[R-390] R390A RF deck advice

Roger Ruszkowski flowertime01 at wmconnect.com
Sun Jan 11 00:49:14 EST 2015


Nelson,
 
There is a lot of good stuff in the Pearls.
Over the years us fellows have been through most of the problems and
hashed the topics over pretty good. So the answers are in the Pearls some where as we have been there
and done that all at least once. 
 
There are reasons to leave the oven heaters on as you found in the Pearls.
 
If you feel your solder skills are up to it then jump in and replace some parts as you see fit.
You have taken the measurements and have reason to change parts.
Your just not into it because you feel it needs to be done.
 
If your slugs come from fair radio, I think the guys there would have gotten you the right parts.

We just do not know every bit of electronic and part engineering property.
So we get to just use our best judgment.

Keep working on the receiver and get it back in use.

Enjoy.

Roger AI4NI
 
 
-----Original Message-----
From: ngietz <ngietz at mymts.net>
To: r-390 <r-390 at mailman.qth.net>
Sent: Sat, Jan 10, 2015 10:58 pm
Subject: [R-390] R390A RF deck advice


Guys, I’ve been reading your comments with great interest.
Roger makes a fair point about considering my skill level, since I’m new in this 
group.
FWIW, I’ve been soldering in old radios for more decades than I want to count.  
On this
R390A, I’ve been through the resistors and caps on the AF and IF decks so far, 
and have 
dismantled, cleaned lubed, reassembled and synced the gear train.

I’m no EE or mathematician, but some online research about the parasitic 
suppressor 
resistors suggests that (at least in audio circuits, and I don’t see why that 
wouldn’t apply 
to HF circuits) if the resistor values are too high they can roll off the gain 
on the higher 
frequencies where good gain might be most needed.  In view of that and after all 
the 
other work done, it would be a waste not to finish the job, and replace the 
over-value 
suppressor resistors.  I have no idea whether carbon comp resistors get quieter 
with age.

Re the brass-screw RF slugs; I’ll do what I probably should have done in the 
first place and 
check with Fair Radio on whether these are indeed correct.  No big deal to 
reorder if it gets
this radio up to or near spec.

As far as disconnecting the heater of HR202, my reading of the “RF Deck 
Electric” section of 
W. Lei’s “Pearls” leads me to think it’s not a good idea after all, considering 
the crystals are 
cut to run on frequency with the heater operational.  When I was running the 
receiver before
the RF deck overhaul began, the thermostat seemed to be “tinking” off and on 
just fine. I
guess I was just surprised at how warm to the touch HR202 was.

So, those are my conclusions so far.
Thanks for your observations.
Nelson
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