I've got an oldish (~7 years) Panasonic microwave/grill/oven that has
developed a bizzare fault.
When the house temp drops below 15°C the microwave exhibits the fault.
Microcontroller madness. Damned thing keeps beeping, and oscilating the
display, 'pork...fish...' or somut.
And refuses to actually let me microwave anything.

Just about to whip the back off, clean between pcb tracks etc.

Anyone suggest a more focused plan of attack?

I don't believe it is condensation related, the house is really dry.
I guess some component has just tightened up its temp operating tollerances
in favour of a warmer climate.

--
Mike W

"visionset" wrote in message
...
I've got an oldish (~7 years) Panasonic microwave/grill/oven that has
developed a bizzare fault.
When the house temp drops below 15°C the microwave exhibits the fault.
Microcontroller madness. Damned thing keeps beeping, and oscilating the
display, 'pork...fish...' or somut.
And refuses to actually let me microwave anything.

Just about to whip the back off, clean between pcb tracks etc.

Anyone suggest a more focused plan of attack?

I don't believe it is condensation related, the house is really dry.
I guess some component has just tightened up its temp operating
tollerances in favour of a warmer climate.

--
Mike W


Hmmm, that's a curious fault.

All I can say is that our Panny microwave gave up the ghost at around the
same age but was due to something called the megatron or something. Which
apparently is the main part in it.

We were advised that we should have vacced out the rear air intake more
often as that being blocked had caused the fault.

Our local microwave warranty repairer wanted £120 to fix it when a new one
was only £149! Needless to say we went for a brand new one.

on 07/02/2007, RedOnRed supposed :
"visionset" wrote in message
...
I've got an oldish (~7 years) Panasonic microwave/grill/oven that has
developed a bizzare fault.
When the house temp drops below 15°C the microwave exhibits the fault.
Microcontroller madness. Damned thing keeps beeping, and oscilating the
display, 'pork...fish...' or somut.
And refuses to actually let me microwave anything.

Just about to whip the back off, clean between pcb tracks etc.

Anyone suggest a more focused plan of attack?

I don't believe it is condensation related, the house is really dry.
I guess some component has just tightened up its temp operating tollerances
in favour of a warmer climate.

-- Mike W


Hmmm, that's a curious fault.

It sounds vaguely like the oscillator for the CPU is failing the
oscillate properly at low temperatures. I'm not suggesting you do this,
but if you can find the crystal and put your finger end on it to warm
it it might confirm the fault. The crystal will be a small flat silver
metal cased component 3/8 inch square, or perhaps one similar to those
you see in a digital watch - small silver metal cased and rod shaped,
both with two wires.

Another possibility is moisture between the diaphragm of the switches,
shorting the buttons, if it is that type of microwave control panel.

All I can say is that our Panny microwave gave up the ghost at around the
same age but was due to something called the megatron or something. Which
apparently is the main part in it.

Magnetron (sp?). A common failing and the replacement part will be
common to many ovens.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

"Harry Bloomfield" wrote in message
...
on 07/02/2007, RedOnRed supposed :
"visionset" wrote in message
...
I've got an oldish (~7 years) Panasonic microwave/grill/oven that has
developed a bizzare fault.
When the house temp drops below 15°C the microwave exhibits the fault.
Microcontroller madness. Damned thing keeps beeping, and oscilating the
display, 'pork...fish...' or somut.
And refuses to actually let me microwave anything.

Just about to whip the back off, clean between pcb tracks etc.

Anyone suggest a more focused plan of attack?

I don't believe it is condensation related, the house is really dry.
I guess some component has just tightened up its temp operating
tollerances in favour of a warmer climate.

-- Mike W


Hmmm, that's a curious fault.

It sounds vaguely like the oscillator for the CPU is failing the oscillate
properly at low temperatures. I'm not suggesting you do this, but if you
can find the crystal and put your finger end on it to warm it it might
confirm the fault. The crystal will be a small flat silver metal cased
component 3/8 inch square, or perhaps one similar to those you see in a
digital watch - small silver metal cased and rod shaped, both with two
wires.

I'll give it a whirl in the morning, should be cold enough with all that
snow about!

Thanks!!


Another possibility is moisture between the diaphragm of the switches,
shorting the buttons, if it is that type of microwave control panel.


It seems to be such an exact temperature the problem develops I'd guess the
former.

--
Mike W

"Harry Bloomfield" wrote in message
...

if you can find the crystal and put your finger end on it to warm it it
might confirm the fault. The crystal will be a small flat silver metal
cased component 3/8 inch square, or perhaps one similar to those you see
in a digital watch - small silver metal cased and rod shaped, both with
two wires.

Nearest thing I could find was a 4mm long cylinder, 1.5mm diam, graphite
coloured, with axial leads.
There are 3 processors. 1 large I think is the display driver and 2 smaller
ones.
If I get it off again I'll take a photo.

--
Mike W

visionset explained :
"Harry Bloomfield" wrote in message
...

if you can find the crystal and put your finger end on it to warm it it
might confirm the fault. The crystal will be a small flat silver metal
cased component 3/8 inch square, or perhaps one similar to those you see in
a digital watch - small silver metal cased and rod shaped, both with two
wires.

Nearest thing I could find was a 4mm long cylinder, 1.5mm diam, graphite
coloured, with axial leads.
There are 3 processors. 1 large I think is the display driver and 2 smaller
ones.
If I get it off again I'll take a photo.

Be aware there will be some seriously high voltages in there,
especially around the transformer and the magnetron.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

"Harry Bloomfield" wrote in message
...
visionset explained :
"Harry Bloomfield" wrote in message
...

if you can find the crystal and put your finger end on it to warm it it
might confirm the fault. The crystal will be a small flat silver metal
cased component 3/8 inch square, or perhaps one similar to those you see
in a digital watch - small silver metal cased and rod shaped, both with
two wires.

Nearest thing I could find was a 4mm long cylinder, 1.5mm diam, graphite
coloured, with axial leads.
There are 3 processors. 1 large I think is the display driver and 2
smaller ones.
If I get it off again I'll take a photo.

Be aware there will be some seriously high voltages in there, especially
around the transformer and the magnetron.


Thanks, I'm used to dealing with the like inc TV's. Just basic faults I'm
upto, no electronics engineer.
I can replace the crystal if that's what it is and it's broke though.

http://i9.tinypic.com/2i74l7d.jpg

Component I was querying is the one just above the green ribbon partially
obscured. 'L10' is printed on the pcb next to it.

Now it is reassembled, it does similar though different logic wierdness.
Jumped into the middle of a entry sequence at start up when it shouldn't.

--
Mike W

On 7 Feb, 23:26, "visionset" wrote:
"Harry Bloomfield" wrote in message
...
visionset explained :
"Harry Bloomfield" wrote in message
...

if you can find the crystal and put your finger end on it to warm it it
might confirm the fault.

Theres no way its the crystal, couldnt cause that.

I'd disconnect the keypad and see if the fault recurs, if it doesnt
then your keypad needs sorting.

Otherwise really it could be any of numerous bits, and you'd need to
become an electronic engineer to sort it,

Hae you been cooking beef in it? Maybe it got BSE

Recalcitrant microwave

maybe it needs limescale remover.


NT

In article ,
"visionset" writes:
I've got an oldish (~7 years) Panasonic microwave/grill/oven that has
developed a bizzare fault.
When the house temp drops below 15°C the microwave exhibits the fault.
Microcontroller madness. Damned thing keeps beeping, and oscilating the
display, 'pork...fish...' or somut.
And refuses to actually let me microwave anything.

Just about to whip the back off, clean between pcb tracks etc.

Anyone suggest a more focused plan of attack?

This type of fault is easy to find if you can run the appliance
live with the covers off (which you can't with a microwave, unless
you can disconnect the HT transformer primary for safety). Wait
until it's warmed up and working, and spray freezer spray on the
components and joints until you find the one which stops it working
again. If you don't have any freezer spray, a dusting can held
upside down works the same way (but watch for the liquid leaking
out over your fingers and giving you frost bite).

There is a range of small electrolyic capacitors which can fail
when cold as they age. I can't remember the make, but they have no
insulating sleave, and include a tiny plastic spacer between themself
and the PCB which is integral with the capacitor, but can be separated
when capacitor is not mounted on a board. I had one fail in an old
VCR, and discovered this is a common failure.

I don't believe it is condensation related, the house is really dry.
I guess some component has just tightened up its temp operating tollerances
in favour of a warmer climate.

Yes.

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

Harry Bloomfield wrote:
on 07/02/2007, RedOnRed supposed :
"visionset" wrote in message
...
I've got an oldish (~7 years) Panasonic microwave/grill/oven that has
developed a bizzare fault.
When the house temp drops below 15°C the microwave exhibits the fault.
Microcontroller madness. Damned thing keeps beeping, and oscilating
the display, 'pork...fish...' or somut.
And refuses to actually let me microwave anything.

Just about to whip the back off, clean between pcb tracks etc.

Anyone suggest a more focused plan of attack?

I don't believe it is condensation related, the house is really dry.
I guess some component has just tightened up its temp operating
tollerances in favour of a warmer climate.

-- Mike W


Hmmm, that's a curious fault.

It sounds vaguely like the oscillator for the CPU is failing the
oscillate properly at low temperatures. I'm not suggesting you do this,
but if you can find the crystal and put your finger end on it to warm it
it might confirm the fault. The crystal will be a small flat silver
metal cased component 3/8 inch square, or perhaps one similar to those
you see in a digital watch - small silver metal cased and rod shaped,
both with two wires.

Oscillators tend to either work, or not.
Probably a faulty set of chips that get logic faults in the cold.

Another possibility is moisture between the diaphragm of the switches,
shorting the buttons, if it is that type of microwave control panel.

True..
All I can say is that our Panny microwave gave up the ghost at around
the same age but was due to something called the megatron or
something. Which apparently is the main part in it.

Magnetron.

Magnetron (sp?). A common failing and the replacement part will be
common to many ovens.

Component I was querying is the one just above the green ribbon partially
obscured. 'L10' is printed on the pcb next to it.

Now it is reassembled, it does similar though different logic wierdness.
Jumped into the middle of a entry sequence at start up when it shouldn't.



The blue one, label ' cx1 ' is the crystal.

Dave

--
Foot Massage @ Home
http://footmass.mysite.orange.co.uk

The message
from gort contains these words:

The blue one, label ' cx1 ' is the crystal.

Probably a ceramic resonator rather than a crystal.

--
Skipweasel
Pay no attention to that man behind the curtain.

"visionset" wrote in message
...


Now it is reassembled, it does similar though different logic wierdness.
Jumped into the middle of a entry sequence at start up when it shouldn't.


Okay, now I'm 95% certain that it is indeed the keypad. It is the diaphragm
type - ie film pcb and pressure causes contacts. Unfortunately it seems the
most in accessible part. It is basically stuck on to the front fascia, and
completely moulded in from behind. Removing it will likely destroy it
completely, and with little hope of getting a new one - I'll investgate the
new part option. Although is is moulded behind, there are two small holes
you can see the film pcb through. I poked these a bit to change the
pressure status quo.
On reassembly I left the keypad connection off and it started up fine. I
then reconnected the keypad to the live system and it now operates fine...
For now...
I cleaned the contacts on the film pcb connector yesterday so I don't think
it is that. If I can get a new pad I'll probably solve it. See how it goes
for now. Thanks all.

--
Mike W

visionset submitted this idea :
"Harry Bloomfield" wrote in message
...
visionset explained :
"Harry Bloomfield" wrote in message
...

if you can find the crystal and put your finger end on it to warm it it
might confirm the fault. The crystal will be a small flat silver metal
cased component 3/8 inch square, or perhaps one similar to those you see
in a digital watch - small silver metal cased and rod shaped, both with
two wires.

Nearest thing I could find was a 4mm long cylinder, 1.5mm diam, graphite
coloured, with axial leads.
There are 3 processors. 1 large I think is the display driver and 2
smaller ones.
If I get it off again I'll take a photo.

Be aware there will be some seriously high voltages in there, especially
around the transformer and the magnetron.


Thanks, I'm used to dealing with the like inc TV's. Just basic faults I'm
upto, no electronics engineer.
I can replace the crystal if that's what it is and it's broke though.

http://i9.tinypic.com/2i74l7d.jpg

Component I was querying is the one just above the green ribbon partially
obscured. 'L10' is printed on the pcb next to it.

L would either be an inductor or a simple wire link, that component
looks like a simple link.

Now it is reassembled, it does similar though different logic wierdness.
Jumped into the middle of a entry sequence at start up when it shouldn't.

Keyboard ! Try pulling the green ribbon cable out with the power off,
then re apply the power. If the display still works - if not on that
ribbon, then you will have confirmed the problem as the keyboard pad.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

gort wrote :
Component I was querying is the one just above the green ribbon partially
obscured. 'L10' is printed on the pcb next to it.

Now it is reassembled, it does similar though different logic wierdness.
Jumped into the middle of a entry sequence at start up when it shouldn't.



The blue one, label ' cx1 ' is the crystal.

Dave

I agree, except it is not an actual crystal. They have used what is
known as a ceramic resonator. They are a cheaper, though less accurate
option to a crystal. It probably has three pins going into the PCB. Try
warming that with your finger end when it is misbehaving.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

On Thu, 08 Feb 2007 18:01:37 GMT, Harry Bloomfield
wrote:

gort wrote :
Component I was querying is the one just above the green ribbon partially
obscured. 'L10' is printed on the pcb next to it.

Now it is reassembled, it does similar though different logic wierdness.
Jumped into the middle of a entry sequence at start up when it shouldn't.



The blue one, label ' cx1 ' is the crystal.

Dave

I agree, except it is not an actual crystal. They have used what is
known as a ceramic resonator. They are a cheaper, though less accurate
option to a crystal. It probably has three pins going into the PCB. Try
warming that with your finger end when it is misbehaving.

Was looking at a uW circuit the other day. Capacitor in there rated at
2.5 kV - keep away from that won't you.