[R-390] Update on R390A, open question regarding scope and options fir lubrication

[David Wise]

ERRATA TIME!

In Figure 6-21, the annotations for C327 and C328 are swapped.  C328 is a 5nF ceramic disk bypass, while C327 is 100pF mica forming a tuned circuit.

Jacques, did you typo?  Figure 6-21 is on page 6-59, not 6-47, at least in my file which says Revision 10, 2006-March-17.

Dave Wise
________________________________
From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> on behalf of Barry <n4buq at knology.net>
Sent: Friday, June 28, 2024 1:07 PM
To: Jacques Fortin <jacques.f at videotron.ca>
Cc: R-390 Mailing List <r-390 at mailman.qth.net>
Subject: Re: [R-390] Update on R390A, open question regarding scope and options fir lubrication

I just opened the Y2K-R3 document and on page 6-47,  Figure 6-21 shows a picture of C327 which appears to be a ceramic disc.  Is that a mistake in the Y2K documentation?  Apologies if this has already been discussed but I found it odd in light of all this recent conversation regarding C327.

Thanks,
Barry - N4BUQ

> John, unless that you are equipped to test the Micamold cap with 300Vdc applied
> (their manufacturing voltage rating) to confirm that they have less than 10nA
> of leakage, wait for the new manufacture 1kV one.
>
> I believe that the recommendation to change C327 was made because of the trouble
> involved with the RF deck removal to change any of the parts within.
> Since then, many original mica caps inside the IF transformers were reported to
> fail (the thunderstorm noise problem).
> But here also, they will not ALL exhibit failures, as this is just a
> probability.
> Failure of the early type "postage stamp" mica caps is essentially due to their
> long-term casing permeability.
> Some mica caps were made to never fail, like the Corning Glass Works (CGW) ones
> that have a glass encapsulation.
> But as with any electronic equipment ever made, all depended on the cost vs
> reliability criteria.
>
> 73, Jacques, VE2JFE in Montreal
>
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