uBitx V3 low power continues

Ted
 

This is a follow-up to another thread that is months old. I'm now recovering from cervical spine surgery & attendant complications of infection, so I've had time to repeat tests though not necessarily any clearer mind. Having only 15-20 degrees of rotation of my neck isn't helping, either, with bench work.

To review: a perfectly-functioning radio with typical RF out levels (12w out in 80, 10w in 40, 8w on 20, etc) has devolved to less than a watt on CW on all bands and even less on SSB. The exception is 20 meters, where a couple of watts in CW show up.

Let us assume the finals are fine and that all drivers and pre-drivers are OK. They all get warm, in fact. Suggestions were made to trace the RF thru the LPF array to ensure power wasn't being eaten by a stuck relay or bad filter. I think that this possibility has been eliminated, though I can't explain why the finals get warm and yet the output generally stinks AND worse on one mode than on another.

Again, the SSB signal is far below the CW/dead carrier level, perhaps it is 25-30% of carrier level (according to my oscillscope).  Output at the antenna connection shows approximately the same level as measured at the final transistors.

What dies, prior to Q90, that kills SSB and CW as described?   My sledge hammer works just fine and requires little skill to operate - and at this point makes a better communication tool than my uBitx. I'm not allowed to pick up 15 lbs, though, so that option is on standby. I just don't get it. 


Thanks,

Ted   K3RTA

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