Problem with Yaesu FP-757GX power supply

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Sep 1, 2012
I've been having some difficulties getting my Yaesu FT-757GX radio working. My latest problem seems to be an issue with the power supply. I had successfully setup the system and made a few contacts on 80m. Then, I decided to try my hand at some CW on 10m. In the middle of a transmission (just a second or two in to the transmission) the whole rig just up and died. I turned everything off, turned it back on and everything worked again. I went back to 80m to confirm everything was working, and it seemed OK. I then tried 10m again, and in the middle of my transmission (within a few seconds), it died again. This time, turning it off and on didn't fix the problem. I checked the back of the power supply, and sure enough, the fuse had blown. Fair enough, that's what fuses are for (though I'm not sure why it blew). I replaced the fuse. Then, before I connected the power supply back to the radio, I turned the power supply on, just to make sure it would power up. The front LED didn't light, then a moment later a puff of smoke appeared at the back just near where the AC feeds in. Needless to say, I turned it off.

Am I doing something wrong? How did it blow out when I wasn't even drawing any current? Could I have been overloading the power supply by setting the drive too high? Wouldn't the fuse protect against this? I really don't know what to make of the situation, but I'd appreciate any suggestions.




Dec 4, 2006
A fuse would normally handle things I would think. But, they can do nothing about something giving up the ghost inside that power supply (bad part?). It sounds like that power supply was over stressed by the current draw using CW. That makes me think that the power supply wasn't 'big enough' to start with, or, it had internal problems that just reached their limits.
I would think that your best bet would be to have that power supply looked at by a competent tech. I would have to 'lift the hood' to see for my self. The problem may be very evident, and you might be able to repair/replace it. But, it's still a good idea to have someone else do that if you aren't comfortable with electronics repair. (Me either!)
Good luck.
- 'Doc
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