# My life as a retired engineer, today's small challenge

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#### Tony Stewart

##### Well-Known Member

(,? how fast can I fix her "dead" over the stove Microwave oven .

She depends on the 300 cfm fan for cooking and other things.

I could shop,and get in a few hours maybe and fix....maybe..

... wasted an hour removing it from under cabinets when I just had to figure out the front panel removal trick next sourcing a suitable replacement , maybe 1uF 2100Vac

#### DerStrom8

##### Super Moderator
I've got about a dozen of those capacitors lying around, all pulled out of old MOs.

#### AnalogKid

##### Well-Known Member
Lots of them on ebay.

ak

#### crutschow

##### Well-Known Member
I recently fixed mine.
I thought it was the capacitor but it turned out to be a shorted high voltage diode.
Does it hum loudly when you turn it on?

#### Nigel Goodwin

##### Super Moderator
I'd be happier with a simple ohms test across the capacitor, showing that it's S/C - doing an AC test at a frequency far above it's designed usage 'may' perhaps give a false reading?, and there's no advantage in doing so.

I've repaired hundreds (probably thousands) of microwave ovens, and the capacitors do very occasionally fail - however, it's also quite possible that it takes out other components as well. It rather depends on the actual design, later ovens have protection diodes (a seriously HV zener), and these are designed to go S/C if the rectifier or capacitor fail - on older models failure of the rectifier or capacitor doesn't always blow the fuse, resulting in the transformer dying. The protection diode ensures that the fuse blows, and protects the transformer.

As others have said, the easiest place to get one is out of an old microwave, they fail very rarely, so an old faulty microwave if most likely to have a good capacitor you can remove. The value isn't critical, they are all pretty well the same.

#### crutschow

##### Well-Known Member
Do a DC ohms test of the capacitor with a standard multimeter.

#### Tony Stewart

LCR meter said 0.7Ohm short,, found supplier 30 minutes away $12 1% tolerance 0.3 Ohm ESR Q> 1000, built-in 1M parallel R Fixed it and it seems to have 50% more power that seemed to have dropped in last 6 mos. Hot water in 1 cup in 60 sec vs 90sec... #### large_ghostman ##### Well-Known Member Most Helpful Member Should have got a new oven, kept the transformer from old one . Now your retired, how come you need things like water faster? #### Tony Stewart ##### Well-Known Member Most Helpful Member Should have got a new oven, kept the transformer from old one . Now your retired, how come you need things like water faster? Nice try. Wife needed immediate solution and Over Stove microwave ovens of this size with a 300 CFM external blower are more expensive. I preferred the$12 solution.

Today's problem with A Lenovo Win8 laptop and friend hates it and wants Win7. I said OK ( mistake) DVD was no good scratched and was rubbing the disk, now scratched and not repairable, so made SD flash bootable with Win7 x64 but no CD emulation drivers in legacy mode to complete install , so installed from Win8 , now Win7 runs but no SD card drivers work so cannot complete install. Catch 22 with no factory restore.

#### large_ghostman

##### Well-Known Member
What make is it? I have a 15GB pack of legacy drivers somewhere on the NAS

#### large_ghostman

##### Well-Known Member
is there anyway you can download a 9.5GB iso file? It has a program in it that goes through the indexed drivers on the ISO. Otherwise I will need to try and go through the iso file

#### Tony Stewart

##### Well-Known Member
I have tried the drivers from Lenovo including D: drive Oem drivers for Win7 x64 and changed bios from EUFI to legacy first non win8 OS and tried but with no DVD and now no SD under Win7, the Win7x64ISO is stuck on the file install without CD emulation drivers to recognize the SD. catch22 If I browse during boot install, it does not see the SD card but it was bootable from it using BIOS. Also the OEM MPT format partition table is now non-std so no factory restore.

#### large_ghostman

##### Well-Known Member
I sent you a PM, your problem is enforced driver signing, follow the directions in the link I sent. Turn off enforced signing and you will be able to load the correct drivers.

#### large_ghostman

##### Well-Known Member
Now can I have that MOT??

#### Tony Stewart

##### Well-Known Member
I believe I disabled driver signing already using

MOT? I fixed mine

#### large_ghostman

##### Well-Known Member
I believe I disabled driver signing already using

MOT? I fixed mine
I think you disabled the wrong thing!!! Your looking for disable driver enforcement

for win 8.1 (because it is different from win 8) follow these instructions exactly

https://learn.sparkfun.com/tutorial...abling-signed-driver-enforcement-on-windows-8