Kompromat only works in bypass

[notanelectricalengineer]

I recently built the Kompromat compressor, but I'm only getting a signal through to my amp when the pedal is turned off. I'm getting 9V on the power jack and the voltages on the ICs seem to be more or less correct. The transistors all have a ground reading, which isn't what should be happening according to the voltages page for the Kompromat. I'm thinking this is where my issue is, but I'm not sure how to resolve such a thing. Lastly, the LED isn't turning on when I turn the pedal on either. Any help is appreciated; I'm new to building pedals so hopefully the issue is some oversight on my part and a relatively easy fix. Thanks!

[jimilee]

Look for solder bridges and reflow all your solder joints.

Then take clear all lit close up photos of both sides and the off board wiring. Ho ahead and list the voltages too, please.


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[notanelectricalengineer]

From what I can tell there are no bridges.

Voltages (all in mV):
TL072: 1) 27.7 2) 27.8 3) 27.8 4) 0 5) 27.8 6) 28.0 7) 23.5 56.3
LM13700: 1) 2) 124.6 3) 30.0 4) 30.2 5) 18.6 6) 0 53.0 11) 57.0 (The PDF says to ignore 7, 9, 10, 12, 13, 14, 15 and 16)



I've attached a couple pictures. Let me know if you need more or if I should zoom in somewhere.

[notanelectricalengineer]

Oh and #1 for LM13700 seems to not sit still. It climbs from ~30 to ~120 mV from what I can tell.

[jimilee]

Do you get any voltage on Q5 pin 3?

[notanelectricalengineer]

Sorry for the late response. Busy weekend.
Pin 3 for Q5 is 54.6mV

[matmosphere]

Are both sides of the resistor right above the opamp soldered?

[notanelectricalengineer]

Yes from what I can tell

[jimilee]

Sorry for the late response. Busy weekend.
Pin 3 for Q5 is 54.6mV

That is connected to the diode that's connected to the 9v power terminals. Measure both sides of D3 if you would, please.

[Bio77]

Did you try the circuit outside of the box?  I'm a bit worried about the metal DC jack.  The convention is pedals is center negative, which would short your power to ground unless I don't understand the jack you are using.   

[jimilee]

Did you try the circuit outside of the box?  I'm a bit worried about the metal DC jack.  The convention is pedals is center negative, which would short your power to ground unless I don't understand the jack you are using.

I didn't even notice that. There's a definite power issue.


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[Zerro]

TL072 has to have power supply value 9V at pin 8. And at pin 4 must be zero value - ground. And another pins about 4.5V or cca around it.

[notanelectricalengineer]

The positive side of D3 is 61.8mV and the negative side is 9V. Pin 8 for TL072 is not reading 9V and the rest are reading similar to what I said earlier in the post. So from what I understand, I have the wrong jack?

[jimilee]

The positive side of D3 is 61.8mV and the negative side is 9V. Pin 8 for TL072 is not reading 9V and the rest are reading similar to what I said earlier in the post. So from what I understand, I have the wrong jack?

You should have about 9v on both sides of that transistor. It's just there as a reverse polarity diode. Is it in properly and how does the solder joints look? That goes directly to Q5. If you look at the build doc you can kind of make that out on the traces page.


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[notanelectricalengineer]

I don't have 9V on each side of D3. The negative end of D3 has the same reading as pin 3 on Q5. The solder joints look fine as far as I can tell. Some joints have a yellowish color to them and I'm wondering if that's an issue. I've attached a picture; the red circle is one that has the yellowish tint and the blue circle is one that does not.