On 17/11/2015 16:03, N_Cook wrote:
Inside the amp (high voltages etc) a shard of thick aluminium foil.
Does anyone fully strip off the screening foil on the insides of the
cab, both ends of the amp, and spray with "Tempest" proofing nickel
RF/EMI spray.
Or as valve stuff anyway, just remove those sheets of aluminium foil and
how much extra noticeable hum?
Was it just to save the cost of closing the chassis, at both ends, with
expensive full thickness steel?

Hot air and the remnants of that foil soon came off.
Masked off the edges and sprayed the nickel spray on the cabinet sides.
When wet , the point contact across a diagonal , 6 or 8 inches,
30M, 20K after 1hr, 90R after 3 hr, 30R after 6hr. So hopefully by
tomorrow and distributed ground contact along 3 edges will be sufficient.
For safety reasons that foil had to go.
I suppose the
proper way round this notorious problem is, strip of the foil, depth
stopped fly cuttter, router, end mill or whatever and then full
thickness metal sheet set in the recess.