I used an Excalibur food dehydrator for video tapes.
The temperature setting on the control is next to meaningless as it uses
a bi-metal strip to regulator the temperature. In steady state the
temperature would easily swing over a range of 25 degrees and not about
the nominal setting.
1) I used a DVM with a thermal probe ($25) and monitored the temperature
under a tape at the center rack.
2) Added a light dimmer (SCR -controlled and cheap ) in series with the
3) Turn the oven temperature to the high end of the temperature I
wanted, as a fail safe, and then slowly raised the power with the light
dimmer checking every 15 min in order to get the desired temp. If the
original bi-metal strip triggers, then raise the original oven
temperature controller setting a bit.
The overall goal here is to use the light dimmer to reduce power to the
heater coil to that you get to the desired temperature with NO thermal
cycling at all.
Using this simple approach I could maintain a target temperature within
2 degrees. This is predicated on the ambient temperature being
controlled - (air conditioner).
The set point the light dimmer changes with the amount of material in
the oven as more material retards air flow and raises the temperature.
1) the input air to the oven was the output of a separate
de-humidifier. - not essential.
2) You have to be willing to wire up a light dimmer and take stuff apart.
3) fresh chives are better than dehydrated chives.
On 5/30/2015 3:32 PM, Richard L. Hess wrote:
> On 2015-05-30 1:42 PM, John Chester wrote:
>> I note that all those who report no damage to plastic reels are
>> maintaining good control of baking temperature. My nominal baking
>> temperature is 53 degrees C, and I am very careful to never exceed 55
>> degrees C.
> Yes, I think that is key. The food dehydrator never goes above 55
> degrees C. Tapes will survive a higher baking temperature as my early
> uncontrolled experiments showed (and they bake up faster that way), but
> we don't know what other damage occurs, so it's best to follow the
> recipe in the Ampex patent with the only modification the extension of
> time as we've discussed here many times.
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