[Racal] MA 1101 schematics

[Frank Zürneck]

Hello to everybody

 

I recently acquired a MA 1101/A automatic preselector. I plan to operate it
with a RA 6790/GM, but for testing purposes I hooked the LO/IN to a
frequency generator covering 40-70MHz. The preselector itself is working
with four subranges. 2-4, 4-8, 8-16 and 16-30 MHz. Within the range 8-16MHz
(corresponding IF 48.455-56.455MHz) the preselector does not tune but sets
itself to wideband. The other subranges seem to work OK. Due to overlapping
(I suppose) of the subranges only the area between IF 49.900-55.400MHz is
inflicted.

My guess is that it is an electronic and not a mechanical problem (the
variable capacities turn free); I’m suspicious about the driving?
transistors on board ST77975 >RANGE LOGIC<  to not working as they are
supposed to.

I don’t have any documentation on the MA 1101/A and I did not find anything
within the net. Does somebody have schematics/documentation or can point me
to a resource? There is a male 37pin 2rows sub HD connector on the backside
which I’m eager to gain info as well.

Expenses for copying manuals etc. are covered by me.

Thank You

Frank Zuerneck