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

[jkharvie]

Jacques,
I will wait and install the newcapacitor and give this a try.  I will also keep the old unit if it isneeded.  I will look to see how the performance curves look for the new and old capacitors.  
Measuring down to 10nA is not acurrent capability (no pun intended).  >From the information you areproviding, it sounds like the "older style mica caps within the IFtransformers that are not the newer Micamold style should be replaced with theMicamold style or a new high Q mica cap. I will review each of the internal components to assess what type ofcapacitor is located within each unit.  I extend a thank you for sharing thisrather interesting information, as it helps advance my understanding of care forthis receiver.  This RF sub chassis is from TeledyneSystems Corporation, serial 7099 within a receiver by Imperial Electronics, Serial2901.
73John N3JKE






    On Friday, June 28, 2024, 4:07:34 PM EDT, Barry <n4buq at knology.net> wrote:   

 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
> 
> ______________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:R-390 at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html