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MEXICOWANDERER's avatar
MEXICOWANDERER
Explorer
Aug 15, 2016

Megawatt Dissection & Notes

This is "Jim In Denver's" unit.

Circuit board fuse found to be "good"
One 330 uf cap has a domed top. My ESR tester located far far away.
Bridge rectifier tested good
Bi-polar transistors: One shorted. One open. 2-remaining tested questionable

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Quality of electrolytic caps could be better. Low ESR Panasonic caps will replace. Will try for 330v rather than 200 volt if they'll fit.

TI and ON both make same-case higher rated bi-polar transistors. I'll replace Q-1 for drill as well.

Heat sinking needs help. Thinner, better thermal rated sil-pad material. Silver instead of zinc-oxide thermal paste.

Fan vent as usual is a joke. Will chop out the slots and open things up and replace with a wire fan guard.

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Don't know how I managed to run out of solder-sucking braid. This is not the place to run out of anything.


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UNRELATED. Found 15-amp board fuse of 55 amp Whiffie blown. That's a lot of wattage. Unless some techhie forum member comes forth and says "Hey that's not unusual!" I am tempted to not waste 5-minutes of time troubleshooting the unit. The Schizophrenic Design is not worth repair. This is an older unit.
  • MEXICOWANDERER's avatar
    MEXICOWANDERER
    Explorer
    Aug 15, 2016
    Grumble snarf. I was tempted to purchase some marine AC breakers on sale a couple of months ago. Melted ice-cream, now.

    Finding -anything- in this dust bowl burg is impossible. No cartridge 120-240 volts fuses of any kind. A breaker? Yeah. Buy a square D duplex box and breaker. Thirty dollars.

    But your response halted me from doing a sneering Hannibal Lectur on the Whiffie. I'm angry enough at myself for not buying several feet of de-soldering braid when I was north. But I checked a couple of years ago and Radio Shed demanded six bucks for eight feet of braid. And it was gar-bagh grade.

    A 15-amp is a pretty hefty element fuse. I've seen 3-5-7.5- and 10 amp fuses open because of age but a 15 is new to me. I left the Whiffie cooling it's heels at 13.20 volts when I went north several weeks ago. Came back to a 12.49 Lifeline (LED meters, and other assorted bleed loads).

    I might try a 25 gauge (solid wire, unloaded), as a fusible link. If it smokes then the game is over. Shouldn't blow with no-load inrush (I hope). Man the vents and fans!
  • westend's avatar
    westend
    Explorer
    Aug 15, 2016
    Following along.

    Mex, I now have to recycle broken electronics or spare stuff that I've found. Sure put something across the Whiffie's fuse contacts and power it up. May have been an output connected event that took it down. Stranger things have happened.
    If it doesn't come back to life, recycle it. Maybe chop out some innards for Grandkid education. I have to limit myself on electronics acquisition. Otherwise I become overwhelmed with storing the stuff. I still have three laser cutter power supplies sitting in a storage trailer.

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