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!
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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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 8) 56.3
LM13700: 1) 2) 124.6 3) 30.0 4) 30.2 5) 18.6 6) 0 8) 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.
Oh and #1 for LM13700 seems to not sit still. It climbs from ~30 to ~120 mV from what I can tell.
Do you get any voltage on Q5 pin 3?
Sorry for the late response. Busy weekend.
Pin 3 for Q5 is 54.6mV
Are both sides of the resistor right above the opamp soldered?
Yes from what I can tell
Quote from: notanelectricalengineer on February 06, 2022, 04:31:14 PM
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.
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.
Quote from: Bio77 on February 06, 2022, 08:40:05 PM
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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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.
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?
Quote from: notanelectricalengineer on February 06, 2022, 11:27:44 PM
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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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.
The yellow is probably just flux, you can clean that off with a little isopropyl alcohol. You're either not getting power through that diode or there is a ground somewhere after the cathode. Do you have continuity between the cathode and any ground point? You can see how the power runs from the cathode to Q5, CY, pin 7 of the IC2, C20 and so on. Clean around those areas and look for any shorts. A magnifier helps.
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I just tested the diode and I'm getting 0.18V through the diode in the right direction and nothing in the other direction. There isn't any continuity between any of the mentioned points and ground. Only the grounded points on the PCB have connection with ground, which is as expected. Still unable to find any shorts in the circuit.
Quote from: notanelectricalengineer on February 07, 2022, 08:22:53 PM
I just tested the diode and I'm getting 0.18V through the diode in the right direction and nothing in the other direction. There isn't any continuity between any of the mentioned points and ground. Only the grounded points on the PCB have connection with ground, which is as expected. Still unable to find any shorts in the circuit.
Wait, you don't have continuity along your power traces? Can you see any traces there?
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I have continuity along my power traces, but not between any point on the power traces and ground.
Quote from: notanelectricalengineer on February 07, 2022, 08:57:17 PM
I have continuity along my power traces, but not between any point on the power traces and ground.
Ohhhhh, ok. [emoji16]And D3 is a 5817? I can't figure out why you don't have power past the input, essentially. I've reached out to rain, he will chime in later.
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Yeah its a 1N5817. I appreciate the help!
Simply find power supply source, measure what is going from it. Connect it to your device and measure this power supply at jack to device. If power is shut down after connecting it to jack, you have some hard shortage at very start of power rail, maybe protecting diode, especially, if polarity at your power supply is (was) reversed. Power must go to pcb to opapms and so on. If protecting diode at very start of power rail is damaged, it can do this shortage.
Its a 9V power supply coming in, and I'm getting 9V on the anode of D3, but the cathode of D3 reads ~60mV. I tested D3 using a multimeter and it seems to work, but maybe its restricting too much voltage from going on to the rest of the circuit.
Quote from: Zerro on February 07, 2022, 10:16:05 PM
Simply find power supply source, measure what is going from it. Connect it to your device and measure this power supply at jack to device. If power is shut down after connecting it to jack, you have some hard shortage at very start of power rail, maybe protecting diode, especially, if polarity at your power supply is (was) reversed. Power must go to pcb to opapms and so on. If protecting diode at very start of power rail is damaged, it can do this shortage.
You do make a good point. Using a wrong polarity power supply will shut it right down.
The power supply I'm using is positive on the outside and ground on the inside. I use it to power a looper I have and it works fine.
I read 9V when measuring the power supply, but when I plug it into the jack, the power coming from the jack is -9V, would this be the issue?
Quote from: notanelectricalengineer on February 07, 2022, 10:51:04 PM
I read 9V when measuring the power supply, but when I plug it into the jack, the power coming from the jack is -9V, would this be the issue?
Nope, that's where you want it to be. I'm curious about that diode, but I don't want o suggest removing it just yet.
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Maybe shortage is after this diode shooting down all. But this D3 is suspiscious. If polarity of your power is ok, try to bridge for a moment this D3. And again measure power at rail.
Quote from: Zerro on February 08, 2022, 12:47:21 PM
Maybe shortage is after this diode shooting down all. But this D3 is suspiscious. If polarity of your power is ok, try to bridge for a moment this D3. And again measure power at rail.
See, that's what I was thinking, but there's no continuity between power and ground.
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Let's give him time to make some trials and measurements and then we all will be smarter.
Quote from: Zerro on February 08, 2022, 03:51:03 PM
Let's give him time to make some trials and measurements and then we all will be smarter.
Im thinking it's got to be that diode.
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That jack is kind of unusual. I'm wondering if it could be the problem. Since our pedals all use center negative I wonder if the metal casing, which is probably connected to the positive barrel of the power supply is causing a short.
Any link to that part?
No problem to swap that power jack polarity. Center + and body -. Seems to me, it was always better concept.
Quote from: Zerro on February 08, 2022, 08:15:36 PM
No problem to swap that power jack polarity. Center + and body -. Seems to me, it was always better concept.
Yeah, but then standard power supplies won't work
Quote from: matmosphere on February 08, 2022, 07:13:17 PM
That jack is kind of unusual. I'm wondering if it could be the problem. Since our pedals all use center negative I wonder if the metal casing, which is probably connected to the positive barrel of the power supply is causing a short.
Any link to that part?
It doesn't look as if the jack is mounted. It won't be a problem until it's connected to an enclosure.
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Quote from: jimilee on February 08, 2022, 08:37:10 PM
Quote from: matmosphere on February 08, 2022, 07:13:17 PM
That jack is kind of unusual. I'm wondering if it could be the problem. Since our pedals all use center negative I wonder if the metal casing, which is probably connected to the positive barrel of the power supply is causing a short.
Any link to that part?
It doesn't look as if the jack is mounted. It won't be a problem until it's connected to an enclosure.
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I was thinking the same thing, but it looked a little like there were three wires connected to it, so I wasn't sure.
Couple things jump out:
#1 Get rid of that DC jack. Use a proper insulated (plastic) jack. Even outside of an enclosure it's possible to cause a short between the barrel of the DC plug (which is +) and the metal casing of the jack.
#2 Ideally, you'd want to have the ICs socketed especially for a case like this. That allows you to remove the ICs and rule out any issue of a current sink on one of them. IOW, it would let you more clearly determine where the issue with the 9v supply in the circuit resides. Since it appears they are soldered directly to the PCB it may make debugging more challenging. At the very least, do step #1 then see what voltage readings you get on pin8 of the TL072. That might help us narrow down the issue :)
Would this jack work?
Absolutely. I may have a spare or two I can mail you. I can check.
That'd be great because it would probably get here sooner than any website would ship.
Quote from: notanelectricalengineer on February 09, 2022, 06:43:15 PM
That'd be great because it would probably get here sooner than any website would ship.
Okay, looks like I can spare one or two. Pretty low but I have enough. I should have your address from your order. I'll get back with you.
Little update: With the new jack, the whole pedal works! I'm never buying a metal jack again haha. I appreciate everyone's help in the matter.
Quote from: notanelectricalengineer on February 20, 2022, 03:03:50 PM
Little update: With the new jack, the whole pedal works! I'm never buying a metal jack again haha. I appreciate everyone's help in the matter.
Pretty sure we've all mad that mistake once.
Quote from: notanelectricalengineer on February 20, 2022, 03:03:50 PM
Little update: With the new jack, the whole pedal works! I'm never buying a metal jack again haha. I appreciate everyone's help in the matter.
Nice, congratulations!
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