[R-390] The R-390A Mechanical Fillter ‘killer’ cap C553

[David Wise]

Since my C553 is hermetically sealed, rather than remove it, I inserted a current limiter.  It's extremely simple, just a high-voltage depletion-mode MOSFET: the Microchip (nee Supertex) LND150.  Drain towards positive, source+gate towards negative.  If the cap ever lets go, the FET limits the current to Idss, i.e. 1 to 2 mA.

Dave Wise
________________________________
From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> on behalf of Larry H <address removed>
Sent: Sunday, May 5, 2024 4:40 AM
To: R-390 Forum <r-390 at mailman.qth.net>
Subject: [R-390] The R-390A Mechanical Fillter ‘killer’ cap C553

Hi all,  I just updated my document (R-390 Newbie Support Info) on our
website with a new paragraph at the end called:  Replace the R-390A
Mechanical Filter ‘killer’ cap C553.  This is something that all folks new
to the R-390A should know.  Here's a link to the document: R390 Newbie
Support Info <https://www.r-390a.net/R390%20Newbie%20Support%20Info.pdf>

Regards, Larry
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