uBITX finals get hot very fast #ubitx #ubitx-help #v5


Rob French (KC4UPR)
 

I've got a new uBITX v5.  I've only been using it for CW so far (haven't gotten around to wiring up the mic yet), but I've noticed that, after calling CQ a half dozen times, the finals get way hot... too hot to hold my finger on for more than a second or so.  

As far as I can tell, my antenna is good to go... according to my antenna analyzer, < 2:1 SWR across 40 meters, which is where I'm using it currently.  I guess I could try doing the same thing into a dummy load to verify that it's not due to an SWR problem.  

Other than loading the KD8CEC firmware and making some firmware configuration settings, I have not deviated from the stock configuration--same finals, same heatsinks, no change to PA bias settings.  

I'm assuming this is not normal.  Any thoughts on resolution?  I'm using a metal case that doesn't quite let me mount the board close enough to back to bolt the finals to the back panel, but I've thought of making a hole in the back panel to accomodate bolting on a larger heatsink.  But I'm also thinking that there may be bigger underlying problem that I address, regardless of whether or not I add a bigger heatsink, fan, etc.

Things I'm thinking I should do:
- Recreate my CQ calling into a dummy load, see how hot they got (does anyone have any metrics for key-down time versus temperature?)
- Measure the current draw on transmit, and/or perform the PA bias calibration from the HF Signals web site
- Build one of those LED SWR meters to back-up my antenna analyzer
- Any other thoughts?

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