Troy Peterson via GreenKeys wrote:
> Does anyone know where I can find a replacement? I did a
> cursory search of my usual (UK) component suppliers and 850 ohm
> doesn't even seem to be a common value, let alone available in high
> power. I'm not sure what the power rating of this resistor is, or
> really even what kind of resistor it is...
According to the wiring diagram, that 183081 printed on it is the
Teletype part number. I would ask Paul at RTTY Electronics
(mr_rtty@pacbell.net, he's on this list) if he has that part number,
since you say you'd like things to remain original.
Keep in mind tha thet wires don't have to carry a large current if
they are carrying a large voltage! Many current loop devices in
Teletype circuits may drop a small number of mA over a large voltage,
which is a significant amount of power. I don't actually know what
the valid range of voltages for a 20 mA current loop is (I'd be
interested to know, in fact), but for a 60 mA current loop it's quite
likely to drop 60 mA at 120 V or more, which is over 7 watts -- but
can be easily carried on 30 gauge wire (or even smaller!).
I doubt the precise resistance is critical here, although a different
resistance may entail (for example) adjustments to the current source.
It looks like you need to chase down the schematic for the board
that's on (the wiring diagram I checked just shows the resistor wired
to "Board Assembly Reader Power Pack", part 183087) and see what it's
doing. Wire wound resistors are often relatively precise, so I could
be wrong.
Ethan
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