hmmm.... I'm having a problem finding the input cap on this pedal.
Referencing GGG schematic (which looks pretty close)
I'm trying to find C1
http://www.generalguitargadgets.com/v2/diagrams/tube_driver_sc.gif
I found D1, D2, C2 but not C1. errrr!
Here are my continuity points so far:
http://www.diystompboxes.com/temp/IMG_0366.JPG
This board is a nightmare!
http://www.diystompboxes.com/temp/IMG_0356.JPG
http://www.diystompboxes.com/temp/IMG_0358.JPG
There is no .033 cap and for some reason, none of the cap ends show continuity to C2 or D2.
hmmm......
Seems like you should be able to just start at the input jack and work your way in....gotta be connected to pin 3 of the TL072.
There's a bunch of switching circuitry to go through and the board is double sided with a ton of flux on it. :x
Aron is the effect using a CMOS switch? if so look around the input of the switch. Is anything hidden under the tubes between the sockets and board?
It mght not even be on the board because of the use of +- supplys and a fet input opamp. With this circuit it would be a good design practice to use C1 :however if the circuit before has a leaky output cap it could cause problems without it.
.....in the lower right hand side of the picture just above the pot marked 500,and to the right of the blue electrolytic cap sits what looks like a orange-tan looking disc cap which appears to say "331"-could that be your .033 cap?.......
I know I buzzed that cap, but my mind instantly said 331 = 330pf.
Thanks, I will test it again anyway.
Quote from: dr.....in the lower right hand side of the picture just above the pot marked 500,and to the right of the blue electrolytic cap sits what looks like a orange-tan looking disc cap which appears to say "331"-could that be your .033 cap?.......
if it was .033 the cap would read 333; 331 = 33pf x 10 to the 1 = 330pF
I used to have the 9V tube driver, it behaved like it was true bypass, ie you could get a sound thru it when it wasn't powered up when in bypass.
The input cap on that was a .047uf (473) polyester cap IIRC .... maybe the one on this is .047?
Aron,
I just finished tracing out a Tube Driver I borrowed from a friend, Serial # 6100309. It seems like it is a bit older than the model you have. The board is plain epoxy glass. And, yeah it was a mess to trace out. But, I just got mine up and running. Sounds just like the original.
Anyway...I found a couple of differences in what I have, and the schematic at GGG. One of those being the input cap, should be .047uF - not .033uF.
You guys are both correct.
The input cap is .047uF.
I changed it and did a tiny mod and now....
Well, I will start another thread :roll:
Just for the sake of completeness, the reason it was difficult to find the input cap by continuity was that there is a series resistor (not shown in the schematics) before the input cap. So "buzzing" doesn't work.
Good old fashioned tracing with a lamp (light behind board) worked.
Thanks!
Aron