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Thunderbolt AC/DC Sabotage, and, Your Predictions Please

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  • Thunderbolt AC/DC Sabotage, and, Your Predictions Please

    Late 70s era TB AC/DC. When I removed the cover, I could see someone had pulled out one of the fan motor wires, and, instead of a dirty plastic fan atop the fan motor, there was only a tiny elliptical remnant of plastic. Someone has broken off the blades, and removed all the debris from inside the cabinet. Expecting the lack of fan cooling to cause an increase in heat somewhere, I carefully examined the transformer coils, and after some sweat and effort, I was able to locate an area of heat build up. The lower transformer had previously been soldered/brazed by a blind man, and the soldered connection to the coil underneath the glass tape had broken.

    Oddly, nothing else inside the cabinet appears to have been tampered with. This guy just hated fan noise I guess, or, wanted to send a message to the future.

    I have two questions:

    1) IF there is enough of a stub of square coil wire under the tape, would a mechanical connection be better than a soldered/brazed connection? I can make a square hole in a copper round, with compression screws that could couple the two ends.

    2) I have not yet tested the four tube diodes. It does not appear flames have shot from them. So, I wonder what the experts here predict: Are the diodes necessarily fried from the 'non-fan', or, even though the heat fried the coil, did the diodes escape injury?



  • #2
    I dont have enough welder repair experience to make a prediction on the diodes, but I would guess that an overheat hot enough to melt the solder connection may have melted the varnish on some of the transformer windings also. I would solder it with a big enough iron/gun to get in, solder it, and get out without overheating the varnish around the joint. The mechanical approach sounds second-best to me but be careful not to nick adjacent turns' varnish. Watch for overheating with the cover off so you can see that area when you put it in service. Just my two cents worth. Maybe someone with more welder fixing experience will chime in. Pix are too small to see, and resolution is too low to see if you zoom them up.


    • #3
      Aeronca-Thanks for your info.

      I did not realize that the photos on this forum were as useless as they are. I am figuring out how to get them to a photo sharing site, so they can be enlarged, not reduced. Come on Miller, experts think with their eyes too!