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 Barrell<[email protected]>
Sent: Feb 13, 2012 2:30 PM
To: Peter Ravn<[email protected]>
Cc: [email protected]
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 TR-4/C Service Supplement CDs
<www.k4oah.com>
Peter Ravn wrote:
The otherwise comprehensive R4B preselector alignment instruction does not
mention the position of
the passband selector during alignment. Should it be in the same position as
during passband tuner
alignment, i.e. with the passband selector to .4, and the passband tuning knob
to the shortest of
the curved lines on the panel. Or does it matter at all?
The manual suggests to use the S-meter when adjusting the preselector trimmers
for maximum. I find
it much better to use an VTM. Finally the idea of using alignment resistors on
S5C and S5D escapes
my understanding.
Thanks
OZ8CTH, Peter
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