Repair of 31 Year Old Samsung Microwave Oven
My +31 year old Samsung model M6146 Microwave oven manufactured in december 1991 suddenly last week after a loud bang ended its lifelong service. Luckily I still had another old 800Watt working microwave oven to cook my meals in the meantime. Which gives me plenty of time to fix my old Samsung Classic Collection oven waiting for the new replacement parts to arrive.
See manufacturing date ‘1991 12 02’ in above photo! Which was just about a few months after I had my own apartment in 1991. In that period (+31 years!) until yesterday 17-2-2023 this microwave oven worked splendidly. All that time serving my life saving hot meals and drinks! Until the 0.91 uF 2100WVAC capacitor apparently shorted with a big loud bang and took the 5KV HV 0.7A safety fuse with it.
About replacing the original now shorted HV 0.91uF capacitor by for instance a used good 0.97uF also 2100(W)VAC capacitor, it probably won’t make much difference. And after observing all the adverts on these HV caps it seems that they often sell slightly different values around the 1uF value only depending on the value that at that moment was measured. And all for the same price.
So even if we search to order for that exact 0.91uF capacitor it still will be uncertain if we will get that exact same capacitor delivered to our door.
And the used good replacement high voltage 0.97uF capacitor came out a very similar microwave oven that had all the parts my Samsung had but without the special 5KV 0.7A glass safety fuse. Next photo shows the original now completely shorted 0.91uF capacitor.
Next photo shows the new glass high voltage safety fuse that was ordered:
Next photos show the completely burned through 5KV 0.7A hv safety fuse that was hidden in the white plastic holder. Followed by a photo of the Samsung label sticker that was at the oven back.
After measuring the microwave ‘tube’ filament it still showed a intact internally electron emitting spiral. Without any unwanted short to the outside metal to the anode of the mw ‘tube’. But from what I read it may still be uncertain if the ‘tube’ is still good to go when measured this way by just using our multimeter. But in case the ‘tube’ no longer heats up my meals and drinks I will know for certain it is a goner! Provided that it not again also burns through my replacement hv safety fuse that protects the secundary microwave power transformer with its about 2KV high voltage output from shorting out! Which no doubt already saved my microwave hv voltage power transformer from going to kingdom come.
And in case the microwave ‘tube’ indeed is gone I do have another spare used one to replace it with and check out.
Next photo shows the probably still good microwave ‘tube’ type OM755(31)-D with measured good filament. Followed by more photos of my longlife but momentary out of order good old trusted Samsung 700 Watt oven. That according to online info probably after all that time no longer provides the same amount of microwave power emission effectively. But still dissipates the same input power.
That is because the microwave ‘tube’ in time deteriorates slowly from its new state.
Above photo shows the front of my Samung Classic Collection microwave oven. Next photo shows the topview of my oven after the metal cover was removed. Also the one-time round metal safety temperature fuse mounted in the top of the microwave metal ‘tube’ holder (with brown and red wire in the middle) was still fine measuring a very low ohmic value. And also the long glass 8A 250V fuse was still fine.
Above circuit shows a clear example of how this microwave oven and many other ovens work!
Following photo shows a good close-up sideview onto the OM755(31)-D ‘tube’ and the hv power transformer. Everything looks still very good after 3 decennia of frequent daily use apart from some dust on the cooler fan. (which I cleaned up a bit after this photo was taken).
Above photo shows the used but good replacement high voltage 2100VAC 0.97uF cap that was used to replace the now original defect capacitor.
My Samsung microwave oven is back in action as soon the new 5KV 0.7A fuse is received and connected. This way again safely connecting the about 2000V coming out of the HV transformer secundary to the right connectorside of the 0.97uF high voltage capacitor. (Which is the + side of the transformer wire in the above given example circuit). So for just spending 2,26 euro (mainly on shipping!) ordering a new safety fuse, my oven will be fixed and ready. Again at minimal costs!
But anyway…Whatever you do…Be happy, always stay safe and try to be successful!
Albert van Bemmelen, Weert, The Netherlands.
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Note: You can read his previous article on Stairway Recessed Indoor Lighting Repair- Randy LED 1.5W White-Ledkia