Warhead Univibe: DEAD

[kinski]

So I built the Warhead Univibe and I get nothing as far as I can tell. I turn the pedal on and there is no sound of any kind and the lamp does not even light up.

I have tried a wall wart and my Voodoo Lab Pedal Power. Nothing.

As far as I can tell, all of the parts are oriented correctly.

I only subbed one part. I used a 78L15 in place of the 7815T.

I DO own a multimeter, but I have never really used one to probe a circuit, only to get cap and resistor values. I can give you guys readings but if somebody would be kind enough to let me know where to make contact with the circuit I'd greatly appreciate it.

Its a bummer to make and populate such a big board and have it end up completely dead!

Thanks for the help!

[kinski]

Nobody? 

I put my multimeter to the 78L15 and all pins came up ZERO. Any help from here?

[lloyd17]

Well if there is no voltage at the regulator everything from the power jack to that regulator is suspect. Follow the volts starting at the power jack, where do they stop?

[madbean]

Are you sure you haven't plugged you power into the rectifier section on the PCB? IOW, you have power and ground going to the 18vDC pads, not the AC ones, correct?

0v on all pins of the regulator could also indicate some kind of solder bridge to the grounding plane somewhere.

[kinski]

Okay, i found a very small break in one of the traces leading to the 78L15. I now get about 16v on the two outer legs of the 78L15 and 0 on the middle one. Still no sound.

[kinski]

Oh yeah, and I have been using my voodoo lab pedal power which is DC. And yes, I have wired up the DC pads, not the AC pads.

[kinski]

Okay, made some progress.

I get sound and it does do the univibe thing, however, its not very strong, its quieter than the bypassed sound, and it distorts a tiny bit.

When I switch to the vibrato mode, its distorts a lot and is much quieter.

Any ideas? 

[the3secondrule]

Voltages on all of the transistors would be a good start

Okay, made some progress.

I get sound and it does do the univibe thing, however, its not very strong, its quieter than the bypassed sound, and it distorts a tiny bit.

When I switch to the vibrato mode, its distorts a lot and is much quieter.

Any ideas? 

[kinski]

Okay:

Q1     0.9 / 0.9 / 1.8
Q2     1.5 / 1.8 / 4.8
Q3     8.7 / 4.9 / 4.3
Q4     4.4 / 3.9 / 13.2
Q5     3.8 / 4.3 / 9.8
Q6     15.9 / 3.9 / 4.2
Q7     3.3 / 4.0 / 9.8
Q8     13.2 / 0.6 / 0.6
Q9     0.1 / 0.5 / 13.1
Q10   13.5 / 5.2 / 5.5
Q11   15.9 / 2.7 / 5.8
Q12   9.3 / 10.0 / 15.8
Q13   14.8 / 2.2 / 4.3
Q14   9.3 / 1.7 / 3.5

[kinski]

Does that look about right?

[the3secondrule]

I can't help much i'm afraid - I was hoping someone else would chime in once you posted voltages 

Okay, i found a very small break in one of the traces leading to the 78L15. I now get about 16v on the two outer legs of the 78L15 and 0 on the middle one. Still no sound.

you should be getting ~18v on the input leg of the 78L15, 0 on the middle (this pin is ground) and ~15v on the other pin. if you are getting 16v on the two out legs something is not quite right...

[kinski]

the middle leg is a steady 0v.

The two outer legs are constantly changing.

One of the outer legs keeps jumping between 16.6v and 17.3v

The other leg jumps between 13.6v and 15.6v. Could it be that this substitute is not a proper sub?

[madbean]

Yes, something is wrong with the regulator. It either has a different pin layout or needs to be replaced.

[kinski]

Alright, thanks. I'll order the proper part with my next parts order. That order will also include the parts for the Weener Wah, and maybe one of your phasers, whenever they get published on your site! Can't wait!

[kinski]

Where do you buy an LM7815T?

I can't find one anywhere. Even ebay.