MPP

Jump to Latest
RCruz

RCruz

Member
Joined 2006
Paid Member
hesener said:
Just took another look at your new measurements, and I have a suspicion around Q49 and Q50. Can you please check these two (or even replace them), and see if there is no shortcircuit to ground on the base of Q50, R5 or R46?
Click to expand...

I have triple checked all bjt´s polarities and find no errors... Anyway I think it would be very difficult because I populated first the 327 in both boards, compared them and then populated the 337.

I believe the measurements would not be so good if one polarity was incorrect.

I will replace Q50, R5 and R46 and report back.
 
RCruz

RCruz

Member
Joined 2006
Paid Member
Using the trimmer in R8, there is a point wen the trimmer is around 1k5r so total resistance would e 111r, where values over the 200k R45 and R46 get near 1 volt and output swings between -1 and +1V

if I reduce R8 further, output stabilizes at -13.3v... if not using the trimmer, output is +13.3v

So there is a point where everything should be perfect if there was no oscilation.
 
H

hesener

Member
Joined 2005
Paid Member
RCruz said:
Using the trimmer in R8, there is a point wen the trimmer is around 1k5r so total resistance would e 111r, where values over the 200k R45 and R46 get near 1 volt and output swings between -1 and +1V

if I reduce R8 further, output stabilizes at -13.3v... if not using the trimmer, output is +13.3v

So there is a point where everything should be perfect if there was no oscilation.
Click to expand...

That is very similar to what I saw. But I did have a fair amount of high frequency stuff going on. Do you have a scope that you can use to check if you have RF oscillations?
 
You must log in or register to reply here.
Top Bottom