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pjw73nh

Dead Samsung OTR Microwave ME18H704SFS

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pjw73nh
Totally dead Samsung OTR Microwave Mod ME18H704SFS Ser 07867WTF700650E.
 
This unit is about 16 months old, it belongs to my son.  It has worked fine since we installed it.
 
He went away for the weekend, came back home and the unit was totally dead.  Nothing.  No lights, no panel, no fan. DEAD. Tried a new outlet on a different, (known good) circuit.  Same thing. DEAD !!.  there was no bad weather or any other signs of electrical malfunction in the house. It is on a dedicated 20 A circuit. 
 
I couldn't find a schematic for it.  I guess gone are the days of including one with the appliances. 
 
After properly discharging the HV cap, I tested as many components as I could easily get to.
 
Fuses on the power board were good. All (I think I found 3) thermal switches/cutouts had continuity.  I am not sure I was able to get to ALL the door switches (or for that matter, all the contacts on all the door switches) but the ones I was able to get to tested fine on open/close. 
 
I was able to test for AC up to the power board. I did not go into any board components further. 
 
When I was testing the thermal cutouts and the door switches, I was careful to remove at least one connect or from each before testing it.  All connectors looked fine, and disconnected / reconnected without incident. EXCEPT the one on the thermal cutout for the magnetron. 
 
The thermal cutout on the magnetron had one normal looking connector, and one that was badly heat discolored. possibly slightly melted and because of it's location, I was not able to get the required "oomph" on it to disconnect it. I tried wiggling it, pulling it, I tried some needle nose pliers. I just couldn't get a decent grip on it.  So I disconnected the normal, unblemished one, and tested continuity fine via the contacts on the cutout itself, NOT via the connector crimp.
 
At this point I had gone as far as I could/wanted to without a schematic.  
 
As a "last ditch" effort before calling it a day, I plugged it back in and all was well.  It fired right up, heated fine.  I remounted it on the wall and it's been good for the last 24 hours.
 
My guess is that one of the connectors I wiggled/removed/reattached etc while testing fixed the issue.  Which one?  My guess is probably the discolored one on the mag cutout.  But who know at this point.  Next time I'll test one thing at a time and try to fire it up each time.
 
Any other thoughts, comments or suggestions?
 
Thanks.
 
 
 

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DJR050403

To fix this microwave I used schematic and wiring diagram from model ME21F707MJT. To test if the wiring and TCO on top of the magnetron is good or bad test the continuity between the bare connector on the TCO on the top left behind the control panel, which is for the chamber, to the black wire with a white connector on the lower door interlock behind the control panel. It is easiest to remove the connector and test directly. Continuity shows it good or bad. My microwave went out after 1.5 years and using an inspection camera it was easy to see the burnt connector. Order KSD-150LC thermal cut out.

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Chat_in_FL

Power confirmed to the board and it is dead? If you're reading the input into the board transformer, then most likely the board

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appliancint

responding to  pjw73nh -- not all the thermostats are supposed to be closed.  There is one that is normally in the "open" position and when it heats up it runs the fan to cool down the unit. That one is on the base of the microwave below the control board, towards the left.

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pjw73nh

My apologies to all in this post as I have not updated it is several months. I am pleased to report that since the initial incident in my original post, the unit has not malfunctioned since.

Thanks to all who replied.

P.../NH

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