Great thank you. I see I forgot to list FR807 but you caught it.
Great thank you. I see I forgot to list FR807 but you caught it.
"Eagle eye"
"Eagle eye"
Ok, finally got parts and have time. I changed all the fusibles as indicated. I measure +BE and +B7 and both are just above 52V DC.
What should they measure?
The schematics I have are illegible. 52vdc looks about right.
Ok, I am resurrecting this thread...finally coming back to it after a year.
I've replaced electrolytics, fusibles, relay, and a couple 458c's on the amp.
Current status:
1) relay engages and I get adjustable bias voltage
2) midpoint voltage is bouncing all around between 0 to several hundred MV (left channel seems to jump higher...and relay will cycle, at times, when adjusting left trim pot)
3) no sound via speaker A, get R channel on speaker B (white noise on L channel)...also smoke started from main amp l channel but can't pinpoint where (dbt didn't go bright?).
4) main filters measure ~36.5 vdc when ground to chassis (not back); 0vdc when grounded to back
5) lights working fine on front
6) ~13.5vdc to blue/violet supplies to main amp board
7) ~48.5vdc to both EQ board and preamp.
For the midpoint, both zenners (d701/702) tested fine by diode function, but I'm suspicious that these may possibly be causes for bouncing voltage?
Regarding 0v drop when grounded to back...am I possibly shorted or is this just due to negative return to filter caps from speaker terms and coupler board?
I do have continuity from black speaker terminal to ground (clear covered wire) on preamp, amp, eq.
I'll do more checking on left channel amp, but have to run for now.
Hoping you might see something that may be suspicious or worth checking.
Appreciate the input!
I've replaced electrolytics, fusibles, relay, and a couple 458c's on the amp.
Current status:
1) relay engages and I get adjustable bias voltage
2) midpoint voltage is bouncing all around between 0 to several hundred MV (left channel seems to jump higher...and relay will cycle, at times, when adjusting left trim pot)
3) no sound via speaker A, get R channel on speaker B (white noise on L channel)...also smoke started from main amp l channel but can't pinpoint where (dbt didn't go bright?).
4) main filters measure ~36.5 vdc when ground to chassis (not back); 0vdc when grounded to back
5) lights working fine on front
6) ~13.5vdc to blue/violet supplies to main amp board
7) ~48.5vdc to both EQ board and preamp.
For the midpoint, both zenners (d701/702) tested fine by diode function, but I'm suspicious that these may possibly be causes for bouncing voltage?
Regarding 0v drop when grounded to back...am I possibly shorted or is this just due to negative return to filter caps from speaker terms and coupler board?
I do have continuity from black speaker terminal to ground (clear covered wire) on preamp, amp, eq.
I'll do more checking on left channel amp, but have to run for now.
Hoping you might see something that may be suspicious or worth checking.
Appreciate the input!
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Ok, so more checking has revealed no L (only white noise) from phono 1 as well. DBT flickered a litte when playing with balance on this setting.
With coupler off, I can get sound via Main In on both A and B speakers.
I had checked all transistors on the EQ and PreAmp and they checked good via diode testing. Seems like it's originating out of the PreAmp (or possibly EQ) and I will re-check soldering to see if any bridges or loose connections.
Should I be suspicious of the balance control? I did fully disassemble and clean function control and checked all components in the muting region of the preamp (all ok).
With coupler off, I can get sound via Main In on both A and B speakers.
I had checked all transistors on the EQ and PreAmp and they checked good via diode testing. Seems like it's originating out of the PreAmp (or possibly EQ) and I will re-check soldering to see if any bridges or loose connections.
Should I be suspicious of the balance control? I did fully disassemble and clean function control and checked all components in the muting region of the preamp (all ok).