From Newsgroup: uk.d-i-y

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.
--

Mike
--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Try replacing it (with an identical type and rating). A bit like people,
they can get tired.
I replaced the fuse in my Panasonic microwave a couple of years ago -
fine since.
The general rule with fuses and circuit breakers is to replace/reset
once; if they drop out again then it's time to investigate (and not to reset/replace a second time shortly after the first).
--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 21/02/2026 14:59, Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Microwaves have interlocks with several microswitches which ensure that
they cannot operate unless the door is firmly closed. It is a design
feature that they blow the fuse if anything is wrong with the
interlocks. I would check the door switches first. Be very careful if
you dismantle it - there are some high voltage caps which retain their
charge after the power is switched off.
--
Cheers,
Roger
--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On Sat, 21 Feb 2026 22:45:07 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:

On 21/02/2026 14:59, Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Microwaves have interlocks with several microswitches which ensure that
they cannot operate unless the door is firmly closed. It is a design
feature that they blow the fuse if anything is wrong with the
interlocks. I would check the door switches first. Be very careful if
you dismantle it - there are some high voltage caps which retain their >charge after the power is switched off.

There's one big bastard in particular that'll murder you. Loads of
people get killed by those every year. Make certain you discharge it
as soon as the case comes off!
--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 22/02/2026 13:23, Cursitor Doom wrote:

On Sat, 21 Feb 2026 22:45:07 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:

On 21/02/2026 14:59, Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Microwaves have interlocks with several microswitches which ensure that
they cannot operate unless the door is firmly closed. It is a design
feature that they blow the fuse if anything is wrong with the
interlocks. I would check the door switches first. Be very careful if
you dismantle it - there are some high voltage caps which retain their
charge after the power is switched off.

There's one big bastard in particular that'll murder you. Loads of
people get killed by those every year. Make certain you discharge it
as soon as the case comes off!

How many is "loads"? There seems to be very little reliable
information about electrocution by stored charge in microwave
oven capacitors. Perhaps it doesn't happen very often.
The best I could find was this:
https://www.cpsc.gov/s3fs-public/micro.pdf

"The U. S. Consumer Product Safety Commission (CPSC) warns against do-it-yourself repairs of microwave ovens. From 2006 through 2008
there was an annual average of two electrocution deaths associated
with consumers attempting to repair microwave ovens."

There is no indication whether this was from live working or
stored charge.

John



--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

Cursitor Doom <cd@notformail.com> wrote:

On Sat, 21 Feb 2026 22:45:07 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:

On 21/02/2026 14:59, Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Microwaves have interlocks with several microswitches which ensure that >they cannot operate unless the door is firmly closed. It is a design >feature that they blow the fuse if anything is wrong with the
interlocks. I would check the door switches first. Be very careful if
you dismantle it - there are some high voltage caps which retain their >charge after the power is switched off.

There's one big bastard in particular that'll murder you. Loads of
people get killed by those every year. Make certain you discharge it
as soon as the case comes off!

Do loads of people really get killed by these every year? I'm not
denying the lethality of a large, high voltage, capacitor, but how
many people take microwaves apart?
--
Chris Green
-+
--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On Sat, 21 Feb 2026 16:16:59 +0000, No mail <nomail@aolbin.com> wrote:

Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Try replacing it (with an identical type and rating). A bit like people, >they can get tired.
I replaced the fuse in my Panasonic microwave a couple of years ago -
fine since.
The general rule with fuses and circuit breakers is to replace/reset
once; if they drop out again then it's time to investigate (and not to >reset/replace a second time shortly after the first).

That advice seems to be within my range of capabilities. Thanks for
the replace once tip.
--

Mike
--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On Sat, 21 Feb 2026 22:45:07 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:

On 21/02/2026 14:59, Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Microwaves have interlocks with several microswitches which ensure that
they cannot operate unless the door is firmly closed. It is a design
feature that they blow the fuse if anything is wrong with the
interlocks. I would check the door switches first. Be very careful if
you dismantle it - there are some high voltage caps which retain their >charge after the power is switched off.

That's interesting the problem seems to have coincided with the
sagging of the door on its possibly adjustable hinges.
If I get as far as dismantling, I don't have the test equipment to
ensure non-leakage after the event. which the service manual tells me
that I would need. Maybe it would be less expensive and dangerous to
buy a new one. This current one is 5 years old.
--

Mike
--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 22/02/2026 14:21, Chris Green wrote:

Cursitor Doom <cd@notformail.com> wrote:

On Sat, 21 Feb 2026 22:45:07 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:

On 21/02/2026 14:59, Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Microwaves have interlocks with several microswitches which ensure that
they cannot operate unless the door is firmly closed. It is a design
feature that they blow the fuse if anything is wrong with the
interlocks. I would check the door switches first. Be very careful if
you dismantle it - there are some high voltage caps which retain their
charge after the power is switched off.

There's one big bastard in particular that'll murder you. Loads of
people get killed by those every year. Make certain you discharge it
as soon as the case comes off!

Do loads of people really get killed by these every year? I'm not
denying the lethality of a large, high voltage, capacitor, but how
many people take microwaves apart?

"Cursitor Doom" is a Brexiteer...

--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 22/02/2026 16:33, jkn wrote:

On 22/02/2026 14:21, Chris Green wrote:

Cursitor Doom <cd@notformail.com> wrote:

On Sat, 21 Feb 2026 22:45:07 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:

On 21/02/2026 14:59, Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Microwaves have interlocks with several microswitches which ensure that >>>> they cannot operate unless the door is firmly closed. It is a design
feature that they blow the fuse if anything is wrong with the
interlocks. I would check the door switches first. Be very careful if
you dismantle it - there are some high voltage caps which retain their >>>> charge after the power is switched off.

There's one big bastard in particular that'll murder you. Loads of
people get killed by those every year. Make certain you discharge it
as soon as the case comes off!

Do loads of people really get killed by these every year? I'm not
denying the lethality of a large, high voltage, capacitor, but how
many people take microwaves apart?

"Cursitor Doom" is a Brexiteer...

So what?
--
Labour - a bunch of rich people convincing poor people to vote for rich
people by telling poor people that "other" rich people are the reason
they are poor.

Peter Thompson

--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 22/02/2026 14:21, Chris Green wrote:

Cursitor Doom <cd@notformail.com> wrote:

On Sat, 21 Feb 2026 22:45:07 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:

On 21/02/2026 14:59, Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Microwaves have interlocks with several microswitches which ensure that
they cannot operate unless the door is firmly closed. It is a design
feature that they blow the fuse if anything is wrong with the
interlocks. I would check the door switches first. Be very careful if
you dismantle it - there are some high voltage caps which retain their
charge after the power is switched off.

There's one big bastard in particular that'll murder you. Loads of
people get killed by those every year. Make certain you discharge it
as soon as the case comes off!

Do loads of people really get killed by these every year? I'm not
denying the lethality of a large, high voltage, capacitor, but how
many people take microwaves apart?

A few years ago I looked at accidental electrocution (meaning death) in
the UK for a safety course. In the UK there were about 30 deaths per
year, the great majority of which were through digging up cables or
touching overhead wires with machinery.

But that's just what /they/ want us to know. Microwave ovens are in
fact controlled by a secret cabal of lizards.
--
SS

--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

Cursitor Doom wrote:

On Sat, 21 Feb 2026 22:45:07 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:

On 21/02/2026 14:59, Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Microwaves have interlocks with several microswitches which ensure that
they cannot operate unless the door is firmly closed. It is a design
feature that they blow the fuse if anything is wrong with the
interlocks. I would check the door switches first. Be very careful if
you dismantle it - there are some high voltage caps which retain their
charge after the power is switched off.

There's one big bastard in particular that'll murder you. Loads of
people get killed by those every year. Make certain you discharge it
as soon as the case comes off!

Yes, large capacitors can be dangerous to the uneducated, but I doubt
people are killed by those in microwave ovens. The caps that might zap
people are those in large electrical installations, and these
installations have shorting bars to deal with dielectric absorption
recovery. Large caps in equipment are usually required to have a
resistor across them to ensure discharge within a short'ish time (that I forget). Manually discharging a large cap without proper precautions may
cause a f'ing loud bang (BTDTGTTS).

If I was the OP I would not be worried. Unplug the thing, leave it for a
day, open it up, find and replace the fuse, close it up, try it ... and
award yourself un verre de vin for the money you've saved (or to drown
the sorrow that you'll have to buy a new microwave).
--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On Sun, 2/22/2026 10:58 AM, Mike Halmarack wrote:

On Sat, 21 Feb 2026 16:16:59 +0000, No mail <nomail@aolbin.com> wrote:

Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Try replacing it (with an identical type and rating). A bit like people,
they can get tired.
I replaced the fuse in my Panasonic microwave a couple of years ago -
fine since.
The general rule with fuses and circuit breakers is to replace/reset
once; if they drop out again then it's time to investigate (and not to
reset/replace a second time shortly after the first).

That advice seems to be within my range of capabilities. Thanks for
the replace once tip.

In the old days, you would look at this.
This was written before inverter-type microwave ovens were invented.

https://www.repairfaq.org/REPAIR/F_micfaq.html

Start with

4.5) Safe discharging of the high voltage capacitor

The high voltage is on the secondary side, the fuse is on
the primary side (mains voltage).

*******

With your fuse idea in mind, you're working on the primary side,
which is safe once you unplug. Your choices are, to discharge the
oil-filled cap (on a legacy microwave), or to stay away from
the two terminals on top. That means not dropping any tools
in that area, wires or the like. Considering the number of joules
potentially inside the oil filled cap, any "discharge lead" needs
a resistor in the center (and insulated paddle-handles).

The oil-filled cap, if fully energized and you drop a bare
copper wire across it, the sound effect is like a shotgun blast.
It can cause a loss of hearing in one ear (the ear facing the
oil filled cap) for a period of ten minutes (that's what happened
to me). The microwave in question, was fully assembled, a unit
at work, and it just decided to arc over right after the
power button had been depressed on the front. Microwave ovens
that cook a lot of microwave popcorn (with butter and salt in
the bag), the vapour is too much for the conformal coating
on some PCBs.

As a topic, this is similar to replacing the fan on an ATX PSU.
It can be done safely, but mainly because for units where replacement
is supported, the connector just slides off the pin header, and
the operator does not need to approach the mains cap inside the unit.
Your hands don't touch the bottom of the ATX PCB.
That means it is mostly safe, as long as you are not a klutz. Same
goes for the microwave oven. It can have its own drain resistor across it,
but a good tech assumes the drain resistor is non-functional while
working in there. By assuming the capacitor is fully charged
and you could lose an eardrum, it makes you a safer worker.

The voltage on the two terminals of the oil-filled cap, is on
the order of 5kV or so (varies). This is too much for a home multimeter,
which has a max voltage of 750v or 1000V (usually printed in white
on the selector area). There are devices which divide the voltage
(the meter impedance being in parallel with one of the resistors),
so it is possible to scale a voltage down so a multimeter
can read it. The commercial probes have plastic discs near the handle,
in an attempt to prevent arcing. The individual here, uses plastic
tubing and there are no additional fixings for HV. You would not
use a home made "40kV" design, on an actual 20kV source, as that
is just asking for trouble. Commercial versions of these would be
tested that they withhold some voltage, for a period of time.

https://www.instructables.com/High-Voltage-Probes/

Electronic equipments, have more than one input impedance,
which means the scaling of the probe would not be accurate,
if the probe is used with the wrong equipment. A multimeter
might be 10 Megohm. A scope maybe 1 megohm (when not set
to 50 ohm termination via a switch setting). If mixing things
of unknown parentage, you'd start with a voltage source
which is high enough to register with the probe in place,
and then see what the attenuation factor happens to be. AS that
builder demonstrates, it's not unusual at all for the assumed
attenuation factor to be "off a bit".

My purpose in explaining that, is to mainly point out the
safety issue, that the multimeter just cannot be connected directly.
If you were to plan to do that or need to do that, then
some sort of probe kit would be needed. And the probe kit
makes an assumption about the input impedance of the instrument.
The instructables article is to demonstrate the principle of operation,
and it has pictures of the impressive resistors used (don't
handle the HV resistors with your fingers, wear gloves, don't
contaminate the body of the gigohm resistor and degrade flash over
voltage). If soldering HV components, try not to leave sharp
points (which arc) and you may need corona dope over
exposed areas. I've built one safety device myself for
a project and doped the conductive portions. That was the
power supply for my laser in university (nitrogen laser, UV output).

I love high voltage... as long as someone else is handling it.

Paul
--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On Sun, 22 Feb 2026 14:21:45 +0000, Chris Green <cl@isbd.net> wrote:

Cursitor Doom <cd@notformail.com> wrote:

On Sat, 21 Feb 2026 22:45:07 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:

On 21/02/2026 14:59, Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Microwaves have interlocks with several microswitches which ensure that
they cannot operate unless the door is firmly closed. It is a design
feature that they blow the fuse if anything is wrong with the
interlocks. I would check the door switches first. Be very careful if
you dismantle it - there are some high voltage caps which retain their
charge after the power is switched off.

There's one big bastard in particular that'll murder you. Loads of
people get killed by those every year. Make certain you discharge it
as soon as the case comes off!

Do loads of people really get killed by these every year? I'm not
denying the lethality of a large, high voltage, capacitor, but how
many people take microwaves apart?

I don't think I'm exaggerating very much at all with my claim. Figures
are only available for more advanced Western countries. No figures for
the 3rd world where this will be far more likely. Here's what AI says
on the subject:

"The high-voltage capacitor in microwaves is a proper sneaky
killeruholds thousands of volts (often 2,000u4,000V) even after the
thing's unplugged for hours or days, thanks to how it stores charge
for the magnetron. One accidental brush across the terminals while
poking around inside, and bam: potentially lethal shock, heart
fibrillation, the lot. Bleeder resistors are meant to drain it slowly,
but they fail, get bypassed, or just aren't fast enough in some
cases.As for solid figures on annual deaths from DIY fixes? It's
surprisingly low and not well-tracked in recent years, but here's what
reliable sources pin down:The most cited stat comes straight from the
U.S. Consumer Product Safety Commission (CPSC): From 2006 through
2008, there was an annual average of about 2 electrocution deaths
linked to consumers trying to repair microwave ovens themselves. (They
issued a specific warning alert about it back then, highlighting the
hazard of touching live parts after removing the cover.)Some older or
secondary sources (YouTube vids, repair blogs, forums) throw around "4
people per year" in the US, but that seems to stem from
earlier/misremembered CPSC estimates or broader appliance
electrocutionsuit's not backed by their more recent public reports.
Newer CPSC overviews on electrocutions (like 2004u2013 or 2011u2020
aggregates) lump microwaves into "small appliances" or don't break out specifics for DIY microwave repairs, and total consumer-product
electrocutions hover around 50u60 per year overall (mostly from things
like power tools, large appliances, lighting, etc.).
Microwave-specific DIY deaths don't pop as a big category
anymoreulikely because people heed warnings more, or incidents are
rare enough not to trend.There are scattered case reports:A few
documented fatalities (e.g., a guy in Georgia in 2012, a non-qualified
worker in BC Canada around 2022u2023, an appliance repair pro in
Maryland back in '94/'99 era).
But these are individual incidents, not annual talliesushows it
happens, but not epidemic levels.

Globally? Even harder to pinudata's mostly US-centric via CPSC/NCHS,
and places like the UK/EU report very few (if any) publicized cases
tied specifically to microwave DIY. It's a niche hazard: scary as hell
when it strikes, but probably under a handful worldwide per year at
most, given how common microwaves are (hundreds of millions in homes)
versus how few people actually crack one open to fix.Bottom line: It's
rare enough that official stats don't scream alarm annually anymore,
but the risk is real and non-zerouenough that pros and safety bodies
still say "don't do it yourself unless you're qualified and discharge
the cap properly with insulated tools." If your microwave's kaput, bin
it or call a techubetter safe than zapped."


--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 22/02/2026 16:40, The Natural Philosopher wrote:

On 22/02/2026 16:33, jkn wrote:

On 22/02/2026 14:21, Chris Green wrote:

Cursitor Doom <cd@notformail.com> wrote:

On Sat, 21 Feb 2026 22:45:07 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:

On 21/02/2026 14:59, Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of >>>>>> there being a DIY repair option would be much appreciated.

Microwaves have interlocks with several microswitches which ensure
that
they cannot operate unless the door is firmly closed. It is a design >>>>> feature that they blow the fuse if anything is wrong with the
interlocks. I would check the door switches first. Be very careful if >>>>> you dismantle it - there are some high voltage caps which retain their >>>>> charge after the power is switched off.

There's one big bastard in particular that'll murder you. Loads of
people get killed by those every year. Make certain you discharge it
as soon as the case comes off!

Do loads of people really get killed by these every year? I'm not
denying the lethality of a large, high voltage, capacitor, but how
many people take microwaves apart?

"Cursitor Doom" is a Brexiteer...

So what?

Typical made up statistics, obvs

--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On Sun, 22 Feb 2026 18:29:13 +0000, jkn <jkn+nin@nicorp.co.uk> wrote:

On 22/02/2026 16:40, The Natural Philosopher wrote:

On 22/02/2026 16:33, jkn wrote:

On 22/02/2026 14:21, Chris Green wrote:

Cursitor Doom <cd@notformail.com> wrote:

On Sat, 21 Feb 2026 22:45:07 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:

On 21/02/2026 14:59, Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of >>>>>>> there being a DIY repair option would be much appreciated.

Microwaves have interlocks with several microswitches which ensure >>>>>> that
they cannot operate unless the door is firmly closed. It is a design >>>>>> feature that they blow the fuse if anything is wrong with the
interlocks. I would check the door switches first. Be very careful if >>>>>> you dismantle it - there are some high voltage caps which retain their >>>>>> charge after the power is switched off.

There's one big bastard in particular that'll murder you. Loads of
people get killed by those every year. Make certain you discharge it >>>>> as soon as the case comes off!

Do loads of people really get killed by these every year? I'm not
denying the lethality of a large, high voltage, capacitor, but how
many people take microwaves apart?

"Cursitor Doom" is a Brexiteer...

So what?

Typical made up statistics, obvs

I never quoted any statistic at all. The only thing "made up" is your criticism.
--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 22/02/2026 17:15, No mail wrote:

Cursitor Doom wrote:

On Sat, 21 Feb 2026 22:45:07 +0000, Roger Mills

There's one big bastard in particular that'll murder you. Loads of
people get killed by those every year. Make certain you discharge it
as soon as the case comes off!

Yes, large capacitors can be dangerous to the uneducated, but I doubt
people are killed by those in microwave ovens.

Indeed no. They have dropper resistors inside to discharge them rapidly
once power goes off

The caps that might zap
people are those in large electrical installations, and these
installations have shorting bars to deal with dielectric absorption recovery. Large caps in equipment are usually required to have a
resistor across them to ensure discharge within a short'ish time (that I forget). Manually discharging a large cap without proper precautions may cause a f'ing loud bang (BTDTGTTS).

Yes. as described.
Most (all?) microwave caps come with an internal 10Mohm resistor. Its
such a cheap addition no one thinks of pushing safety by having it external

e.g. https://www.amazon.co.uk/Meter-Star-Universal-Household-H-V-Capacitor/dp/B07P9HFG8B

1.0uF probably up to 5kV and a 10Mohm shunt inside

If I was the OP I would not be worried. Unplug the thing, leave it for a day, open it up, find and replace the fuse, close it up, try it ... and award yourself un verre de vin for the money you've saved (or to drown
the sorrow that you'll have to buy a new microwave).

Disconnect the power, leave it for as long as it takes to get it on the
bench, and dismantle it.

If the mains fuse has gone that's probably the transformer gone, if it's
the big HV fuse its the magnetron.

Either is likely to cost the same as a new cheap microwave.

I did re-magnetron and re-fuse mine - cost about -u80 for a 1KW magnetron
and fuse.
Absolutely get the exact same part number for the magnetron


It was a -u200 machine though
--
"Women actually are capable of being far more than the feminists will
let them."



--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 22/02/2026 16:50, Simon Simple wrote:

But that's just what /they/ want us to know.-a Microwave ovens are in
fact controlled by a secret cabal of lizards.

Fucking stupid frogs I reckon. Amazingly crude devices. very easy to fix
--
"A point of view can be a dangerous luxury when substituted for insight
and understanding".

Marshall McLuhan


--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 22/02/2026 18:11, Cursitor Doom wrote:

"The high-voltage capacitor in microwaves is a proper sneaky
killerrCoholds thousands of volts (often 2,000rCo4,000V) even after the thing's unplugged for hours or days, thanks to how it stores charge
for the magnetron.

That is total bollocks.

The caps have internal bleed resistors.

People like me who have serviced them know more than a fucking AI
getting its info from keyboard warriors who never saw the inside of one.

As I said earlier, typically 1-|F and 10 Megohm. Time constant 10 seconds

So by a minute its down to safe voltages. And it takes longer to get the screws out than that.

I wouldn't test it live with the cover off though, but mine had
microswitches to make sure you couldn't

The HV bit is 4 components. A transformer, a stack of diodes making a
5kV capable assembly in series with a (physically) large fuse and the smoothing cap. This puts the heater winding in the transformer down to
-5kV and the that's the magnetron cathode, and the anode is earthed.

If there is any measurable resistance between either heater pin and
earth the magnetron is toast.

You cant test the diode stack without less than 5V to drive it as there
are a lot of diodes in series in it. My old analog Avometer did quite
well with a 9V cell.

You can use a standard ohmmeter to test the cap isn't shorted, or the
fuse has blown

The transformer should show continuity in its windings and no short to
ground other than the winding feeding the anode.


https://www.4mcculloch.co.uk/images/mediator/559/599510968.pdf

has an excellent diagram on P14. Cheapo manufacturers omit the HV fuse
in many cases.
--
"An intellectual is a person knowledgeable in one field who speaks out
only in others...rCY

Tom Wolfe

--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 22/02/2026 18:29, jkn wrote:

On 22/02/2026 16:40, The Natural Philosopher wrote:

On 22/02/2026 16:33, jkn wrote:

many people take microwaves apart?

"Cursitor Doom" is a Brexiteer...

So what?

Typical made up statistics, obvs

ITYM europhile
--
Climate Change: Socialism wearing a lab coat.

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From Newsgroup: uk.d-i-y

On Sun, 22 Feb 2026 16:07:02 +0000
Mike Halmarack <mikehalmarack@gmail.com> wrote:

On Sat, 21 Feb 2026 22:45:07 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:

On 21/02/2026 14:59, Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Microwaves have interlocks with several microswitches which ensure
that they cannot operate unless the door is firmly closed. It is a
design feature that they blow the fuse if anything is wrong with the >interlocks. I would check the door switches first. Be very careful
if you dismantle it - there are some high voltage caps which retain
their charge after the power is switched off.

That's interesting the problem seems to have coincided with the
sagging of the door on its possibly adjustable hinges.

Before 'turn it off and back on again' there was 'take it apart and reassemble'. I fixed (for a year so far) a microwave oven by this
technique, as the door mechanism wasn't working reliably. I've no idea
what changed, but after reassembly it was positive again. I didn't find anything obviously wrong.

If I get as far as dismantling, I don't have the test equipment to
ensure non-leakage after the event. which the service manual tells me
that I would need.

The one I fixed had a separate inner shell inside the outer cover, and
I didn't need to disturb anything containing RF. The outer cover had a
couple of screws and no obvious additional screening materials (braid,
fingers etc.).

Maybe it would be less expensive and dangerous to
buy a new one. This current one is 5 years old.

If it's genuine Japanese, it will probably last for years more. I know
someone who had an AEG one die irreparably after two years. We had a
Panasonic one which we replaced at more than thirty years old, as the
case was starting to rust.
--
Joe

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From Newsgroup: uk.d-i-y

On Sat, 21 Feb 2026 14:59:26 +0000, Mike Halmarack
<mikehalmarack@gmail.com> wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

You've probably already popped the case and changed the fuse by now,
but others may find this advice of use. Better be safe than sorry (or
dead!)

https://www.repairfaq.org/REPAIR/F_micfaq1.html#MICFAQ_012


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From Newsgroup: uk.d-i-y

The Natural Philosopher wrote:

On 22/02/2026 18:11, Cursitor Doom wrote:

"The high-voltage capacitor in microwaves is a proper sneaky
killerrCoholds thousands of volts (often 2,000rCo4,000V) even after the
thing's unplugged for hours or days, thanks to how it stores charge
for the magnetron.

That is total bollocks.

+1

... snipped

https://www.4mcculloch.co.uk/images/mediator/559/599510968.pdf

has an excellent diagram on P14. Cheapo manufacturers omit the HV fuse
in many cases.

Thanks for posting that link - it's an excellent book.
I didn't know about the monitor switch - one less unknown unknown.
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From Newsgroup: uk.d-i-y

On Sun, 22 Feb 2026 13:00:56 -0500, Paul <nospam@needed.invalid>
wrote:

On Sun, 2/22/2026 10:58 AM, Mike Halmarack wrote:

On Sat, 21 Feb 2026 16:16:59 +0000, No mail <nomail@aolbin.com> wrote:

Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Try replacing it (with an identical type and rating). A bit like people, >>> they can get tired.
I replaced the fuse in my Panasonic microwave a couple of years ago -
fine since.
The general rule with fuses and circuit breakers is to replace/reset
once; if they drop out again then it's time to investigate (and not to
reset/replace a second time shortly after the first).

That advice seems to be within my range of capabilities. Thanks for
the replace once tip.

In the old days, you would look at this.
This was written before inverter-type microwave ovens were invented.

https://www.repairfaq.org/REPAIR/F_micfaq.html

Start with

4.5) Safe discharging of the high voltage capacitor

The high voltage is on the secondary side, the fuse is on
the primary side (mains voltage).

*******

With your fuse idea in mind, you're working on the primary side,
which is safe once you unplug. Your choices are, to discharge the
oil-filled cap (on a legacy microwave), or to stay away from
the two terminals on top. That means not dropping any tools
in that area, wires or the like. Considering the number of joules
potentially inside the oil filled cap, any "discharge lead" needs
a resistor in the center (and insulated paddle-handles).

The oil-filled cap, if fully energized and you drop a bare
copper wire across it, the sound effect is like a shotgun blast.
It can cause a loss of hearing in one ear (the ear facing the
oil filled cap) for a period of ten minutes (that's what happened
to me). The microwave in question, was fully assembled, a unit
at work, and it just decided to arc over right after the
power button had been depressed on the front. Microwave ovens
that cook a lot of microwave popcorn (with butter and salt in
the bag), the vapour is too much for the conformal coating
on some PCBs.

As a topic, this is similar to replacing the fan on an ATX PSU.
It can be done safely, but mainly because for units where replacement
is supported, the connector just slides off the pin header, and
the operator does not need to approach the mains cap inside the unit.
Your hands don't touch the bottom of the ATX PCB.
That means it is mostly safe, as long as you are not a klutz. Same
goes for the microwave oven. It can have its own drain resistor across it, >but a good tech assumes the drain resistor is non-functional while
working in there. By assuming the capacitor is fully charged
and you could lose an eardrum, it makes you a safer worker.

The voltage on the two terminals of the oil-filled cap, is on
the order of 5kV or so (varies). This is too much for a home multimeter, >which has a max voltage of 750v or 1000V (usually printed in white
on the selector area). There are devices which divide the voltage
(the meter impedance being in parallel with one of the resistors),
so it is possible to scale a voltage down so a multimeter
can read it. The commercial probes have plastic discs near the handle,
in an attempt to prevent arcing. The individual here, uses plastic
tubing and there are no additional fixings for HV. You would not
use a home made "40kV" design, on an actual 20kV source, as that
is just asking for trouble. Commercial versions of these would be
tested that they withhold some voltage, for a period of time.

https://www.instructables.com/High-Voltage-Probes/

Electronic equipments, have more than one input impedance,
which means the scaling of the probe would not be accurate,
if the probe is used with the wrong equipment. A multimeter
might be 10 Megohm. A scope maybe 1 megohm (when not set
to 50 ohm termination via a switch setting). If mixing things
of unknown parentage, you'd start with a voltage source
which is high enough to register with the probe in place,
and then see what the attenuation factor happens to be. AS that
builder demonstrates, it's not unusual at all for the assumed
attenuation factor to be "off a bit".

My purpose in explaining that, is to mainly point out the
safety issue, that the multimeter just cannot be connected directly.
If you were to plan to do that or need to do that, then
some sort of probe kit would be needed. And the probe kit
makes an assumption about the input impedance of the instrument.
The instructables article is to demonstrate the principle of operation,
and it has pictures of the impressive resistors used (don't
handle the HV resistors with your fingers, wear gloves, don't
contaminate the body of the gigohm resistor and degrade flash over
voltage). If soldering HV components, try not to leave sharp
points (which arc) and you may need corona dope over
exposed areas. I've built one safety device myself for
a project and doped the conductive portions. That was the
power supply for my laser in university (nitrogen laser, UV output).

I love high voltage... as long as someone else is handling it.

Paul

Thanks for all the excellent and detailed information.
You make it all sound so exciting.
Too exciting for me, I have to admit.
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From Newsgroup: uk.d-i-y

On Sun, 22 Feb 2026 21:20:48 +0000, Joe <joe@jretrading.com> wrote:

On Sun, 22 Feb 2026 16:07:02 +0000
Mike Halmarack <mikehalmarack@gmail.com> wrote:

On Sat, 21 Feb 2026 22:45:07 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:

On 21/02/2026 14:59, Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Microwaves have interlocks with several microswitches which ensure
that they cannot operate unless the door is firmly closed. It is a
design feature that they blow the fuse if anything is wrong with the
interlocks. I would check the door switches first. Be very careful
if you dismantle it - there are some high voltage caps which retain
their charge after the power is switched off.

That's interesting the problem seems to have coincided with the
sagging of the door on its possibly adjustable hinges.

Before 'turn it off and back on again' there was 'take it apart and >reassemble'. I fixed (for a year so far) a microwave oven by this
technique, as the door mechanism wasn't working reliably. I've no idea
what changed, but after reassembly it was positive again. I didn't find >anything obviously wrong.

If I get as far as dismantling, I don't have the test equipment to
ensure non-leakage after the event. which the service manual tells me
that I would need.

The one I fixed had a separate inner shell inside the outer cover, and
I didn't need to disturb anything containing RF. The outer cover had a
couple of screws and no obvious additional screening materials (braid, >fingers etc.).

Maybe it would be less expensive and dangerous to
buy a new one. This current one is 5 years old.

If it's genuine Japanese, it will probably last for years more. I know >someone who had an AEG one die irreparably after two years. We had a >Panasonic one which we replaced at more than thirty years old, as the
case was starting to rust.

Thanks for the encougement.
--

Mike
--- Synchronet 3.21b-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On Sun, 22 Feb 2026 17:15:05 +0000, No mail <nomail@aolbin.com> wrote:

Cursitor Doom wrote:

On Sat, 21 Feb 2026 22:45:07 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:

On 21/02/2026 14:59, Mike Halmarack wrote:

Suggestions about what might have caused this and the likelihood of
there being a DIY repair option would be much appreciated.

Microwaves have interlocks with several microswitches which ensure that
they cannot operate unless the door is firmly closed. It is a design
feature that they blow the fuse if anything is wrong with the
interlocks. I would check the door switches first. Be very careful if
you dismantle it - there are some high voltage caps which retain their
charge after the power is switched off.

There's one big bastard in particular that'll murder you. Loads of
people get killed by those every year. Make certain you discharge it
as soon as the case comes off!

Yes, large capacitors can be dangerous to the uneducated, but I doubt
people are killed by those in microwave ovens. The caps that might zap >people are those in large electrical installations, and these
installations have shorting bars to deal with dielectric absorption >recovery. Large caps in equipment are usually required to have a
resistor across them to ensure discharge within a short'ish time (that I >forget). Manually discharging a large cap without proper precautions may >cause a f'ing loud bang (BTDTGTTS).

If I was the OP I would not be worried. Unplug the thing, leave it for a >day, open it up, find and replace the fuse, close it up, try it ... and >award yourself un verre de vin for the money you've saved (or to drown
the sorrow that you'll have to buy a new microwave).

Yet more encouragment. Much appreciated.
--

Mike
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From Newsgroup: uk.d-i-y

On Sun, 22 Feb 2026 19:59:15 +0000, The Natural Philosopher <tnp@invalid.invalid> wrote:

On 22/02/2026 17:15, No mail wrote:

Cursitor Doom wrote:

On Sat, 21 Feb 2026 22:45:07 +0000, Roger Mills

There's one big bastard in particular that'll murder you. Loads of
people get killed by those every year. Make certain you discharge it
as soon as the case comes off!

Yes, large capacitors can be dangerous to the uneducated, but I doubt
people are killed by those in microwave ovens.

Indeed no. They have dropper resistors inside to discharge them rapidly
once power goes off

The caps that might zap
people are those in large electrical installations, and these
installations have shorting bars to deal with dielectric absorption
recovery. Large caps in equipment are usually required to have a
resistor across them to ensure discharge within a short'ish time (that I
forget). Manually discharging a large cap without proper precautions may
cause a f'ing loud bang (BTDTGTTS).

Yes. as described.
Most (all?) microwave caps come with an internal 10Mohm resistor. Its
such a cheap addition no one thinks of pushing safety by having it external

e.g. >https://www.amazon.co.uk/Meter-Star-Universal-Household-H-V-Capacitor/dp/B07P9HFG8B

1.0uF probably up to 5kV and a 10Mohm shunt inside

If I was the OP I would not be worried. Unplug the thing, leave it for a
day, open it up, find and replace the fuse, close it up, try it ... and
award yourself un verre de vin for the money you've saved (or to drown
the sorrow that you'll have to buy a new microwave).

Disconnect the power, leave it for as long as it takes to get it on the >bench, and dismantle it.

If the mains fuse has gone that's probably the transformer gone, if it's
the big HV fuse its the magnetron.

Either is likely to cost the same as a new cheap microwave.

I did re-magnetron and re-fuse mine - cost about u80 for a 1KW magnetron
and fuse.
Absolutely get the exact same part number for the magnetron

It was a u200 machine though

More useful info, thanks.
--

Mike
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