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TRC-457 no output

Posted: Thursday 15th Oct 2015, 7:37
by smokinone
I have a TRC-457 that has no output on SSB or AM. Heres what I've done so far,

all new electrolytic caps including power supply.
new relay which I can hear clicking and evidently it does send the voltage to the collectors of the finals.
new C179
new upgraded voltage regulator TR25
new berquest insulators for all transistors
tested the 1306 and 1307, they show good, but low gain on the Sencore TF46.
aligned the synthesizer PLL circuit
I was able to set the bias on the 1306 and 1307
the PA works

Still nothing out to the antenna.
I show audio on the collectors of both the 1306 and 1307 output transistors with a scope.

Sure would appreciate any help. I keep thinking the finals are bad, even if they show good for some reason. replacements seem hard to find.

Re: TRC-457 no output

Posted: Friday 16th Oct 2015, 14:55
by smokinone
Seems I have 7.5V at the collectors of both the 1306 and the 1307 in AM and 13.8 on SSB on Xmit..The base does show the correct 0.64 on both finals...I show audio on the scope at the antenna output, and on the SAMS circuitrace at points 125, 126 and 123.
TR45, FET2 and FET6 all show good.

I received 2 new 1306 and 1307 transistors today and they show the same values on the Sencore TF46 transistor checker as far as gain, with no leakage so I assume the finals that are presently in the 457 are good.

I don't think I mentioned that the receive is very good on this radio, and I have cleaned all the pots and channel selector etc. with DoxIT.