Hello there, I have read some posts with kinda the same problem.
No plug into input jacks or power amp jack, the amp makes a little hum that won't go away until I plug a cord, then the hum disappears immediately.
I have read this post from 2015:
https://www.diyaudio.com/forums/instruments-and-amps/200792-fender-frontman-212r-3.html
Here are some readings I took, from Q18, Q19, Q20, Q21
The schematic does not have readings, so I don't know if the values are ok.
None of the transistors get hot, just a little warm.
NO CORD/PLUG - READINGS:
Q18
B= 0.916V
C= 40.10V
E= 0.342V
Q19
B= -1.335V
C= -39.99V
E= -0.170V
Q20
B= 0.351V
C= 40.06V
E= -0.170V
Q21
B= -0.726V
C= -40.00V
E= -0.180V
WITH CORD/PLUG - READINGS
Q18
B= 1.136V
C= 40.16V
E= 0.547V
Q19
B= -1.137V
C= -40.08V
E= -0.538V
Q20
B= 0.542V
C= 40.06V
E= 0.008V
Q21
B= -0.535V
C= -39.99V
E= -0.001V
What should I look for?
Thank very much.
No plug into input jacks or power amp jack, the amp makes a little hum that won't go away until I plug a cord, then the hum disappears immediately.
I have read this post from 2015:
https://www.diyaudio.com/forums/instruments-and-amps/200792-fender-frontman-212r-3.html
Here are some readings I took, from Q18, Q19, Q20, Q21
The schematic does not have readings, so I don't know if the values are ok.
None of the transistors get hot, just a little warm.
NO CORD/PLUG - READINGS:
Q18
B= 0.916V
C= 40.10V
E= 0.342V
Q19
B= -1.335V
C= -39.99V
E= -0.170V
Q20
B= 0.351V
C= 40.06V
E= -0.170V
Q21
B= -0.726V
C= -40.00V
E= -0.180V
WITH CORD/PLUG - READINGS
Q18
B= 1.136V
C= 40.16V
E= 0.547V
Q19
B= -1.137V
C= -40.08V
E= -0.538V
Q20
B= 0.542V
C= 40.06V
E= 0.008V
Q21
B= -0.535V
C= -39.99V
E= -0.001V
What should I look for?
Thank very much.