Garey, that' sinteresting about the different slug colors. I seem to remember
seeing reference to that and had completely forgotten about that.
With respect to setting the pointers, I have discovered, in my disassembly of
these rigs, that if your pointer is off (on all bands) from where it should
be that you can carefully move it on the shaft. The keyword is carefully -
after all, the only way you'll get a replacement is from a donor rig!
I've found that if I peak on 20CW, the pointer should be at the bottom of the
20 zone. I use 20m as the starting point only because it's somewhere in the
middle of the preselector's range and the sensitivity of peaking adjustments
are about midrange as well.
Of course, if everything else is off, check elsewhere first. I always run the
rigs through a quick evaluation before I start changing or replacing anything :)
73,
Steve, W1ES/4
-Original Message-
From: Garey Barrell k4...@mindspring.com
Sent: Feb 13, 2012 5:03 PM
To: Steve Wedge w1es1...@earthlink.net
Cc: drakelist@zerobeat.net
Subject: Re: [Drakelist] R4B preselector alignment
Steve -
One exception. The R-4 had different slug heights, and a different alignment
procedure. Other than
that, all slugs should be at the same height. There is no reason for the
relationship to change
over time, so as long as the glyptol is unbroken, leave 'em alone.
The other situation is the slug height specified for the various 'colors'
described in the T-4XC
manuals. Over time, the length of the slugs received from the manufacturer
changed, shifting where
they were in the coil in relation to the top of the form. They were color
coded with paint on top
of the slugs, around the spring shaft. I don't know what percentage of each
'color' (length) were
used, but I've seen very few with color dots. Again, you should just run the
RF TUNE to maximum
clockwise and check the measurement from the top of the coil to the top of the
coil form. If it is
one of the three measurements in the manual, leave the slugs alone and align
to the appropriate
dimensions for that color. Essentially, the trick is to have the RF TUNE
control cover the entire
range from 1.8 to 30 MHz, and have the pointer to be somewhere in the selected
BAND segment of the
dial. If your unit won't cover the entire range, then you might want to try
starting with another
'colors' dimension.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
www.k4oah.com
Steve Wedge wrote:
I've found the same thing with respect to using the detuning resistor - it
hasn't really made anything easier or more accurate for me. I suppose, when
they were building and testing these sets that it shaved a few minutes off
the technician's test time - which is significant for production testing
but less so when you're the owner.
The other thing I learned long ago - after speaking with a Drake tech on the
phone probably 25 years ago - was that the absolute height of the slugs is
less important (as Garey mentioned) and there should almost NEVER be any
reason to change the individual slug heights in the rack. If nobody has
messed with them over the years, they should all be in the same positions
they were in when the set left the factory. I find the easiest way to see
if someone has been fiddling is to adjust the preselector so that all the
front slug is level with the cardboard tube top. All the other slugs should
also be level with their tube tops. If you see a discrepancy, look to see
if it looks like the glyptol (the substance that keeps them from moving) has
been disturbed.
Other than that, just peak them and be done. 80 is quite sharp and 10 is
quite broad, with everything else somewhere in between.
73,
Steve, W1ES/4
-Original Message-
From: Garey Barrellk4...@mindspring.com
Sent: Feb 13, 2012 2:30 PM
To: Peter Ravnfas...@privat.dk
Cc: drakelist@zerobeat.net
Subject: Re: [Drakelist] R4B preselector alignment
Peter -
The setting of the Passband tuner is not significant when doing the
Preselector alignment. All
you're looking for is an amplitude peak. Sometimes the Calibrator signal
is too strong, especially
on the low bands, driving the AVC too far and making it difficult to see
the peak as you tune.
Alternate Calibrator signals vary in strength, so you can pick a lower one
on either side (+/- 25
kHz). You can also put a smaller resistor on the ANT jack to reduce the
level. Use FAST AVC to
better see the peak.
The resistive loads are to spoil the Q of either T3 and T4 while tuning the
other to minimize
interaction of the adjustments. I have found that it really isn't
necessary, that you can do just
as good an alignment by going through 3-4 iterations of the adjustments
without the loads, as the
interaction refines out.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and
