Our GE JEM25DM3BB 1.0 cubic foot microwave oven crapped out recently
and we couldn't find a suitable substitute. The oven functions would
work, but it wouldn't heat. The problem is the microwave fits inside
an enclosure of our kitchen cabinetry. When we moved into the house
eight years ago there was another microwave there which died a couple
years later. We had trouble finding a replacement then, but the GE
barely fit in there. Now that GE model is discontinued and the only
ones with dimensions small enough to fit are 0.7 cubic foot or less.
The wife was not pleased with the choices.
My first option was to cut out the enclosure a bit more to get a normal
sized microwave in there, but a woodworking friend pointed out it would
look funny because the hole would extend all the way up to the bottom
of the cabinet door above it. The wife was not pleased with that
My next option was to repair the one we have. After researching
microwave ovens, the troubleshooting guides pointed to the overvoltage
diode and the magnetron as the likely suspects for the symptoms of this
oven. I disassembled the oven and took out the items. The diode was
open in both directions so I immediately suspected it. I checked the
magnetron for continuity and the leads had 0.000 ohms resistance
between them. Hmm, that looks bad too. The high voltage capacitor
seemed to be charging and discharging when I put the multimeter leads
on it. I ordered the parts with next day delivery and the total was
more than $200. Ugh...
When the new parts arrived I immediately ohms checked them and found
the very same results as the ones I took out -- the diode was open in
both directions and the magnetron was shorted. This time I was not
Facing no other options I went ahead and installed the diode first and
heated up a cup of water for a minute. Still cold. Next I installed
the magnetron and held my breath while I heated up the cup of water.
After half a minute I noticed steam inside! When I took out the cup
after a minute it was hot. I showed the cup to my wife and this time
she was pleased. The microwave oven is back in the kitchen cabinet and
working fine. Warming up leftovers in a pan or heating up the leftover
morning coffee were good incentives to get this resolved.
I'm still baffled as to why the diode has no continuity. Is it because
my 9-volt multimeter doesn't have enough current to get through the
junction? I don't understand the magnetron properties so perhaps ohms
checking it was a useless test.
Glad you got it fixed.
Though I'm good with electronics I don't profess to be a microwave
expert, but since that's an over voltage diode it would have to have
some kind of series resistance which evidently was off scale for your
meter (Could be as high as 200k in the forward direction)
As to the filament on the magnetron, I'd expect it to be under one ohm
Bottom line: built ins/ons eat your lunch, sooner or later!
We removed the (suspended) over-the-oven microwave when we
removed the upper cabinets (oven is in peninsula so these
things just boxed the kitchen in). For a while, we kept
it on a counter -- wasting precious counter space!
We have since opted to move it to a small cupboard which gets
it off the "counter circuit" and onto its own dedicated
circuit. Also means we can replace it at will!
Be thankful they'd even *sell* you spares! :<
The diode will look like a reasonably HIGH impedance. It's operating
at a few KV -- not the 9V your DMM is probably using.
The maggie will look almost like a dead short. Is your DMM truly accurate
to 3 digits? I.e., is that 0.000 really 0.000 or more like 1.0?
You should also check each of the maggie's leads to case to verify
there isn't a short, there.
You could have monitored load current to the maggie (limiting it
through a resistive load so you can just watch the drop across
I know what I am doing and I would not poke around inside a microwave that was powered up. You should not either. No joke, the voltage in thee are leathal.
there are DIY sites on the net that tell you how to test an HV diode with the power off.
Yes a high voltage diode will test open with a standard vom.
yes the two filament leads will look like a short.
but they should not be shorted to the case.
read a few diy sites and keep the power off.
On 2/16/2016 3:05 PM, firstname.lastname@example.org wrote:
No, it's more than just "keep the power off". Energy is stored in
the HV section (capacitor doubler). The circuit *may* have been
designed with a bleeder to discharge the cap, over time.
But, the device is NOT WORKING. So, you can't assume any of
the things that were designed to protect you are functioning
correctly, either! (does "no user serviceable parts inside"
ring a bell? :> )
I work with electricity all day -- and still treat it like a
youngster who just got zapped for the first time! It's not
like setting your hand on a hot stove -- where you MIGHT have
a chance to correct your mistake before incurring some serious
injury... (electrons are fast little devils!)
On Sat, 22 Mar 1969 14:05:04 -0800 (PST), email@example.com wrote:
replying to Tom Billings , robertjones wrote:
I just purchased a new set of tires, but there is still some ice and
snow on the ground, and a lot of potholes in the roads. I was going to
get them installed on my car, but after reading this, I decided that
maybe I should wait a few more weeks. told the guys at the tire garage
to hold off on installing them for now, and just brought the tires home.
How long should I wait to install them?
Only if I turn it upside down! This is what I was looking at.
The diode is usually made of several diode junctions in one case. Therefore
it takes several volts to make it show up on most multimeters. The 9 volts
of your meter may be enough voltage to break down the junctions and show
something, however most do not apply the total 9 volts to the circuit. Most
less than one volt as not to make diodes show up as a low resistance in one
direction and very high in the other. Some meters will have a diode
function that applies several volts to the leads to test many of the diodes
of up to 1000 volts or so. This is still not usually enough for the
On Tue, 16 Feb 2016 18:28:00 +0000 (UTC), "badgolferman"
No. It doesn't have enough voltage. 9 volts is not enough to get
through some diodes. Especially since you call it an over-voltage
diode, t hat sounds like it shouldn't be passing any current unless
the voltage is too high. 9 volts is not too high!
So how much was the magnetron and how much the diode? I'd think the
diode was much less.
In general it's best to check voltages during operation, rather than
resistance when standing still, but the one place this is almost
impossible** is with a microwave. If you run it with the cage off the
microwaves will harm you, especially the liquid in your eyeballs I
I hope you were careful to assemble the metal cage around the
microwave parts exactly as it was originally. My old one made about
1965, had a woven metal gasket, which woudln't let electromagnetic
waves through, but I don't know what is used now.
**The way to do this would be to solder wires to the places you want
to measure and if possible run the wires outside of the microwave cage
without causing a leak and do the measurements when it's running but
fully shielding those nearby.
The magnetron was $161 and the diode was $35 + $25 next day air
shipping. I could have gotten cheaper ones on Amazon but it would have
taken longer to get them. This place also had a return policy so long
as I didn't install the part. When I first installed the magnetron I
used rubber washers to keep the screws from marring the installation
tabs in case I needed to return it.
Considering the closest sized microwave I could find was $240 and the
fee I would pay for a carpenter to modify the kitchen cabinet, I think
this worked out more cost efficiently.
On Wed, 17 Feb 2016 14:38:42 +0000 (UTC), "badgolferman"
Wow. I don't know any place that takes back electrical parts.
Partly for this reason, although I agree if nothing changes, you
should be able to fairly declare that you didnt' burn it out. 99%
My brother burned out the microwave by putting in a metal rack that
looked almost identical to the rack that was supposed to be there.
He's supposedly known for mistakes but this one would have been easy
to make (whoever washed it should have put the right one back in the
microwave. That was probably the nanny/maid who was washing things
all the time, and maybe she would have with enough time.). There was
burn damage to a plastic shelf peg, so I'm sure it was the rack.
I arrive for a visit and between visits and meals I'm looking for
tools and taking it apart, and I tell my sister in law I might be able
to fix it but she insists on buying a new one. The old one has a
blown fuse inside, a simple glass fuse, but I have no car. There's a
party that night at their house (related to the reason I was visiting)
so I hide the big microwave on the floor behind the wet bar between
the kitchen and the front hall/mini-living room.
The next day the microwave is gone. I find it out by the garbage,
replace the fuse, it works, so I borrow a car and take it to Goodwill.
My sister-in-law has already hired a Mexican/handyman/carpenter to
redo the facade in front of the microwave area. A much smaller effort
than yours would have been, but combined with the MW itself, this is
one of many reasons related to her that my brother is well over 65 and
still working. What she doesn't know about money would fill an
On Tue, 16 Feb 2016 18:28:00 +0000 (UTC), "badgolferman"
This is one reason I dont like the idea of built in appliances. Whether
it's a microwave, range, dishwasher or anything else, sooner or later it
will need to be repaired or replaced. It's hard or impossible to find a
replacement that will fit. And if parts are even available, they cost
more than a new appliance. Of course if your home comes that way, you're
stuck with it.
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