SWAH v5 no sound while on, low voltage readings (SOLVED)

[Anonymous]

Hello, Having some issues with the Swah v5 and hoping someone could point me in the right direction. LED and Bypass are working but when the pedal is powered on the voltage readings are entirely off according to the build document. I reflowed all the solder joints on the back side and still receiving the same power issues with no sound coming out, Also I know its ugly but I was just trying to use the leftover 1/2w resistors and couldn’t find good MLCCs for the 1uf but it still all fits! Pics uploaded here, I can also add them to this forum if that is easier. Also, I tested every component in a transistor tester before adding them to the board and they were all working and within range.

here is my setup.

1 Spot 9v 1500ma adapter comes in and reads 9.45v.
IC1 LM3700N

1. 1.79v     16. 1.79v
2. 1.96v     15. 2.47v
3. 1.92v     14. 2.36v
4. 1.96v     13. 2.27v
5. 1.05v     12. 2.54v
6. 0v          11. 2.82v
7. 1.05v     10. 2.54v
8. 1.51v       9. 1.46v

IC2 TL074

1. 2v          14. 2.02v
2. 2.03v     13. 2.02v
3. 1.96v     12. 1.96v
4. 2.82v     11. 0v
5. 1.40v     10. 1.96v
6. 1.96v       9. 2.06v
7. 1.96v       8. 2.06v

IC3 78L05
I. 2.82v    G. 0v      O. 1.53v
Q1 2N5457
D. 1.78v  S. 2.01v  G 2.82v
Q2 BC550B
C. 1.53v  B. 1.98v  E. 1.53v
Q3 BC550B
C. 1.79v  B. 1.53v  E. 1.53v

the D3 Diode IN34 is reading A: 2v  K: 1.98v and also the D4 1N4001 drops the Voltage to 8.6v before going into R29 100R resistor.

Thank you in advance for any feedback!

-Johl

[Cybercow]

We can better assist if you can provide some good clear photos of both sides of the PCB and all the wiring.

Meanwhile, based on your voltage measurements, there is definitely something pulling down the main supply rail. Try removing the ICs from their sockets and test the voltage supply points. If the voltage supply comes back up to where it ought to be, then you have a bad IC.

Make sure the 78L05 is producing +5v. And check the pin #5 socket of IC2 to ensure it reads ~+4.5v (½ of the incoming supply).

[Anonymous]

Looks like you are spot on! tested without IC1 and IC2, the 78L05 read 8.5 in and 4.99 out. Pin 5 reads 4.23v as well. Guess I should start doubling my IC order next time just in case. Here are some pictures of the board and wiring.

[Anonymous]

Turns out the LM13700N was bad, after swapping the tl074 and no change tried the LM next. My working power coming into the 78L05 was 7.6v and had the full 5v out, thank you Cybercow! I now have a functioning swah and It. Is. Sweet!

[Author]

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