Valvecaster debugging - please help

[tishinator]

Hi there,

In what proved to be too ambitious of a task, I attempted (and failed) to build a working Valvecaster for my brother for Christmas.  He got a gift card this year, and now I'm working on it for his birthday.  I have realized, though, that my skills at measuring / debugging pedal problems are not what they should be. 

(In terms of experience, I know enough to be dangerous - I worked in a shop for two years repairing guitars (but not pedals).  Have previously built working versions of a single transistor fuzz and the dumble from runoffgroove.)

I'm at a point where I'm taking nothing for granted.  The current behavior I observe is:
1.  No sound when pedal is engaged, but sound when bypassed (I added a switch).
2.  The 12AU7 warms slightly, but I don't see it lighting up when using 9V.
3.  I've spent enough time testing continuity that it doesn't appear to be a cold solder joint.

Does anyone have a good resource on where to start?  I'm not sure what types of measurements I should take to isolate my problem, and of what values to expect for those measurements.

Thanks for any input!  I'm new to the forum, so if I should first try something else (other than post immediately) please let me know that too.  I want to make sure I'm following the proper protocol...

[tishinator]

Sorry everyone, I just saw the debugging post.  I think I need to learn to read.

I will follow that process and post some more detailed information later.  Thanks!

[frequencycentral]

Here's voltages taken from my working Valvecaster, which I run at 12 volts:

Pin 1: 3.02v
Pin 2: -0.518v
Pin 3: 0.00v
Pin 4: 0.00v
Pin 5: 11.97v
Pin 6: 8.21v
Pin 7: -1.285v
Pin 8: 0.00v
Pin 9: 5.91v

Take measurements from yours with the tube in the socket, power engaged, and everything set to maximum and post them here. Also measure and post your power supply voltage.

[GeToChKn]

Here's voltages taken from my working Valvecaster, which I run at 12 volts:

Pin 1: 3.02v
Pin 2: -0.518v
Pin 3: 0.00v
Pin 4: 0.00v
Pin 5: 11.97v
Pin 6: 8.21v
Pin 7: -1.285v
Pin 8: 0.00v
Pin 9: 5.91v

Take measurements from yours with the tube in the socket, power engaged, and everything set to maximum and post them here. Also measure and post your power supply voltage.

Not to hijack the thread but I'm just curious Frequency, are those voltage ratios set in stone or can their be some variation.  I notice people change R1 values a lot, so would that not effect pin 1's value or people who run the heaters at 12v and the other portion of the circuit at like 30v or something.

[frequencycentral]

I took those voltages a while back. They are based on a stock 12AU7 Valvecaster with the heater and the B+ at 12 volts. Gain was set to maximum (ie pin 3 grounded). Any changes in power supply voltage to the heater or plate resistors, or in the stock component values would probably give a different set of voltages. I'd imagine the voltages would even vary slightly from tube to tube. Then again, I've never seen anyone but me post working Valvecaster voltages..............

[tishinator]

Thanks.  It may take me a couple of days to get to it - my multimeter is not working properly, so I'm getting another one.  (It is pretty darn old, probably its time to go.)  I've also been recruited to help around the house for a New Year's celebration, so that will slow my progress... 

I'm going to also grab the schematic / layout / etc... that I'm using.  I realize now that I didn't give anyone much to go on, still learning through this process. 

Thanks again, will post more info later!

[tishinator]

Update - I highly suggest using the debugging information from Aron and R.G. in the debugging thread.  Upon preparing to gather the information to post (after a few days to clear my head of frustration at my problem) I realized that my power supply was hooked up backwards.  Once I swapped those wires it worked as expected.  I suppose this sort of thing happens to everyone from time to time, but following their process led me straight to the problem, even before I could break out the meter!

Thanks everyone for your help! 

[Renegadrian]

Yeah, it's like when you end up populating the board, try it to fire it up and go WTF only to realize (after some time) that you put no IC/transistors in their sockets...