original big muff pi transistor question

[rhinson]

i'm working on an original (i'm told) big muff for a friend.   for reference, the outside shell is silver with simple black lettering and it does say made in new york city.  the board resistors are all carbon comps and it does have the on/off switch--no stereo on/off jack.  anyway my question is did any of these use pnp transistors and -9v?  when i opened it up the red was connected to the ground traces.  the transistors are black, round/bowl shaped, and the part number is s37000 (a house number i guess).  these look like some older jfets i've seen.   the collector resistor is 10k instead of 15k like on most of the schematics i've seen.   this thing sounds kinda sputtery like the transistors aren't biased correctly so could it be that someone just put on a new battery clip and hooked it up backwards or are these pnp's for real?  also this version has all 0.1 coupling caps as opposed to the versions i see with mostly 1mf caps.  any help with the transistor type id would be appreciated.      thanks            rh

[R.G.]

did any of these use pnp transistors and -9v?

Yes, that was one of the variations.

the part number is s37000 (a house number i guess).

Yes, probably. Also probably not an EH house number. EH is (was?) notorious for using whatever parts they could find in New York's surplus stores.

this thing sounds kinda sputtery like the transistors aren't biased correctly so could it be that someone just put on a new battery clip and hooked it up backwards or are these pnp's for real?

The transistor pin voltages tell the tale. There was a PNP version, and you can probably get someone... to tell you which devices are misbiased.

However, from experience, I can tell you that for effects like this, you can usually rejuvenate them to like new by replacing ...every... single... electrolytic ... cap and then remelting all the solder connections on the PCB. Read the Guitar Effects Debugging Page at GEO (http://www.geofex.com) for some background.

also this version has all 0.1 coupling caps as opposed to the versions

see above.

[Stuart]

I have a '72 triangle knob BMP wth FS37000 transistors.  They are indeed PNP and it's wired with positive ground.  Can you post the transistor voltages?

[aron]

From Schematics 2

My trace: