zvex sho, super low output

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kaisuke
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Joined: 06 Jun 2021, 21:14

Post by kaisuke »

Hi guys

followed this veroboard layout and my components are placed in the correct positions https://tagboardeffects.blogspot.com/20 ... rsion.html

the effect output of the board is extremely low needs my amp to cranked to full volume to be barely audible. there is no gain or crackle when the pot is turned.

i have used a 22uf cap instead of a 10uf cap for the output cap.

you can see on the solder side of the board some jumpers because i had made 2 resistors too short the 100k and 2k2 resistors to be specific. I have cut traces around these so that they did not connect different areas i have checked this with a multimeter. the jumpers go: r5 c11 to r6 c11 and r5 c10 to r4 c10

i have cuts at the places specified on the layout and between the jumpers on row 5

Im likely to take the parts out and move them to a fresh board once a batch of sockets and a new output capacitor arrives.

In the meantime is there anything obvious that you guys could suggest i fix?

link to pcb photos - https://1drv.ms/u/s!AqWrcFukAsPujzLnIj6 ... x?e=gQbhh4

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stolen
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Post by stolen »

Hi!

The pictures you posted are quite low resolution, it's hard to make out anything. However, there is one peculiarity about this circuit that you might not have considered: MOSFETS such as the BS170 are very susceptible to electrostatic discharge and easily destroyed if you're not careful about that. It might be something different, but we would suspect this as a likely issue if the circuit has been assembled properly.

Careful handling includes the following steps:
- Stay away from carpets
- Ground yourself during handing, for example by an electrostatic wristband or keeping a bare foot on a grounded heater/desktop computer case (check grounding, not all cases are)/etc.
- If the transistor is delivered on anti-static foam, ground (touch) the foam prior to touching the transistor as well.
- Touch the PCB during handling to ground it as well

A good safeguard is to install a transistor socket instead of soldering it in directly so that it is less of a pain if accidents happen.

Not following these steps doesn't mean the transistor _has_ to be dead, but assuming you can't find any other bug this could be the issue.

All the best,
stolen

PS: You can keep the 22uF output cap. It doesn't make a difference.

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