Harmonic Percolator gut shots

[Stevo]

WERENT THERE GERMANIUM DIODES AS WELL :?

[Dan N]

The markings on the photos from HC Forum are something like Tl 196

No, it says 1%.

http://users.rio.com/senorris/junk/unkn1.jpg

The value is facing the board. It would be nice if the guy at HC would post some values...

Stevo, it does have 3 G diodes.

[nelson]

the 1N34's on layout are germanium diodes...

:oops:

[MartyB]

Beautiful Dan.  I'm convinced.  Somehow your re-posted pic is better than my orig download pic.

[vortex]

I PMed the chap at Harmony Central who posted the pics asking him if he might take a second look at the components for us.

Here's hoping...

[theehman]

I drew out a schematic of this a year or 2 ago when one came thru for repair.  
Here's my schematic w/ a few notes.  It jives pretty close to Alfonso's but I have a 4.7K resistor between the clipping diodes instead of a series resistor on one leg.

http://www.ronsound.com/ebay/aimhp.gif

[MartyB]

Thanks Ron for sharing the schematic!  The pcb shots at HC forum tha Vortex linked to seem to show 6 resistors (plus 2 pots).   :?:   Can you help decipher the transistor type "CAKK GE6624 USA 1598" ?  I'm taking it that its a germanium something-or-other PNP.

MartyB

[Doug_H]

I drew out a schematic of this a year or 2 ago when one came thru for repair.  
Here's my schematic w/ a few notes.  It jives pretty close to Alfonso's but I have a 4.7K resistor between the clipping diodes instead of a series resistor on one leg.

http://www.ronsound.com/ebay/aimhp.gif

Ron,

Does the output really come off of the base of Q2 or the collector?

I took it off the collector, as that is what Alf's schems showed. Hmmm... Never tried it off the base...

This is a subtle but important difference.

Doug

[Doug_H]

In case anyone's interested, there are companies putting out pedals now that seem to be based on some of the ideas behind the Percolator:

http://www.stereoscope.ca/ho.shtml

http://www.pedalgeek.com/cgi-bin/new_shop.cgi?config=&uid=gNlMHAAA1124108378&command=link--us


There used to be a clip of the "Harmonic Overdriver" at their site. I put the clip up on my site so you can hear it. I think it's the older (not "MK2") version. They are either varying the gain control or guitar volume, can't remember. Notice how the character changes as the gain is turned up. My perc does this but I don't think it gets quite as heavy. That's easy to tune with coupling caps though:

http://home.cfl.rr.com/dbhammond/harm_ovdr.mp3

Doug

[theehman]

Does the output really come off of the base of Q2 or the collector?

I took it off the collector, as that is what Alf's schems showed. Hmmm... Never tried it off the base...

This is a subtle but important difference.

Doug

That's what I've got on mine.  I think I removed the transistors and checked the pinouts with my B&K tester, but it's been so long I may be mistaken.

[Doug_H]

Does the output really come off of the base of Q2 or the collector?

I took it off the collector, as that is what Alf's schems showed. Hmmm... Never tried it off the base...

This is a subtle but important difference.

Doug

That's what I've got on mine.  I think I removed the transistors and checked the pinouts with my B&K tester, but it's been so long I may be mistaken.

That's pretty interesting. I'm going to sim that and try it with mine. I suspect  the output vol would be lower, coming off the base.

Doug

[Doug_H]

Wow, I just simmed it and it looks like a 20db boost if you take the output from the base. I didn't expect that... Not sure how accurate the sim is, but it definitely warrants giving it a try.

Thanks, Ron!

Doug


EDIT: Never mind... Tried it last night and the output definitely needs to come off of the collector.

[ragtime8922]

Any further developments on this? Doug H?

[Doug_H]

No, other than I suspect taking the output off the base is a typo.

Doug

[MartyB]

That thread from Harmony Central had a couple of additions.  The poster graciously carefully read out all the readable markings on his component side.  AFAIK the only true unknowns left are the values of the trannies (and whether our assumptions on Q2's orientation are accurate) and that weird-looking component in the center that has been accused of being a 1uF cap.  I think the DIYers will have this before too long.  I'll update my layout in the gallery. (My own build is waiting on a coupla parts).

MartyB

[Dan N]

Hi Marty,

I'm ickystay at HC. Here's the pcb for the one I built. The black parts are confirmed, the pink- guesses, and the purple are what I used. The pcb is for pos photo etch and would need to be reversed for PnP. The 1uf np was  a tight squeeze.

http://users.rio.com/senorris/junk/perc-try.gif

I used a metal can silicon (BC108B) for the Q2 and a 2SB77 germ for Q1. Had to cover the BC with shrink wrap because when it touched the germ, it shorted out. Maybe the original potting is just to avoid shorting?

Good luck with your build!

[MartyB]

Hey Dan!

Sweet layout.  Just about a postage stamp!  One clue you probably hit on is the visible leads from the photos.  They're gold and in a triangular, as opposed to a linear arrangement.  They are round wire instead of flat, like most new manufacturing.  Based on the size of the tranny pics, I've also been playing with a buncha old trannies.  I'm gettin some nice creamy distortion that my jerkulator really never got.  Here's a pic of my unboxed build:

http://www.freewebs.com/martyb/harmonicpercolator.htm

I'll post a soundclip soon!

MartyB

[ragtime8922]

Nice layout. I'm going to do this asap...actually #2 on list. Even though it's a quick, small build I know it's going to turn in to a long project swapping every component 1000x....COOL!

[MartyB]

Okay see if this link works:

http://webzoom.freewebs.com/martyb/harprc.mp3.zip

It's a sound sample of my build.  First two twangs are my tele straight into a small tube amp.  Next is with the HP full throttle.  Cheezy  lick stolen from a cool song by Jim Weider called "Bigfoot".

[Doug_H]

Hi Marty,

I'm ickystay at HC. Here's the pcb for the one I built.

The 220k in the upper left-hand corner should go from the base to the collector.

Doug