[Premium-Rx] Watkins Johnson DRO-333 reprogramming

[Ray Robinson]

Hi Gang,

The early WJ and CEI receivers had analog tuning and analog dials.
A later option was a 19" rack mounted digital readout,
called the DRO-333.
It used the local oscillator of the receiver 
then added the IF offset,
to give a digital readout of the received frequency.
These are fixed.
It works fine on my RS-111, 
and gives accuarate readings from 30 mhz to 1000 mhz.

I have looked at the counter board,
and there are 4 modules which look like large SIP resistors,
and each has 2 coloured dots on it,
like a resistor colour code.
They are arranged in 6 rows.
I therefore deduce that there are 6 offsets,
that preload the 4 counter ICs.
They are selected by the front panel switch,
and the rear toggle switch.
I have measured one module,
and it appears to be 4 diodes connected to a common,
and this is used to program the decimal counter.

Does anyone know if this reasoning is correct?
or has anyone reprogrammed one before?
or does anyone have a circuit or manual.

Regards
Ray vk22no