Adrian -
Just a guess, but is your counter sensitive enough to measure the 8.05
MHz signal, it's only about 0.1V p-p. It's unlikely that the oscillator
is wandering that much if it's running at all. Are you sure you're not
in AM mode? The BFO has to be ON. It's also possible that your counter
has a low impedance input and is loading the oscillator down too much.
32 MHz output in the 28 MHz position indicates an unlocked VCO. The
first thing to check is the +24V DC supply line. If this voltage is
low, the VCOs will lock on the lower bands in it's range, i.e., 21 MHz,
but not the higher, 28 MHz band. If this voltage is low, check the core
on DC-DC converter on the Power Supply board to be sure it's present,
and tight.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs
<www.k4oah.com>
Adrian Rees wrote:
Hello all
I am trying to re-align my TR7. So far I have followed the Service Manual
and am now trying to align the 8.05MHz Oscillator. (Section 3-5 in the
Service Manual).
I can't seem to measure a stable output on pin 40. It seems to be wandering
around between 2 and 7 MHz. Additionaly on the 28MHz setting the display is
showing 32MHz, which I guess is the VCO.
Should I fault find the VCO problem first or the 8.05MHz Oscillator. Any
help gratefully received !
Thanks
Adrian MW1LCR
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