Retrograde squel and hiss

[bangerang101]

Hey, just finished a retrograde board, and I have it wired up to my breadboard "station", and it's working good, and basically sounds like an octavia is supposed too, but I'm just having this problem w/ it squeling and hissing at the end of the fuzz pots rotation. It is alot more noticable, and crazier sounding on the octave side, and it does it when I turn the volume pot up too loud, as well... All the parts are exactly stock, as per the MB schematic and has no substitutions for any of the parts... was wondering, if this is just because it's not boxed up yet (not input grounded, ect...), or if this might a problem somewhere on the board. Also, was thinking, mabey I need a small filtering cap on one of the transistors to tame it, or something? IDK, thanks in advance for any help.

[madbean]

The Fuzz control works by reducing the resistance between C3 and ground. I haven't run into the problem you are describing, but it should be easy enough to fix.

If you have an extra pot, try subbing that first, just in case the wafer is damaged on the one you currently have hooked up. If that doesn't fix the problem, put a small resistor between lugs 3&2 of the Fuzz pot. This will prevent C3 from being connected directly to ground and should stop the squeal. I would try something like 100R or 47R.

Let us know what happens.

Also, what type of cap are you using for C3? I mean, brand and voltage rating? Just curious.

[night-B]

I haven't got that problem too, if it only happens at full pot rotation, like Madbean said, replace the pot with a bigger value or add a resistor...

[bangerang101]

Ok, great... thanks for the advice, I'll give the added resistance to the fuzz pot a shot...

Ive been recentley ordering all my components from mouser and Ive been trying out different components and trying to find the best deals vs. quality, ect... anyway, the capacitor for c3 is a nichicon, 100uf, 35v, electrolytic... not sure what the tolerance is but I think it's 10%... anyway I used those for the electrolytic capacitors and these blue, Epcos polyester film, box capacitors, for the smaller values , and multilayer ceramic for the pf values (not sure what brand off hand, but... there those little yellow ones)...  are these decent parts? or should stick w/ WIMA, Panasonic, xicon, ect..?

[bangerang101]

 Ok, so I tried a 100r resistor to lugs 2 and 3, but it's still giving a squealing oscilation noise at the end of the fuzz and volume pots (in fuzz octave mode), and it seems this resistor added more compression/squelchines to the sound and a less distinctive octave sound ... anyway, I don't think it's to do w/ the pots being bad, but almost seems like it's not biased correctly or something, like a misbiased transistor or something... almost sounds like when Q1's gain is too high in a fuzz face, w/ the squeling and hiss at the end of the pot's turn and all. IDK, any other ideas?

[bigmufffuzzwizz]

All the brands you mentioned are good choices. I wouldnt worry about any of those.
Have you checked the voltage on the transistors? Someone with a working build could check theirs for you to compare to. Also some big clear photos if possible.

[bangerang101]

hmm... just noticed it says on the project documents to use 16v electrolytic capacitors. I'm using 1, 35v one and the rest 50v ones... could this be my problem? I was thinking, maybe it's affecting the transformer somehow?

[bigmufffuzzwizz]

the voltage rating on capacitors has to do with how much voltage the cap can handle before it malfunctions and blows up. the reason it says to use 16v caps is anything under that wouldn't be reliable. the transformer was the first thing I though would cause this noise but I don't know enough about them to tell you what to test.
If you have an audio probe, you could follow the signal and see where it begins.

[bangerang101]

yeah, I should have done this all ready but.... heres the voltages on the 3 transistors

Q1 (2n5087)
E - 4.36
B - 2.87
C - 2.89

Q2 (2n4401)
E - 2.38
B - 2.89
C - 9.53

Q3 (2n4401)
E - 1.76
B - 2.38
C - 5.03

[bangerang101]

 ok, so Ive changed a couple things to eliminate them being bad or defective....

I replaced all three transistors w/ new ones, changed out c3 to a xicon, 35v, 100 uf. Also, I checked for solder bridges, bad solder joints, ect... and found nothing wrong. I also checked all the values of components, and found they were all perfect, and the orientation of everything was correct, as well.

At this point, it's working perfectly except for 1 - it's a little noisy. Don't know if this is inherent in the design of this pedal, or if it's because it's on the breadboard.  and 2 (more importantly) - It hisses really loud and oscillates at about a little more than 3/4 of the fuzz pot rotation, or if I turn the volume pot all the way and the fuzz about halfway. It only does this on the octave side though, so I'm thinking...could it be the transformer, or maybe the diodes (I used the nte replacement ones from mouser, anyone know if these are unreliable or something?)?... It doesn't really make sense to me but, I'm sure theres a simple fix for this. Any more ideas?

[madbean]

I'll get some voltages off my build tomorrow morning and dig into this a bit more.

Some of these issues may resolve once boxed up, but it would be bet if we can eliminate them as much as possible before-hand.

[bangerang101]

Ok, great...appreciate you taking the time. Also, thanks for the help, everyone.

[bangerang101]

the the big metal tabs on the top and bottom of the transformer are just to secure it in place, correct? I'm just trying to eliminate any little thing that might be wrong w/ it... 

[night-B]

Yeah these are mounting pins. They shouldn't be soldered 

[bangerang101]

yeah, thats what I figured, well... I just soldered them in where the pads are for the tabs. I still can't find anything wrong w/ my board, and it's still giving this horrible high pitch squeling at the end of the pot turns. Its really making me nuts because it's such a simple circuit, and I just can't seem to get rid of it, although, maybe I should just box it up and see what happens? IDK, just afraid I'll box it all up and the noise will still be there. Also, I changed out the fuzz pot w/ a new one, just so I could rule out the fact that it could have been a broken pot, which... I knew it wasn't. The fact that this circuit uses pnp and npn transistors makes me think it's really susceptible to noise and oscillation, though... Any other thoughts, or could anyone tell me if my voltages are correct?