[R-390] Intermittent Dial Lamps R-390A

[ToddRoberts2001 at aol.com]

Hi All,
I ran into a problem recently with  the dial lamps in an R-390A and thought 
I would pass along
a fix that seems  to work. I was looking at an R-390A for a friend that had 
a problem I haven't  seen before
with intermittent dial lamps that sometimes work, sometimes  don't. There 
was
nothing intermittent in the connections from the dial lamp  escutcheon to 
the
terminal board resistor R-124 and nothing wrong with  resistor R-124.  
There is a wht-blk colored wire that feeds 6.3V to the  resistor and gets lost 
inside a nearby wiring harness. This line reads 0  volts
when the lamps are off.

I have been looking at the chassis  wiring diagram and it looks like the 
line from
the dial lamps resistor R-124  goes directly to the power supply plug P111
terminal 10. The mainframe wiring  diagram lists that lead from the 
resistor as 27 wht-blk and it
looks like  there is a matching lead wht-blk 27 that goes to terminal 10 on
power supply  plug P111.

All the other 6.3V filaments in the radio continue to work  normally when 
the dial lamps go off and on 
so it made me think the dial  lamps must have their own separate line 
directly to the
power supply plug  P111. Terminal 10 has two wht-blk colored wires soldered 
to it.

I did  find that if I wiggled the main plug P111 that plugs into the power 
supply  module, the dial lamps
would go off and on but all the other 6.3V tube  filaments remained lit so 
that seemed to pinpoint the trouble around plug P111.  I slid the cover back 
from the plug and reheated the solder joints on terminal  10 as best I 
could with a small iron. That seemed to cure the intermittent and  the dial 
lamps stay on normally now. Perhaps there was a cold solder joint in  the plug?

73 - Todd WD4NGG