imo

Building Purple MC76 - troubles and solutions
« Reply #40 on: September 25, 2007, 09:00:51 PM »
I had the exact same thing happen. I adjusted the size of the dropper resistor before the zener, which stabilized it. I have been on tour for a while so out of sorts on the exact resistor, but i would try doubling it or so and see what happens
Ian


dissonantstring

Building Purple MC76 - troubles and solutions
« Reply #41 on: September 25, 2007, 09:21:29 PM »
cool.  i'll try messing with the R80 (75R/3W resistor) and see what happens.
thanks for the help ian - greatly appreciated! :thumb:
kind regards,
grant

dissonantstring

Re: Building Purple MC76 - troubles and solutions
« Reply #42 on: March 27, 2009, 03:49:37 PM »
hi everyone,
this is quite funny since i lasted posted 18 months ago!  :o ::) ;D
i've finished my MC76 quite sometime ago, but only partially calibrated it (it seems) because somethings wonky with my recent attempt.
i am able to set the Q-bias no problem.  i cannot proceed with the calibration as i am finding that i cannot set the input to reduce gain by 10dB.  the most gain reduction i get in 20:1 is 8.3x dB reduction.
i've checked my parts and traced everything with the schematic and cannot find any thing wrong.  i've even changed the fet out and it's still the same.
i'm thinking my problem is either in the input section or the comp amp section.
if anyone has any ideas on what might be cause this i would be very appreciative.
thank you.
-grant
« Last Edit: March 27, 2009, 03:51:15 PM by dissonantstring »


 

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