Hoping to fix food dehydrator

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Joined Aug 27, 2020
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I have a NESCO FD1040 food dehydrator, which functioned quite well when it worked, but the electronic components appear to be very cheap and it burned out after a couple of years. As a first try to get it working again, I replaced the thermal fuse, and sure enough it ran again, but then stopped again after a couple of hours. It seemed to be running very hot and probably blew the thermal fuse again. I started to wonder if its thermostat went bad.

It has a simple digital control panel, with temperature control. The manufacturer refuses to sell parts, or even provide a description of what the parts are. But I noticed the part in the attached image, which has a five-pin connector at one end that plugs into the control panel, and a small circuit board at the other end that was positioned down in the compartment with the heating element. I wondered if it is the thermostat, and if so, where such a thing might be purchased as a replacement. Perhaps it's a long shot to find an equivalent part that would be compatible with the control panel of this particular device, but worth a try.

This dehydrator seems to maintain its temperature by constantly switching the heating element on and off, which seems like a dumb design. But it's hard to find a competing product that works as well and doesn't also get endless numbers of complaints.
 

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Joined Aug 27, 2020
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On further research, it seems that the small black box with 8 pins on the circuit board is an IC temperature sensor, and those are easy to find online. But the whole assembly of sensor, board, cable, and connector seems difficult to find. I am not sure what terminology to use in searching. Perhaps these things are much too specialized to be sold off the shelf, and making one from parts would be a daunting task for the non-expert, but any advice is appreciated.
 

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Joined Aug 27, 2020
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I noticed this part, which seems to function the same way as the one in my dead dehydrator, but has only four pins instead of five, and aside from that, hard to tell if it would be compatible with the control unit of the dehydrator.
 

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Joined Aug 27, 2020
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The item in the photo is not really a replacement board, just the closest thing I could find for sale online. The thermal sensor chip on the original part is labeled MCP9801M. If I found a replacement board with that exact chip and five pins, would it have a chance of working?
 

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sghioto

Joined Dec 31, 2017
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If I found a replacement board with that exact chip and five pins, would it have a chance of working?
Probably your only chance (assuming it's defective) as that chip is digital and the other analog.

EDIT: That chip is still available, could you try replacing it?
SG
 
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Dodgydave

Joined Jun 22, 2012
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The item in the photo is not really a replacement board, just the closest thing I could find for sale online. The thermal sensor chip on the original part is labeled MCP9801M. If I found a replacement board with that exact chip and five pins, would it have a chance of working?

It's a Digital temperature sensor by Microchip..using a I2C data bus.

https://www.microchip.com/wwwproducts/en/MCP9801#:~:text=The MCP9801 is a digital,C to +125°C.&text=The MCP9801 notifies the host,a user programmed set point.
 

sghioto

Joined Dec 31, 2017
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If you have the equipment I would re-solder the pins on the chip. Pin #7, second from the top on the right, looks suspicious.
SG
 

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Joined Aug 27, 2020
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I don't have equipment to solder at such a small scale. The board appears to have corrosion in lots of places, so it's hard to tell why it doesn't work -- maybe the chip is fine and something else failed. My only hope would be to find the chip already mounted on a board with a five-pin connector. I was hoping someone might know what such a part would be called or where to find it, but perhaps it is not standard enough to be found. (The chip by itself is easy to find.) Even if boards existed with these chips, they might not be sufficiently standard to plug-and-play anyhow.
 
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