2017-11-28 Royal 500 And 3.5mm Phone Jack

I finally got around to spending some time online to search for a replacement jack for the corroded one in the Zenith Royal 500 I’m working on (#473430).  I had to destroy the jack to get the nut off, the whole jack was green.  The hole was so corroded the plug wouldn’t fit.  I ordered jacks from Arrow.  They are Switchcraft 35PM2A and cost about 3 dollars US each.  

I poured straight white vinegar into a squirt bottle and squirted it around the jack and battery terminals.  I didn’t see it bubble or foam.  So I sprayed some cheap imitation CLR on the same places and nothing much seemed to happen after tens of minutes.  I squirted water on it to wash off the chemicals and dried it with a paper towel.  I should remove the whole battery holder and soak it in the vinegar to neutralize the battery juice.  But I’m concerned that the vinegar might dissolve the corrosion on the battery connections and they might crumble, and have to be replaced.  Also the copper wires might be corroded inside or on the ends.

The jack’s ground lug served as a terminal for connecting the leads of two electrolytic capacitors, but I replaced them with tiny ones that fit on the trace side of the PC board.  The jack’s ground lug will be free to be used just for the ground wire and wire from the output transformer.

Bigger problems

I have been handling the chassis a lot while working on it.  I finally got it back together and connected power but I got nothing.  I traced it down to the driver transformer primary which was open.  My expert analysis (heh) found that the transformer’s primary side had two leads coming out.  But one of those was on the top of the transformer.  So they left a length of wire long enough to reach to the hole in the PCB.  The other lead came out the bottom and is the only lead supporting that side of the transformer.  The transformer is close to the edge.  As the chassis is handled, the forces on the transformer push on that single lead, and the lead moves vertically and laterally, and the movement tears the very fine primary wire loose, causing the open.  The transformer is built so that it’s very difficult to repair the break.  The solution is to replace it.

I believe the best way to prevent this is to squirt some hot glue under that side of the driver transformer so that it can’t move.  Also, avoid handling the chassis anywhere near that transformer.

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