[Milsurplus] Fwd: Re: VRC-12 continued

[Bruce Gentry]

-------- Forwarded Message --------
Subject: 	Re: [Milsurplus] VRC-12 continued
Date: 	Mon, 12 Dec 2016 15:07:37 -0500
From: 	Bruce Gentry <ka2ivy at verizon.net>
To: 	Ray Fantini <RAFANTINI at salisbury.edu>



Contacts get dirty in many ways. If a connector of any kind is never 
disturbed, airborne dirt, not corrosion, can get slowly work it's way  
between  contact surfaces and cause poor contact. Vibration and 
temperature excursions cause this to happen quicker. This problem is 
especially bad with relay and switch contacts that simply touch and 
don't wipe.  It was a constant problem with circuit boards in elevator 
door operators and controllers, even when all the contacts were gold 
plated. Wiping the contact surfaces clean with or without cleaning 
solvent, then re-seating the boards and connectors gave immediate good 
results. In the RT-246/524 PA, if the screen ring got cruddy there is no 
telling what could happen. It's unlikely the band switches or condensors 
in  the PA were responsible because they are a wiping contact and will 
make good contact unless terribly cruddy or corroded. RT-246s are cool 
to repair and see and hear the servo operating, and they are good 
performers too.

         Bruce Gentry, KA2IVY




On 12/12/16 2:39 PM, Ray Fantini wrote:
>
> Over the weekend had the opportunity to pull the 6100/6200 power 
> amplifier from the RT-246 and removed the ten thousand little screws 
> that secure the cover over the PA tube and its base. Everything looks 
> very clean and did not see any issues but decided to clean the band 
> switch S6202 and removed the 7843 PA tube but was not able to find any 
> reason for the power dropping off. Did change the orientation of the 
> PA tube being that’s easy with those coaxial power tubes and after 
> reassembly the radio puts out full power now. Go figure. Maybe it was 
> a dirty PA band selector but it looked as clean as if it were new. I 
> have had issues with this radio before with the band switch in the 
> receiver front end needing to be disassembled and cleaned so maybe 
> it’s just the nature of these contacts that after years of not being 
> used they oxidize or something. Lot like the problems that I have had 
> with DC servo motors in radios like the GRC-106 sticking and needing 
> just that little bit of attention to get them working again. If the 
> problem reoccurs will be changing the PA tube for another and see if 
> that fixes it.
>
> Ray F/KA3EKH
>
>
>
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