[Amps] Drake L-4B PSU burned resistor

[Ian White G/GM3SEK]

Steve Thompson wrote:
>
>
>R. Measures wrote:
>>
>
>>> Vishay do a 'bolt down' 50W resistor which lists:
>>> Dielectric strength 3500V rms
>>> Limiting ekement voltage 1285V rms
>>> Maximum overload voltage 2500V rms
>>
>>
>> Sounds adequate to me for typical Ham amps.   However, my experience
>> with bolt down resistors is that they act not unlike a double ended
>> cannon during failure.
>Yes, I've had that happen with the ones built into an extruded aluminium
>casing. The Vishay ones I was looking at are flat, with a moulded
>covering. I imagine that the resistive element is a film on ceramic,
>which is then bonded to a metal carrier. If there's any shrapnel, it's
>likely to be smaller pieces, and lower velocity.

The metal-clad resistors have a very poor voltage rating, either 
end-to-end or to ground, and they seem to get worse with heat and 
ageing. They are totally unsuitable as glitch resistors.

Also they are only available in smooth-bore.


-- 
73 from Ian G/GM3SEK
http://www.ifwtech.co.uk/g3sek