[R-390] Carrier Level Meter Issues

[Larry H]

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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