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last step C84 voltage measurement... 295mv! Can't get to 0V.

PostPosted: Sun Jul 16, 2006 9:23 am
by billkahler
Step 43 of assembly - I've tried to adjust R33 so that voltage at Pins 2 and 3 shows 0v, but it will not go lower than 295mv. I'm sure I'm measuring the correct pins.

Everything else checks out fine. U1 is considerably warmer (hotter) than U2 if that means anything. I do have the correct R33 - it's labeled 202.

Sure am looking forward to recording some acoustic guitar with this pre. . . .

Thanks in advance for the help.

no luck yet

PostPosted: Tue Jul 18, 2006 8:33 am
by billkahler
After trying some other things, I replaced Q5 which I thought might be damaged.

I did some more adjusting. Voltages at Conn 2, pins 2 and 3, showed 280mv, and if I turned R33 clockwise, those voltages got up to around 350 mv. Then I realized R29 was fully clockwise, so I checked voltages with it fully counter clockwise and came up with the lowest voltage reading 120 mv. Maybe R33 is bad?

Should I plug in a mike and try it out or do I still have a major problem somwhere? Everything up to this point has checked out.

U1 is hot to the touch if that tells anything. U2 is pretty warm but not as warm as U1.

Any help would be greatly appreciated.

PostPosted: Wed Jul 19, 2006 12:47 pm
by tpryan
What's happening at step 40 and 41?

step 40 and 41 check out fine

PostPosted: Wed Jul 19, 2006 7:20 pm
by billkahler
Step 40 and 41 check out fine - 0V, or very close considering the accuracy of the DMM.

PostPosted: Sat Jul 22, 2006 7:18 am
by billkahler
Still trying to figure out this voltage thing. Everything up to this point checks out fine but can't get the last voltage down to 0V. Anything else I can check?

PostPosted: Sun Jul 23, 2006 1:00 pm
by billkahler
Got the voltage all reading correctly and plan to try it out tomorrow!