W076/M452 replacement cards

From: vrs <vrs_at_msn.com>
Date: Mon Dec 1 17:40:26 2003

> Sorry about the delay...I'm afraid its 100ma, apparently there is
> a R/C network across the relay, I go a reading of 196 ohms
> (close enough to 200 ohms to call it that). This may be a
> 'fast acting' relay of higher ohmage, but the circuit might be
> designed for a worst case of character by character control.
>
> I'm afraid it's back to the drawing board.....

That is just weird. According to my calculations, DEC's circuit applies
15.7V across this relay and it's series resistor, with at most 57ma before
the components exceed their ratings. 15V/200 ohms = 75ma, so the circuit
can't work like that

I was expecting *at least* 300 ohms for the relay and it's series resistor.
Did you measure at the relay, or at the cable?

Assuming what you say is true, the 0.7V supply will be drug below ground,
and the whole circuit will draw 20V/350 ohms = 57.1ma. That puts the
components right at their operational limits, but might actually be the way
things work.

    Vince
Received on Mon Dec 01 2003 - 17:40:26 GMT