Blue"palomar"skipper 2 transistor amplifier Low output

[jtrouter]

So i have a blue"palomar" skipper 2 transistor amp that is very low on output.
Starting on low.med,high to max it goes from 10w to 20,30,40 and max out about 50w.
When testing it SWR was good and it did not get unusually hot, and both transistors got warm.
At first i thought maybe one of the two transistors went bad but my thought is that if one went bad
then they both would not have been warm? Is that correct? I do not see anything that looks burnt
or damaged. As this is the way i got it i do not know the history of what may have happened before.
So I would like to know if anyone can see anything that looks bad they i might have missed and or
what should i be checking to figure out how to fix or troubleshoot to find the problem(s)?
Thank you for your thoughts.

 

[nomadradio]

When only one transistor goes bad, you usually get about a quarter of the normal output power. Not half, but closer to one-fourth.

Not every transistor fails in the exact same way, so your mileage may vary.

73

 

[kc8mob]

This amp runs 2879s. Toshibas at that!

The transistors are most likely fine. The base 10 ohms are good and if by chance one final shorted in the rare method, leaving the 10 ohm smoke resistor as they're known ok, then it would have put 13Vdc on the bases and that would destroy the 2nd final and you'd get no output at all.

So. You should check the input tune of the amplifier and also make sure you are seeing 12Vdc at the finals or output transformer under load.

Might try removing the fuse and running it I'm and out of the socket. Or really bypass the crappy automotive fuse all together. It won't ever protect the finals just cause a voltage drop under best conditions.

And finally. Do you have a big enough power supply to run the amp?

It'll draw every bit of 25 amps when running full tilt.

Crappy solder joints in various places would cause you trouble like this. Like the output tuning etc.

It is wave bath soldered save for the finals.

 

[DoctorAudio]

Check the value of the silver mica cap across the output transformer. It's probably gotten hot and dropped substantially in value.