Hi all, been away for a while and in the process I lost my login info. Thanks to CableGuy and AuduoShockWave for getting me back up. I truly appreciate you guys.
Today we have a Mark 8 (8 Tube - 17DQ6B) amplifier on the desk. Yes, I'm now starting to do little repairs on these, although I don't know much about them and I'm supposed to stay away from high voltage (heart problems from 3 massive widow maker heart attacks). Reason being, amp guys are limited around here that will work on them. The radio gig fizzled out because everyone around here is ditching these old radios for the new surface mount rigs.
Anyway, here is the amp and details of issues.
Note: the pics have red circles around suspect and obvious damaged parts.
The issues are:
Input match was a 5 between the radio and the amp. I adjusted the air variable capacitor in the second pic and that brought the SWR down to around a 2.5 between the radio and the amp, but I can't get it any lower.
Output power is around 500w pep at first key, but gradually drops to settle at around 350w PEP after 10 seconds of holding the key with modulation.
Input power - 3w carrier, 45w PEP swing.
Above results are in high gear with super mod (SM) turned on, or off. Low gear does the same thing but with lower wattage of course.
Most of the overheated resistors in the top pic I have laying around (470 ohm, yellow, violet, brown) but the two cooked ones, left of center circled in red and one next up against the second tube on the right/bottom circled in red.
Any better eyes out here see anything else I didn't catch? Any insight on the two cooked resistors values?
What a mess right, lol ....
Today we have a Mark 8 (8 Tube - 17DQ6B) amplifier on the desk. Yes, I'm now starting to do little repairs on these, although I don't know much about them and I'm supposed to stay away from high voltage (heart problems from 3 massive widow maker heart attacks). Reason being, amp guys are limited around here that will work on them. The radio gig fizzled out because everyone around here is ditching these old radios for the new surface mount rigs.
Anyway, here is the amp and details of issues.
Note: the pics have red circles around suspect and obvious damaged parts.
The issues are:
Input match was a 5 between the radio and the amp. I adjusted the air variable capacitor in the second pic and that brought the SWR down to around a 2.5 between the radio and the amp, but I can't get it any lower.
Output power is around 500w pep at first key, but gradually drops to settle at around 350w PEP after 10 seconds of holding the key with modulation.
Input power - 3w carrier, 45w PEP swing.
Above results are in high gear with super mod (SM) turned on, or off. Low gear does the same thing but with lower wattage of course.
Most of the overheated resistors in the top pic I have laying around (470 ohm, yellow, violet, brown) but the two cooked ones, left of center circled in red and one next up against the second tube on the right/bottom circled in red.
Any better eyes out here see anything else I didn't catch? Any insight on the two cooked resistors values?
What a mess right, lol ....
