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osq low voltages

Started by chombo, October 05, 2007, 04:35:08 PM

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chombo

hi there,
havin a bit of trouble with my osq build.
it seems to be passing a signal through it completely but the voltages on the transistors are acting a bit strange.
i used the exact same circuit found on GGG. (no subs on parts or mods)http://www.generalguitargadgets.com/pdf/ggg_osq_sc.pdf?phpMyAdmin=4a28f86a515b7883e7bc35a68d4e7b6d

here are my voltages:
Battery:  9.04v
Voltage at the circuit board end of the red battery lead = 8.97v
Voltage at the circuit board end of the black battery lead =  0v
Q1
Gate = 1.59v        2.4v
Source = 2.43      4.4v
Drain = 8.97        8.8v
Q2
Gate = 0v            0.6v
Source = 1.59v    2.6v
Drain = 1.23v      2.1 to 2.6v

IC1
1= 8.39v             8.3v
2= 8.39               8.3v
3= 0v                  0v
4= 0v                  0v
5= 4.76v             4.7v
6= 4.86v             4.8v
7= 4.85v             4.8v
8= 8.98v             8.8v

my voltages are on the left and what its supposed to be is on the right.  my ic voltages seem to be good but its the transistor voltages that are baffling me. could they be burned?  there are no solder bridges, and i probes the signal path and there dont seem to be any cold joints.  thanks in advance!

chombo

ok, so i realized that i can raise and lower the bias trimmer, and change the voltages on the transistors go get them relatively correct.  i can get them to go to 0 and a little bit above the correct voltages that i posted, however, the gate on Q2 is always 0, it wont go up at all. i socketed the transistors and tried new ones but no dice.  any suggestions?

chombo

oh and the drain of Q2 is consistantly at 1.37.  it doesnt change unless the trimmer is closed then it goes to 0.  its really Q2 that is acting funny...