[GreenKeys] Siemens T 100 garbles when hot

[Duncan Brown]

  [resending this to the list, not just Ken]

Thanks to all who responded to my problem.

I am presently running this T 100 only in local mode, powered by a
Telefonbau U. Normalzeit 514 53/12 Telex box that came with the T 100.
There is no external connection.  When I removed one of the wires from
the selector magnet (easiest way to measure open circuit loop voltage),
I measured 20VDC between the selector magnet wire and the terminal it
came off of, which was surprising.

However, Heinz, DC4GL says that is normal.  Can anyone confirm that the
loop from the Telex box to the T 100 Selector magnet is only 20V?

When the unit is cold, it runs OK with the 20V loop.  When it is hot and
starts misprinting, the open-loop voltage  still measures 20V on a DC
scale.  But I did not measure it on an AC scale.  Perhaps a filter
capacitor is going and it is producing a lot of ripple when hot.

I forgot to mention before, the error pattern: the selector magnet is
seeing extra marks.  for example, repeated "R"s on the keyboard will
produce mostly "R", but occasionally "C" or "LTRS" . (this is easy  to
see on the punched tape).

If the problem was low loop current or voltage, I would expect to see
the opposite effect, so maybe there is some crud on the selector magnet
that gets sticky when it warms up??

I will be at the Museum tomorrow and I'll try to check on AC ripple and
clean the SM pole pieces before digging into the Telex box.

Is the SM current limiting resistor in the T 100 chassis or in the Telex
box?

Thanks,

Duncan
K2OEQ


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