[Racal] RA117 faults

[Dan Rae]

Ed greetings,

 The fault that your South African e-mail describes could be just about 
anything...  Hard to diagnose exactly what is wrong from what just 
sounds like a severe lack of sensitivity.

But having recently re-built two RA17s, an -L and a -C12, one of the 
first things I found necessary was to replace *all* the Hunts paper 
capacitors in both, some of which were leaking a noxious dark brown oily 
substance.  Assuming then that you have a good set of valves / tubes, 
the other thing to check is the Rs.  A lot of those will have gone high 
in varying degrees, usually the ones that have been hot, carrying 
current.  Only last would I check the alignment and if  necessary 
attempt that; without adequate test gear it's hard, nay impossible, to 
get the 40 and 37.5 Mc/s filters right.  I had another one a while back 
where some of the silver mica caps in these filters had disintegrated; 
for some reason they can become very fragile with age.  Luckily I had a 
good stock of 39pF ones!

The other things to check on the older RA17s are the wiring in the 
hotter areas near the power supply;  the PVC insulation gets hard and 
brittle with age.  If the three big wire wound Resistors have not been 
replaced with metal clad ones, heat sunk to the chassis, it's probably 
worth doing that also.  This was done usually when they were serviced or 
reconditioned.

There's an on line manual for the RA117 somewhere; probably BAMA.

73 Dan
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