[R-390] Y2K Errata

[Craig Heaton]

Hello All,

The last few days I've been going over and comparing two R-390/A's. One
being a Motorola and the other a Amelco. The trouble has been located, I
think. But in the process a few items might be amiss in the Y2K manuals.

So:
#1: In section 5 on page 20, where the AF sub-chassis, voltage and
resistance diagram is shown; the LOCAL AF OUTPUT V603 pin #1 voltage should
be 0 (zero) volts, not 10 volts. Ten volts is a lot of grid voltage. IMHO

#2: Same page, V604 a 6AK6, the description should be LINE AF OUTPUT, not
LOCAL.

#3: In section 7 on page 43; this is the IF Amplifier Sub-Chassis section;
the value for C537 should be 180 pf, not 1800 pf.

The trouble with the Motorola seems to be silver migration on C532, C537, &
C546. I've pulled all three from a spare hanger queen victim and checked the
values. C537 is without a doubt 180 puffs. The Sprague TO-6A does well with
the value & insulation resistance, but it can't handle the silver migration
stuff. All else checks good; tubes, wiring, resistors, etc. The voltage
readings on V507, pins 1,2,3 & 6,7,8 are bizarre to say the least. Same with
V509 on pins 1 &2. The common item, silver mica capacitors. 

Happy Holidays,

wd8kdg
Craig