Psychtar Motorboating. Help!

[Jamforthelamb]

Hello friends,

I have a Psychtar I recently put together using this layout with a pcb thanks to John Lyons 



It seems to work fine when the mode switch is not engaged, but as soon as you flip the switch all you get is a motorboating sound, and no signal from the guitar at all. In other words I have one of the two modes working (I'm thinking the oct up portion).

Suggestions?

Thanks!
Kevin

[PRR]

I wonder which way the switch goes, side-side or up-down?

Schematic:

http://www.jiggawoo.eclipse.co.uk/guitarhq/Circuitsnippets/snippets.html

Your layout does not match.

Remove C2 and put in a jumper.

Lift one of the Green (on layout) wires to the switch and put C2 in series.

I still don't see how this CAN motoboat.

[Jamforthelamb]

Thanks PRR.

That took care of my issue. I was confused by the way the switch was to function too, and after closer inspection of the schematic found I had wired wrong. I fixed the pcb mistake as per your suggestion, and now everything is working great.

Another question. Would this circuit work with other kinds of diodes, or are the Ge ones my only option?

Thanks!
Kevin

[amptramp]

Germanium diodes have a low forward voltage and the use of any other diode would cause zero output until the higher turn-on voltage of the alternate diode was reached.  There is a cure for this: the centre tap of the transformer is connected to ground in the circuit diagram.  If it was raised above ground by one diode drop of the same type of diode as used for the fullwave rectifiers, the circuit would essentially have no dead zone.  It may even help the circuit with germanium diodes.  This would mean lifting the ground at the transformer centre-tap and pulling it high with a resistor and also keeping a diode anode connected to the tap with the cathode to ground.  Size the resistor to pull less than a milliamp through the added diode.