Electronics > Repair

MC Preamp no gain when DC Power Applied

(1/12) > >>

pulsed_power:
With no B+
RI & LI = 75mv pp
RO & LO = 2v pp

With B+ and no change in signal value from signal generator
RI & LI = 3mv pp
RO & LO = 300mv pp

How can a amp circuit create gain with no B+ and then when B+ is applied the gain drops to such low levels?

TimFox:
When asking about such an apparently absurd result, it behooves you to post more details about your measurement.
1.  How do you connect the generator to RI/LI?
2.  How do you measure the voltage at RI/LI?
3.  What frequency do you measure at, and is the output at the same frequency (i.e., no important noise or oscillation)?
4.  How do you measure the voltage at RO/LO?  Are your voltage measurements true differential, or does it ground LO?

pulsed_power:
When asking about such an apparently absurd result, it behooves you to post more details about your measurement.

1.  How do you connect the generator to RI/LI? BNC to RCA to inputs
2.  How do you measure the voltage at RI/LI? Scope
3.  What frequency do you measure at, and is the output at the same frequency (i.e., no important noise or oscillation)? 1khz
4.  How do you measure the voltage at RO/LO?  Are your voltage measurements true differential, or does it ground LO? scope

pulsed_power:
More photos

pulsed_power:
With power on

Navigation

[0] Message Index

[#] Next page