[R-390] Carrier Level Meter Issues

[gary.biasini at shaw.ca]

Larry,

How would you check cap to can leakage?  With an ohmmeter or at a higher voltage?

Thanks.

Gary

-----Original Message-----
From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> On Behalf Of Larry H
Sent: March 6, 2022 8:30 PM
To: R-390 Forum <r-390 at mailman.qth.net>
Subject: Re: [R-390] Carrier Level Meter Issues

Hi all,  There is a second type of leakage in this style of cap (cap in a can), from cap to can (which is grounded).  This is just a damaging to the agc circuit as the other normal type of leakage.  Both types of leakage need to be checked.

Regards, Larry

On Sun, Mar 6, 2022 at 9:27 AM <gary.biasini at shaw.ca> wrote:

> Renee,
>
>
>
> Thanks for your thoughts.  What do you use to heat the C551 can to 
> disassemble it?
>
>
>
> Thanks again.
>
> Gary
>
>
>
> From: Renee K6FSB <k6fsb.1 at gmail.com>
> Sent: March 6, 2022 10:16 AM
> To: Jordan Arndt <Outposter30 at shaw.ca>; gary.biasini at shaw.ca; R390A 
> List < R-390 at mailman.qth.net>
> Cc: 'R-390 Forum' <R-390 at mailman.qth.net>
> Subject: Re: [R-390] Carrier Level Meter Issues
>
>
>
> Hi All-
> I replace C551 on sight....on 16 (IIRC) IF decks I have never found 
> one that does not have leakage current ( maybe just my bad luck, 
> tested on Sencor LC102)...oil/paper....i went with mylar anywhere 
> between 1.5uf or
> 1.8 uf ( I liked these best) to 2.2uf.
> I machined small rectangular aluminum cans (with teflon feed thru for 
> the
> leads) for them to fit in the original space. and as Jordan suggests 
> the 1.5uf will fit in the original can......I drill a small hole 
> before heating to disassemble the can. I do not like hot oil everywhere......
> some of the postage stamp Micas are starting to have shorting issues 
> due to impurities, moisture intrusion and what is called silver 
> migration...so do not rule them out because they are mica.
> Renée, K6FSB
>
>
> On 3/6/22 4:25 AM, Jordan Arndt wrote:
>
> Hi again group...
>
> Any leakage of C551 will dramatically alter the AGC characteristics, 
> with the results of leakage being seen as a longer to much longer AGC 
> recovery time and a lower and "softer" AGC voltage.
>
> I rebuilt C551 in my three 390As using non-polarized 1.5uF @ 450Vdc 
> film caps which just fit inside the original square can. The result is 
> a "stiffer" AGC voltage, and a noticeably quicker return to receive 
> than with a 2uF cap.
>
> I use a restored Sprague TO-6 to detect leakage, and these film caps 
> show no measurable leakage at all, where all of the original C551 caps 
> clearly showed varying degrees of leakage. I'd expect that most, if 
> not all, of the original C551 caps are leaky by now and should be replaced/rebuilt...
>
> 73...Jordan VE6ZT
>
> ----- Original Message ----- From:  <mailto:gary.biasini at shaw.ca> < 
> gary.biasini at shaw.ca>
> To: "'Larry H'"  <mailto:larry41gm at gmail.com> <larry41gm at gmail.com>
> Cc: "'R-390 Forum'"  <mailto:R-390 at mailman.qth.net> 
> <R-390 at mailman.qth.net>
>
> Sent: Saturday, March 05, 2022 10:13 PM
> Subject: Re: [R-390] Carrier Level Meter Issues
>
>
>
>
>
> Larry,
>
>
>
> Thanks. In fact, I started on one tonight which will be the subject of 
> a separate post once I do a bit more work.
>
>
>
> I checked the manual for the IT-11 and in fact, when properly 
> calibrated, on the setting for “Paper, Mica, etc.” capacitors – i.e. 
> anything other than Electrolytic or Mini-Electrolytic capacitors, the 
> eye will not open if the leakage is more than 2 ua so, the C551 that I 
> tested leaks less than 2ua.
>
>
>
> By the way, the threshold for Mini-‘lytics is 15ua and the threshold 
> for Electrolytics is the 2ma.
>
>
>
> Thanks again for your response.
>
>
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