[R-390] Carrier Level Meter Issues

[Jordan Arndt]

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: <gary.biasini at shaw.ca>
To: "'Larry H'" <larry41gm at gmail.com>
Cc: "'R-390 Forum'" <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.