Need help debugging Tube Driver

[ranchak]

I just built the Tube Driver from GGG. It doesn't work properly. I substitute a 200pf for C8 (330pf) and a 100pf for C5 (120pf). I didn't have any 1N4148s so I used 1N914s. I have very little signal completely through the circuit. I have tripled checked the orientation of my diodes and caps. I did find that I had a higher voltage on the - side of C4, even though it's installed properly. I did take some voltage readings:

Source  11.09v

Pin 1    7.34v
Pin 2    7.34v
Pin 3    .302v
Pin 4    .772v
Pin 5    0
Pin 6    6.59v
Pin 7    7.13v
Pin 8    7.96v


Tube Socket

Pin 1  6.62v
Pin 3  .771v
Pin 4  11.06
Pin 7   1.215v
Pin 8  .771v


I believe there is a problem in the power supply, I should have V+ and V- at the tube socket. Is C4 the culprit?

[sfx1999]

Pin 8 and pin 3 should have a negative voltage on it. Measure V+ to V-. You should have something like 20V.

[ranchak]

Yeah, I don't have a V-. Have you built this layout? I need to recheck C3 and C14 to see what voltages I'm getting.

[sfx1999]

What do you mean you don't have a V-? If it's registering as 0, you're diodes are probably not in correctly or the caps are bad in that section.

[sfx1999]

Looking back on it, I was probably wrong with the 20V thing.

But why don't you have all of the voltages of the tube pins? 8 of them should be connected.

[ranchak]

I'm looking at Paul Marossy's layout of the Shaka tube:

http://www.diyguitarist.com/PDF_Files/ST1590BB-PCB_9-9-06.pdf

I see that the four 470uF caps are series to ground. It looks like the caps on the GGG layout might not be orientated correctly, specifically C13 and C14? Here's the layout from the GGG site:

http://generalguitargadgets.com/diagrams/tube_driver_lo.gif

[sfx1999]

They are oriented correctly on the layout and schematic. If you look at the schematic, V- is at a lower potential than ground (V- is negative). It is the same way on that Shaka tube layout. The negative terminal of the capacitor goes to V-, and the + to GND.

PS if you put the caps in backwards and corrected it you may have fried them.

[ranchak]

OK, I agree that C13 and C14 are orientated correctly to provide V-. I didn't have the caps installed backwards. I have no idea what the problem is, I'm about to the point of giving up on this one. It's got to be something simple that I'm overlooking, but I can't find it.

[sfx1999]

Can you post pictures?

Here are some things I can think of:
1) you are not supposed to connect the jacks to V-; it goes to ground (look where the heaters are).
2) Are you letting the tube heat up?
3) Are you using a 12AX7/ECC83/ECC803?
4) Do you have another tube to try?