Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Jason Buchanan wrote:
If you peak the RF Tune and immediately dip the PLATE control, then
"two-hand" the PLATE and LOAD controls for maximum output power,
(using an external wattmeter, holding down that meter switch button
makes it a LOT more difficult,) and then DIP the PLATE control as the
last adjustment, (which shouldn't be required if the transmitter is
properly neutralized, but should be done anyway,) finals will last
for 5-10 years of "normal" amateur use. I have a T-4XB and T-4XC
that have been running for over 10 years with the same finals. Both
are used several times a week, primarily on CW.
Sounds like it is absolutely imperative that the 6JB6's be neutralized
as best as possible. Mine aren't producing maximum output at the
bottom of the dip. When I replace T-4XB R26 I will make sure they are
neutralized as good as I can. Right now I have to rotate the plate
control a wee bit CW for max output. But the bottom of the dip vs.
max output is about a needle's width so I don't feel too bad about it.
Is it necessary to neutralize the finals at 28.500 or can I do this on
15 or 20 into a resonant antenna?
Neutralization "should" be done at 28.5, since the setting becomes more
critical at higher frequencies. I usually neutralize first on 15M for
this reason, the setting is easier to spot, then only a tiny touch-up is
necessary on 10M. If you don't have a dummy load (you REALLY should!)
you can do it on 15. Just try and "center" the adjustment as accurately
as you can.
By the way, a small fan on the receiver certainly won't hurt
anything, (as long as it is quiet!,) but as noted above, three units
ran 24/7 for 8-9 years with no fans, and NO failures. I turn my
receivers on in the morning, and turn them off when I am through for
the day. I have known guys who turn their receiver off when they
leave the room for lunch!! NOT a recipe for long life of electronic
equipment.
When my parents bought the B line I have now I used to turn it on and
leave it on for days (no drift!), plus it looked cool hi. I did that
for years until I was out of high school and they were shut off for 15
years until I got married, bought a house and put an antenna up at the
new QTH. I remember reading somewhere that a day's worth of useful
filament life is consumed by simply turning the rig on, so I leave
them on unless I know i'm not going to use them for another 24 hours.
Most of the tubes in this B line are the same ones that it came with
from the factory in 1971. I replaced the 6EH5 because it started
sounding nasty but I suspect that it's actually the filter cap.
I noticed the other day that there is a mustard yellow Sprague ATOM
electrolytic can tied from the R-4B power supply board to chassis
ground, and I noticed there is a guy selling these exact parts on an
auction site listed as a fix for faulty electrolytics - does this
sound familiar? I was thinking about replacing the R-4B filter can
with the kit from WA9TGT but i'm wondering what kind of work I need to
"un-do" to use this cap replacement kit.....
The electrolytic (the ones I have seen are "aluminum" colored) that is
between the chassis and the PS board is the filter for the calibrator
power supply. It's 1000 uF at 15V, positive end to the chassis. I have
only seen a couple of these fail, going high in ESR and supplying some
interesting modulation to the calibrator signal. I think Donnie's kit
is just the four section Twist-Lok cap. There are a couple of other
electrolytics, the 8 uF at 150V on the PS board, and another 200 uF at
6V on the Calibrator board itself.
--
73, Garey - K4OAH
Atlanta
Drake C-Line Service Manual
<http://www.k4oah.com>
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