[Collins] R-388 second mixer weirdness

[EA2IG]

Hi Craig.
Perhaps a bad contact on the socket of the 6BE6
Good lack
Pedro EA2IG

----- Original Message ----- 
From: "Craig Roberts" <crgrbrts at verizon.net>
To: "Collins Mail List" <collins at mailman.qth.net>; "Collins" 
<collins at listserve.com>
Sent: Monday, December 05, 2005 6:49 PM
Subject: [Collins] R-388 second mixer weirdness


> Here's a baffling problem that's been plaguing me for months.  It's one of 
> those "every time I think it's fixed, it comes back" weirdnesses:
>
> After my R-388 has been playing for awhile (anywhere from a couple of 
> hours to a couple of days), the sensitivity drops off dramatically. 
> Replacing the second mixer tube (V-106 -- a 6BE6) solves the problem.  The 
> strange thing is, the tube doesn't have to be a new one.  It can be a used 
> one, a JAN tube, a civilian tube, or even a tube that's been used in the 
> same position before -- as long as it's different than the one currently 
> employed.  This sounds heat related, but V-106 doesn't get unduly warm and 
> the priblem may not show up for many, many hours and -- 
> apparently -- the tube's not being destroyed.  Voltages seem okay.
>
> Upon the advice of an old Collins factory tech, I replaced all the 100 pf 
> micas in the set -- but still...
> Anyone else run into this?
>
> Thanks and 73,
>
> Craig
>
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