[R-390] Smoke got out

[Barry]

Do you have a way to connect just the filament supply through an ammeter (e.g. pull the plug and connect just the filament pin)?  You could pull all (or, at least, the pertinent) tubes and see if anything's drawing current without them.  If so, then go from there; else, plug the tubes back in, one-by-one, watching the ammeter.  That might help isolate the problem.

Thanks,
Barry - N4BUQ

----- Original Message -----
> From: "dog" <agfa at hughes.net>
> To: R-390 at mailman.qth.net
> Sent: Wednesday, August 1, 2018 2:13:27 PM
> Subject: [R-390] Smoke got out
> 
> The wire to P108-B comes from P112-20, the connector to the IF strip.
> That pin also has several other B/W wires on it including a heavy gauge
> B/W wire that comes right from the PS 6.3V. Only the wire to P108-B is
> burned, so it will be easy to replace right in the harness.
> 
> Actually that 6.3V on those RF tubes is all connected one after the
> other in series from P108B and the last tube on the burned string is
> V205. It must be there somewhere and it's really tight in there. There's
> still no sign of a short though, that tube measures 3.3Ω cold. The 5814
> for the calib osc buffer.
> 
> I didn't have any #20 stranded wire so I ordered some mil spec Teflon
> wire for a few bucks.
> 
> I'll measure that tube alone in the other RF module I have.
> 
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