Confused about whats up - GGG Baa Baa content

[LaceSensor]

I built another Roland Baa Baa cos a mate wants one.
I used the GGG board for it. Ive built one previously that was perfect.

This one, the sustain (gain control) crackles through its turn, and at the extreme (fully up) drops in gain. The sounds seem generally correct and all the switching and stuff works.

The Boost control also exhibits scratchyness in the pot turn .
The voltages on the Qs all seem ok based on the GGG doc.

I tried changing the sustain pot for a new one, same deal.
What can cause pots to sound all scratchy?
Im at a bit of a loss. As I say, other wise I tnink it sounds ok, need to test on a proper amp tho.

thanks

[Scruffie]

DC across the pot i'd wager, got the schematic?

[LaceSensor]

Here ya go
http://www.generalguitargadgets.com/diagrams/geo_baa-baa.pdf?phpMyAdmin=4a28f86a515b7883e7bc35a68d4e7b6d&phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

Across both pots tho?
Cheers for the heads up. I need to troubleshoot, but ive been away for a few days

[Scruffie]

Across both pots tho?

Well if you look at the schematic, they both attenuate your input signal, just in one version the switch removes the 'fuzz' part of the circuit and just runs through the boost so i'd suggest trying to enlarge and/or replace C1 on that schematic, it's blocking DC from coming back to those pots so...

[LaceSensor]

will give it a go,thanks for the tip

[LaceSensor]

Across both pots tho?

Well if you look at the schematic, they both attenuate your input signal, just in one version the switch removes the 'fuzz' part of the circuit and just runs through the boost so i'd suggest trying to enlarge and/or replace C1 on that schematic, it's blocking DC from coming back to those pots so...

That fixed it. Phew, thanks so much AGAIN

[gtr2]

Good to hear!

I'm thinking I should change C1's spacing on my own beebaa layout to accommodate a film cap easier.  Then leaky electro's wont be a problem.  Although a tantalum would work.

Josh

[LaceSensor]

Yeah could be an idea. I am learning new stuff all the time.
Im glad it was a quick fix.

I was using these micro-mini caps, are they less trustworthy or did I just get a lemon?

[gtr2]

Electrolytics are always more prone to DC leakage than film.  Most of the time it's unnoticed because they are tied to a ground in our builds or a pull down resistor bleeds the leaky DC.

Josh

[LaceSensor]

Electrolytics are always more prone to DC leakage than film.  Most of the time it's unnoticed because they are tied to a ground in our builds or a pull down resistor bleeds the leaky DC.

Josh

Thanks for the info learning every day