[Milsurplus] R-390 hints

[David Olean]

Wow, I received at least three valuable tips on fixing up the 
receiver.   I have some pretty good contact cleaner and lube but it is 
not DE OXIT. I'll get some DE Oxit and compare it along with the WALMART 
offering.   I was not aware of the R-390 archives on QTH.net wither. 
Thanks!!   The syringe idea is pretty good too, and I see that you can 
get DeOxit in several forms, not all are in a spray can.

I tried washing the crystal switch with contact cleaner and it has 
gotten much better..almost great, and with more use will probably clear 
up entirely. I have DeOxit on order!

Thanks for all the input. The receiver is coming along just fine. At the 
moment, I have the PTO out and am getting ready to attempt to fix the 
end point adjustment. It is off by 7 kHz, which seems like a lot, but 
this is an early Collins R-390 from the original order I think!  Old 
ferrite was not so good I suspect.  I spent a bunch of time aligning the 
entire radio, starting with the IF strip. I was impressed with the 
ultimate sensitivity of the 455 kHz stages. Some of the RF bands needed 
an alignment badly. Others not so much. I have not done an MDS 
measurement yet, but I can tell it is now a hot receiver.  A -73 dBm 
(S-9) signal shows as 55 dB or more on the signal meter. A 1 uv signal 
at the input raises the diode load voltage by about 7 volts.

If I get the PTO perking accurately, I will have a winner for sure. 
Thanks for all the tips.

Dave K1WHS

On 10/7/2019 2:08 PM, KD7JYK DM09 wrote:
> "I used a small syringe with de-oxit to get to the contacts."
>
> I've recently discovered, and been using QD Plastic/Sensor Safe 
> Electric Contact cleaner, from WalMart, in a red can, to hose down 
> things I can't easily get to, without any ill affects.  Initially, I 
> was nervous, because I've destroyed, or melted far too many things 
> over the decades, but I have yet to find anything this damages, other 
> than grease, dirt, dust, grime, et cetera.  I've used this product 
> dozens of times, over several years, on wiring harnesses, motors, 
> circuit boards, bearings, plastic connectors of many, many types, 
> plastic case, screens, paints, things you usually wouldn't want to 
> expose to much more than just air, with no problems at all. It's 
> something to take into consideration.  I would NOT, personally, try 
> soaking an item, I'm sure everything has a failure point, but to 
> blast, and hose out, I've yet to see an issue.
>
> Kurt
>
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