Mudbunny Green Russian Issues

[massaibrisbane]

Hi All,

[I just tried to post this and it didnt work, so apologies if there is a double somewhere].

Ive had a Mudbunny 2011 PCB sitting around semi populated for a while now and just decided to finish it off for a friends Bday.

Problem is i cant get any sound. The pots scratch and and the volume pot will scratch until you turn it down when it will kill all noise - so i can assume that is working..??

It is all to Green Russian Specs except:
C10= 3n3
C2= 330pf

2n5088 Voltages [ive double checked all the transistors, replaced them all and tried again, etc]

Q1
e-0.137
b-0.73
c-4.5

Q2
e-1.07
b-1.528
c-8.76

Q3
e-0.94
b-1.35
c-8.12

Q4
e-0.88
b-1.48
c-4.9



Ive just reflowed all the solder joint, so i can be relatively sure it isnt that.

I've also traced the PCB using a probe and found signal until the far side of C7.  I have also replaced C7 to make sure it isnt that. 


Im really running out of ideas here - if anyone had any ideas that would be amazing.

Thanks in advance!!
steve

[harrisxr650]

check the pads of C7, one of them it might sorting with the ground or R18 from solder blobs or bad etching. take a closer look with a magnifying glass if possible or with DMM continuity check.

[hammerheadmusicman]

Is it the etched one? The etch 2011 mudbunny layout is for a different transistor pinout, if it is (or if its the same but fabbed) the 5088 need to be flipped 180degrees. I did this myself on the first one I built!

George

[midwayfair]

the 5088 need to be flipped 180degrees

Being flipped would give pretty much exactly those voltage readings. I think this is it.

The scratchy pots, though -- especially the volume pot -- have me worried that there is DC across them. There could be other issues.

[hammerheadmusicman]

Hey, I must be learning!