Monroe electromechanical calculators

[Jim Beacon]

----- Original Message -----
From: "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
To: <cctalk at classiccmp.org>
Sent: Friday, June 17, 2005 12:49 PM
Subject: Re: Monroe electromechanical calculators


> > > There's some earth leakage which would be useful to track down -
> > > possibly a break-down in cable insulation? I've not worked out what
the
> >
> > Most of the time, that's due to tracking across the impregnated fibre
> > insulators used in things like the automatic on/off swtich.
>
> Aha, well I can isolate and test easy enough there without any severe
> dismantling of things. Can anything be done to fix the problem (short of
> making new insulators)?

I have had some success on Tektronix 'scope switches. I soak the sitch wafer
in de-greaser (I've used the RS aerosol version), changing the solution a
couple of times, then I allow the switch to air dry, before lubricating it
SPARINGLY with contact lubricant, and a suitable grease for the mechanical
detent and bush.

The other thing to check is the filter capacitors on the motor and mains
input - the can be temporarily disconnected for a quick check (but if you
leave them off, the neighbours will complain -TV and radio wiped out for
about 200yds!)

> > Almost certainly a governor. Do not be tempted to bypass it, many of
> > these machines used series wound motors which will get up to a
ridiculous
> > speed if not controlled and do considerable damage.
>
> Yep, I saw somewhere that 180rpm is typical for governed motor speed...

If the governor is similar to the type used on Creed teleprinters, then make
sure that the contacts are properly cleaned and burnished - they have a
tendency to "hook" and make a permanent contact, allowing the motor to
overspeed.

Jim.