[R-390] caps redux

[Ken Harpur]

Good Morning list,

Well, I'm glad this subject was brought up again despite some of the yawns and moans from a few...it's been very informative!
It would be fair to say most of us don't have access to the kind of test equipment needed to perform definative tests on which cap is best in which parts of the radio along with how the cap in question will behave at certain frequencies...etc
So to hear from those that have done this kind of work and have years (decades) experience with R-390s and know them inside and out is about as good as it gets. 

On my first rebuild of an R-390A I used the 716P Orange Drops and Cornell Dublier Silver Micas...yes it was expensive and at the time I thought I was doing the right thing. Am I happy with the result? Not really...In spite of me working as close to the Mil Spec re termination and soldering as I possibly could, the Orange Drops look horrible in there...

So...Thanks to Charles post, the next radio on the workbench is going to get Ceramics for the bypass and 716P for coupling caps and in my mind that will give me a better than original performance as well as a tidier looking rebuild...

Kind Regards,
Ken


On 4/05/2013, at 4:07 AM, Johnsay Johnsay <groundwave at yahoo.com> wrote:

> Hi all.
> I guess I stirred up a bee hive with my original question about caps.
> What I was hoping to resolve is the suitability of metalized film caps for replacement use in this equipment.
> There has been a lot of useful information posted but I haven't seen any data that would actually correlate their use with field failures.  Reviewing the archives (pearls?) I know they have been used in quite a few cases and they do have their adherents.  
> So what I take away from this, is that I'll use film foil for C553 and C275 (I don't want to have to pull the RF deck out again any time soon).  I'll use the Panasonic PP metalized films that I have in stock for the rest.  Those would be easier to replace.  Interestingly I noticed that R525 had been very crudely replaced, probably while in govt. service due to a failure of  BB C539.  
> Thanks all....  John, W8KX
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