A15MK2 completed. Gain at zero buzz?

Hi, this it my first post.

I just finished assembling my A15MK2 (with footswitch option).

After assembling everything i went through every net according to the schematic making sure all the components were correctly connected. When i was confident everything was ok, i turned it on briefly without tubes, nothing smoked or glowed.
With tubes i checked all the voltages and they were all very close to the schematic. Checked bias and got R51 and R52 at ~33mV.

With all the knobs at zero there was a buzzing sound, even with the guitar connected it was there and it went away by just turning the gain knob a little off zero. Is this normal? It's not a big problem user-wise, as it wont stay at zero but i just wanted to make sure there wasn't a problem with anything i've done. All the switches and knobs work as they should, even the Gain knob. The footswitch also functions correctly.

Zitat von eBernd;285327

Hi

and welcome...

As far as I understood your problem you should examine all ground connections - especially all pots, where ground is involved.

Even solder joints which look "good" could be "cold" solder joints (Just do a resoldering of them).

Bernd

Thanks, i retouched all the ground connections close to the Gain pot and the buzz is gone.

Zitat von eBernd;285996

Hi,

thanks for your reply. I like to know whether my guess(es) were right or wrong...

Have fun with your amp...:D

Bernd

No prob

Maybe you could look at this thread and maybe you can help :
http://forum.musikding.de/vb/showthread.php?t=26930