Built a Marshall Guvnor....what went wrong?

[deacy]

Hi,

i just built a marshall Guvnor based on the schematic of GGG. It sounds ok, but something is strange with the settings....if i turn the volume pot all the way up, it sounds totally crappy und fuzzy....if i set it up half way, it is ok, as long as i turn off the gain minimum half way - if i set the gain lower, it also sounds crappy and has no sustain....anyone an idea what went wrong??

Checked the pcb an values.....couldn't find anything!

Thanks a lot for your help!


Hannes

[aron]

As usual, check your voltages. It sounds like a component is not biased correctly.

[96ecss]

Hi, the best way to get help here is to follow these instructions http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

If you do that, we will be able to help you.

Dave

[deacy]

OK, first of all thanks for your reply.....
I built the guvnor exactly like the ggg layout....seems to be fine so far. I measured the voltages on all pins and biased components - all fine.
I audioprobed it and heard the following:

if i connect "probe needle" to pin 3 of the opamp, everything is fine - just a clean sound. but if i connect it to pin 1 OR the output of the gain pot to the second stage, the sound is very distorted and after hitting a string, immediately fades away. I think there must be the fault somewhere. i checked the stage, changed the ic, but coudn't find something.

Thanks for your help men!!

PS: I got the following voltages:

pin: 1:4,5V, pin 2: 4,5V, pin 3: 4,2V, pin 4:0V, pin 5:4,5V, pin 6:4,5V, pin 7:4,5V and pin 8: 9V. (as recommened on ggg, built instructions)

[deacy]

ok, sorry, the problem is solved.....used another supply for the measurements than for the audio test.....the supply is broken and prduces 10,3V instead of 9V....sorry guys, my fault, but thanks for your help!!!