Microwave repair...

[Ricky]

My microwave stopped working last night. Looks like it\'s the fuse. I can barely make out 15A on the metal cap, but no indication of fast or slow blow. The case is ceramic. Any ideas?

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

[Fred Bloggs]

On Saturday, June 17, 2023 at 6:07:57 PM UTC-4, Ricky wrote:

My microwave stopped working last night. Looks like it\'s the fuse. I can barely make out 15A on the metal cap, but no indication of fast or slow blow. The case is ceramic. Any ideas?

https://www.homedepot.com/p/Cooper-Bussmann-ABC-Series-15-Amp-Microwave-Oven-Fuses-2-Pack-BP-ABC-15/100180250

Looks like a pig in a poke.

Fuse didn\'t just blow on its own, there was a reason for it. What kind of power supply in the uwave?

If you can\'t describe it using standard engineering terminology, don\'t bother responding.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

[Phil Allison]

Tricky Ricky wrote:
--------------------------

My microwave stopped working last night.
Looks like it\'s the fuse.
I can barely make out 15A on the metal cap, but no indication of fast or slow blow.
The case is ceramic.

** You\'ll need an ohm meter test to tell if a ceramic case fuse is blown.
Any 15A ceramic of the correct size will work, but best find a HRC ( high rupture current) type.

Any ideas?

....... Phil

 

[Ricky]

On Saturday, June 17, 2023 at 6:58:32 PM UTC-4, Fred Bloggs wrote:

On Saturday, June 17, 2023 at 6:07:57 PM UTC-4, Ricky wrote:
My microwave stopped working last night. Looks like it\'s the fuse. I can barely make out 15A on the metal cap, but no indication of fast or slow blow. The case is ceramic. Any ideas?
https://www.homedepot.com/p/Cooper-Bussmann-ABC-Series-15-Amp-Microwave-Oven-Fuses-2-Pack-BP-ABC-15/100180250

Looks like a pig in a poke.

Fuse didn\'t just blow on its own, there was a reason for it. What kind of power supply in the uwave?

If you can\'t describe it using standard engineering terminology, don\'t bother responding.

LOL You are a trip. I\'ve already ordered some fuses. Enjoy.

--

Rick C.

+ Get 1,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209

 

[Ricky]

On Sunday, June 18, 2023 at 1:42:35 AM UTC-4, Phil Allison wrote:

Tricky Ricky wrote:
--------------------------
My microwave stopped working last night.
Looks like it\'s the fuse.
I can barely make out 15A on the metal cap, but no indication of fast or slow blow.
The case is ceramic.

** You\'ll need an ohm meter test to tell if a ceramic case fuse is blown.
Any 15A ceramic of the correct size will work, but best find a HRC ( high rupture current) type.

Any ideas?


...... Phil

The only other option is the door switches. Seems they use three. Two are actuated when the door latch is fully engaged, one on each side of the line. Another is deactivated when the latch is first engaged, i.e. latch is pushed in, but not fully latched. This one shorts the circuit side of the other two switches. I can\'t get why this is there, other than to act as a crowbar in case the other two don\'t work and power is applied with the door open.

I can\'t verify that one of the line switches is working. Looks like the plastic mechanism is not moving to activate the switch. But it\'s hard to reach, so I\'ll try the fuse first. Besides, according to the schematic, the fuse, timer switch and pilot light are on the power input side of the door switches, so the light would come on anytime the timer switch is closed and the unit is plugged in... if the fuse is good. I\'m not seeing a pilot light. I suppose the pilot light could be failed, but neon bulbs typically last a long time.

--

Rick C.

-- Get 1,000 miles of free Supercharging
-- Tesla referral code - https://ts.la/richard11209

 

[Bertrand Sindri]

Ricky <gnuarm.deletethisbit@gmail.com> wrote:

The only other option is the door switches. Seems they use three.
Two are actuated when the door latch is fully engaged, one on each
side of the line. Another is deactivated when the latch is first
engaged, i.e. latch is pushed in, but not fully latched. This one
shorts the circuit side of the other two switches. I can\'t get why
this is there, other than to act as a crowbar in case the other two
don\'t work and power is applied with the door open.

Sigh... I little use of internet search engines can often help here:

https://www.answers.com/movies-and-television/What_does_an_interlock_monitor_switch_do_in_a_microwave_oven

That third which is present *exactly* to be a crowbar to prevent power
application with the door open.

 

[John Larkin]

On Sat, 17 Jun 2023 22:42:32 -0700 (PDT), Phil Allison
<pallison49@gmail.com> wrote:

Tricky Ricky wrote:
--------------------------
My microwave stopped working last night.
Looks like it\'s the fuse.
I can barely make out 15A on the metal cap, but no indication of fast or slow blow.
The case is ceramic.


** You\'ll need an ohm meter test to tell if a ceramic case fuse is blown.
Any 15A ceramic of the correct size will work, but best find a HRC ( high rupture current) type.

Any ideas?


...... Phil

A DVM (with thermocouple input) is a fundamental home appliance. As is
a bench power supply, a Dremel, some test leads, and a glue gun.

I\'ve considered having a cheap LCD oscilloscope around, but it would
be rarely or never used at home.

 

[Fred Bloggs]

On Sunday, June 18, 2023 at 4:03:42 AM UTC-4, Ricky wrote:

On Saturday, June 17, 2023 at 6:58:32 PM UTC-4, Fred Bloggs wrote:
On Saturday, June 17, 2023 at 6:07:57 PM UTC-4, Ricky wrote:
My microwave stopped working last night. Looks like it\'s the fuse. I can barely make out 15A on the metal cap, but no indication of fast or slow blow. The case is ceramic. Any ideas?
https://www.homedepot.com/p/Cooper-Bussmann-ABC-Series-15-Amp-Microwave-Oven-Fuses-2-Pack-BP-ABC-15/100180250

Looks like a pig in a poke.

Fuse didn\'t just blow on its own, there was a reason for it. What kind of power supply in the uwave?

If you can\'t describe it using standard engineering terminology, don\'t bother responding.
LOL You are a trip. I\'ve already ordered some fuses. Enjoy.

Eaton says those fuses are fast-blo, but they\'re rated for 200% rated for a full 120 seconds or something, which should be plenty to coast through power supply turn-on surges- unless there\'s a problem with the power supply.

\"The only other option is the door switches. Seems they use three. Two are actuated when the door latch is fully engaged, one on each side of the line.. Another is deactivated when the latch is first engaged, i.e. latch is pushed in, but not fully latched. This one shorts the circuit side of the other two switches. I can\'t get why this is there, other than to act as a crowbar in case the other two don\'t work and power is applied with the door open..\"

It\'s a safety switch to disable the oven in the event the door does not properly seat which can result in excessive microwave leakage to the external environment. The door could have been damaged- hypothetically, not your specific case. That\'s just one of many failure modes leading to excessive leakage, but probably the most common since it\'s directly accessible to the consumer. Leakage used to be capped at 5mW/cm^2 at 2 inches from any surface of the appliance.

https://www.fda.gov/radiation-emitting-products/resources-you-radiation-emitting-products/microwave-ovens

\"I can\'t verify that one of the line switches is working. Looks like the plastic mechanism is not moving to activate the switch. But it\'s hard to reach, so I\'ll try the fuse first. Besides, according to the schematic, the fuse, timer switch and pilot light are on the power input side of the door switches, so the light would come on anytime the timer switch is closed and the unit is plugged in... if the fuse is good. I\'m not seeing a pilot light. I suppose the pilot light could be failed, but neon bulbs typically last a long time.\"

Fuses are placed so as to completely remove voltage relative to safety ground every place in and on the appliance. That necessitates fusing the \"hot\" lead.

Remove the cover. Clip lead your voltmeter to the safety GND, the use the other lead to probe for voltage. If you don\'t have 120VAC on the load side of the fuse, then it\'s obviously open isn\'t it. Most common fault is power supply. Your oven sounds simple. Could be a shorted doubler cap, diode, or xformer winding ( 2x magnetron electrode and filament power).

--

Rick C.

+ Get 1,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209

 

[Ricky]

On Sunday, June 18, 2023 at 8:38:40 AM UTC-4, Bertrand Sindri wrote:

Ricky <gnuarm.del...@gmail.com> wrote:
The only other option is the door switches. Seems they use three.
Two are actuated when the door latch is fully engaged, one on each
side of the line. Another is deactivated when the latch is first
engaged, i.e. latch is pushed in, but not fully latched. This one
shorts the circuit side of the other two switches. I can\'t get why
this is there, other than to act as a crowbar in case the other two
don\'t work and power is applied with the door open.
Sigh... I little use of internet search engines can often help here:

https://www.answers.com/movies-and-television/What_does_an_interlock_monitor_switch_do_in_a_microwave_oven

That third which is present *exactly* to be a crowbar to prevent power
application with the door open.

Why are you sighing? I sussed out what the switch does and you confirmed it.
Thank you.

--

Rick C.

-+ Get 1,000 miles of free Supercharging
-+ Tesla referral code - https://ts.la/richard11209

 

[Fred Bloggs]

On Sunday, June 18, 2023 at 11:25:06 AM UTC-4, John Larkin wrote:

On Sat, 17 Jun 2023 22:42:32 -0700 (PDT), Phil Allison
palli...@gmail.com> wrote:

Tricky Ricky wrote:
--------------------------
My microwave stopped working last night.
Looks like it\'s the fuse.
I can barely make out 15A on the metal cap, but no indication of fast or slow blow.
The case is ceramic.


** You\'ll need an ohm meter test to tell if a ceramic case fuse is blown..
Any 15A ceramic of the correct size will work, but best find a HRC ( high rupture current) type.

Any ideas?


...... Phil
A DVM (with thermocouple input) is a fundamental home appliance. As is
a bench power supply, a Dremel, some test leads, and a glue gun.

I\'ve considered having a cheap LCD oscilloscope around, but it would
be rarely or never used at home.

Microwave leakage detectors have REALLY come down in price- as in 10% the price from 30 some odd years ago.
https://www.amazon.com/s?k=microwave+oven+tester&crid=1563A4HS6W6JI&sprefix=microwave+oven+tester%2Caps%2C107&ref=nb_sb_noss_1

 

[Fred Bloggs]

On Sunday, June 18, 2023 at 11:54:32 AM UTC-4, Ricky wrote:

On Sunday, June 18, 2023 at 8:38:40 AM UTC-4, Bertrand Sindri wrote:
Ricky <gnuarm.del...@gmail.com> wrote:
The only other option is the door switches. Seems they use three.
Two are actuated when the door latch is fully engaged, one on each
side of the line. Another is deactivated when the latch is first
engaged, i.e. latch is pushed in, but not fully latched. This one
shorts the circuit side of the other two switches. I can\'t get why
this is there, other than to act as a crowbar in case the other two
don\'t work and power is applied with the door open.
Sigh... I little use of internet search engines can often help here:

https://www.answers.com/movies-and-television/What_does_an_interlock_monitor_switch_do_in_a_microwave_oven

That third which is present *exactly* to be a crowbar to prevent power
application with the door open.
Why are you sighing? I sussed out what the switch does and you confirmed it.
Thank you.

He couldn\'t find an excuse to post a link to an amazon product for commission.

--

Rick C.

-+ Get 1,000 miles of free Supercharging
-+ Tesla referral code - https://ts.la/richard11209

 

[Ricky]

On Sunday, June 18, 2023 at 11:25:06 AM UTC-4, John Larkin wrote:

On Sat, 17 Jun 2023 22:42:32 -0700 (PDT), Phil Allison
palli...@gmail.com> wrote:

Tricky Ricky wrote:
--------------------------
My microwave stopped working last night.
Looks like it\'s the fuse.
I can barely make out 15A on the metal cap, but no indication of fast or slow blow.
The case is ceramic.


** You\'ll need an ohm meter test to tell if a ceramic case fuse is blown..
Any 15A ceramic of the correct size will work, but best find a HRC ( high rupture current) type.

Any ideas?


...... Phil
A DVM (with thermocouple input) is a fundamental home appliance. As is
a bench power supply, a Dremel, some test leads, and a glue gun.

I\'ve considered having a cheap LCD oscilloscope around, but it would
be rarely or never used at home.

Other than checking the fuse, it would all be pointless here, because I can\'t get to the switches to probe. Easier to just give the fuse a try, then toss the unit in the bin if that doesn\'t fix it.

Like I\'ve said, the microwave has a debugging tool built in, the pilot light, which says it\'s the fuse.

--

Rick C.

+- Get 1,000 miles of free Supercharging
+- Tesla referral code - https://ts.la/richard11209

 

[Fred Bloggs]

On Sunday, June 18, 2023 at 11:59:44 AM UTC-4, Ricky wrote:

On Sunday, June 18, 2023 at 11:25:06 AM UTC-4, John Larkin wrote:
On Sat, 17 Jun 2023 22:42:32 -0700 (PDT), Phil Allison
palli...@gmail.com> wrote:

Tricky Ricky wrote:
--------------------------
My microwave stopped working last night.
Looks like it\'s the fuse.
I can barely make out 15A on the metal cap, but no indication of fast or slow blow.
The case is ceramic.


** You\'ll need an ohm meter test to tell if a ceramic case fuse is blown.
Any 15A ceramic of the correct size will work, but best find a HRC ( high rupture current) type.

Any ideas?


...... Phil
A DVM (with thermocouple input) is a fundamental home appliance. As is
a bench power supply, a Dremel, some test leads, and a glue gun.

I\'ve considered having a cheap LCD oscilloscope around, but it would
be rarely or never used at home.
Other than checking the fuse, it would all be pointless here, because I can\'t get to the switches to probe. Easier to just give the fuse a try, then toss the unit in the bin if that doesn\'t fix it.

You don\'t have to get to the switches. Just probe the circuit at a point where the switch is supposed deliver continuity. Oven is unplugged and meter set to ohms. Beyond astounding you can\'t figure that out. Switches are unlikely cause of blown fuse.

Like I\'ve said, the microwave has a debugging tool built in, the pilot light, which says it\'s the fuse.

--

Rick C.

+- Get 1,000 miles of free Supercharging
+- Tesla referral code - https://ts.la/richard11209

 

[Martin Brown]

On 17/06/2023 23:07, Ricky wrote:

My microwave stopped working last night. Looks like it\'s the fuse.
I can barely make out 15A on the metal cap, but no indication of fast
or slow blow. The case is ceramic. Any ideas?

Such protective fuses seldom blow without a very good reason.
Usually that the magnetron PSU has failed in some interesting way.

I had one fail that way and repaired under warrantee.

Replacing the fuse may only result in blowing it again immediately.

--
Martin Brown

 

[Ricky]

On Sunday, June 18, 2023 at 5:49:22 PM UTC-4, Martin Brown wrote:

On 17/06/2023 23:07, Ricky wrote:
My microwave stopped working last night. Looks like it\'s the fuse.
I can barely make out 15A on the metal cap, but no indication of fast
or slow blow. The case is ceramic. Any ideas?
Such protective fuses seldom blow without a very good reason.
Usually that the magnetron PSU has failed in some interesting way.

I had one fail that way and repaired under warrantee.

Replacing the fuse may only result in blowing it again immediately.

What is your point? Are you suggesting I try replacing the power supply to prevent wasting a fuse?

--

Rick C.

++ Get 1,000 miles of free Supercharging
++ Tesla referral code - https://ts.la/richard11209

 

[Dave Platt]

In article <u6nu4r$1oter$1@dont-email.me>,
Martin Brown <\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

My microwave stopped working last night. Looks like it\'s the fuse.
I can barely make out 15A on the metal cap, but no indication of fast
or slow blow. The case is ceramic. Any ideas?

Such protective fuses seldom blow without a very good reason.
Usually that the magnetron PSU has failed in some interesting way.

I had one fail that way and repaired under warrantee.

Replacing the fuse may only result in blowing it again immediately.

On the one I had for years (an Amana commercial microwave) the fuse
blew for the reason others have mentioned.

Part of the door-switch assembly failed (some plastic wore down, I
think), and the \"disconnect the mains if the door is opened\" switch
didn\'t open properly when the door was opened.

The secondary (safety) switch in the door-switch assembly operated as
intended. It was/is designed to close (creating a short circuit
across the power to the magnetron) an instant after the primary switch
is supposed to open. Since the primary was still closed, the
secondary shorted the supply and blew the fuse.

I replaced the fuse (figuring that it might have just been an
age-related failure). Nope. The microwave worked OK for a day or so,
but the next time somebody opened the door before pushing the \"off\"
button, the fuse blew again.

Replacing the failing switch (or its actuator) wasn\'t practical or safe,
as they aren\'t made available separately. The tech replaced the whole
multi-switch assembly, and the microwave worked fine for several years
more. The cost (including service) was about a quarter of the cost of
a new microwave of equivalent type.

 

[Dennis]

On 6/18/23 16:49, Martin Brown wrote:

On 17/06/2023 23:07, Ricky wrote:
My microwave stopped working last night.   Looks like it\'s the fuse.
I can barely make out 15A on the metal cap, but no indication of fast
or slow blow.  The case is ceramic.  Any ideas?

Such protective fuses seldom blow without a very good reason.
Usually that the magnetron PSU has failed in some interesting way.

I had one fail that way and repaired under warrantee.

Replacing the fuse may only result in blowing it again immediately.

The fuse on ours blew and I found a replacement at Home Depot. They had
a couple of ones labeled for microwave use - I got the one that matched
the part number (it had several part numbers on the label).

It seems it just died of old age (~15-20 yr). The replacement has worked
fine for several month and is still going.

 

[Ricky]

On Sunday, June 18, 2023 at 6:29:57 PM UTC-4, Dave Platt wrote:

In article <u6nu4r$1oter$1...@dont-email.me>,
Martin Brown <\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

My microwave stopped working last night. Looks like it\'s the fuse.
I can barely make out 15A on the metal cap, but no indication of fast
or slow blow. The case is ceramic. Any ideas?

Such protective fuses seldom blow without a very good reason.
Usually that the magnetron PSU has failed in some interesting way.

I had one fail that way and repaired under warrantee.

Replacing the fuse may only result in blowing it again immediately.
On the one I had for years (an Amana commercial microwave) the fuse
blew for the reason others have mentioned.

Which was what?

Part of the door-switch assembly failed (some plastic wore down, I
think), and the \"disconnect the mains if the door is opened\" switch
didn\'t open properly when the door was opened.

This is actually two switches. So they both had to fail.

The secondary (safety) switch in the door-switch assembly operated as
intended. It was/is designed to close (creating a short circuit
across the power to the magnetron) an instant after the primary switch
is supposed to open. Since the primary was still closed, the
secondary shorted the supply and blew the fuse.

I replaced the fuse (figuring that it might have just been an
age-related failure). Nope. The microwave worked OK for a day or so,
but the next time somebody opened the door before pushing the \"off\"
button, the fuse blew again.

Replacing the failing switch (or its actuator) wasn\'t practical or safe,
as they aren\'t made available separately. The tech replaced the whole
multi-switch assembly, and the microwave worked fine for several years
more. The cost (including service) was about a quarter of the cost of
a new microwave of equivalent type.

The switches can be bought. They come with many lever arrangements, so you have to match up to the one in the oven, but they are not so hard to find. The problem is getting to the suckers. I\'m pretty lazy when it comes to this sort of repair. My concern is one of the primary safety switches does not seem to be activating because of the plastic bits I can\'t see. So if the fuse doesn\'t repair it, it\'s going in the bin.

I tried getting a friend\'s microwave repaired last year and there was no one who works on these anymore. Most microwaves sold are under $100, so not much room for profit in repairing them.

I wouldn\'t even have bothered with the fuse, but I can\'t find one with dial controls, medium sized internal dimensions and a sub $300 price tag.

--

Rick C.

--- Get 1,000 miles of free Supercharging
--- Tesla referral code - https://ts.la/richard11209

 

[Jan Panteltje]

On a sunny day (Sun, 18 Jun 2023 08:54:44 -0700 (PDT)) it happened Fred Bloggs
<bloggs.fredbloggs.fred@gmail.com> wrote in
<214b80e8-c23b-45ac-90ef-c6ba90042c50n@googlegroups.com>:

On Sunday, June 18, 2023 at 11:25:06 AM UTC-4, John Larkin wrote:
On Sat, 17 Jun 2023 22:42:32 -0700 (PDT), Phil Allison
palli...@gmail.com> wrote:

Tricky Ricky wrote:
--------------------------
My microwave stopped working last night.
Looks like it\'s the fuse.
I can barely make out 15A on the metal cap, but no indication of fast =
or slow blow.
The case is ceramic.


** You\'ll need an ohm meter test to tell if a ceramic case fuse is blown=
.
Any 15A ceramic of the correct size will work, but best find a HRC ( hi=
gh rupture current) type.

Any ideas?


...... Phil
A DVM (with thermocouple input) is a fundamental home appliance. As is
a bench power supply, a Dremel, some test leads, and a glue gun.

I\'ve considered having a cheap LCD oscilloscope around, but it would
be rarely or never used at home.

Microwave leakage detectors have REALLY come down in price- as in 10% the p=
rice from 30 some odd years ago.
https://www.amazon.com/s?k=microwave+oven+tester&crid=1563A4HS6W6JI&sprefix=microwave+oven+tester%2Caps%2C107&ref=nb_sb_noss_1

More universal is this:
https://www.ebay.com/itm/374555008463?
it has a pot to set sensitivity
detects any RF, beeps if you use a microwave from several meters away.
I calibrate it by holding it next to a Raspberry Pi and then turning the pot so it just beeps.

Any RF will then trigger it.

Guy with celphone walking past the house makes it beep too..
Better turn your WiFi off (I do not use WiFi, security is broken)!
Also have a normal microwave leakage detector with small analog meter, it never shows anything on the microwave oven.

Only scope I have is the old Trio analog 10 MHz one... from 1979 or so, very portable, visible here:
https://panteltje.nl/pub/h501s_drone_remote_power_test_ground_control_1_IMG_6276.JPG
the frog is thinking
An other essential tool on that table:
voltage sensing screwdriver
https://www.tinytronics.nl/shop/en/tools-and-mounting/tools/screwdrivers/screwdriver-set-with-voltage-detector-3-pieces

All RF via spectrum analyzers with RTL-SDR sticks, up to 1.6 GHz
https://www.ebay.com/itm/185946399375
https://panteltje.nl/panteltje/xpsa/index.html
old version, new one has more features and FM stereo
https://panteltje.nl/pub/xpsa-0.7.gif
and a downconverter for it for 2.4 GHz
https://panteltje.nl/pub/2.4_GHz_to_1.5_GHz_down_converter_closeup_IMG_4660.JPG

So, bacics tools : soldering iron, .1 inch holes perfoboard (no peeseebees), brain,
and understanding.
https://panteltje.nl/panteltje/raspberry_pi_dvb-s_transmitter/
and programming experience in C and asm

But having huge femto second scopes in your workshop does of course impress customers...
That has always been the case

To test a f*cking fuse use a battery and lightbulb (Edison type) or LED with resistor if you wannabee modern.
else your tongue!

It is all simple, will be I my book: \'The Fart of Electronics\' provided I will ever write it.

Wonder, maybe I should, but then again after the nukes fall it will be back to spark transmiters
and what\'s that detector ?
https://earlyradiohistory.us/1917de.htm

OK, smoke signals then !

beep AI I am beep
hehe

 

[Jan Panteltje]

On a sunny day (Sun, 18 Jun 2023 22:49:15 +0100) it happened Martin Brown
<\'\'\'newspam\'\'\'@nonad.co.uk> wrote in <u6nu4r$1oter$1@dont-email.me>:

On 17/06/2023 23:07, Ricky wrote:
My microwave stopped working last night. Looks like it\'s the fuse.
I can barely make out 15A on the metal cap, but no indication of fast
or slow blow. The case is ceramic. Any ideas?

Such protective fuses seldom blow without a very good reason.
Usually that the magnetron PSU has failed in some interesting way.

I had one fail that way and repaired under warrantee.

Replacing the fuse may only result in blowing it again immediately.

Yep,
check diode and capacitor in HV part to the magnetron
I had a magnetron tube with a short not so long ago, ordered a new one spare part, working again.
Ohm meter showed a few hundred ohms short on the magnetron,
took the old magnetron assembly apart, so bsve 2 nice strong round magnets now for experiments.
Kids stuff.