Re: [Amps] SAFETY WITH HIGH VOLTAGE

[R.Measures <r@somis.org>]

On Aug 22, 2004, at 11:58 PM, peter.chadwick@Zarlink.Com wrote:

> I'd agree that the 53 ohm one sounds suspiciously low: I suppose it's
> possible it arced from turn to turn and fused that way. can you see
> anything wrong with it on a visual inspection?

- - I would autopsy the 53-ohm resistor with a 2oz ball-peen hammer to 
see whether is was a mis-marked 50-ohm unit or one that had an 
end-to-end carbon path.

> The usual reason for open
> circuits in wirewounds is, I was told by a manufacturer,  frequently
> corrosion where the coating has a pinhole.
>
> These days, I use two bleeders in parallel, and even then, I don't 
> trust
> them!

- - High-resistance wirewound resistors are seemingly one of the most 
unreliable type of resistors made.    This is why I am using MOF 
resistors wherever possible in the current amplifier project.  For 
example, the anode-supply's electrolytic filter-C equalizer resistors 
are 22, 100k-ohm, 3w MOF resistors.  The (1500v) screen-supply will use 
4 of the same resistors  However, the screen-supply shunt-I resistor 
(protects against revere screen-I) will be a 50k-ohm, 100w, wirewound 
unit.
cheerz, Peter.
>
Richard L. Measures, AG6K, 805.386.3734.  www.somis.org

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