[time-nuts] Restoring GR 1120-AB Frequency Standard - Need

[Max Robinson]

The same thermostat was used in the GR 1113-A which I have one of.  That may 
lead you to another source for a replacement.

Regards.

Max.  K 4 O D S.

Email: max at maxsmusicplace.com

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----- Original Message ----- 
From: <wa3frp at aol.com>
To: <time-nuts at febo.com>
Cc: <holrum at hotmail.com>
Sent: Tuesday, August 19, 2008 4:55 PM
Subject: Re: [time-nuts] Restoring GR 1120-AB Frequency Standard - Need


> Sorry for missing enough detail on the original thermoswitch.
>
> The original thermoswitch was a unique design that I have not seen
> elsewhere.  The Princo thermoswitch was a modified mercury thermometer
> with two electrodes installed.  When the temperature rises, the column
> of mercury comes into contact with both electrodes and completes the
> electric circuit.  The inner oven stays within  +/-0.05 degree C of 78C.
>
> Since the design involved a mercury thermometer, the form factor is
> 0.25 by 4.25 inches.
>
>
>
>
> -----Original Message-----
> From: Mark Sims <holrum at hotmail.com>
> To: time-nuts at febo.com
> Sent: Tue, 19 Aug 2008 1:54 pm
> Subject: [time-nuts] Restoring GR 1120-AB Frequency Standard - Need
>
>
>
> The original thermoswitch sounds like is is a mechanical switch,  so it
> can't be
> all that accurate or stable.
>
> I would use something like one of those TO-92 temperature sensor chips.
> I would
> probably use a 8 pin micro with an A/D to read it and drive a reed
> relay (or
> transistor).  Analog people would use a comparator and voltage
> reference
> chip/pot.
> ----------------------------------------
>
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