My microwave oven, now 15+ years old, blew its fuse yesterday.

It's a slow-blow fuse (T10 AL 250V P).

I'm going to replace it tomorrow, but how likely is it that whatever caused it to go is just going to do it again straight away?

Daniele

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 28/01/2025 20:22, D.M. Procida wrote:

My microwave oven, now 15+ years old, blew its fuse yesterday.

It's a slow-blow fuse (T10 AL 250V P).

I'm going to replace it tomorrow, but how likely is it that whatever caused it
to go is just going to do it again straight away?

Daniele

Quite likely.

I am surprised the high voltage fuse didn't blow. That's what happened
to mine - the magnetron had an anode cathode short and had to be
replaced . That and a failure of the high voltage capacitor or the high
voltage diode are really the most common problems, and are trivial to
replace.

It is possible to remove the HT fuse mostly, and if the thing doesnt
blow the mains after that, there are only 5 components on the HT side
to check - the magnetron, the HT fuse itself, the diode the capacitor
and the HT transformer. If THAT goes you are in trouble with likely
magic smoke coming out.

You can check the magnetron off power by putting a resistance meter
between cathode heater and ground. Should be open circuit. The
capacitor you can use a resistance meter to see if the needle jumps and
then goes back to open circuit.

The fuse is obvious to test but the diode is not - its stacked diodes in
series and needs a few volts to turn on.

If the magnetro9n has gone its generally around 50% of the unit cost, or
more, (somewhere in the £30-£150 range) and you should consider
scrapping the unit.

Diodes fuses and capacitors are all sub £5.

Apart from that I found mine easy enough to fix, with the proviso you absolutely dont want to power it up with the covers off.


All in all its not worth the faff for a sub £100 unit, but mine was a
£250 catering unit, and a £75 magnetron and a 90p fuse was in budget.


--
"The most difficult subjects can be explained to the most slow witted
man if he has not formed any idea of them already; but the simplest
thing cannot be made clear to the most intelligent man if he is firmly persuaded that he knows already, without a shadow of doubt, what is laid
before him."

- Leo Tolstoy

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 28 Jan 2025 at 23:40:43 GMT, "The Natural Philosopher"
<[email protected]d> wrote:

On 28/01/2025 20:22, D.M. Procida wrote:

My microwave oven, now 15+ years old, blew its fuse yesterday.

It's a slow-blow fuse (T10 AL 250V P).

I'm going to replace it tomorrow, but how likely is it that whatever caused it
to go is just going to do it again straight away.

I am surprised the high voltage fuse didn't blow. That's what happened
to mine - the magnetron had an anode cathode short and had to be
replaced . That and a failure of the high voltage capacitor or the high voltage diode are really the most common problems, and are trivial to replace.

<useful advice>

Thanks for all that, interesting and informative. It did indeed blow the fuse again, with a an angry buzz, so I am just going to take it to a shop - if such a thing exists any more - and see if someone else can repair it.

Daniele

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

"D.M. Procida" wrote:

It did indeed blow the fuse
again, with a an angry buzz, so I am just going to take it to a shop - if such
a thing exists any more - and see if someone else can repair it.

Economically?

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 29/01/2025 17:54, D.M. Procida wrote:

On 28 Jan 2025 at 23:40:43 GMT, "The Natural Philosopher" <[email protected]d> wrote:

On 28/01/2025 20:22, D.M. Procida wrote:

My microwave oven, now 15+ years old, blew its fuse yesterday.

It's a slow-blow fuse (T10 AL 250V P).

I'm going to replace it tomorrow, but how likely is it that whatever caused it
to go is just going to do it again straight away.

I am surprised the high voltage fuse didn't blow. That's what happened
to mine - the magnetron had an anode cathode short and had to be
replaced . That and a failure of the high voltage capacitor or the high
voltage diode are really the most common problems, and are trivial to
replace.

<useful advice>

Thanks for all that, interesting and informative. It did indeed blow the fuse again, with a an angry buzz, so I am just going to take it to a shop - if such
a thing exists any more - and see if someone else can repair it.

Daniele

Simply not worth it, Parts and labour likely to be more than its worth

--
I would rather have questions that cannot be answered...
...than to have answers that cannot be questioned

Richard Feynman

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 29 Jan 2025 at 21:02:39 GMT, Andy Burns wrote:

"D.M. Procida" wrote:

It did indeed blow the fuse
again, with a an angry buzz, so I am just going to take it to a shop - if such
a thing exists any more - and see if someone else can repair it.

Economically?

There is a cost to /not/ getting it fixed . . . and indeed benefits to fixing it. Not always all about money . . .
--
Cheers, Rob, Sheffield UK

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 30/01/2025 09:07, RJH wrote:

On 29 Jan 2025 at 21:02:39 GMT, Andy Burns wrote:

"D.M. Procida" wrote:

It did indeed blow the fuse
again, with a an angry buzz, so I am just going to take it to a shop - if such
a thing exists any more - and see if someone else can repair it.

Economically?

There is a cost to /not/ getting it fixed . . . and indeed benefits to fixing it. Not always all about money . . .

Well there is a good You tube video about testing and fixing the high
voltage side which is most likely what is gone.

The circuits are pretty much all the same - a high power high voltage transformer that drives the magnetron, with a winding for its heater,
then a diode to rectify and voltage double the HT voltaqe and a fat
capacitor to smooth it., and usually a fuse in it.

You test the capacitor for leakage with an ohm meter.
You test the fuse for breakage with an ohm mketer.
Unless you have 9V plus batteries in your meter you cant test the diode
as its forward drop is about 7V (Its a stack of lower voltage diodes in
series) but you can fake it with a 9V battery and a resistor and a
current meter.,
You test the transformer for winding continuity and no shorts between
windings or grounded wiring.
If it is the transformer you are in for a hefty bill and trouble getting
a spare.

Also be absolutely careful to see if the broken parts are in fact
obtainable - a 15 year old machine is somewhat likely to not have a
great range of spares.

And 'taking it to a man' is likely to incur a repair bill up towards
£200 or a 'I cant fix that' response.


--
The biggest threat to humanity comes from socialism, which has utterly
diverted our attention away from what really matters to our existential survival, to indulging in navel gazing and faux moral investigations
into what the world ought to be, whilst we fail utterly to deal with
what it actually is.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 30/01/2025 09:45, The Natural Philosopher wrote:

On 30/01/2025 09:07, RJH wrote:

On 29 Jan 2025 at 21:02:39 GMT, Andy Burns wrote:

"D.M. Procida" wrote:

It did indeed blow the fuse
again, with a an angry buzz, so I am just going to take it to a shop
- if such
a thing exists any more - and see if someone else can repair it.

Economically?

There is a cost to /not/ getting it fixed . . . and indeed benefits to
fixing
it. Not always all about money . . .

Well there is a good You tube video about testing and fixing the high
voltage side which is most likely what is gone.

The circuits are pretty much all the same - a high power high voltage transformer that drives the magnetron, with a winding for its heater,
then a diode to rectify and voltage double the HT voltaqe and a fat
capacitor to smooth it., and usually a fuse in it.

You test the capacitor for leakage with an ohm meter.
You test the fuse for breakage with an ohm mketer.
Unless you have 9V plus batteries in your meter you cant test the diode
as its forward drop is about 7V (Its a stack of lower voltage diodes in series) but you can fake it with a 9V battery and a resistor and a
current meter.,
You test the transformer for winding continuity and no shorts between windings or grounded wiring.
If it is the transformer you are in for a hefty bill and trouble getting
a spare.

I forgot...

You test the magnetron for no short between the cathode/heater and
ground, and for heater continuity.
Magnetrons are also expensive

Also be absolutely careful to see if the broken parts are in fact
obtainable - a 15 year old machine is somewhat likely to not have a
great range of spares.

And 'taking it to a man' is likely to incur a repair bill up towards
£200 or a 'I cant fix that'  response.

--
The urge to save humanity is almost always a false front for the urge to
rule.
– H. L. Mencken, American journalist, 1880-1956

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 29/01/2025 17:54, D.M. Procida wrote:

Thanks for all that, interesting and informative. It did indeed blow the fuse again, with a an angry buzz, so I am just going to take it to a shop - if such
a thing exists any more - and see if someone else can repair it.

our local repair cafe sees quite a few faulty microwaves and fix over half.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 30/01/2025 09:48, The Natural Philosopher wrote:

Magnetrons are also expensive

Do they lose vacuum over time?

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 30/01/2025 11:09, ajh wrote:

On 30/01/2025 09:48, The Natural Philosopher wrote:

Magnetrons are also expensive

Do they lose vacuum over time?

I dont think so. The article I read and my own magnetron failed with a
soft short between anode and cathode. It also showed signs of rough
treatment before I got it. I suspect metal was being deposited from the
cathode onto whatever insulates it all inside, and eventually it arced
over.

50 year old valves still work.
--
The urge to save humanity is almost always a false front for the urge to
rule.
– H. L. Mencken, American journalist, 1880-1956

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 30/01/2025 09:45, The Natural Philosopher wrote:

On 30/01/2025 09:07, RJH wrote:

On 29 Jan 2025 at 21:02:39 GMT, Andy Burns wrote:

"D.M. Procida" wrote:

It did indeed blow the fuse
again, with a an angry buzz, so I am just going to take it to a shop - if such
a thing exists any more - and see if someone else can repair it.

Economically?

There is a cost to /not/ getting it fixed . . . and indeed benefits to fixing
it. Not always all about money . . .

Well there is a good You tube video about testing and fixing the high
voltage side which is most likely what is gone.

The circuits are pretty much all the same - a high power high voltage transformer that drives the magnetron, with a winding for its heater,
then a diode to rectify and voltage double the HT voltaqe and a fat
capacitor to smooth it., and usually a fuse in it.

Don't forget there's usually a bleed resistor to discharge the
capacitor. I've never heard of one going short-circuit, but you never know.

You test the capacitor for leakage with an ohm meter.

Not without first making sure it's fully discharged! If the bleed
resistor has gone o/c and the capacitor's decent it could keep a charge
for quite a time. At best you'd destroy the meter, at worst... :-(

You test the fuse for breakage with an ohm mketer.
Unless you have 9V plus batteries in your meter you cant test the diode
as its forward drop is about 7V (Its a stack of lower voltage diodes in series) but you can fake it with a 9V battery and a resistor and a
current meter.,
You test the transformer for winding continuity and no shorts between windings or grounded wiring.
If it is the transformer you are in for a hefty bill and trouble getting
a spare.

When an old microwave oven went belly-up (magnetron died), I wondered if
I could use the transformer. however, it seemed so firmly fixed in I
gave up (perhaps a bit of self-preservation clicked in as well!).

Also be absolutely careful to see if the broken parts are in fact
obtainable - a 15 year old machine is somewhat likely to not have a
great range of spares.

And 'taking it to a man' is likely to incur a repair bill up towards
£200 or a 'I cant fix that' response.

Yep. When I tried to source a replacement magnetron I found I was
looking at £50+.

--
Jeff

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Jeff Layman <[email protected]d> wrote:

On 30/01/2025 09:45, The Natural Philosopher wrote:

On 30/01/2025 09:07, RJH wrote:

Also be absolutely careful to see if the broken parts are in fact
obtainable - a 15 year old machine is somewhat likely to not have a
great range of spares.

And 'taking it to a man' is likely to incur a repair bill up towards
£200 or a 'I cant fix that' response.

Yep. When I tried to source a replacement magnetron I found I was
looking at £50+.

If you get the model number of the *magnetron* rather than the microwave
you may well find that a compatible magnetron is still available. When our
44 year old Toshiba microwave had a hiccough and panicked me into looking
for a new magnetron, I found a compatible replacement without too much
trouble (and it wasn’t particularly expensive as far as I can recall).

Tim


--
Please don't feed the trolls

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 31/01/2025 20:25, Tim+ wrote:

Jeff Layman <[email protected]d> wrote:

On 30/01/2025 09:45, The Natural Philosopher wrote:

On 30/01/2025 09:07, RJH wrote:

Also be absolutely careful to see if the broken parts are in fact
obtainable - a 15 year old machine is somewhat likely to not have a
great range of spares.

And 'taking it to a man' is likely to incur a repair bill up towards
£200 or a 'I cant fix that' response.

Yep. When I tried to source a replacement magnetron I found I was
looking at £50+.

If you get the model number of the *magnetron* rather than the microwave

I started with that, and then the seller asked me what microwave it was for!

A lot of magnetromss sent back because they 'didn't fit' apparently

you may well find that a compatible magnetron is still available. When our 44 year old Toshiba microwave had a hiccough and panicked me into looking
for a new magnetron, I found a compatible replacement without too much trouble (and it wasn’t particularly expensive as far as I can recall).

I found lower power ones as low as £35 and higher power ones in he £75-£110 area. I think mine was £85 from an Ebay seller. But it was a pukka
branded Samsung unit.

Tim

--
"It is an established fact to 97% confidence limits that left wing
conspirators see right wing conspiracies everywhere"

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)