Marsha valve PCB? And verified?

[thermionix]

No offense taken. If you could post photos of your Marsha Valve, hopefully one of us can spot something that will help.

I thought this was already solved.  He had the trimmer installed wrong, shorted out.

[Cozybuilder]

OP didn't report back; the trim might have been the problem, but if it was soldered onto the board as the layout indicated, it would be correct (assuming the trim pot had the same pin-out as the illustrated postings).

[davepedals]

I tried the trim the corrected way but still no dice.  Changed out transistor as well.  I would take some pics but  if you saw my "sho" pedal pics, this Marsha is much the same, less than 1x1 inches and board mounted pot.  Clear photos showing the entire circuit are impossible since the pot blocks the view.  I'll just have to wait until my meter arrives back to troubleshoot that "troublemaker", ha ha. I do appreciate all the help.

[deadastronaut]

breadboard it, tweak the trim to the sweet spot, measure,  then replace the trim with a resistor..
will make for a tiny pot board.



while i'm here, is there any reason a simple voltage divider couldn't be used to get 4.5v on this?

[davepedals]

Excellent idea, Rob!

[davepedals]

Update

First of all I would like to thank everyone who has helped me get this thing running!

The last one I built is working fine! It turns out that I did have the trim wired incorrectly.  Also there was a very tiny solder bridge that kept things from working properly. It was tough to see even with my glasses and a magnifying glass but I've gotten rid of it and everything is fine.  It does have somewhat of a marshal tone, output is like a medium boost with J201, which sounded the best to me.   Pretty quiet to boot.

Below is the new layout spacing a couple of things out to keep me from making that solder bridge again!  If anyone wishes to try the PCB layout print at 300 dpi.  PCB is in my gallery here:
http://www.aronnelson.com/gallery/main.php/v/davepedals/Mashavalve/

Because I use positive emulsion PC boards I print the pcb  As Is  not reversed!  The parts layout image shows everything you need to know. Trim is supposed to be adjusted to 4.5 V, however I just adjusted to it to where yet sounded best to me.  Pcb is 1.18" L x 0.98" H.  I used J201 transistor.  Again this is not my design, only my layout.  Whoops.... A500k PCB mount potentiometer.

[bluebunny]

You don't really need a Zener to protect a JFET: it's a lump of silicon.  A MOSFET on the other hand has a thin-thin-thin sliver of glass at its gate.  This is easy to zorch, and Zener protection is more appropriate here.

[davepedals]

Thanks, yeah I thought they were pretty sensitive.  Oh well... I will upload the original files again later.

[J0K3RX]

Run pin 3 of the trim pot to ground and there's your voltage divider... 

pin 1 > +9V / pin 2 > drain / pin 3 > GND

[davepedals]

I wanted to add a bit more information on the print out for this PCB. Since I designed it to be used with a pre-sensitized PCB, you will print as shown. However you will be flipping the transparency over to place the toner side of transparency against the PCB . Transparency film is thin, but still thick enough to cause shadows and/or undercuts.  It is laid out correctly for flipping over this way which will eliminate these possible problems.  Short version – print PCB as shown. Flip transparency over . Place transparency on PCB , then exposed to light.

[temol]

Three days ago I made a breadboard version of the MV. In my opinion this  little flea sounds pretty good. Just boxed and finished a pcb version of the layout.






T.

[davepedals]

Nice!  Yes... for so few parts it really has a nice tone .