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Pork Barrel - wet signal only with higher voltage

Started by thpm, March 23, 2017, 03:30:29 PM

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thpm

Hello,

I am having troubles with my Pork Barrel (2015 rev 1 board). Dry signal path is ok, but there seems to be a problem with wet, and all the voltages I measured are way off...

First: The MN3007 and the clock are from Musikding, so should be legit. The LFO works, and reacts to the rate pot as it should (judging from the indicator led). Only part substitution are the 1uF film caps C2 and C7 (didn't have any, substituted with tantalum for now, orientation is correct) and a dry kill switch (aka "vibe mod") at R9, which was actually helping a lot with my debugging efforts so far...

With 9,03V at board in, only with the trim fully clockwise I get a very weak, very distorted wet signal. If I supply 12V to the board, it gets noticeably better - cleaner and louder (I discovered this by chance, first testing with a not-so-fresh 9V battery (no wet at all), then with the 9V wall wart which gave me a little signal, so I tried with 12V.)

So it "works" but I am loosing power somewhere?! For the life of me, I can't figure out the problem. The measurements make me scratch my head... they don't make sense:

9,03V at board in

4558 (IC1)
1: 6,43
2: 0,29
3: 0,75
4: 0
5: 2,2
6: 0,3
7: 6,43
8: 8,77

MN3007 (IC2)
1: 8,54
2: 4,28
3: 0,71
4: 0,36
5: 0
6: 4,27
7: 0,26
8: 0,26

MN3101 (IC3)
1: 8,55
2: 4,29
3: 0
4: 4,28
5: 1,16
6: 3,4
7: 0,38
8: 0,36

TL062 (IC4)
1: 7,6 (varies)
2: 1,23
3: 0,39 (varies)
4: 0
5: 1,23
6: 0,01
7: 6,76 (varies)
8: 8,77


Q1:
C 8,78
B 0,02
E 1,42

Q2:
C 8,77
B 0,08
E 1,86

Q3:
C 8,77
B 0,02
E 1,49

Q4:
C 3,49
B 0,44
E 0


I already double-checked all parts and did a reflow on the joints. No luck. Any ideas? Would be greatly appreciated, thanks guys!

somnif

Pardon my idiot level electrical engineering skills (its been too many years since intro physics) but would having a polarized cap on the audio line cause issues? I know pickup signal is AC and would the "reverse" portion of the wave be blocked or interrupted by the polarization? Especially with a tanta cap which are so notoriously fragile to reverse current?

(Feel free to mock or ridicule me if I'm wrong, this is barely above a guess)

thpm

Hey, thanks for your reply! If you have a look at the original CE-2, you'll notice C17 (=C7 on the Pork Barrel) is a polarized Elko, C2 is 0.47 in the original (non-polarized) – Be that as it may, in the meantime I changed both of them to non-polarized film caps but it didn't change anything.

The more voltage I give it, the cleaner and louder the wet signal gets (didn't try over 12V for now), but the chorus is still nowhere near as "deep" as it should be, and the wet signal is still to quiet I think (Shouldn't it be the same level as dry?)

I just don't know where to go from here... (especially since *all* voltages are way off)