Super '64 OD troubleshooting

pcb rookie

Active member
Fishing building the Super '64 OD. LED is working fine. I'm getting sound on by pass mode and clean low volume sound when engaged. All pots are turned fully clock wise including the trimpots. I looked at all solders for cold solders, bridge etc. Then cleaned the PCB. I refloweds all sorders, cleaned the PCB before inspecting again. I took some basic voltage mesures on IC, JFETs, Diodes and LED. Here are some pictures. Anything stands out in those values and pictures? This is my fourth built so I do not have much experience or knowledge. I will take all the help I can get! Thank you in advance for assisting with this troubleshoot.

Build docs: https://docs.pedalpcb.com/project/Super64.pdf

IC TL1044SCPA - data sheet: https://www.mouser.ca/datasheet/2/268/21348a-29235.pdf
Pin1: 9.09v
Pin2: 4.84v
Pin3: 0.1mV
Pin4: 131.5mV
Pin5: 0.337v
Pin6: 4.24v
Pin7: 5.61v
Pin8: 9.09v

J201's - data speet: https://www.mouser.ca/datasheet/2/308/1/MMBFJ202_D-2316065.pdf
Pin1/Pin2/Pin3
Q1- 7.71 / 0.39 / 0
Q2- 14.1 / 0.322 / 0
Q3 - 17.72 / 0.635 / 0

Diodes (1N5817) - A/K
D100 - 9.31/ 9.1
D101 - 9.1 / 13.73
D102 - 13.72 / 17.78

IMG_3387.jpeg IMG_3381.jpeg IMG_3375.jpeg IMG_3373.jpeg IMG_3372.jpeg IMG_3371.jpeg IMG_3379.jpeg
 
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pcb rookie

Active member
Do you have continuity between your foot switch board and the circuit board through the ground wire, it looks like there is no solder there
Wish it would ... would have been a simple fix. It's just the angle of the shot. I took the opportunity check for continuity on all the wires from the the main board to the off board components (switch board and in/output jacks). They all connect using the continuity fonction. Thanks for looking into this. Let me know if you see anything else.

IMG_3389.jpeg
 

Mcknib

Well-known member
Do the trimmers not need to be adjusted to set correct bias voltage

I've never built it so don't know try setting them to around 9v on the drain pins

If you're getting clean sound in effects mode audios getting through the circuit which makes me think you need to adjust bias voltage or check transistor pinout is correct

We can't see all your resistor colour bands one pic half are covered and other pics out of focus
 
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carlinb17

Well-known member
I know on the Aion build you want the drain set to 12v to start with on all three j201s. Obviously this isn’t the same build but it might give you some idea to start with
 

pcb rookie

Active member
Do the trimmers not need to be adjusted to set correct bias voltage

I've never built it so don't know try setting them to around 9v on the drain pins

If you're getting clean sound in effects mode audios getting through the circuit which makes me think you need to adjust bias voltage or check transistor pinout is correct

We can't see all your resistor colour bands one pic half are covered and other pics out of focus
Following your recommendation, I adjusted Q1 & Q2 to get as close as possible to 9V on the drain pin. Curiously, voltage on the drain pin of Q3 will only adjust from 17.61 to 17.78. Is that normal?

Adjusted readings ...

Pin1/Pin2/Pin3
Q1- 9.13 / 0.39 / 0
Q2- 9.02 / 0.321 / 0
Q3 - 17.71 / 0.635 / 0
 

pcb rookie

Active member
Ok so I just tried adjusting the trimpots to get Q1 and Q2 drain to 12v and adjusted Q3 with my ear. Now I can get the guitar tone to clip but there is still a huge volume drop when stomp is engaged compared to bypass signal (at least half if not less). Volume and gain pots are maxed out.
 

carlinb17

Well-known member
If their being run in parallel the you would get 95k. One is connected to your toggle switch so their on parallel one way and not in the other. If I’m not correct please someone else let me know.

Flip the switch and you should get what they are normally.
 

carlinb17

Well-known member
I believe the issue is still with the trimmer, you should be able to get it down closer to 9-12. There are far smarter people here, and I’m sure one will weight in.

In the meantime you may be able to use an audio probe to walk through the circuit to see if there are any other issues or confirm the volume loss at Q3/ trimmer
 

PJS

Active member
I agree with carlinb17 that the trimmer on Q3 should be able to get more adjustment. With the power off measure resistance from the middle lug of the trimmer to one of the outside lugs and then turn it through it's range. You should get smooth adjustment from 0 to 50K. Sometimes these little trimmers can be a bit fragile.
 

pcb rookie

Active member
I was going to move on and start with a fresh PCB before I started this post but figured it was part of the learning curve to troubleshoot. I sure learned a lot tonight navigating through this challenge. I'm happy I didn't just move on. I'll pick this up tomorrow starting with measuring the trimmer's ohms range as you both pointed out. I'll also try to build an audio probe and experience with it. I'll report back once I've done my home work. Thank you Carlinb17, McKnib, PJS for walking me through this and sharing your experience. It's highly appreciated!
 

jimilee

Well-known member
Yep, also check the continuity in the traces, the power goes straight from +18 to the trimmer pin3 -> trimmer to pin 2 -> transistor. Pretty much a straight shot. Reflow your solder here to see if it helps. If you look at the schematic, you can see the flow of power. I thought that may be handy since you’re new to this.
 

pcb rookie

Active member
I agree with carlinb17 that the trimmer on Q3 should be able to get more adjustment. With the power off measure resistance from the middle lug of the trimmer to one of the outside lugs and then turn it through it's range. You should get smooth adjustment from 0 to 50K. Sometimes these little trimmers can be a bit fragile.

I believe the issue is still with the trimmer, you should be able to get it down closer to 9-12. There are far smarter people here, and I’m sure one will weight in.

In the meantime you may be able to use an audio probe to walk through the circuit to see if there are any other issues or confirm the volume loss at Q3/ trimmer
I checked the range of the 3rd trimmer. It does sweep from 0 - 47 ohms.

Just finished building an audio probe. I get why it's an essential tool.

I am getting a full volume tone on Q1 and Q2 so tested all the components between Q2 and Q3.

C7 = tone @ full volume
Tone pot and C8 = tone @ full volume
R6 = tone @ full volume
Switch = tone @ full volume on top lug when switched up. No tone on either lug when switched down
R8 = tone @ full volume on one side and no tone on the other
Q3 - Pin1: there is tone but the volume is at least half as loud if not less
Q3 - Pin2: there is tone but the volume is at least half as loud if not less
Q3 - Pin3: tone @ full volume
C9 = there is tone but the volume is at least half as loud if not less

So I decided to decided to reflow the 3rd trimmer and Q3. The solder on pin2 of Q3 acted strange. The solder would not flow. Took the solder sucker and sucked out the solder on all 3 pins of Q3 and ... I think I may have found my problem. I see no contact eyelets on the PCB @ pin2 of Q3 (back side/solder side).

Looks like I'm going to start fresh after all ... unless one of you as another trick up is sleeve. Obviously there's a bit of deception finding out this pedal assembly ain't going work... but I learned a lot through this process thanks to your help so this is very far from a total lost.

Thank you for assisting and sharing your experience. That was very helpful to troubleshoot this project and all the upcoming ones!
 
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