Zvex SHO clone troubleshooting help

[dehughes]

Hello there,

First post here...howdy.

I have a SHO clone pedal here and wanted to see if I could re-build it (it was a bit hissy when I got it), so I designed my own layout on perfboard and wired it (back) up.  I turned it on and no sound came out...LED lighted up, but no sound when the pedal was engaged.  I swapped out the BS170 (yes, oriented correctly...) for another one, and the pedal worked for about 30 seconds or so but then stopped working (LED is on, but when the pedal is engaged it totally cuts out the sound).  I tried replacing the BS170 with yet another, and that didn't solve the problem....still dead.  

HOWEVER, when the pedal is engaged and I turn the pot, I can hear the scratchy-ness coming through my amp (DC on the pot), so I know it's sending something OUT of the pedal...but my guitar signal doesn't seem to be getting through the circuit.

The diodes seem to test fine, and the pedal is clearly getting DC (about 4 to 7-ish volts on the transistor), so I don't know....

I've built amps from scratch, etc....so I'm not an electronics newb so much as I'm a pedal newb.  FETs and ICs are something new, so I'm stuck as far as troubleshooting goes.

Thanks in advance!

[wormfooduk]

Which one did you build? the new version has one 9.1v zener diode and the old one uses 2 x 1n4148?

As you say your not a newb I guess you must of checked your caps and diodes are round the right way.

Theres not much to this one so should be easy ish to find the problem. I had problems with poping though the amp when switching the pedal on and off but it turned out to be the switch. If your resoldiering this pedal I think it maybe quite hard to not damage the switch. You shouldn't get any hiss if its working right.

I notice on one of the many layouts for the SHO the guy had wired the output jack the wrong way round. If we had your layout it would be easier to help.

heres the one i did

[dehughes]

Thanks for the reply.

I'm a newb to pedals...have built a couple amps from scratch....so I get the general "rules"...just stuck for troubleshooting this one....

Here is the schematic I used...it differs from yours.  Sorry it's so big....  I have a 3PDT switch with LED in there, which I  know is working as it should, so it's not the switch.

I notice that with the FET in the socket I can tap my finger against the solder points (of the socket) and get a noticeably loud hiss/bump noise out of the pedal when it's on, so I wager the FET is okay...don't see any wiring issues to speak of, but obviously something isn't right...  I'm getting an open circuit from S to D with my negative DMM lead on S and positive on D, and when that's reversed the FET is testing out at about .630 on the diode test setting on my DMM.  I'm also getting an open circuit from both D and S to G, so again I assume the FET is okay?  I'm not, however, measuring any resistance from the D to the S...I believe there is supposed to be a large resistance between these?  I'm getting an open circuit...

[dehughes]

Okay.....I'll start testing and writing on each part of the circuit.  Pics to follow.

The diodes test good (.591 on my DMM)

The resistors test good (all their "stated" values)

I'm getting connectivity from ground to the pot to the MOSFET source.

I'm getting connectivity from the input cap to the resistors to the whattheheck?...huh...not getting from the 10m resistor/diode junction to the Gate of the MOSFET.  The solder joint looks good....but I'm not getting a "beep" from my DMM....huh...lemme go solder...

[dehughes]

So yeah...one of the component leads which was oh-so-neatly bent and formed a "trace" to the Gate wasn't quiiiite touching the next solder point.  Looked good from afar, tested bad, and upon super close inspection was actually not connected.  Soldered it up and voila!  Sounds great.  Kind of a lot of work for little benefit, but I learned a lot and am more comfortable with FETs now.  (I still prefer to work on amps, though...tube amps....big things...).

Anyway, thanks for listening to me blah blah....I'll try to "contribute" more on this board in the future.  Next up is a MXR Micro Amp with LED, I believe...(clone....Lord knows I'm not going to hack up a real one!   ).

[wormfooduk]

Nice one, glad you found your fault. Id love to try to build some valve stuff but haven't enough info as yet. Have you thought about make a valve pre pedal?

[dehughes]

You know....now that you mention it...a valve pedal would be cool, and something I could totally do.....but I'd need a full power supply (120v, etc...) right?