Maytag M7DH65B2A Dehumidifier - No power-up

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Old 05-13-12, 09:39 PM
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Maytag M7DH65B2A Dehumidifier - No power-up

I've had this dehumidifier for a few years and suddenly one day it stopped working entirely. It does not power up at all - no lights, no nothing.

I've taken the case off and for the most part nothing looks out of the ordinary. The circuit board looks 100% normal. The only thing I noticed was that the lower right corner of the case, where it's vented (in front of the condenser), the case shows a bit of melting.

Any thoughts on how to diagnose further? I have the benefit of having another one of these to use for diagnostic purposes, but I'm a bit afraid to randomly toss in good parts and risk frying them.
 
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Old 05-14-12, 07:46 PM
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i would check to see if you are getting power to the board/transformer.... I have not serviced these units, so I don't know what to look for.
 
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Old 05-15-12, 06:48 AM
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Thanks for the input - I realize it's difficult when you don't have specific experience with a given appliance. There are several connectors coming in to the system board - thoughts on how to determine which one(s) I should be seeing 120V on? Or, thinking as I type, I imagine it should be something less than 120V if it's going through a transformer first, yes?

Do these things typically have a fuse? That would be the easy thing to check first, but on my first scan I didn't find one.
 
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Old 05-15-12, 06:54 AM
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I don't think there's any fuse on it. Were you able to get a reading for power up to the board/transformer?
 
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Old 05-15-12, 07:38 AM
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I haven't checked for voltage yet. Here's a couple pics for reference. I'm guessing that the red wires carry 120V over to the transformer and the white wires bring it back as 10.8V.
 
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Old 05-15-12, 09:22 AM
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Not sure what wire is what.. follow the power cord, that will be your 120v to the transformer. I'm sure there are some branch off to power the compressor, and fan.
 
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Old 05-15-12, 10:18 AM
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Nothing goes directly to the transformer - that white wire plugged into the IC along-side the dual-red-wire connector is the power feed I believe. That's why I was thinking the red brings 120V to the transformer.
 
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Old 05-16-12, 10:50 PM
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Check the cord for continuity.

Check the resistance of both sides of the transformer.

If the cord and transformer seem are okay, check to see if the board is getting power. (both 120 volt and low voltage)

If it is, you probably need a new machine* if it's out of warranty. I don't think those circuit boards are available.

*Or, rig it up with mechanical controls at your own risk.

Edit:

The lower circuit board looks corroded.
 
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Old 07-12-12, 05:29 PM
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Finally getting back to this and I've made some progress today. Fortunately, I have another machine at my disposal, and that allowed me to swap in the IC that I suspected might be the problem. Indeed, that was it - machine works fine with the swapped-in board.

There was some corrosion on the suspect board. I cleaned it up and tried to re-solder the most suspect joints, to no avail.

What do you think my chances are of finding a replacement board, new or used?
 
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Old 07-12-12, 07:53 PM
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I did a quick search, and found this. (Used) Not able to find a new one else where.
 
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Old 07-12-12, 08:12 PM
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Thanks for the link - yes, that's it!
 
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Old 09-21-12, 09:51 AM
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Just to close this thread out, I purchased the replacement circuit board - BTW, they're tough to find now that Fedders is gone - and machine works again like new.
 
 

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