[R-390] More "Must Replace" Caps

[chuck.rippel at cox.net]

With the IF deck upside down and the bandwidth and BFO shafts facing 
you, C529 is a .033 ufd capacitor mounted right hand forward, on the 
side of the IF deck chassis right behind V504 on stand-off's.  This cap 
bypasses the screen of V504 and with screen voltage on one side and 
ground on another, is a prime candidate for leakage.

Add this to your "must replace" list using a .033 600VDC tubular.  While 
"you're there," also replace C528 mounted just above it with .1ufd @ 400 
or 600V.  Its the cathode bypass cap for the same tube.  Be VERY CAREFUL 
not to overheat or break the now brittle stand-offs.

You folks whose radio I am either working on or will work on, will have 
this done "automatically."

If you're in the RF deck, make sure you have a 100pf, 600V or better 
yet, 1KV ceramic disc on hand to replace (always) C327, across the 
primary of T207.  After replacement, be sure to re-tune T207.  Just had 
an e-mail exchange with an owner experiencing low 1st oscillator output. 
Named several possibilities but have seen C327 fail before.  Its been on 
my rather large list of "must replace" caps for some time.  Again, if 
I'm doing your radio or have worked on it in the last 10 years, that cap 
has been replaced.


A question to the group.  Anyone have documentation on how to tune T401 
on the 2nd xtal oscillator deck?  I've never found any documentation on 
that.  Got a few ideas on how that MIGHT work but nothing firm.  Its 
interactive with all the ceramic caps used to peak the individual xtal 
outputs.   Its my GUESS those caps are pre-set to a certain capacitance 
then the coil is peaked, perhaps at the lowest fundamental xtal 
frequency then the caps for each band(s) are subsequently peaked. 
That's not gospel, I've not tried it, don't turn your radio into a brick 
by experimenting.  Lets try and find out.

Chuck Rippel