[Drake] TR4C BAL MOD

[WQ9E at btsnetworks.net]

Dick,

The idea is to get enough current above the base idle amount so that you can properly peak T-14.  
The reason for .15 amp (150 mils) is that it is a level that will not cause excessive heating in the final or power supply during the alignment procedure but is high enough to exceed idle current.

I believe most of the 4 line was built with a 10 turn precision pot although I believe the earlier ones had a standard ~270 degree rotation but it has been several years since I have been inside my early T-4X.

You should see an increase in plate current as you unbalance the modulator and I would certainly expect a measurable increase within +/- 2.5 turns assuming it is a 10 turn precision pot.    

Is your carrier oscillator on frequency?  If it is way off then it may be far enough outside the filter passband that the attenuation is pretty much complete.

Rodger WQ9E

----------------------------------------
From: "Dick KF4NS" <kf4nsradio at verizon.net>
Sent: Monday, November 15, 2010 2:34 PM
To: "DrakeRadio list" <DrakeRadio at yahoogroups.com>,	<drake at mailman.qth.net>
Subject: [Drake] TR4C BAL MOD 

Still puting the finishing touches on the ole rig and was using 
Garey's great CD for reference while determining the real condition of 
the filters. That completed (one is bad), then I proceeded to check 
the adjustment of the BAL MOD for proper CXR BAL as per the section 5 
steps for alignment.

Right off the diving board I got twisted around. It says to adjust the 
bias according to the earlier steps in para 5-6 which says adjust for 
.1A, now key the rig in X-CW and if the plate current exceeds .15A 
adjust RF TUNE for .15 and if it is less than .15A adjust the CXR BAL 
pot for .15A , what is the deal with this ".15A" ?

Why do that after setting the bias for 1.0A at the beginning? I tried 
to adjust the pot and it does nothing. How critical should the reading 
be while adjusting the pot? How many turns are there to this pot?

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

______________________________________________________________
Drake mailing list
Home: http://mailman.qth.net/mailman/listinfo/drake
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Drake at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html