Help me debug my SHO...

[ACS]

 

Such a simple circuit but I can't for the life of me get it runnning..

Using Rick's layout from here, but built onto perf.

Voltages I'm getting are:

V(battery) - 8.93V

With pot at minimum:
D - 8.89V
G - 0.01V
S - 0.00V

With pot at full - Gate drops to zero.

No substitutions other than using a 5Klin pot rather than a rev.log.  Haven't put any protection in for the FET as yet, but have tried a couple of different ones with the same symptoms - passes very low signal, no difference when pot is turned.

Everything is hardwired at the moment - no switching to worry about.

Cheers
Aidan

[diydave]

You shouldn't get 0 volts on the gate off the mosfet.
Maybe there's something wrong with the voltage divider formed by R2 and R3, or the diodes.
Is your mosfet correctly placed?

[frequencycentral]

Didn't I read somewhere that BS170 from some manufacturerers are SGD and not DSG? Maybe that's it?

[ACS]

Thanks gents - as is so often the case, it was simple...

Dave - you were on the money with the voltage divider being off - there was a jumper in this vicinity that appeared to be connected, but turns out it wasn't.  Resoldered and I'm off and crackling!

Need to get a protection diode in and get it all cased up.  Great layout, thanks Rick!

Aidan

[frequencycentral]

Cool, and thanks Aiden. Now you should try it Superheated

[ACS]

Cool, and thanks Aiden. Now you should try it Superheated

Haha, looks to be worth a crack.  Silly question Rick: I'm assuming that a pull down resistor is required, as per most circuits; this will affect the input impedance, which I've read is part of the charm of the SHO - is that going to change the sound substantially?

[frequencycentral]

Surely the input cap will discharge through the 10M to ground when the effect is bypassed? Or if you use the input-grounded-when-bypassed 3PDT wiring scheme.......

[ACS]

My knowledge in this area is VERY shaky, but I think that it's the side of the cap that is left floating that could cause a pop. The 10M resistor is only grounding the circuit side of the the cap.

But yes, input-grounded-bypass seems to be the go - have just been reading about it!

Cheers

[diydave]

Glad to been a help.