[R-390] Rebuilding a R-390A IF Deck

[rbethman]

Ken,

I would highly recommend replacing the old paper capacitors.

The next step I'd do, would be to clean the switch contacts and tube 
sockets.

However, in lieu of running around replacing resistors, I'd give a crack 
at performing an alignment.

You may well find that the resistors, while not necessarily meeting 
specified values, will be adequate to allow the circuits on the IF Deck 
to function within range of alignment.

I'd only go into replacing resistors after attempting the above.  It has 
worked for me with an old R-390A IF deck from a Collins branded module.  
I have been able to leave almost all the resistors in place.

My two cents worth.

Bob - N0DGN

On 9/10/2011 11:57 PM, Ken Harpur wrote:
> Good Evening List, I have started restoring one of my R-390As....so 
> far I've rebuilt the Audio Deck and have now turned my attention to 
> the IF Deck and I was wondering what the general thoughts are on the 
> list as to resistor and capacitor replacement. I have Cornell-Dublier 
> silvered Micas and SBE 716 series going in and have a full set of 
> resistors arriving from Mouser. Obviously all the paper caps are going 
> to be replaced and the Micas are sometimes problematic so my idea was 
> to go ahead and replace all the caps with the long term view of never 
> having to worry about them again. My conundrum is with the 
> resistors...I measured every one and about 40% of them are on, about, 
> or just over 10% of their marked value so I figured I'd go ahead and 
> replace those ones..apart from those that were at the edge of their 
> tolerance when new my way of thinking is that they will just go even 
> more out of spec over time. But what about the ones that are still 
> well within their 10% tolerance? Is it reasonable to assume that if 
> they haven't drifted out of spec by now they probably never will? Or 
> do you guys think that in time they could be candidates for 
> trouble/replacement if left alone? Any advice, thoughts or tips would 
> be greatly appreciated as I want to make sure I do it right the first 
> time! Best Regards, Ken