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

[Ken Harpur]

Yes doing damage is my concern too...particularly with military specs regarding the 180 to 270 degree wrap of component leads and wires around terminals and on tube sockets getting those parts out cleanly without co-lateral damage is something I'm weary of...I want to enhance my radio not ruin it! Hihi.
I am using 2 watt vishay-dale metal film resistors and the original 2 watters will be upgraded to 3 watt metal films if I decide to replace them...certainly the ones that are easy to get to will probably be replaced...it's all good experience for when I eventually go through the resistors in my Non-A IF deck.
I haven't looked at the ceramic composition resistors...hmm...could be worth looking into perhaps?

Ken


On 11/09/2011, at 6:22 PM, Bernie Doran wrote:

> On any items that I have rebuilt, I always fear doing more damage getting the old ones out.    Then there is also the question of how much of the apparent change is do to other elements in the circuit. If the voltage on the tube pins are withen range, assuming good tubes, I would probably leave those along.   any resister  that has any significient power being disapated is, from I have observed, more likely to drift and perhaps should be replaced with a higher wattage.      I assume you are using all carbon composition.  I have wondered if the current ceramic composition resistors are a good replacement.   Did not get an answer from this did you ?  I am not sure there is one.  Bernie
> ----- Original Message ----- From: "Ken Harpur" <igloo99nz at yahoo.co.nz>
> To: <r-390 at mailman.qth.net>
> Sent: Saturday, September 10, 2011 11:57 PM
> Subject: [R-390] Rebuilding a R-390A IF Deck
> 
> 
>> 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
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