[R-390] R391 Audio Deck Question

[g4gjl at btopenworld.com]

Thanks for the information, Don.

 Ill put the cap on the to do list. I notice a few or the resistors in there are outside 20% so Ill have a session this week and replace them whilst the module is out.

I have yet to locate the actual fault which is pulling the HT down, the reason for the initial investigation :o(

Pete




________________________________
 From: Don Heywood <wc4g at knology.net>
To: g4gjl at btopenworld.com; R-390 at mailman.qth.net 
Sent: Tuesday, 1 January 2013, 16:33
Subject: Re: [R-390] R391 Audio Deck Question
 
Hello Pete, you are correct, the addition of C612 (8uf cap) was added by MOD 2 to the AF Deck. It is mounted on the opposite side of the board across R608.
When I go through an R390 audio/regulator deck I am sure to replace/add this cap, I use a 10uf 25Vdc or so electrolytic.
Happy New Year.
Don WC4G
Charleston, SC

-----Original Message----- From: g4gjl at btopenworld.com
Sent: Tuesday, January 01, 2013 8:26 AM
To: R-390 at mailman.qth.net
Subject: [R-390] R391 Audio Deck Question

Im investigating why my R391 has gone dead, so I pulled out the audio / power deck...

In looking around I noticed one of the liquid / acid tantalums decoupling the cathode of V603 (6AK6). I need to replace this cap as it has all but disintegrated (obviously this is not the fault Im looking for, just colateral observation) however I cant find reference to this cap in the R391 manual.

This is a Collins manufactured deck bearing dated components no later than 1955. It is COL serial No 203, FWIW.


Was this cap a later addition? Is it part of MOD2 by any chance? The deck is stamped thus.

Comments appreciated, chaps, and by the way Happy New Year to you all.

Pete
G4GJL
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