# Burroughs parts?

Tony Duell ard at p850ug1.demon.co.uk
Tue Aug 21 14:23:46 CDT 2007

```>
> >Date: Sun, 19 Aug 2007 23:53:02 -0400
> >From: "Roy J. Tellason" <rtellason at verizon.net>
> >Subject: Burroughs parts?
>
> >I have some of the following parts,  maybe you guys can help me ID this stuff?
>
> >-- Several tubes of what appear to be resistor packs,  branded "Beckman" and
> >bearing the part number 1899-258-0,  not found under Beckman anywhere
>
> Shouldn't be too hard to figure out with an ohmmeter... ;-)

It's slightly harder if the resistors are not either indidual pin-pin, or
n resistors with one common pin, or a resistor chain with pins at all the
tappings.

If you assume the resistors link pins (although there may be 'deltas' and
other parallel paths in the network), you can actually solve it by taking
2 sets of measurments :

1) Resistance between each pin an all the other pins shorted together.

2) Measuring the output voltage, using the network as a portential
divider. Link all but 2 pins together (and call that ground), apply a
known voltage to one of the 'free' pins and measure the voltage on the
other 'free' pin. Repeat for all combinations.

Now, if you consider 2 pins a and b with a resistor Rab between them and
an effective restor of Rbg between pin b and all the other pins (not
including a and b) shorted togther (this will be all the 'other'
resistors connected to pin b in parallel), then:

Fro mthe first set of measurements, you get the resistance from pin b to
all other pins shorted. THis is Rab // Rbg (since you've conencted pin a
to the common point too)

>From the second set of measurements, with power on a and output on b, you
get Vout = Vin * (Rbg / (Rab + Rbg)).

Solve those for Rab, and repeat.

I did this once for a resistor array in an HP printer....

-tony

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