[R-390] R390 Re-cap kit

[rbethman]

Charles,

Would you be so kind to send this to Tom N0JMY?

His Email address is: n0jmy at hayseedhamfest.com

It would be greatly appreciated!

It would make the kit become VERY good!

I do know he provides solder wick in his kits.

I had the teflon tubing in my collection of parts and components, so 
never gave it a thought.

Regards,
Bob - N0DGN

On 3/2/2014 7:07 PM, Charles Steinmetz wrote:
> Bob wrote:
>
>> We will have to wait and see if he can do this kit, and if he will.
>
> If someone is going to the trouble to put together a re-cap kit, 
> PLEASE get 1kV ceramics (X7R or X7U) for all bypass capacitors, and 
> 600v film-and-foil (NOT metallized film) caps for the few coupling 
> caps (for example, genuine SBE/Vishay/Sprague Orange Drop P225 Series 
> -- but watch out for metallized film "orange dip" imposters sold by 
> some vendors).  Also use film-and-foil caps for the AGC capacitors, 
> but you don't need 600v parts there -- 100v is fine.
>
> The ceramics do the job much better than any plastic cap in bypass 
> applications, they are much easier to squeeze into the tight spaces in 
> a 390A, and they are much less expensive as well.  Some of the money 
> saved can then be invested in getting high-quality film-and-foil caps 
> for the non-bypass applications without the total cost getting out of 
> hand.  And the radios so equipped will have the best parts available 
> for each spot.
>
> A kit should also come with 10 feet of teflon (and only teflon) 
> spaghetti tubing to fit the capacitor leads.
>
> All that said, I am generally NOT a fan of replacing capacitors 
> shotgun-style in a 390A.  I have looked after several hundred of them 
> in my day, and am still in touch with the owners of many of them.  
> With a few rare exceptions (notably, radios that had been underwater 
> for a time or were otherwise badly abused, and a very few that seem to 
> have been built with a bad batch of caps), the 390A does not seem to 
> suffer from serial capacitor failure.  So, I believe the best approach 
> is to replace the few known troublesome caps and then just run the 
> radio.  If you have two or three cap failures within a few years, then 
> you might conclude that you have one of the rare, failure-prone 
> exceptions and consider wholesale replacement.
>
> The above does not apply to the electrolytic filter caps, IMO -- at 
> the first sign of trouble, I'd replace all of them with brand new, 
> high-reliability, high-temperature aluminum electrolytics. At this 
> point (2014), the best commonly available (in the US) high-voltage 
> aluminum electrolytic caps seem to be the United Chemi-Con "KJX" 
> series.  For low-voltage applications (<= 50v), the United Chemi-Con 
> "EKZM" series seem to be the best.  Mouser has both, as most of the 
> major parts distributors probably also do.
>
> In brief response to those who may ask, "Why not shotgun the caps -- 
> there's nothing wrong with improving the radio, is there?":  To change 
> the caps in a 390A, you are working in very tight quarters, and some 
> of the caps are attached to standoff terminals that are quite fragile 
> and hard to obtain these days.  It is almost certain that a person 
> with average electronic construction/repair skills will burn a bunch 
> of wires with the soldering iron and break a few standoffs in the 
> process of replacing all of the caps in a 390A, as well as knacker a 
> few other things along the way.  "If it ain't broke, don't fix it" is 
> a valuable piece of advice taught by those with lots of experience.
>
> Best regards,
>
> Charles