[R-390] Variac Startup for Stored R390

[Jim Whartenby]

JacquesThis assumes that the R-390 is stock and has not been repaired with aluminum electrolytics.  Looking in the manuals for stock "electrolytic" we find:
TM 11-5820-357-35P (R390NonA): C231 and C612 are both Tantalum electrolytic caps.  C103 is listed as oil filled paper but the schematic shows polarity markings, curious. 
TM 11 5820-358-34P (R-390A): C603, C606 and C609 are electrolytic caps.  C603 and C606 are aluminum electrolytics, C609 is Tantalum.
There is no telling what the "dreaded" previous owner has done.  With the ongoing stuffing the old components with new, there is no telling what is hidden.  Not to mention the circuit "improvements."Regards,Jim

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

    On Monday, June 3, 2024 at 02:07:34 PM CDT, Jacques Fortin <jacques.f at videotron.ca> wrote:   

 Jim, Jerry,

There is no electrolytic capacitors in the power supply of a R-390 (non-A).
Put a voltmeter in the B+ test point of the power supply/audio module wrt to GND to monitor the regulated +180V.
If the value there stabilizes at +180 ± 2V after power on, you are good to go.
If there is too much current drawn by the + 180V line, the output of the regulator will not be able to climb up.
If there is an internal fault in the power supply circuitry, the output can go higher than 250 V.
If this happens, shut the power off and diagnose the circuit.
Last time I seen this type of problem, it was because the filament of V509 gave up.

73, Jacques, VE2JFE in Montreal