SMH7174BC Microwave - Instructions

I looked up the #1 reason for no heat for my microwave on the site , and using my model number found that 92% of the time it was the Black Sleeve Diode. Ordered the $15 part, and installed it within 30 minutes. Most of the time was used for removing the built in microwave and removing the cover. Replaced the diode by finding it on the diagram that I printed from this site (free). Very relieved that we don't need to have our custom cabinetry re-sized to accommodate a new microwave. Thank you!

Initially I called a Samsung recommended appliance repair outfit to fix the latch. The technician informed me that he does not fix latches. I need to buy a full new door for the microwave for $215 plus he charges $165 to come to my house. I got angry and did some research and it turned out that this is a very common problem. I ordered part PS4229162 "door key" $6.67 then followed the instructions on a youtube video by zimsjeep
"Repair a Broken Microwave Door Latch" to install. At first I struggled a bit hooking up the spring to the frame, but then I used a slim plier to hold the spring (instead of my fingers) and that did the trick.

I r/r the bulb cover, I then removed the burned out bulbs w/ a rag in case they broke they wouldn't have cut my fingers. You turn the bulbs lefty loosy. Installation is just the reverse. Install each bulb and turn righty titey, just snug the bulbs into place. Replace Glass cover and insert one phillips screw in plate and re-tighten

Removed control panel, discharged HV capacitor. Removed old diode, tested to confirm failure. Replaced part. Other than the removal of the panel swapping the part was almost as easy as replacing a light bulb.

The high voltage tired was shorted. I replaced it with a new one, but that did not solve the problem.

You can test the high voltage tired with a voltmeter and a 9 V battery. Search Search for it on YouTube.

You can also test the high voltage capacitor, the high-voltage transformer, and the magnetron with a multi meter. Search for the procedures on YouTube.

I tested all these high-voltage components with a low-voltage multi meter, and they all checked out OK (after replacing the diode). However the microwave still did not heat food.

When working on a microwave it is important to unplug it and also discharge the high voltage capacitor. The capacitor has a 10 megaohm resister to automatically discharge itself, but it may have failed – – so discharge it manually.

In the end I ordered a new microwave.

First I read through the customer comments, reviews, questions, etc. at Parts Select, which is always a good bet. Then I put "samsung microwave door switch replacement" into youtube and watched some videos. They don't even have to be for Samsung. From what I can tell, many of the appliance companies use the same design and the same junk parts, so watching a GE video is almost the same for example. Watch some videos to familiarize yourself with the steps. There are maybe six to disassemble and install the new part. I replaced all three switches. They are not expensive and to replace 3 is only 5% more work than to replace just one; you have to take the microwave apart in either case. UNPLUG THE MICROWAVE FROM THE WALL. Start taking it apart. I use my phone to take a picture of any thing I remove, unscrew or disconnect, especially wires, BEFORE I disconnect them. Thee pictures serve as a reference when I go to reconnect and reassemble. If I am uncertain then I check the picture. Good luck!

Removed case,
Discharged HV capacitor and removed cooling fan.
Unscrewed ground end of HV diode and unplugged from HV capacitor.
Installed new diode by reversing the order. In my case, the problem was the magnetron was bad, so I replaced it as well.

Unplugged Microwave, Removed vent cover (2 screws on top of microwave, then slide cover to the left, then forward) Removed control panel (1 screw at top of panel) then removed the two screws that hold in the door switch assembly. (these you will only see by opening the microwave). Located lower door switch, removed connecting wires, and pulled switch by releasing small plastic tab which held it in. Put new switch in place, reconnected wires, then reconnected door switch assembly. Reconnected control panel, and then put the vent cover back on. Tested microwave and it no longer runs when the door is open. Super easy fix, and was done in under 5 minutes.

I replaced all 3 door switches. Once you remove the top vent then remove the panel. Then remove the two screws holding the door switches in place and pop them out and replace them. It was tricky getting around all the wires but eventually was able to get around them. Took less than 20 mins to do and was less than $40 to fix. Much better than having to replace our over the stove microwave.

After minimum research, it was identified as a micro switch in the door. There is a total of 3, The top and bottom switches are the same in the odd one is in the middle just above the lower switch. Problem i had was one of the you tube videos said to grab the switches with pliers and force them out.;not a good idea. it breaks the lever in the switch holder bar. Solution is to remove the plastic switch holder bar from the door frame removing the 2 screws on the inside of the frame and then you can flip the lever in the bar which secures the switches on the door side. Use a small screwdriver to release the lever and they will slide right out. FYI the plastic switch holder bar is no longer available. I used electrical tape to secure my switches since the levers were broken from forcing them out.

Good Luck

Other tools that are usefull long needle nose pliers, long thin blade screw driver and small magnetic flashlight. Place the microwave on a work bench and remove the case it cover 3 sides. Place the microwave on a chair so it can stand with the controls up. You are replacing the lower door microswitch. The switch is located behind the control panel in the lower part of the area. The switch is several inches inside this area and your hands will not fit. Take care when moving wires and a couple of sensors. Use the thin blade screwdriver to release a tab holding the switch in place. Do not break this tab. Take the needle nose pliers and remove the switch. Put the wires on the new switch, open the door a short distance so a door lever moves enough to put the microswitch back into the bracket.

Unplugged the unit. With a screwdriver removed two screws on the top plastic vent. This exposed the screw holding the control panel. Removed that screw to access the switches. Removed the visible connected wiring from the switches. Grabbed each switch with pliers to gentle pull them from their holders. Inserted new switches and reconnected wiring, ensuring the correct orientation of switches in their holders.
Recommend replace all three switches.

This is the 2nd broken part that I have received in 2 weeks. You cant install something that is broken. I spoke with customer service and advised that they not send the part in a soft pouch.

I had to unmount the over-the-range microwave oven to be able to gain access to the interior of the oven. Complicating removal (and re-installation) was the fact that there is a "pot-filler" faucet installed directly underneath the oven. In retrospect, I should've removed the faucet before doing the repair, but "c'est la vie."

After I got the microwave down, removing the case was also "interesting." I get bonus points for the fact that the previous owner must've had to replace the same diode before - and then re-assembled the microwave case incorrectly - thereby adding to the confusion (BTW, the service manual that I found online said nothing about how to remove the oven's case).

To remove the case, undo all the screws holding it on, and then rotate the case upwards from the back while also pulling the case backwards. There are crimped folds on the inside of the case that mate with the back edges of the front of the oven's chassis, and these folds have to be unclipped from the chassis in order to remove the case.

Replacing the diode itself was the easiest part of the job. The two connectors on the diode are of different types, making it impossible to install the diode with the wrong polarity.

BTW, the diode that had failed was not an OEM diode; I suspect it was a generic component that had been installed by a repairman sometime between 2004-2008 (when our home's original owners still owned the home). On the other hand, the new diode from PartSelect is an OEM part (it came packaged in a sealed Whirlpool bag).

The fact that the oven had stopped heating indicated that it was either the high-voltage diode or the magnetron that had failed. Since a replacement diode costs ~ 1/10th as much as a replacement magnetron, I figured it made sense to replace the cheaper part first. Fortunately, this fixed the problem.

One last thing: I tried testing both the old and new diodes for conductivity and polarity using my volt-ohm meter (VOM), but I was unable to get either diode to "turn on," even though my VOM is powered by a 9-v battery, and I used the 2-Mohm range setting. I guess the test voltage of my el-cheapo VOM isn't high enough to exceed the diode's threshold voltage, (even though I have successfully used this same VOM to test low-voltage diodes).

removed a dozen screws-discarded large cap-replaced diode-replaced a dozen screws(took longer to replace them than remove for some unknown reason). Microwave now works(wife happy).