Q's About GEO Tychobrahe Parapedal Layout (What is C3?!)

[Paul Marossy]

Just a few questions:

1. The electrolytic caps - do the negative leads connect to +9V?
2. What is the value of cap C3? It's not labeled...
3. The layout has two "Pot A"s labeled. That is really a dual ganged pot with A & B sections, right?
4. Where do I find a heavy duty dual 10K pot?!

[petemoore]

Just a few questions:

1. The electrolytic caps - do the negative leads connect to +9V?
  Doesn't sound right...
2. What is the value of cap C3? It's not labeled...is that the one across the 1k?, there's a cap across a small resistor, series in signal path...silly?
3. The layout has two "Pot A"s labeled. That is really a dual ganged pot with A & B sections, right? Yes.
4. Where do I find a heavy duty dual 10K pot?!
   I happened upon the O'l reciever for that...I don't know about the availability of heavy duty 10k dual Lin?.
  I haven't looked lately, there was a schematic, first one, I think RG did a second one that was 'cleaned up?'...anyway there were 'things modern' missing ['addendum' stuff that we now see like on about everything we'll use...like pulldown R's] and the power supply...I forget but I reworked that for running the opamps on mine. I don't know which schematic you're looking at.
  /quote]

[Paul Marossy]

petemoore-

1. In a positive ground pedal, I believe that the negative terminal of electrolytic caps would normally go to the +9V. Kind of like some of the old Fuzz Faces. Looking for verification...
2. Yeah, C3 is the one in parallel with the 1K resistor labeled "R7". I'm assuming that it's a 0.1uF, but I need to confirm that.
3. Thanks.
4. Both schematics are very similar, except for the bypass switching and the addition of 1M pulldown resistors on the input and output.

All-

I really need to know the value of C3! Anyone have the answer? I think I'm going to have to devise a way to use two wah pots simultaneously, somehow. 

EDIT: I see that the Chicago Iron repro has a dual ganged pot. You must be able to get them from somewhere. Check out this picture. It's kind of hard to see, but it's definitely a dual ganged pot...

[petemoore]

petemoore-

1. In a positive ground pedal, I believe that the negative terminal of electrolytic caps would normally go to the +9V. Kind of like some of the old Fuzz Faces. Looking for verification...
  IIRC Vref isn't 1/2v, the divider resistore being unequal..
  I basically trashed the power supply section, opting for negative gnd., quite similar to 'anything' except what was on the schem I was working on, which didn't look right to me, the redo seemed to have enabled cct function also...
2. Yeah, C3 is the one in parallel with the 1K resistor labeled "R7". I'm assuming that it's a 0.1uF, but I need to confirm that.
  I'm not the calc type, but it would seem that whatever the cap in question is passing, a small R like a 1k would pass most all of that without the caps help?
3. Thanks.
4. Both schematics are very similar, except for the bypass switching and the addition of 1M pulldown resistors on the input and output.
  Yupp...you know what of the 'extras' [modern amenities liek above] you want...the circuit had no RPolarity diode protection, etc.
  IIRC I just mainly made the power supply divider section so that all the polarities..basically that section looks like...most anything modern....messing with values only to bring Vref at 1/2v for a try...it's been a while since the last look...

All-

I really need to know the value of C3! Anyone have the answer? I think I'm going to have to devise a way to use two wah pots simultaneously, somehow. 

[Paul Marossy]

Hmm... I wonder if it sounds different with a negative ground. I'm going with the positive ground myself. 
I think that C3 is something not to overlook too much - it's there for a reason.

[Paul Marossy]

OK, I found one thread that talks about the value of C3. I guess I'll try 0.01uF to start and go from there. 

http://www.elixant.com/~stompbox/smfforum/index.php?topic=38687.0

I still need to find one of these dual pots, though. 

EDIT: Uh, the taper on the pot(s) - is it linear, log, or reverse log? Anyone know the answer to that one?!

[troubledtom]

all i know is that it's a 10K dual gang pot.
               - tom

[Paul Marossy]

all i know is that it's a 10K dual gang pot.
               - tom

Do they look like 1/2 watt pots? Any markings on them?

EDIT: Antique Electronics has some audio taper Neohm pots with long shafts that will probably work. I'm buying a few of them!

[petemoore]

OK, I found one thread that talks about the value of C3. I guess I'll try 0.01uF to start and go from there
  I should have been more specific, I socketted that cap, couldn't tell it doing anything, whatever it does probably goes right through the 1k it's paralleled to, for any listening diff...[ie none]...don't know exactly Why...kind of suspect it's completely unnecessary.
  I used regular 'ol pots, I don't see why this circuit would need anything 'special in wattage rating for the dual gang.
  The fact that it is dual ganged, and thus 2x as suspect for glitch or fault, I made sure no scritches were in it before building the treadle case/actuator assemlbly for it.
 

[Dan N]

inexpensive pots:

http://www.goldmine-elec-products.com/prodinfo.asp?number=G13281&variation=&aitem=1&mitem=40

[Paul Marossy]

Dan N-

Thanks, but that pot doesn't look like it would work in a standard Crybaby shell, plus it won't accommodate a pinion gear. The ones I ordered from Antique Electronics will work OK, though. I'll just have to add a resistor in parallel to make them 10K pots. No big deal. 

[alteredsounds]

C3 has been asked about alot and although actually may not be crucial, I will take the pedal apart tonight and see if I can find any more clues to hel you.

Cheers,
Nick,

[Paul Marossy]

Thanks Nick, you rock!