[Premium-Rx] Racal 6778C - Diagnostic/Fault

[Dan Rae]

Paul/Julie wrote:
> Attempting to identify cause/board that is responsible for a "Fault" 
> Display on the front panel, and DS-3 a small red LED to light on the 
> top edge of the third main board from the front of the receiver, and 
> has the board number A08356. I am seeking a manual, to help diagnose 
> the problem, but so far not successful. The other symptom is above 
> 17.999 MHz, the fault light goes on and the audio basically 
> disappears. However, the frequency continues to count up and down as 
> the tuning dial is rotated. Below 18.0  MHz, the receiver performs 
> correctly and all fault lights are off.
> I would appreciate any assistance, that might be available from the group.
>  

Paul, If you can't get a manual from Gary Wingerd,  who left Racal 
Maryland with their entire stock of paper manuals,  I don't know where 
you will find one.

Try gewingerd at netzero.net

If that doesn't work then try Toronto Surplus, since most of those were 
sold to Canada.

The receiver you have there is a mixture of RF boards from the 1772 
series and the cpu stuff from the 6790/GM.  The 6778A and B in fact were 
the first iteration of the A8 series microprocessor control for a 
receiver from Racal.  The C version used a single CPU card, the one from 
the 6790/GM in fact.

The fault light is presumably for the main loop synthesiser being out of 
lock.  Since that card has three separate VCOs in it, at least in the 
177* series, I suspect that the one that should operate from 18 MHz up 
to 29.999 is not working. 

This is about the only Racal receiver that I don't have here so I can't 
help you further...

Dan

ac6ao / g3ncr