Most digital meters will not bias a diode into conduction. That is why they
have a didoe check on some of them. Even that may not check a microwave
diode.

"Stormin Mormon" wrote in message
...
Should be infinite ohms one way, and then reverse the leads, and get some
where between 2k (about that) ohms the other way. My SWAG at the moment is
the diode went. If the diode shorted, the cap may be discharged now.

.

"Smitty Two" wrote in message
...
That looks more like a "block diagram" than a schematic.

Why do you say that? It sure looks like a schematic
to me. It shows the various components and the circuit
connections between them.


Seems a little light on detail.

The control board is more like a block diagram, but the other circuit shows
all that should be there.

In article ,
"Ralph Mowery" wrote:

"Smitty Two" wrote in message
...
That looks more like a "block diagram" than a schematic.

Why do you say that? It sure looks like a schematic
to me. It shows the various components and the circuit
connections between them.


Seems a little light on detail.

The control board is more like a block diagram, but the other circuit shows
all that should be there.

I don't see the thermal cutoffs anywhere on that diagram, and I'm the
one who thinks that one of those is the most likely culprit.

On Tue, 18 Dec 2012 04:49:48 -0500, "Stormin Mormon"
wrote:

Should be infinite ohms one way, and then reverse the leads, and get some
where between 2k (about that) ohms the other way. My SWAG at the moment is
the diode went. If the diode shorted, the cap may be discharged now.


Hehe. What good does "maybe" do??? ;-)

--
croy

croy wrote:
On Tue, 18 Dec 2012 04:49:48 -0500, "Stormin Mormon"
wrote:

Should be infinite ohms one way, and then reverse the leads, and get some
where between 2k (about that) ohms the other way. My SWAG at the moment is
the diode went. If the diode shorted, the cap may be discharged now.


Hehe. What good does "maybe" do??? ;-)


I was looking at what method Sam would use to test diode. I would simply
hook 9 volt battery in series with diode and analog meter on high ohms.

On my mirror page.....
http://zekfrivolous.com/faq/sam/micfaq.htm

Greg

On 12/18/2012 8:44 AM, Ralph Mowery wrote:
Most digital meters will not bias a diode into conduction. That is why they
have a didoe check on some of them. Even that may not check a microwave
diode.

"Stormin wrote in message
...
Should be infinite ohms one way, and then reverse the leads, and get some
where between 2k (about that) ohms the other way. My SWAG at the moment is
the diode went. If the diode shorted, the cap may be discharged now.

.


A microwave diode is a bunch of lower voltage diodes in series.
I don't remember exactly how many, but a typical multimeter won't
test it...unless it's shorted. Need more volts to forward bias it.
9V battery and a light bulb might do it. Two 9V in series probably will.

In article
,
" wrote:

On Dec 18, 12:06*pm, Smitty Two wrote:
In article ,
*"Ralph Mowery" wrote:

"Smitty Two" wrote in message
...
That looks more like a "block diagram" than a schematic.

Why do you say that? *It sure looks like a schematic
to me. *It shows the various components and the circuit
connections between them.

Seems a little light on detail.

The control board is more like a block diagram, but the other circuit
shows
all that should be there.

I don't see the thermal cutoffs anywhere on that diagram, and I'm the
one who thinks that one of those is the most likely culprit.

What's the "magnetron thermostat" that is right after the
fuse on the incoming AC? Sounds like a thermal protection
device to me......

Perhaps it is, at that. But if that one were shot, there wouldn't be any
power anywhere. My microwave has three thermal cutoffs.

Danny D. wrote:
On Mon, 17 Dec 2012 22:08:35 -0600, The Daring Dufas wrote:

That's the diode I saw in the pictures and the diagram.
Diodes come in all shapes and sizes. ^_^

Ah. Thanks. I'll figure out how to discharge the capacitor first.
It has been sitting all day, so maybe by tomorrow it will have discharged.
My Fluke DMM has a diode test mode, so I can at least run that baseline.

Hi,
Magnetron needs high voltage to function. That diode is HV diode some
times in series to raise voltage rating. Usually Magntron buzzes when
working. Is it silent when turned on? Also oven door has multi sequenced
interlock switches which can go bad.

On Monday, December 17, 2012 10:02:16 PM UTC-7, Danny D. wrote:

On Mon, 17 Dec 2012 19:45:33 -0800, hr(bob) wrote:

If you can locate the two wires going to the magnetron filament,
you should see someting less than 100 ohms for the filament.

I was wondering WHERE the magnetron lay. If these are the
magnetron leads, they read 0.4 ohms with the Fluke in ohms mode:
http://www2.picturepush.com/photo/a/...g/11714385.jpg
And, the diode reads OL in both directions, both forward biased
and reverse biased with the Fluke 75 in the diode mode:
http://www3.picturepush.com/photo/a/...g/11714386.jpg

The electronics great RepairFAQ.org has information about microwave
oven repair: http://www.repairfaq.org/sam/micfaq.htm

Those high voltage diodes will read open with a digital meter because
they're made of several diodes in series to handle the thousands
of volts, and usually digital meter won't apply enough voltage to
make all those diodes conduct. So either try an old-style analog
meter set to a higher ohms scale (x100, x1000, x10,000), or
apply at least 6V - 9V DC through a 1,000 ohm resistor and measure
directly across the diode. If the diode is open, you'll see the
source voltage, but if it conducts, the voltage will be lower.

The big high voltage capacitor has to be discharged before handling
it. It almost always contains a bleeder resistor to do that, but
bleeders fail in use, so assume it's not there. Get a screwdriver
with a plastic handle on it (it's not enough to wrap electrical tape
around a metal handle; the voltage is way too high), and wrap several
turns of BARE solid copper wire around it. Connect the other end of
that wire to a 10,000 ohm, 10 watt resistor, and connected the other
resistor lead securely to bare metal of the oven's chassis. Touch
the tip of the screwdriver to each lead of the capacitor for 30
seconds. Finally, touch the screwdriver shaft to both leads of the
capacitor simultaneously.

Prices for microwaves oven parts vary greatly, and sometimes
electronics parts dealers are cheaper than appliance dealers. Some
of the former include MCM Electronics, Dalbani, Premium Parts, and
Parts Express.

You don't need an exact replacement magnatron, just somethign
compatible mechanically and electrically, and for our Sharp
onvection/microwave ovens I've used L-G magnatrons. Also any
replacement high voltage capacitor should have the same microfarad
(uF) rating as the original because using one with a different
capacitance rating changing it changes the power output roughly
proportionally, meaing the programmed cooking modes may not work
right because they're not calibrated for a higher or lower power.

The magnatron is usually held in place with 3-4 bolts or nuts, and
you absolutely want them to be secured so the magnatron is completely
flush with the mounting surface. Otherwise microwavess will leak past
the brass braided ring seal.

The magnatron has to be cooled with a fan, so be sure that fan works
by feeling for air through the rear vent. There's probably a bimetal
thermostat mounted on the magnatron to shut it off if it gets too
hot, and you may want to replace it because I had one that got stuck
in the on position. They're made with several different temperature
ratings.

I wouldn't turn on a microwave without the cover completely reattached,
including with all its screws, to prevent electrical shock and also
injury in case the capacitor explodes.

On 12/18/2012 7:55 PM, Tony Hwang wrote:


Danny D. wrote:
On Mon, 17 Dec 2012 22:08:35 -0600, The Daring Dufas wrote:

That's the diode I saw in the pictures and the diagram.
Diodes come in all shapes and sizes. ^_^

Ah. Thanks. I'll figure out how to discharge the capacitor first.
It has been sitting all day, so maybe by tomorrow it will have
discharged.

NO!!!! DO NOT UNDER ANY CIRCUMSTANCES ASSUME THAT THE CAP IS
DISCHARGED...EVER...!!!
Mine was dead for a week and still had enough charge go explode the wire
I shorted across it.

NO!!!! DO NOT UNDER ANY CIRCUMSTANCES ASSUME THAT THE CAP IS
DISCHARGED...EVER...!!!

If you wanna risk blowing up your Fluke, you can measure the voltage on
the cap...and possibly blow up your meter.

Death is final...don't risk it...no matter how small you think the risk.

My Fluke DMM has a diode test mode, so I can at least run that baseline.

Hi,
Magnetron needs high voltage to function. That diode is HV diode some
times in series to raise voltage rating. Usually Magntron buzzes when
working. Is it silent when turned on? Also oven door has multi sequenced
interlock switches which can go bad.

It gives you the option of not being killed?

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"croy" wrote in message
...
On Tue, 18 Dec 2012 04:49:48 -0500, "Stormin Mormon"
wrote:

Should be infinite ohms one way, and then reverse the leads, and get some
where between 2k (about that) ohms the other way. My SWAG at the moment is
the diode went. If the diode shorted, the cap may be discharged now.


Hehe. What good does "maybe" do??? ;-)

--
croy

I WONDER. IF YOU TOOK A COTTON SWAB!!!! AND
TAPED THAT TO A ***WOODEN STICK**** AND
THEN DIP!!!! THE SWAB INTO WATER, AND PUT THAT
ACROSS THE TERMIANLS, THE E*N*E*R*G*Y
OF THE "CAPACITOR" WOULD =DISCHARGE= THROUGH
THE ?MOISTURE? AND THAT WOULD BE ^SAFER^????

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"mike" wrote in message
...


Ah. Thanks. I'll figure out how to discharge the capacitor first.
It has been sitting all day, so maybe by tomorrow it will have
discharged.

NO!!!! DO NOT UNDER ANY CIRCUMSTANCES
ASSUME THAT THE CAP IS
DISCHARGED...EVER...!!!
Mine was dead for a week and still had enough charge go explode the wire
I shorted across it.

NO!!!! DO NOT UNDER ANY CIRCUMSTANCES
ASSUME THAT THE CAP IS
DISCHARGED...EVER...!!!

If you wanna risk blowing up your Fluke, you can measure the voltage on
the cap...and possibly blow up your meter.

Death is final...don't risk it...no matter how small you think the risk.

On 12/19/2012 3:37 AM, mike wrote:
On 12/18/2012 7:55 PM, Tony Hwang wrote:


Danny D. wrote:
On Mon, 17 Dec 2012 22:08:35 -0600, The Daring Dufas wrote:

That's the diode I saw in the pictures and the diagram.
Diodes come in all shapes and sizes. ^_^

Ah. Thanks. I'll figure out how to discharge the capacitor first.
It has been sitting all day, so maybe by tomorrow it will have
discharged.

NO!!!! DO NOT UNDER ANY CIRCUMSTANCES ASSUME THAT THE CAP IS
DISCHARGED...EVER...!!!
Mine was dead for a week and still had enough charge go explode the wire
I shorted across it.

NO!!!! DO NOT UNDER ANY CIRCUMSTANCES ASSUME THAT THE CAP IS
DISCHARGED...EVER...!!!

If you wanna risk blowing up your Fluke, you can measure the voltage on
the cap...and possibly blow up your meter.

Death is final...don't risk it...no matter how small you think the risk.


I do believe I mentioned discharging the capacitor through a 110k ohm
1/2 watt resistor. O_o

TDD

On 12/19/2012 8:18 AM, The Daring Dufas wrote:
On 12/19/2012 3:37 AM, mike wrote:
On 12/18/2012 7:55 PM, Tony Hwang wrote:


Danny D. wrote:
On Mon, 17 Dec 2012 22:08:35 -0600, The Daring Dufas wrote:

That's the diode I saw in the pictures and the diagram.
Diodes come in all shapes and sizes. ^_^

Ah. Thanks. I'll figure out how to discharge the capacitor first.
It has been sitting all day, so maybe by tomorrow it will have
discharged.

NO!!!! DO NOT UNDER ANY CIRCUMSTANCES ASSUME THAT THE CAP IS
DISCHARGED...EVER...!!!
Mine was dead for a week and still had enough charge go explode the wire
I shorted across it.

NO!!!! DO NOT UNDER ANY CIRCUMSTANCES ASSUME THAT THE CAP IS
DISCHARGED...EVER...!!!

If you wanna risk blowing up your Fluke, you can measure the voltage on
the cap...and possibly blow up your meter.

Death is final...don't risk it...no matter how small you think the risk.


I do believe I mentioned

What you mentioned is irrelevant. All that matters is what the OP read and
is gonna do.

discharging the capacitor through a 110k ohm
1/2 watt resistor. O_o

Since you asked for a critique on your method, here it is.
Check my math. Using round numbers...
4000V / 110k is ~36ma.
36ma * 4000v is 145454 mw = 145WATTS peak.
Half watt resistor.
Methinks a metal film might vaporize before that cap
discharged. Carbon might take the energy, if you can find one.

I'd suggest, from the experience level suggested by the tone of the OP,
that your advice is more harmful than helpful.


TDD

"mike" wrote in message
...
On 12/19/2012 8:18 AM, The Daring Dufas wrote:
On 12/19/2012 3:37 AM, mike wrote:
On 12/18/2012 7:55 PM, Tony Hwang wrote:


What you mentioned is irrelevant. All that matters is what the OP read
and
is gonna do.

discharging the capacitor through a 110k ohm
1/2 watt resistor. O_o

Since you asked for a critique on your method, here it is.
Check my math. Using round numbers...
4000V / 110k is ~36ma.
36ma * 4000v is 145454 mw = 145WATTS peak.
Half watt resistor.
Methinks a metal film might vaporize before that cap
discharged. Carbon might take the energy, if you can find one.

I'd suggest, from the experience level suggested by the tone of the OP,
that your advice is more harmful than helpful.


No need to worry about the power rating, a 1/2 watt resistor is only rated
for less than 500 volts. When the resistor blows apart, the arc will finish
discharging the capacitor.. Big grin..

The microwave is one place that if you do not have any idea what you are
doing and how to do it safely , you beter keep your hands out of it or have
a good insurance policy for your wife and kids to collect on.
Once you pass about 1000 volts, many things that seem to be insulators are
not.

On 12/19/2012 5:44 PM, mike wrote:
On 12/19/2012 8:18 AM, The Daring Dufas wrote:
On 12/19/2012 3:37 AM, mike wrote:
On 12/18/2012 7:55 PM, Tony Hwang wrote:


Danny D. wrote:
On Mon, 17 Dec 2012 22:08:35 -0600, The Daring Dufas wrote:

That's the diode I saw in the pictures and the diagram.
Diodes come in all shapes and sizes. ^_^

Ah. Thanks. I'll figure out how to discharge the capacitor first.
It has been sitting all day, so maybe by tomorrow it will have
discharged.

NO!!!! DO NOT UNDER ANY CIRCUMSTANCES ASSUME THAT THE CAP IS
DISCHARGED...EVER...!!!
Mine was dead for a week and still had enough charge go explode the wire
I shorted across it.

NO!!!! DO NOT UNDER ANY CIRCUMSTANCES ASSUME THAT THE CAP IS
DISCHARGED...EVER...!!!

If you wanna risk blowing up your Fluke, you can measure the voltage on
the cap...and possibly blow up your meter.

Death is final...don't risk it...no matter how small you think the risk.


I do believe I mentioned

What you mentioned is irrelevant. All that matters is what the OP read and
is gonna do.

discharging the capacitor through a 110k ohm
1/2 watt resistor. O_o

Since you asked for a critique on your method, here it is.
Check my math. Using round numbers...
4000V / 110k is ~36ma.
36ma * 4000v is 145454 mw = 145WATTS peak.
Half watt resistor.
Methinks a metal film might vaporize before that cap
discharged. Carbon might take the energy, if you can find one.

I'd suggest, from the experience level suggested by the tone of the OP,
that your advice is more harmful than helpful.


I've probably dealt with a lot more high voltage sources than you have
over the past four decades. I've never had a problem using a 100k
resistor to discharge a cap in a microwave oven. The danger I would
warn anyone about microwave ovens is to be careful not to expose
yourself to the non-ionizing radiation from the output of an operating
magnetron. Damage to the lens of the eye is quite possible. Of course,
I've also been known to use The Jesus Method to discharge capacitors
and find circuit breakers,........because it's fun. ^_^

TDD

Me, too. As to circuit breakers, I did make a plug
in breaker popper. I don't use it on FPE Stabloc
panels. Ah ain' 'tupid, y'know.

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"The Daring Dufas"
wrote in message ...

I've also been known to use The Jesus Method to discharge capacitors
and find circuit breakers,........because it's fun. ^_^

TDD

mike wrote:
On 12/19/2012 8:18 AM, The Daring Dufas wrote:
On 12/19/2012 3:37 AM, mike wrote:
On 12/18/2012 7:55 PM, Tony Hwang wrote:


Danny D. wrote:
On Mon, 17 Dec 2012 22:08:35 -0600, The Daring Dufas wrote:

That's the diode I saw in the pictures and the diagram.
Diodes come in all shapes and sizes. ^_^

Ah. Thanks. I'll figure out how to discharge the capacitor first.
It has been sitting all day, so maybe by tomorrow it will have
discharged.

NO!!!! DO NOT UNDER ANY CIRCUMSTANCES ASSUME THAT THE CAP IS
DISCHARGED...EVER...!!!
Mine was dead for a week and still had enough charge go explode the wire
I shorted across it.

NO!!!! DO NOT UNDER ANY CIRCUMSTANCES ASSUME THAT THE CAP IS
DISCHARGED...EVER...!!!

If you wanna risk blowing up your Fluke, you can measure the voltage on
the cap...and possibly blow up your meter.

Death is final...don't risk it...no matter how small you think the risk.


I do believe I mentioned

What you mentioned is irrelevant. All that matters is what the OP read and
is gonna do.

discharging the capacitor through a 110k ohm
1/2 watt resistor. O_o

Since you asked for a critique on your method, here it is.
Check my math. Using round numbers...
4000V / 110k is ~36ma.
36ma * 4000v is 145454 mw = 145WATTS peak.
Half watt resistor.
Methinks a metal film might vaporize before that cap
discharged. Carbon might take the energy, if you can find one.

I'd suggest, from the experience level suggested by the tone of the OP,
that your advice is more harmful than helpful.


TDD


Your going to have to find the discharge time, capacitance, voltage,
resistance. I don't see the cap value listed here. I'd be more inclined to
use at least a 2 watt resistor, but I like sparks.

Greg

On 12/17/2012 9:04 AM, Danny D. wrote:
This Jenn-Air (model M170B) 1,350 Watt microwave just stopped heating:
http://www2.picturepush.com/photo/a/...g/11709330.jpg

I called Jenn-Air customer support who said there's no troubleshooting for
when it doesn't heat. They said the magnetron may need to be replaced:
Jenn-Air 800-536-6247 Customer Care

A replacement microwave oven has to fit over the electric oven:
http://www5.picturepush.com/photo/a/...g/11709333.jpg

Interestingly, (since it was above the oven) the back sticker says:
"May be built into a cabinet structure, but not for use adjacent
to (with 2 feet of) any gas or electric range, cooktop or oven."
http://www4.picturepush.com/photo/a/...g/11709332.jpg

But, that sticker also says:
This microwave is approved for mounting directly over Jenn-Air
wall ovens as follows:
W2700 Series Using MK271 Trim Kit, W3000 Series Using MK301 Trim Kit

Having never worked on a microwave, I ask what the conventional wisdom is.
Q: Is it generally feasible to replace just the magnetron?
no,
First you have to determine that it's bad. Then why it failed to
make sure the new one doesn't fail too.
Then you have to find the exact magnetron...at an affordable price.
If you know what you're doing, you might be able to find an equivalent
magnetron...whatever that means...or cobble in a different magnetron.
That's just not practical for most of us.
Q: Will similarly sized microwave ovens fit (22" widex13"tallx15" deep)?
The only person who can answer that question is the one with the tape
measure
and the candidate oven.
Q: Is it generally best to stick within the same brand? (e.g., JMC1116AB)?
The standard answer is, microwaves are cheap, go buy a new one.
If you must fit the same hole, your quest is complicated to the extent that
most people won't be able to offer any useful advice.
Call up someone who refurbishes kitchens and ask them.

On 12/19/2012 7:21 PM, gregz wrote:
mike wrote:
On 12/19/2012 8:18 AM, The Daring Dufas wrote:
On 12/19/2012 3:37 AM, mike wrote:
On 12/18/2012 7:55 PM, Tony Hwang wrote:


Danny D. wrote:
On Mon, 17 Dec 2012 22:08:35 -0600, The Daring Dufas wrote:

That's the diode I saw in the pictures and the diagram.
Diodes come in all shapes and sizes. ^_^

Ah. Thanks. I'll figure out how to discharge the capacitor first.
It has been sitting all day, so maybe by tomorrow it will have
discharged.

NO!!!! DO NOT UNDER ANY CIRCUMSTANCES ASSUME THAT THE CAP IS
DISCHARGED...EVER...!!!
Mine was dead for a week and still had enough charge go explode the wire
I shorted across it.

NO!!!! DO NOT UNDER ANY CIRCUMSTANCES ASSUME THAT THE CAP IS
DISCHARGED...EVER...!!!

If you wanna risk blowing up your Fluke, you can measure the voltage on
the cap...and possibly blow up your meter.

Death is final...don't risk it...no matter how small you think the risk.


I do believe I mentioned

What you mentioned is irrelevant. All that matters is what the OP read and
is gonna do.

discharging the capacitor through a 110k ohm
1/2 watt resistor. O_o

Since you asked for a critique on your method, here it is.
Check my math. Using round numbers...
4000V / 110k is ~36ma.
36ma * 4000v is 145454 mw = 145WATTS peak.
Half watt resistor.
Methinks a metal film might vaporize before that cap
discharged. Carbon might take the energy, if you can find one.

I'd suggest, from the experience level suggested by the tone of the OP,
that your advice is more harmful than helpful.


TDD


Your going to have to find the discharge time, capacitance, voltage,
resistance. I don't see the cap value listed here. I'd be more inclined to
use at least a 2 watt resistor, but I like sparks.

Greg


I didn't say hold the freaking resistor in your hand. ^_^

TDD

mike wrote:
On 12/19/2012 8:18 AM, The Daring Dufas wrote:
On 12/19/2012 3:37 AM, mike wrote:
On 12/18/2012 7:55 PM, Tony Hwang wrote:


Danny D. wrote:
On Mon, 17 Dec 2012 22:08:35 -0600, The Daring Dufas wrote:

That's the diode I saw in the pictures and the diagram.
Diodes come in all shapes and sizes. ^_^

Ah. Thanks. I'll figure out how to discharge the capacitor first.
It has been sitting all day, so maybe by tomorrow it will have
discharged.

NO!!!! DO NOT UNDER ANY CIRCUMSTANCES ASSUME THAT THE CAP IS
DISCHARGED...EVER...!!!
Mine was dead for a week and still had enough charge go explode the wire
I shorted across it.

NO!!!! DO NOT UNDER ANY CIRCUMSTANCES ASSUME THAT THE CAP IS
DISCHARGED...EVER...!!!

If you wanna risk blowing up your Fluke, you can measure the voltage on
the cap...and possibly blow up your meter.

Death is final...don't risk it...no matter how small you think the risk.


I do believe I mentioned

What you mentioned is irrelevant. All that matters is what the OP read and
is gonna do.

discharging the capacitor through a 110k ohm
1/2 watt resistor. O_o

Since you asked for a critique on your method, here it is.
Check my math. Using round numbers...
4000V / 110k is ~36ma.
36ma * 4000v is 145454 mw = 145WATTS peak.
Half watt resistor.
Methinks a metal film might vaporize before that cap
discharged. Carbon might take the energy, if you can find one.

I'd suggest, from the experience level suggested by the tone of the OP,
that your advice is more harmful than helpful.


TDD


I see the diagram including bleeder resistor, and may have internal 10m
bleeder, but might be external. I would not trust an internal resistor as
being good.

Ok, a 1 uf cap and 110k resistor tc if .1 sec, so 80% of the voltage will
disappear in .22 seconds. A half watt resistor could smoke.

Greg

On Tue, 18 Dec 2012 20:55:20 -0700, Tony Hwang wrote:

Usually Magntron buzzes when working.
Is it silent when turned on?

Hmmm... I don't remember hearing buzzing but there is the loudness of the
microwave sounding like it's working. The turntable and lights do what
they should, as do the control.

The food just comes out cold.

I'm going to fully test that diode - and report back.
I went to Fryes last night but they didn't have a single 13x22 inch
microwave!

On Wed, 19 Dec 2012 10:18:05 -0600, The Daring Dufas wrote:

I do believe I mentioned discharging the capacitor through a 110k ohm
1/2 watt resistor.

I have some resistors but they're the teeny tiny ones with stripes.

I will need to go to Radio Shack and get a roughly 100 ohm resistor that
is a half watt or so first then.

I wonder though: Why wouldn't a screwdriver across the terminals work?
(Assuming a non-conductive handle.)

On Wed, 19 Dec 2012 15:44:03 -0800, mike wrote:

36ma * 4000v is 145454 mw = 145WATTS peak.

OK. I will read further before going to Radio Shack for that resistor.

On Wed, 19 Dec 2012 01:02:09 -0800, larrymoencurly wrote:

The electronics great RepairFAQ.org has information about microwave oven
repair: http://www.repairfaq.org/sam/micfaq.htm

Wow. Lots of good reading there! Thanks.

Those high voltage diodes will read open with a digital meter ...
apply at least 6V - 9V DC through a 1,000 ohm resistor and measure

I am getting the test jig set up at Radio Shack & will report back.

The big high voltage capacitor has to be discharged before handling
10,000 ohm, 10 watt resistor

OK. Now I see why a bare screwdriver isn't used.
I'll get a 10K ohm 10 Watt resistor at Radio Shack.

There's probably a bimetal thermostat mounted on the magnatron
to shut it off if it gets too hot, and you may want to replace
it because I had one that got stuck in the on position.

I have that bimetallic switch mounted on my magnatron.
Is it supposed to be on or off when the microwave is unplugged?
Mine reads at 0.4 ohms resistance with the microwave unplugged.

On 12/20/2012 4:30 PM, Danny D. wrote:
On Wed, 19 Dec 2012 10:18:05 -0600, The Daring Dufas wrote:

I do believe I mentioned discharging the capacitor through a 110k ohm
1/2 watt resistor.

I have some resistors but they're the teeny tiny ones with stripes.

I will need to go to Radio Shack and get a roughly 100 ohm resistor that
is a half watt or so first then.

I wonder though: Why wouldn't a screwdriver across the terminals work?
(Assuming a non-conductive handle.)

It will certainly discharge the cap.
Don't use the tip, because it will make a divot in the blade.
In theory, nothing happens.
As a practical matter, it doesn't take a huge transient to
take out the controller board. It's not likely, but why risk it.

On 12/20/2012 6:30 PM, Danny D. wrote:
On Wed, 19 Dec 2012 10:18:05 -0600, The Daring Dufas wrote:

I do believe I mentioned discharging the capacitor through a 110k ohm
1/2 watt resistor.

I have some resistors but they're the teeny tiny ones with stripes.

I will need to go to Radio Shack and get a roughly 100 ohm resistor that
is a half watt or so first then.

I wonder though: Why wouldn't a screwdriver across the terminals work?
(Assuming a non-conductive handle.)


Shorting it with a screwdriver is similar to The Jesus Method where you
shout JESUS! when the bright flash and boom melts the terminals and tip
of your screwdriver. A hundred thousand ohm resistor may pop which is
why you use insulated needle nose pliers and not your fingers to hold
the resistor when you use it to discharge the capacitor. Resistors are
cheaper than fingers. ^_^

TDD

Hey!! I know this was posted a few years ago but I'm wondering if you fixed/gave up on/still have this model M170B. Some door parts on ours broke and fell out recently and we're looking for those parts or the whole door. We would be willing to pay a good price.
Lee Bloomquist