The microwave part of our oven has stopped working, though the electric
oven and grill work normally.

Will the magnetron or its control board be likely to have fuse separate
from the main fuse? Or is this most likely a failed magnetron?

Thanks,

Daniele

On 06/01/2019 14:05, D.M. Procida wrote:
The microwave part of our oven has stopped working, though the electric
oven and grill work normally.

Will the magnetron or its control board be likely to have fuse separate
from the main fuse? Or is this most likely a failed magnetron?


I'm sorry I can't help you - but those who can, can better if you give a
make and model number.

I just wanted to mention that if you saw the Doctor Who New Year Special
last week THESE ARE NOT OFFICIAL DISASSEMBLY INSTRUCTIONS FOR A
COMBINATION MICROWAVE/OVEN.

Nick

D.M. Procida wrote:

The microwave part of our oven has stopped working, though the electric
oven and grill work normally.

I somehow forgot to mention: it's a Siemens Microlle Plus. The full part
number is HF83950NL, though I suspect HF839 is the basic model number.

Daniele

On 06/01/2019 16:18, D.M. Procida wrote:
D.M. Procida wrote:

The microwave part of our oven has stopped working, though the electric
oven and grill work normally.

I somehow forgot to mention: it's a Siemens Microlle Plus. The full part
number is HF83950NL, though I suspect HF839 is the basic model number.

Daniele


Going by the price of parts shown here :-


https://www.ransomspares.co.uk/parts...hf83950nl__02/

You might be better off getting a replacement.

Ominously, most of the hits on Google are in Dutch. Was this
ever an official UK import ?.

Magnetron shown if you then select Images.

Andrew wrote:

On 06/01/2019 16:18, D.M. Procida wrote:
D.M. Procida wrote:

The microwave part of our oven has stopped working, though the electric
oven and grill work normally.

I somehow forgot to mention: it's a Siemens Microlle Plus. The full part
number is HF83950NL, though I suspect HF839 is the basic model number.

Going by the price of parts shown here :-


https://www.ransomspares.co.uk/parts...hf83950nl__02/

You might be better off getting a replacement.

Ominously, most of the hits on Google are in Dutch. Was this
ever an official UK import ?.

I think the equivalent is HF83951GB for the UK, and that the basic model
number is HF8395.

Daniele

On Sun, 6 Jan 2019 15:05:46 +0100,
(D.M. Procida) wrote:

The microwave part of our oven has stopped working, though the electric
oven and grill work normally.

Will the magnetron or its control board be likely to have fuse separate
from the main fuse? Or is this most likely a failed magnetron?

It may have its own fuse so check that first. Some of the Dutch
articles mention this model has two fuses. One at least will probably
be a slow blow type to cope with the high current draw when it
switches on. Failure of fuses for no other reason than stress is
fairly common so if one has failed just replace it. If the
replacement blows then the problem is obviously elsewhere.

Is the turntable working when the microwave part should be on?

Magnetrons rarely fail but the High Voltage diodes and the large high
voltage capacitor sometimes do. Fortunately they are fairly easy to
test. Because the "diode" is actually several integrated into one
package in series a normal test meter diode test function won't do.
There are several Youtube videos showing how to do it with a test
meter and 9V battery.

https://www.youtube.com/watch?v=a6lrKf2PdVA and
https://www.youtube.com/watch?v=PdwbjNCK-xw explain it all.

The HV capacitors also fail,

https://www.youtube.com/watch?v=5fOC3rDy8Rs

explains how to test them.

Do remember that the capacitor potentially stores a lethal high
voltage (about 5,000V) high current charge so do make sure it is
discharged by leaving the microwave unplugged for a day or three
before prodding inside. The capacitor has a bleed resistor across it
to discharge the capacitor when the oven is off but if it fails you
have no indication in normal use that it has done so so its best to
assume it has.

After leaving the oven unplugged take an insulated length of wire
with bare ends and touch the ends across the capacitor terminals. You
should have nothing happen but if the capacitor is charged the results
are impressive. Having shorted out the capacitor check it is empty by
using a multi meter on its highest DC range. Don't do this before
shorting out the capacitor.

If it is an inverter microwave then the very heavy high voltage
transformer (which rarely fails) is replaced by a switch mode power
supply which can also fail. Because of the high energy bits inside
failures often leave visual clues such a soot marks so a detailed
visual inspection is always a first action.

There is no DIY way of testing the magnetron.

On Sunday, 6 January 2019 18:40:08 UTC, Peter Parry wrote:
On Sun, 6 Jan 2019 15:05:46 +0100,
(D.M. Procida) wrote:

The microwave part of our oven has stopped working, though the electric
oven and grill work normally.

Will the magnetron or its control board be likely to have fuse separate
from the main fuse? Or is this most likely a failed magnetron?

Failed magnetron is an unlikely cause of such a fault.
You could help yourself by describing the symptoms exactly.


NT

On 06/01/2019 14:05, D.M. Procida wrote:
The microwave part of our oven has stopped working, though the electric
oven and grill work normally.

Will the magnetron or its control board be likely to have fuse separate
from the main fuse? Or is this most likely a failed magnetron?

Thanks,

Daniele


There's probably a 10A slow-blow fuse hidden inside somewhere. If that's
blown, replacing it may fix the problem - but it's more likely that it's
blown due to something else.

Once common cause of failure is the microswitches on the door. These are
to prevent the microwave from operating unless the door is fully closed.
These are wired in a way which causes the fuse to blow if one of them fails.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

Peter Parry wrote:

On Sun, 6 Jan 2019 15:05:46 +0100,
(D.M. Procida) wrote:

The microwave part of our oven has stopped working, though the electric
oven and grill work normally.

Will the magnetron or its control board be likely to have fuse separate
from the main fuse? Or is this most likely a failed magnetron?

It may have its own fuse so check that first. Some of the Dutch
articles mention this model has two fuses. One at least will probably
be a slow blow type to cope with the high current draw when it
switches on. Failure of fuses for no other reason than stress is
fairly common so if one has failed just replace it. If the
replacement blows then the problem is obviously elsewhere.

Is the turntable working when the microwave part should be on?

Well, it's of the type that has no turntable, but there's no sign of
life from it whatsoever. The timer doesn't count down, for example, and
no light comes on.

Daniele

D.M. Procida was thinking very hard :
Well, it's of the type that has no turntable, but there's no sign of
life from it whatsoever. The timer doesn't count down, for example, and
no light comes on.

Likely the magnetron and etc. are fine, the issue is the control PCB
and maybe just a blown fuse on that PCB - a simple fix.

On Sunday, 6 January 2019 19:56:12 UTC, D.M. Procida wrote:
Peter Parry wrote:
On Sun, 6 Jan 2019 15:05:46 +0100,
(D.M. Procida) wrote:

The microwave part of our oven has stopped working, though the electric
oven and grill work normally.

Will the magnetron or its control board be likely to have fuse separate
from the main fuse? Or is this most likely a failed magnetron?

It may have its own fuse so check that first. Some of the Dutch
articles mention this model has two fuses. One at least will probably
be a slow blow type to cope with the high current draw when it
switches on. Failure of fuses for no other reason than stress is
fairly common so if one has failed just replace it. If the
replacement blows then the problem is obviously elsewhere.

Is the turntable working when the microwave part should be on?

Well, it's of the type that has no turntable, but there's no sign of
life from it whatsoever. The timer doesn't count down, for example, and
no light comes on.

Daniele

Fuse would be the first suspect. Do use the right type, and /always/ check the big shorting resistor when replacing the fuse. If that's faulty, check your interlock switches are working correctly.

'Dead' is usually the easiest fault to fix.


NT

More likely a failed power supply. Its pretty crude normally. a large
transformer, some rectification block and some hv capacitors.
The problem is its a very dangerous area to work on for many reasons as a
day thing. Thousands of volts even when off and microwave leakage when on,
and really hard to get details of the circuit, at least back in the days of
yore.
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"D.M. Procida" wrote in
message
...
The microwave part of our oven has stopped working, though the electric
oven and grill work normally.

Will the magnetron or its control board be likely to have fuse separate
from the main fuse? Or is this most likely a failed magnetron?

Thanks,

Daniele

In article ,
Roger Mills writes:
On 06/01/2019 14:05, D.M. Procida wrote:
The microwave part of our oven has stopped working, though the electric
oven and grill work normally.

Will the magnetron or its control board be likely to have fuse separate
from the main fuse? Or is this most likely a failed magnetron?

Thanks,

Daniele


There's probably a 10A slow-blow fuse hidden inside somewhere. If that's
blown, replacing it may fix the problem - but it's more likely that it's
blown due to something else.

Once common cause of failure is the microswitches on the door. These are
to prevent the microwave from operating unless the door is fully closed.
These are wired in a way which causes the fuse to blow if one of them fails.

In this case, the cause should be found and fixed. Worn door mounting
and catches are common. The manufacturers will also always replace the
microswitches once they have shorted out the supply to blow the supply
fuse. Worn microswitches can be the cause, but they are not designed to
continue providing protection after they've shorted out the supply once.

The high voltage fuse can simply blow with age - they are very closely
rated to the running current, as the transformer is not capable of
providing very significantly more than this when shorted, so a wide
fuse margin would not provide suitable protection. The symptoms
described don't match the HV fuse as having blown though - the
timer/controller would still work in this case.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Monday, 7 January 2019 08:19:45 UTC, Brian Gaff wrote:
More likely a failed power supply. Its pretty crude normally. a large
transformer, some rectification block and some hv capacitors.
The problem is its a very dangerous area to work on for many reasons as a
day thing. Thousands of volts even when off and microwave leakage when on,
and really hard to get details of the circuit, at least back in the days of
yore.
Brian

Nearly all microwaves use the exact same HV circuit.
The diode is the most failure prone part of it, cheap & easy to replace. But the OP doesn't really want assistance as they've not provided the symptoms.


NT

formulated on Tuesday :
Nearly all microwaves use the exact same HV circuit.
The diode is the most failure prone part of it, cheap & easy to replace. But
the OP doesn't really want assistance as they've not provided the symptoms.

Actually, he has. He said something like 'no response from display, no
timer running'.

On Tuesday, 8 January 2019 15:30:58 UTC, Harry Bloomfield wrote:
tabbypurr formulated on Tuesday :

Nearly all microwaves use the exact same HV circuit.
The diode is the most failure prone part of it, cheap & easy to replace. But
the OP doesn't really want assistance as they've not provided the symptoms.

Actually, he has. He said something like 'no response from display, no
timer running'.

you're right. Then the most likely culprit is the power fuse. Which if blown requires a check on the shorting resistor & interlock system. For an electronic controller there may also be a fuse or fusible resistor on the PCB, or a blown dropper cap.


NT

D.M. Procida wrote:

The microwave part of our oven has stopped working, though the electric
oven and grill work normally.

Will the magnetron or its control board be likely to have fuse separate
from the main fuse? Or is this most likely a failed magnetron?

Thanks everyone for the tips.

There were a pair of fuses on the control panel, but both had
continuity.

I also found a large thermal fuse, which hasn't, so I suspect that's my
culprit, pictured in the image below between a pair of hefty 5K
resistors.

https://share.icloud.com/photos/0jZKqbOP5ZakhfAc2pvt8Hk_Q

I'm not entirely sure how to read its specifications.

It's labelled:

Z430KK6E
E065FF51
UK T180

and pressed into the ceramic:

Z42/43
6/250
T250

(also at https://share.icloud.com/photos/0WjYbgCrmYFfjZrPRQvzm0fpw).

Daniele

On Tuesday, 8 January 2019 19:06:41 UTC, D.M. Procida wrote:
D.M. Procida wrote:

The microwave part of our oven has stopped working, though the electric
oven and grill work normally.

Will the magnetron or its control board be likely to have fuse separate
from the main fuse? Or is this most likely a failed magnetron?

Thanks everyone for the tips.

There were a pair of fuses on the control panel, but both had
continuity.

I also found a large thermal fuse, which hasn't, so I suspect that's my
culprit, pictured in the image below between a pair of hefty 5K
resistors.

https://share.icloud.com/photos/0jZKqbOP5ZakhfAc2pvt8Hk_Q

I'm not entirely sure how to read its specifications.

It's labelled:

Z430KK6E
E065FF51
UK T180

and pressed into the ceramic:

Z42/43
6/250
T250

(also at https://share.icloud.com/photos/0WjYbgCrmYFfjZrPRQvzm0fpw).

Daniele

6A 250v. Maybe 180C, can't be sure. Are the resistors it monitors ok?


NT

wrote:

I also found a large thermal fuse, which hasn't, so I suspect that's my
culprit, pictured in the image below between a pair of hefty 5K
resistors.

https://share.icloud.com/photos/0jZKqbOP5ZakhfAc2pvt8Hk_Q

I'm not entirely sure how to read its specifications.

It's labelled:

Z430KK6E
E065FF51
UK T180

and pressed into the ceramic:

Z42/43
6/250
T250

(also at https://share.icloud.com/photos/0WjYbgCrmYFfjZrPRQvzm0fpw).

Daniele

6A 250v. Maybe 180C, can't be sure. Are the resistors it monitors ok?

They seem to be. However the only way I can check continuity on anything
at the moment is to press it to the contact of an electrical screwdriver
(I know, I know) stuck in a socket, as I am without my usual tools.

Daniele

On Tuesday, 8 January 2019 22:19:43 UTC, D.M. Procida wrote:
tabbypurr wrote:

I also found a large thermal fuse, which hasn't, so I suspect that's my
culprit, pictured in the image below between a pair of hefty 5K
resistors.

https://share.icloud.com/photos/0jZKqbOP5ZakhfAc2pvt8Hk_Q

I'm not entirely sure how to read its specifications.

It's labelled:

Z430KK6E
E065FF51
UK T180

and pressed into the ceramic:

Z42/43
6/250
T250

(also at https://share.icloud.com/photos/0WjYbgCrmYFfjZrPRQvzm0fpw).

Daniele

6A 250v. Maybe 180C, can't be sure. Are the resistors it monitors ok?

They seem to be. However the only way I can check continuity on anything
at the moment is to press it to the contact of an electrical screwdriver
(I know, I know) stuck in a socket, as I am without my usual tools.

Daniele

battery & LED would do.


NT

expressed precisely :
6A 250v. Maybe 180C, can't be sure. Are the resistors it monitors ok?

Might that be one of those thermal trips, which does not self reset?

wrote:

6A 250v. Maybe 180C, can't be sure. Are the resistors it monitors ok?

They seem to be. However the only way I can check continuity on anything
at the moment is to press it to the contact of an electrical screwdriver
(I know, I know) stuck in a socket, as I am without my usual tools.

I bought a multimeter today, so now I just need to try finding a
replacement thermosicherung.

Daniele

I'm admitting defeat on this one, especially since I've already bought a
replacement second-hand microwave combination oven to replace it.

For reference, it's a Siemens HF83950NL:
https://www.siemens-home.bsh-group.com/uk/supportdetail/product/HF83950NL/02#/Tabs=section-spareparts/.

I bought a replacement part 15792 for it. This is what I think is a
thermal fuse. When I've looked up the part numbers marked on it:

Z430KK6E
E065FF1
UK T180

and pressed into the ceramic:

Z42/43
6/250
T250

that returns results that describe it as a thermal fuse.

Siemens calls it a "temperature limiter", which I guess might be close
enough. The old one has no continuity. Neither does the new oe I bought
and fitted - but rather thoughtlessly, I only checked that after fitting
it and turning on the machine, so for all I know it has immediately
blown, or maybe it's not actually a fuse and it's normal for it to be
open.

The odd thing is that when the machine is plugged in, one side of this
fuse is at 230V, and the other - following the cabling - seems to be
neutral (or at least, it the cabling disappears into what seems to be
the neutral/0V terminal of the "Capacitor-interference suppre." (part
no. 00065353) which is right next to the mains terminals.

So I am not entirely sure what sort of thing this fuse/temperature
limiter actually is, after all, and my oven is not fixed

I've spent several hours and ¤25 on this, which is disappointing, but I
haven't had an electric shock or microwaved myself, which makes up for
it, a bit.

Daniele

D.M. Procida wrote:
I'm admitting defeat on this one, especially since I've already bought a
replacement second-hand microwave combination oven to replace it.

For reference, it's a Siemens HF83950NL:
https://www.siemens-home.bsh-group.com/uk/supportdetail/product/HF83950NL/02#/Tabs=section-spareparts/.

I bought a replacement part 15792 for it. This is what I think is a
thermal fuse. When I've looked up the part numbers marked on it:

Z430KK6E
E065FF1
UK T180

and pressed into the ceramic:

Z42/43
6/250
T250

that returns results that describe it as a thermal fuse.

Siemens calls it a "temperature limiter", which I guess might be close
enough. The old one has no continuity. Neither does the new oe I bought
and fitted - but rather thoughtlessly, I only checked that after fitting
it and turning on the machine, so for all I know it has immediately
blown, or maybe it's not actually a fuse and it's normal for it to be
open.


How did you fit it? Just soldered it in? Use any heat-sinking? Pre-chill
it?

If you didnt take suitable precautions you may have inadvertently €œblown€�
the new thermal fuse by soldering.


Tim

--
Please don't feed the trolls

Tim+ wrote:

Siemens calls it a "temperature limiter", which I guess might be close
enough. The old one has no continuity. Neither does the new oe I bought
and fitted - but rather thoughtlessly, I only checked that after fitting
it and turning on the machine, so for all I know it has immediately
blown, or maybe it's not actually a fuse and it's normal for it to be
open.


How did you fit it? Just soldered it in? Use any heat-sinking? Pre-chill
it?

If you didn't take suitable precautions you may have inadvertently "blown"
the new thermal fuse by soldering.

No, I just bolted it into place and attched the clamps onto the
terminals.

Here it is in between the two hefty resistors:
https://share.icloud.com/photos/0jZKqbOP5ZakhfAc2pvt8Hk_Q

Daniele

On Thu, 17 Jan 2019 22:27:52 +0100,
(D.M. Procida) wrote:

No, I just bolted it into place and attched the clamps onto the
terminals.

I looks as it might be a fixed-temp thermostat.

It just *might* be a "crowbar": normally open, but if the resistors get above
250° C, it goes closed-circuit, so shorts live to neutral. If wired in behind
some local fuse, this guarantees that the fuse blows immediately, certainly, and
Right Now.

I've spent several hours and ‚¬25 on this, which is disappointing, but I
haven't had an electric shock or microwaved myself, which makes up for
it, a bit.

Not a bad plan. Not the 25‚¬ part, obv.


Thomas Prufer

Thomas Prufer wrote:

On Thu, 17 Jan 2019 22:27:52 +0100,
(D.M. Procida) wrote:

No, I just bolted it into place and attched the clamps onto the
terminals.

I looks as it might be a fixed-temp thermostat.

It just *might* be a "crowbar": normally open, but if the resistors get
above 250° C, it goes closed-circuit, so shorts live to neutral. If wired
in behind some local fuse, this guarantees that the fuse blows
immediately, certainly, and Right Now.

How does one find out? The part numbers on the fuse itself don't seem to
lead to any information about it. Is there some sort of standard
numbering system?

I've spent several hours and ¤25 on this, which is disappointing, but I
haven't had an electric shock or microwaved myself, which makes up for
it, a bit.

Not a bad plan. Not the 25¤ part, obv.

It's not the worst thing to happen.

Daniele

On Friday, 18 January 2019 21:32:21 UTC, D.M. Procida wrote:
Thomas Prufer wrote:
On Thu, 17 Jan 2019 22:27:52 +0100,
(D.M. Procida) wrote:

No, I just bolted it into place and attched the clamps onto the
terminals.

I looks as it might be a fixed-temp thermostat.

It just *might* be a "crowbar": normally open, but if the resistors get
above 250° C, it goes closed-circuit, so shorts live to neutral. If wired
in behind some local fuse, this guarantees that the fuse blows
immediately, certainly, and Right Now.

How does one find out? The part numbers on the fuse itself don't seem to
lead to any information about it. Is there some sort of standard
numbering system?

I've spent several hours and ‚¬25 on this, which is disappointing, but I
haven't had an electric shock or microwaved myself, which makes up for
it, a bit.

Not a bad plan. Not the 25‚¬ part, obv.

It's not the worst thing to happen.

Daniele

Did the resisors check out ok?
What does the circuit diagram say the cutout-like thing is?


NT

On Fri, 18 Jan 2019 22:32:17 +0100,
(D.M. Procida) wrote:

Thomas Prufer wrote:

It just *might* be a "crowbar": normally open, but if the resistors get
above 250° C, it goes closed-circuit, so shorts live to neutral. If wired
in behind some local fuse, this guarantees that the fuse blows
immediately, certainly, and Right Now.

How does one find out? The part numbers on the fuse itself don't seem to
lead to any information about it. Is there some sort of standard
numbering system?


Nope, can't find out from the parts used, just from the circuit.

And if the crowbar does its thing, the fuse will fail in short-circuit mode,
i.e. in a flash, with smoke, rather than overload mode, i.e. just melt through
unspectacularly. So have a look, any such fuse would be connected with a wire of
a hefty PCB trace.

And the thermal cutout may be OK if open-circuit, and it may not be wise to
short it out, even for a quick test.


Thomas Prufer

I had the same 'thermal limiter' (Siemens part no. 00152792, Z430KK6E E065FF1 UK T180). This fuse could very well been produced in or for The Netherlands (I'm also Dutch), as in the metal part of it is puched "KEMA KEUR" which is the Dutch authority on certificates for electrical safety.
Under normal operation it's open. When overheated, it's shorted and will switch on the fans.
So it is indeed a "crow bar".
Never seen one like this before, I was always used to have continuity if the fase is ok, but this one is the other way around apparently.

--
For full context, visit https://www.homeownershub.com/uk-diy...r-1338119-.htm

Well this thread has been going on for a year now and its not clear to me if
this post is anything at all to do with the original problem.

Many devices over the years have used crowbar protection ensuring the fuse
blows, but I've not come across one that turns fans on before!
Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"FAQ" wrote in message
oupdirect.com...
I had the same 'thermal limiter' (Siemens part no. 00152792, Z430KK6E
E065FF1 UK T180). This fuse could very well been produced in or for The
Netherlands (I'm also Dutch), as in the metal part of it is puched "KEMA
KEUR" which is the Dutch authority on certificates for electrical safety.
Under normal operation it's open. When overheated, it's shorted and will
switch on the fans.
So it is indeed a "crow bar".
Never seen one like this before, I was always used to have continuity if
the fase is ok, but this one is the other way around apparently.

--
For full context, visit
https://www.homeownershub.com/uk-diy...r-1338119-.htm

On 04/12/2020 14:31:19, FAQ wrote:
I had the same 'thermal limiter' (Siemens part no. 00152792, Z430KK6E
E065FF1 UK T180). This fuse could very well been produced in or for The
Netherlands (I'm also Dutch), as in the metal part of it is puched "KEMA
KEUR" which is the Dutch authority on certificates for electrical safety.
Under normal operation it's open. When overheated, it's shorted and will
switch on the fans.
So it is indeed a "crow bar".

No it is a simple thermal switch, very common.