{Collins} 6146B Neutralization technique



I've searched the archives but found no direct reference to the following
question (no, this is not about the difference between 6146 tubes). |:>)

Background:
1. RE 32S-3, 6146Bs, late edition neutralization circuit.
2. V6, a 6AH6 RF amplifier, let go after maybe 20 years of service (damn
inconsiderate piece of junk) (btw, that was a joke.)
3. Replaced V6 with a NOS GE 6AH6 (only good for another 20 years)
4. Placed the unit back into service and all works well.
5. Upon tuning, noticed that the 6146Bs were slightly out of neutralization,
i.e. the dip did not coincide with max power out. No problemo, an easy fix
and this may have been the condition for some while.

I opened the 32S-3 manual and found what appears to be a rather complex set
of hoops to jump through just to neutralize the finals. Other than the PA
tubes being slightly out, the transmitter works, and has worked, very well.
Again, the only tube replaced was V6.

Question:
I've neutralized a lot of tube finals in Drake and other radios (even those
with 6146B tubes). The technique I used was to adjust the variable
neutralization capacitor (C71 in this case) a very small increment at a
time, until max power out and dip in PA current coincide... while, of
course, keeping a much reduced RF drive, allowing for ample cool down
periods, and dumping the power into a non-reactive dummy load.

Since my first tenet of bench repair is to "Do no harm, first and always," I
am reluctant to use my "time honored technique" without first consulting the
group. I am quite experienced working safely around live HV circuits. I can
usually neutralize a set of finals in under 10 minutes while the repair
technique described in the manual would take the better part of an hour or
more and involve "surgery" that may cause other problems. The transmitter
does not require a full alignment as power and performance on all bands is
quite good.

Your opinions? Can I use my time honored method to neutralize the PA tubes?

It is with great humility that I say how much I thoroughly enjoy reading
your post and following your sage advice and experience. Collectively, Art
would be proud of the way the group has banded together to keep these
magnificent old rigs glowing and going.

Best regards;
Gene

W5DDW
Gene McCalmont
CCA Member
Argyle Texas
gmcalmo@xxxxxxxxxxxx


Sponsored by the Collins Collectors Association http://www.collinsradio.org
Nets: Tues: 3.805 Mc-2000 Central / Thur: 3.875 Mc-2000 Central
Fri: 3.895 Mc-2000 Pacific / Sun: 14.263 Mc-2000 UTC
1st Wed (of the month) AM Net 3.880 Mc-2000 local (ET, CT, MT, PT)
Sun AM Net: 29.050 Mc-1200 Central






This archive was generated by a fusion of Pipermail (Mailman edition) and MHonArc.