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Total Recall, compander

Started by m-Kresol, March 26, 2016, 08:07:48 PM

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m-Kresol

hey guys,
Finished my total recall today but I'm not getting any love from it. started the biasing procedure but not a sound from the first MN3008 (got them from Paul @diygp). Started taking voltages and I traced the problem to the NE570 compander (got that one from banzai). all voltages check out except for pin 5, 6 and 7. Here are the values, wrong values bold, should-be values in brackets.

NE 570 (all values negative)
13.8   13.8
13.0   13.0
13.0   13.0
14.8   0
7.5 (13.0)    13.0
7.5 (13.0)    8.6
13.5 (4.7)    6.7
13.0   13.0

Supply is the recommended EHX PSU, I'm getting -15.07 V from the 7905 regulator, so that checks out. As a consequence of the increased output voltages from the ne570 (pin 7), also IC3 A pins 2 and 3 are increased. Readings for CD4047BE are also a bit off, but not near as drastic as the NE570.

CD4047BE (all values negative)
7.46 (7.94)    0
7.63 (7.09)    7.4 (7.0)
7.57 (6.91)    15.0
0          7.5
0          7.5
0          15
15.07   15

I've checked the components around the NE570 (R9-R12 & C6-C10), all have the correct value, I also reflowed the area. I measured the components too, everything checks out, but I cant get a reading from C7. Could that mean, it's a bad cap and could that cause the issue? I didn't want to desolder right away as I hate doing that...

I also traced the signal, it reaches Pin 6 of the NE530. Nothing after it.

Here are some pics:



I build pedals to hide my lousy playing.

My projects are labeled Quantum Effects. My shared OSH park projects: https://oshpark.com/profiles/m-Kresol
My build docs and tutorials

czapa tranzystor 2

#1
Sorry
I don't understand this procedure

m-Kresol

#2
the gain trimmers are after the compander, so I don't quite follow. Also I haven't connected the output, I'm just probing around.

had some luck with my cardinal yesterday, which had a broken electric cap... might just try to replace it and see whats happening

EDIT: just replaced C7. Voltages remain the same and the cap was ok to measure out of the circuit.

Any ideas?
I build pedals to hide my lousy playing.

My projects are labeled Quantum Effects. My shared OSH park projects: https://oshpark.com/profiles/m-Kresol
My build docs and tutorials