I was reading about the detective work done on this pedal. Fascinating stuff. There seems to be at least 2 versions of the pedal. The one I'm speculating about is the earlier one, schematic here http://www.bargeconcepts.com/bp/hpschem.html (http://www.bargeconcepts.com/bp/hpschem.html) This is the one with 2 npn transistors. Or so it is assumed. It also has those 2 glass resistors. That's the part I'm wondering about. As far as I can find out those type of resistors were very high value. The markings on them were T1 1% US 60G. Could they be 60G ohms? On the barge schematic they don't mention a value for these or the transistors. If they are such a high value then for what purpose? I don't think they could give enough base current for a transistor. Unless those transistors are darlingtons? Or maybe they are fet's? Has anyone got any info on this or has it already been covered?
There's a big thread on this on the forum. I'd try to find it, but I need to solder right now.
http://www.diystompboxes.com/smfforum/index.php?topic=55987.0
is percOlator spelt percUlator in the US??
Anyway this is an awesome pedal, i would advise playing with the diodes or just leaving them out, it sounds pretty crappy with the germaniums ( i think very different from the actual pedal that you hear on a lot of shellac songs ).
I wonder if we could get some more info on those diodes actually..
I built one using George Giblets(sp?) schemo and it sounds nearly identical to the infamous Albini vids. I used 1n34's for the diodes, a metal can 2n2222 as the NPN and a 2n651 as the GE PNP.
Aparrently there was some discussion saying leaky GE transistors may sound better in this circuit.
as a funny side note, I used to frequent the "Rock Haus" in Milwaukee WI, where the original perkolaters were sold. I tried one out, maybe 10-12 years ago, but decided not to buy it. I guess after the designer died/stopped making em/disappeared the Rock Haus guys made a few more of them using left-over parts from said dude. I heard rumours that they were different, but who knows...
Can you point me to that schematic Idiot Savant?
Thanks
John
Quote from: John Lyons on August 15, 2007, 10:57:44 PM
Can you point me to that schematic Idiot Savant?
Thanks
John
it's somewhere in that big thread aron posted...
here we go!
http://www.geocities.com/george_giblet/effects/percolator_later_rev1_1.png
-morgan
I read through that thread. They got a working version based on the later board with the 750k and 220k resistors. On the earlier one those 2 resistors were glass encased. The diodes on that later board you can see the number it looks like 1N59S. I found an old post where someone said they had one and the diodes were 95S but on the board pic you can see he had it the wrong way round. The diode might not make much difference. In the link above you can see the one from the barge site the 2 resistors are named glass axial with no value. I'm thinking those 2 resistors might be as high as 10 gig ohms. That's what intrigued me about it. The earlier one wasn't followed up because the resistors were a bit odd and unknown value. Those 2 resistors are supplying transistor base current. Theres not going to be enough current to bias a transistor at 10 gig ohms.