[R-390] Broken Line Input Wire in R390?

[Jim Whartenby]

R-391 repair, https://www.youtube.com/watch?v=pr8pXFtA_IU  at about the 12 minute point.
Perhaps an better method then using a torch to open FL101 is to use a hot plate to bring the soldered seam to the melting point and then use a soldering iron to heat the joint above the reflow point and to help remove the cover.  Hopefully, the paint will not blister or burn.Jim

Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy

-----Original Message-----
From: Barry <n4buq at knology.net>
To: R-390 Mailing List <r-390 at mailman.qth.net>
Sent: Mon, Oct 17, 2022 1:13 pm
Subject: [R-390] Broken Line Input Wire in R390?

As I've mentioned, I was observing "chattering" of the antenna relay when in STANDBY mode and, thinking the problem was likely the selenium rectifier on it's way out, I replaced it with a silicon bridge.  Something I hadn't mentioned, though, was when the relay was chattering, the dial lamps were flickering seeming in time to the chattering.  I chalked that up to both possibly being the old rectifier but in retrospect, I'm wondering if the root of the problem was really something else.

When I started testing the new silicon bridge, I noticed the STANDBY lamp flickering was still present; however, it only lasted a very short time at which point I lost all power.  I've traced what I think is a broken wire that runs from the internal connection on the "A" side of FL101 to P118-1 (no continuity between those two points).  Furthermore, the A side of the line input filter is also showing a very high resistance from the A input to the A output and I'm thinking that the chattering/flickering was actually a rapidly intermittent short in the wire from FL101 to P119-1 which has now opened completely and, probably, took out the inductor of the A side of FL101 with it.

If this is the case, then I'm a bit surprised that a wire as large as that would have developed a fracture (stress or otherwise) or some other type of short and am wondering if I'm missing something.  As far as I can tell, that wire goes directly from FL101 to P118 through a large cable but until I can pull FL101, the PTO, and the mounting bracket, I'm not sure I can get a clear picture of that cable.

Anyone have this sort of issue before and can elaborate on it?  If it is a broken wire in that cable, that's going to be a "fun" job patching it (but only for very small values of "fun").

Thanks,
Barry - N4BUQ
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