louder signal. It is a feedback path.

No signal on Base of transistor? But yes on C1? those two things should be attached.

Thanks for that explanation, I'm still getting the hang of reading schematics so that was super helpful. I'll go through and check all those today. I'll try and take the probe to the underside of the board too since it feels like that might be a little easier to get a good connection signal-wise than trying to finagle it in between the resistor leads when they're all grouped up next to each other.

I'm tempted to just buy a new board and start from scratch given how long I've been hitting a wall with this, but I'm also determined to figure out what the hell is causing it to not work properly, since there's nothing blatantly obvious to my eyes and that feels like a good skill to develop.

[duck_arse]

your empty socket voltages would seem to clear the components involved for value [maybe not the emitter resistors] and shows no shorts or like that. you could put a transistor in its place and inject some signal to its base [audio probe - it doesn't need to be from the pedal input, can be stage-injected] and monitor its collector. then pull that trannie and do the next in line. this will prove or not the audio stages one by one, will eliminate a lot of things.


<rant>
circuit diagrams without the component values marked are next to useless in my opinion. if I need to open one file to look at the circuit diagram and designators, and another/copy file to see the values, and then need to flick back and forth to get the board layout diagram, and then need to look and compare a builder's photos, I'm just as likely to do none of that. people writing manuals ought to be able to write them more better than that.
</rant>

[idy]

Yes, the trouble shooting is the main mental exercise you get from this activity, at least when using remade pcbs. When everything works its like paint by numbers. When failure, you have to think. Deduction: it can't be this, its not that, its not this either...oh here it is, the last thing left.

If you did this and didn't learn to "sort of" read schematics you would be missing the good part.

[jwyles90]

Yes, the trouble shooting is the main mental exercise you get from this activity, at least when using remade pcbs. When everything works its like paint by numbers. When failure, you have to think. Deduction: it can't be this, its not that, its not this either...oh here it is, the last thing left.

If you did this and didn't learn to "sort of" read schematics you would be missing the good part.

Oh yea totally. As much as I hate troubleshooting, especially when it's a long drawn out thing, I always try to look at it as a learning experience and feel like I come out the other end having gained a lot from the experience. This one is really tripping me up though, I feel like everything I'm trying doesn't seem to really make much of a difference so it's hard to not get frustrated by the lack of progress after trying everything I can think to try.

[jwyles90]

your empty socket voltages would seem to clear the components involved for value [maybe not the emitter resistors] and shows no shorts or like that. you could put a transistor in its place and inject some signal to its base [audio probe - it doesn't need to be from the pedal input, can be stage-injected] and monitor its collector. then pull that trannie and do the next in line. this will prove or not the audio stages one by one, will eliminate a lot of things.

So if I'm understanding this correctly I would hook up the audio probe to it, and take the red lead to the base, then take my multimeter to the collector to see if I get any kind of voltage reading?

[duck_arse]

no sir. meter is for static readings, in general, will tell us how the circuit stes-up. audio in test for audio out, the dynamic, signal handling.

put the signal to the transistor base, via the probes capacitor, and then the out lead, with its cap, goes on the collector and feeds the amp monitoring. does that make sense?

[jwyles90]

no sir. meter is for static readings, in general, will tell us how the circuit stes-up. audio in test for audio out, the dynamic, signal handling.

put the signal to the transistor base, via the probes capacitor, and then the out lead, with its cap, goes on the collector and feeds the amp monitoring. does that make sense?

I believe so. So basically just hook the two probes up to both the base and collector of the transistor. Instead of having one end of the probe go to ground while the other end touches the component to check for a signal?

Also, I used a B100k pot for the volume instead of A100k since I read that they have a better audio sweep. I figured that wouldn't be an issue, but could that be it?