PT-80: low wet signal - SA571 voltages

[naja]

hey there,
im wondering if my SA571 or my PT-80 circuit is damaged,
because my wet signal is 8dB below my dry signal

ive traced the wet signal using a 360 hz sinewave,
input: -19.4dB
SA571(1) in: -18.5dB
SA571(1) out: -9.3dB
PT2399 in: -9.3dB
PT2399 out: -9.5dB
SA571(2) in: -13.8dB (maybe due to excessive filtering between PT2399 and second SA571 stage?)
SA571(2) out: -27.2dB
output: -27.9dB

the dry signal:
input: -19.4dB
output: -20.3dB

is the compander making the wet signal too quiet in the second stage (before output mixing)?
and is the filtering too hard?

btw, ive replaced all 22k resistors in the MFB filters around the PT2399 with 11k to do a little less filtering

my SA571 voltages:
1:  1.25
2:  1.8
3:  1.8
4:  -0.001 ( ?? )
5:  1.8
6:  7.18
7:  7.18
8:  1.8
9:  1.8
10: 5.43
11: 1.8
12: 1.8
13: 12.1
14: 1.8
15: 1.8
16: 1.38

thanks a lot - im a little desperate 

[duck_arse]

pin 4 should be ground, 0V, not - something. check for continuity; is the 571 in a socket? check for bent pin or bad socket fingers, etc.


may we see a circuit diagram? might we be allowed to gaze upon photos of that which you have built?

[naja]

@duck_arse

sure

i'm using a PCB from "uk-electronic", which i am modding to some extent,
ive only put the mods on breadboard and will start soldering them to a perfboard tomorrow,
i will do measurements again and send pictures and schematics once ive done this

thx so far!

[duck_arse]

in the case of something "not yet soldered", you really want to get it right on the breadbord first. can we see the circuit diagram you are working on/with/against, please?

[naja]

ok, of course

so i bought a PCB and populated the board. i will do some modding, but when i tested the PCB there was just some small things added on a breadboard.

this is the original schematic with notes for the "simple mods" (please note that i didn't put in any "dub switch" yet, so at that point its just as in the schematic):


this is the PCB:


this is my schematic with "simple mods":


this is what i want to do in the end:


when testing the voltages and the audio signal levels (dB values) that i posted above, i only had simple mods and i connected a breadboard to the PCB,
but i double checked everything carefully and i could find neither short circuits nor bad connections.

also, i tried another SA571 chip, which gave me the same results

on the back of the PCB, i soldered 22k resistors in parallel to all 22k resistors to reduce the heavy filtering a little bit (easy and removable mod),
on the front of the PCB, you can see the 78L05 mod, which i also doublechecked and which works (at least the multimeter is showing a constant voltage: 5V, or 6V, whatever i want)




thanks for your help! don't really get what the problem might be.
i also checked the capacitors; ive found a post by someone who also had problems with SA571 output level,
and he had a bad capacitor, but i don't have a multimeter for capacitor measurements, so i checked if any capacitor connected directly to the SA571 was acting as a short circuit, but there wasn't any, and i measured the resistance on the capacitors, which was rising to 20M or above (or the correct parallel resistor value in the circuit) every time i switched the multimeter plus/minus poles around - of course i don't know for sure they are not bad, but i don't think they are

[naja]

today, i tested the SA571 again,
i removed all ICs except for the charge pump and the SA571,
and put a sine wave test signal (something around 400 Hz) to input and output of SA571 respectively to output of PT2399 and input of SA571

i noticed a strange behaviour: when connecting the test signal, on the way from PT2399 (pin 14) to SA571 (pin 2),
it dropped sometimes 3dB, sometimes 4dB, sometimes 8 dB,
while using the same signal and same setup
in the meantime, i was probing the SA571 chip, went back to the circuit path between PT2399 and SA571, and the levels changed

i will put a 6dB boost somewhere in between and hope that'll solve the problem of missing gain, although its more of a temporary solution...