BYOC Swede Feedback Issue

[JT20]

Hello! I've put together a BYOC confidence booster that worked and replaced the pickups on my guitar, so I tried a BYOC Swede kit and am having major feedback issues.

When the distortion pot is all the way off, the feedback goes away and the guitar tone is very clear with a little distortion. The high control changes the pitch of the feedback, and will get rid of it when the pot is turned all the way off. There is also a very loud hiss when my guitar volume is off.

I built a signal tester, and am getting a very heavily distorted and farty sounding guitar signal in my +9V source that dies quickly, and also hear a much clearer distorted guitar signal in my 1/2v source. I also hear a guitar signal when the signal tester is plugged into my amp and connected to the pedal ground with the probe off the pedal. This goes away when I lower the high control or remove IC3 from circuit.

So far I've verified all components are connected correctly by tracing out the signal with a continuity tester. I've check for shorts to ground and tested continuity of all components with the 9V source and V1/2 and everything check out.

I have replaced all capacitors, transistors, IC's, a few resistors, and all diodes excepts for the two 4148's attached to ground. Some of the capacitors were from BYOC and were the same manufacturer.

Any ideas? I'm completely at a loss here and don't want to resort to checking continuity off all components with each other :/

Here is a link to the circuit schematic
http://byocelectronics.com/swedeschematic.pdf

I posted a thread on the BYOC forum that has pictures of my PCB and wiring
http://www.byocelectronics.com/board/viewtopic.php?f=50&t=53797&p=468577#p468577

Pedal is plugged into a regulated 9V power supply, +9V voltage measures 9.82V and 1/2v is 4.893V

IC pin DC voltages
IC1
1: 4.330
2: 4.353
3: 4.352
4: 0
5: 4.904
6: 4.906
7: 4.906
8: 9.82

IC2
1: 4.908
2: 4.908
3: 4.861
4: 0
5: 4.872
6: 4.906
7: 4.906
8: 9.82

IC3
1: 4.906
2: 4.906
3: 4.860
4: 0
5: 4.866
6: 4.905
7: 4.905
8: 9.82

Transistor DC voltages
Q1 (JFET)
G: 4.490
S: 5.639
D: 9.82

Q2 (NPN)
C: 4.763
B: 0.629
E: 0.010

Q3 (PNP)
C: 4.355
B: 8.35
E: 8.99

Q3 (NPN)
C: 9.82
B: 3.837
E: 3.350

Diode DC voltages (diodes aren't labeled in schematic)
D1 (Single 4148 across IC1a)
C: 4.331
A: 4.354

D2 (4148 with cathode connected IC1a Pin 2)
C: 4.354
A: 4.117

D3 (4148 with anode connected IC1a Pin 1)
C: 4.117
A: 4.331

D4 (Top Germanium Diode)
C: 0.024
A: 0.024

D5 (Bottom Germanium Diode)
C: 0.024
A: 0.024

D6 (4148 with cathod to ground)
C: 0
A: 0.028

D7 (4148 with anode to ground)
C: 0.028
A: 0

D8 1N001 attached to 9V
C: 9.82
A: 0

[PRR]

Welcome.

> guitar signal in my +9V source that dies quickly, and also hear a much clearer distorted guitar signal in my 1/2v source.

"+9V" has a 100uFd cap to ground which should absorb most audio.

"1/2V source" has a 10uFd cap to ground which in this higher-resistance area should absorb "all" audio.

So did you forget these caps? Install them backward? Bad connections to + or to ground?

[JT20]

Those caps are installed correctly and have a good connection to + and ground.

I already replaced both caps, is it possible the second capacitor I installed is also faulty?

[JT20]

I took another look at my voltages to try to figure out what's going on. One thing that stuck out to me was my JFET gate voltage being around 0.4V lower than my V1/2 voltage source,  giving around 0.42 uA of current through the connected 1meg resistor. The JFET gate's only other connection is to a 47n capacitor, which is connected to the guitar input signal through a 10k resistor and the 3pdt switch. I noticed this behavior regardless of whether I ground my input signal or not.

Could this behavior indicate a short/faulty component, or should I have some current flow here?

[PRR]

> my JFET gate voltage being around 0.4V lower than my V1/2 voltage source

Only when you look at it with your (10Meg) volt meter. 1Meg to 4.5V, 10Meg to ground, you get 10/11th of the actual voltage.

If you use a second meter to watch the JFET Source, you will see it drops when you poke the Gate and goes back up when you stop poking. It is a measurement artifact.

This is not a problem.

Good thinking though.

[amz-fx]

According to the Boss HM-2 factory schematic, the resistor that you have labeled as R16 (68k) should pull up to +9v and not the 1/2v rail. Measure both ends of R16 and see if one is at 9v, which would mean that the Swede schematic has an error in the drawing. If both ends are close to 4.5v or so, then I would look at that.

Be aware that factory schematics can have errors in them too. 

regards, Jack

[JT20]

> my JFET gate voltage being around 0.4V lower than my V1/2 voltage source

Only when you look at it with your (10Meg) volt meter. 1Meg to 4.5V, 10Meg to ground, you get 10/11th of the actual voltage.

If you use a second meter to watch the JFET Source, you will see it drops when you poke the Gate and goes back up when you stop poking. It is a measurement artifact.

This is not a problem.

Good thinking though.

Ah that makes sense since I'm creating a path to ground.

amz-fx, that's a typo on the Swede schematic. My R16 is connected to the +9V source.

Thanks for the responses, I'm really at a loss here. The only other thing I see is my Q2 NPN collector voltage is around 0.4V too high and my Q3 NPN base voltage is around 0.5v too low based on a Spice simmulation of the pedal (all my other voltages are spot on with the model so I'm inclined to trust it).

Would these also be caused by measurement error?