In message <19980314202033.AAA7609@[205.231.11.91]>, Rich Measures
<measures@vc.net> writes
>The circuit shown in Figure 1 at:
>www.vcnet.com/measures
>is simple, uses a pair of inrush resistors so that it works on 120v and
>240v, and can be powered by the AL-80's 12vdc (?) supply. The timing
>element is the hv supply filter capacitors. When the caps. are 2/3
>charged, the relay closes. For an AL-80 a pair of 7w c. 25 ohm resistors
>should work satisfactorily.
>later, Jack
>
>cheers
>Rich...
You might consider using current limiting resistors with a higher
resistance and power rating, especially where you have a separate HV
transformer. If there is a fault which draws high primary current and
stops the HV output rising to the value that shorts out the resistors,
they sit there with most of your line voltage across them until they go
bang. I guess it's more difficult with a single transformer as you need
to let the auxilliary supplies build up to operate the relay.
Having suffered once, I now use a fixed timer which gives a few seconds
delay - if there's a fault then the line fuse blows.
Steve G8GSQ
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