[Drake] TR-4 S-Meter sensitivity help

[Dick KF4NS]

Yes Bill, I have the same situation. I did the same testing. It seems that mine gets worse with time. 
This is just the opposite of what is bugging me with my Heathkit HW-100, it is so bad that I get S-9 +40 
with the cal and most readable signals are S-9 plus.

Let me know if you get any ideas from the crew. Good  luck.

73, Dick KF4NS
St Petersburg, FL 33714 USA
Keep The Glow!


----- Original Message ----- 
Message: 1
Date: Wed, 26 Sep 2012 11:58:33 -0400
From: Bill Abate <wabate at verizon.net>
Subject: [Drake] TR-4 S-Meter sensitivity help
To: Drake <Drake at mailman.qth.net>
Message-ID: <50632629.6010607 at verizon.net>
Content-Type: text/plain; charset=us-ascii; format=flowed

Hi all, After months of the rig sitting idle, I decided to
tackle the S-meter circuit again.  The rig is a TR-4CW, SN
44XXX.  When I first got the rig a few years back, I aligned
it and fixed a few minor problems.  The rig was working
fine.  Sensitivity was about .5 uv for 10 db on 40M.  S-9
was about 140 uv.  Cal produced about 20/9.

About a year ago the s-meter suddenly went stingy.  Cal only
produced about S-8 on 40M.  A check with the sig gen showed
the sensitivity was OK.  Went into the circuitry and checked
V11, V12, V15, V4 and V17.  I could not find any components
out of spec and tube substitution did not help.

The sensitivity pot is at max sensitivity and it takes 1000
uv to get S-9.  RF sensitivity is slightly lower at 1 uv for
10 db.  Anybody been down this road before?  Any suggestions?

Thanks,

Bill, K3PGB