I wonder if anyone caught Paolo’s article in ER this month regarding detail differences in the R-390 and R-390A?
I think one big reason the heater strings are 25.2V in the R-390(and R-389 and -391) is that there was at least a planned DC power supply module with a dynamotor for 28 VDC operation.
Has anyone ever seen such a beast? It also explains the GRC series 4 pin input connector.
Scott V. Johnson W7SVJ/AFA6SJ
Sunburst Engineering
5111 E. Sharon Dr.
Scottsdale, AZ 85254
M (480) 550-2358
scottjohnson1@ cox.net