I used Harvest Maid FD-1000 dehydrators.
They have very accurate electronic temperature control, +/- 1 C mesured by a
DVM with a thermal probe at the middle rack of my ones.
The scale of the t control is not accurate, but t control itself is good
enough for tapes baking.
G e n n L a b
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Tel: +64 21 238 3056
----- Original Message -----
From: "John Gledhill" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Sunday, May 31, 2015 8:42 AM
Subject: Re: [ARSCLIST] Baking tapes on plastic reels ?
> food dehydrator
> 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.
> Solution -
> 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
> heater coil.
> 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.
> John Gledhill
> BIT WORKS Inc.
> 905 881 2733
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