• ** REMEMBER! **The microwave can still shock you even unplugged!!

    ALWAYS discharge the high-voltage capacitor first if you even think your hands will come close to any HIGH VOLTAGE components.

    Jeff mentions this: Anything in the high voltage ( magnetron, capacitor, diode, wires to and from ):
    ...Use a metal ( not the shiny chrome type ) screw driver with a insulated handle to short across ( touch both at the same time ) the terminals of the high voltage capacitor to discharge it.

    From Jeff's site: http://www.applianceaid.com/component-testing.php

    Jake

FIXED SMH7185STG Not Heating Up after Hurricane Irma

jayta98

Premium Member
Joined
Nov 11, 2015
Messages
17
Location
Orlando, FL
Model Number
SMH7185
Brand
Samsung
Age
1-5 years
Hello, after hurricane Irma I noticed that my Samsung microwave will turn on as normal but the food was cold. I tried all the way up to 3 mins and nothing. The turntable works. Initially I can hear like the magnetron buzzing noise when it was working but it was on and off. After I checked everything and tried again I don't hear the on and off buzzing noise anymore. I did some troubleshooting with the information I have found and this is what I got so far. I have discharged the capacitor prior to start working in the microwave.

1. I checked all 3 door switch with continuity and they all work normal.
2. I checked the HV diode with 9v battery and voltmeter and i'm getting 6.7 volts. When i reverse the probes I get very small mV reading so the diode is good.
3. I checked capacitor after it been discharged with my multimeter. It has an option to check capacitance and it read 0.93 micro F. The capacitor label says it is a 0.91 micro F so it is good then.

4. I checked the transformer primary and secondary with no power. They have continuity in each winding but not to ground so I'm assuming is good. I read on another test to read AC volts only on the primary side only with the microwave running and the primary is getting 16VAC between the two terminals and 16VAC from ground to the red wire. From blue wire to ground I am only getting about 2VAC. Not sure if that is the normal primary voltage. If it is not then I guess it could be a bad control board? I read not to check the secondary voltage going to the magnetron (both red wires) or white wire going to the capacitor because of high voltage.

So I trying to figure out if I have a bad magnetron or bad transformer( if the previous test are normal). I do hear some humming but it sounds like the normal microwave humming. I don't hear the magnetron drawing power when it is working. If I unplug the magnetron and run the microwave the humming stays the same so it most be the transformer/fan making that noise. Again it is not a loud humming noise it sounds like the normal operating noise of the fan/transformer. I do noticed a slight burn odor (not strong at all when the microwave is running (covers off) and the magnetron disconnected. If I plug the magnetron the smell seems a little stronger.

I removed the magnetron and visually looks good. No cracks, burns or discoloration. I measured resistance from both terminals and it has continuity and from each terminal to metal frame it has no continuity so that test is good but I have read it is not a definite test.

Is there anything else I can test or check to figure out if it is the transformer or magnetron before I order? I tried warming up some water in a glass and if i put it in the center of the turntable it won't warm up at all. If take glass turntable out and put the glass close to the wall were the magnetron is i do feel the water warm up a little but after like 3 minutes on timer. So it is not normal.

Any suggestions will be appreciated. Thanks.
 
Last edited:

jayta98

Premium Member
Joined
Nov 11, 2015
Messages
17
Location
Orlando, FL
A few corrections. The blue wire on the primary of the transformer has 0 volts to ground. The small black wire on the primary side of the transformer has 120VAC to ground.
 

jayta98

Premium Member
Joined
Nov 11, 2015
Messages
17
Location
Orlando, FL
A few corrections. The blue wire on the primary of the transformer has 0 volts to ground. The small black wire on the primary side of the transformer has 120VAC to ground.
Also on primary side of transformer I have 120v from black wire to blue wire. 139v from black to red.
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
102,861
Location
McMullen Valley, Arizona
Hi Jay,

Rick and Jeff are our microwave experts here, I will ask them to see if they can assist you.

Jake
 

jayta98

Premium Member
Joined
Nov 11, 2015
Messages
17
Location
Orlando, FL
Thanks Jake. I have a feeling is the magnetron but I will like to confirm the voltage at the transformer.
 

Jake

Appliance Tech - Admin
Staff member
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Messages
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Location
McMullen Valley, Arizona

Jake

Appliance Tech - Admin
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Messages
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Great, please do.:)

Jake
 

jayta98

Premium Member
Joined
Nov 11, 2015
Messages
17
Location
Orlando, FL
Great, please do.:)

Jake
Well I installed the new magnetron and no change :( Not heating up anything. I guess I can try the capacitor but according to my multimeter that reads capacitance is reading 0.93 micro F and the capacitor rating is 0.91 so it should be good. I'm hoping I can figure out it out this week if not I will have to purchase a new microwave. It has been almost 2 weeks without one
 
Last edited:

jayta98

Premium Member
Joined
Nov 11, 2015
Messages
17
Location
Orlando, FL
The other thing I noticed if I run the microwave without the covers and I set it for 3 minutes on high I start to smell like a hot resin smell almost like fresh paint smell. Not sure if it is the transformer. That what i will like to know the input voltage and output voltage of the transformer
 

Jake

Appliance Tech - Admin
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Messages
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Let me ask Rick what he thinks it could be.

Jake
 

rickgburton

Appliance Tech - Moderator
Staff member
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Messages
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Location
Murray, Utah 84107, United States
If there's three primary terminals the one with the blue wire goes to the high power relay on the circuit board and the black wire goes to the low power relay on the circuit board. There's an inline fuse on the blue wire. See if you have continuity between the blue wire on the transformer and the blue wires on the #2 relay on the circuit board. When you checked the door switches do you check them by opening and closing the door and not by just pressing the button on the switch ?
 

jayta98

Premium Member
Joined
Nov 11, 2015
Messages
17
Location
Orlando, FL
I disconnected the blue wire plug from the transformer and relay i check continuity and is good. The blue wire end up is a small board which i think they call it noise filter. I had checked the two fuses on this board(the only fuses in the whole microwave) and they were good as well. I have the capacitor coming in today to try it out. According to my meter is good but I kind of hear some light arcing (very faint noise).

I checked the switches installed and opening/closing the door. They all checked good. If the capacitor doesn't fix it I truly don't know what else could it be beside the main board?
 

jayta98

Premium Member
Joined
Nov 11, 2015
Messages
17
Location
Orlando, FL
So i got the new capacitor today and installed it. Not heating either. I decided since I have all three parts to install one at time and see if maybe there was more than one bad part.

I added the new diode DE91-70063D and I started to hear the old magnetron arcing. I tried to warm up water and felt it a little bit but not much. I decided to install the new magnetron back. once I installed it back the microwave started to heat up. I put a cup of water and in about 50 secs is boiling it. My impressions were that the diode and magnetron were bad. The capacitor could had been bad too but I didn't want to remove it since it was already installed.

Everything is back together and the microwave is back were it needs to be! Repair cost with shipping were $99. Better than $299 plus tax for a new samsung microwave. Thanks guys I really learned a lot about microwaves.
 

rickgburton

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Jake

Appliance Tech - Admin
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McMullen Valley, Arizona
Excellent Jay, glad to hear that.:)

Thanks Rick for helping him out.:)

Jake
 
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