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GGG Rodent (ProCo Rat) Build Problems - VERY Faint Output? Help, please?

Started by Rocket Roll, May 30, 2008, 05:18:48 AM

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Rocket Roll

May 30, 2008, 05:18:48 AM Last Edit: May 30, 2008, 05:24:37 AM by Rocket Roll
I just finished a GGG Rodent (ProCo Rat replica), using the "3PDT Version, No Millenium Bypass": http://www.generalguitargadgets.com/pdf/ggg_rodent_lo_3pdt.pdf (the complete page is at http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=92&Itemid=26 ). Here's how it looks like from the inside:





As far as board modifications go, there's a DPDT switch with LED / Ge diodes combo, and 2N5458 is in different packaging then I've seen:



Good news: I have bypass; I have LED; when I strum the chord, the output is present but it's VERY quiet; when I strum the chord, clipping LEDs light up.

Could somebody pinpoint me towards some ProCo Rat IC & JFET voltages, so I could check them? Also, any advice would be greatly appreciated!
"Goin' down where Southern cross' the Dog"

Rocket Roll

#1
May 30, 2008, 06:16:34 AM Last Edit: May 30, 2008, 06:33:47 AM by Rocket Roll
...and here are my voltages:





All voltages are taken in "Effect On" mode, a cable in input jack (LED working), all pots around noon... Nothing heats up, btw... I'm still not sure that I've got the 2N5458 properly orientated. How should I check this?

One more thing that could be important: there's a jumper. J.D. Sleep says: On the parts layout, note that I show a jumper. This can be connected as shown to bias the JFET source to a higher voltage, which sounded better to me, or you can connect it to the adjacent pad to ground to bias it the same as the original. Its your choice. The jumper sets the voltage on the 1 meg gate resistor, which in turn sets the source voltage.

He connected it like this...



...and I've connected it like this, as in the schematic:



Could it be a problem?
"Goin' down where Southern cross' the Dog"

Rocket Roll

#2
May 30, 2008, 08:01:34 AM
FET was the problem... I've put a 2N5457 and it works...

Any comments on voltages, please? Thanks in advance!
"Goin' down where Southern cross' the Dog"

Rocket Roll

#3
May 31, 2008, 02:10:26 AM
Oh, one more thing.

"Drive" (gain) pot seems to be backwards. I'm positive I've wired it right (as on schematic), but it starts killing the sound after it reaches 2 o'clock and shuts the sound completely off in its final position.

Could that be "the nature of the beast", or a mistake I made?
"Goin' down where Southern cross' the Dog"

plankspank

#4
May 31, 2008, 08:37:04 AM
Quote"Drive" (gain) pot seems to be backwards. I'm positive I've wired it right (as on schematic), but it starts killing the sound after it reaches 2 o'clock and shuts the sound completely off in its final position.
Just reverse the connections on the pot ends (lugs 1 & 3)...
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