....shuts off after 3 seconds. I understand it automatically does this if
it detects that it's not working. So if it's not the door safety switches
which seems to be a common point of failure on these, it's got to be either
the magnetron or the inverter. Anyway to tell which? I doubt either is
worth bothering with but I'd still be curious.

On 2/17/2013 2:49 PM, Steve Kraus wrote:
...shuts off after 3 seconds. I understand it automatically does this if
it detects that it's not working. So if it's not the door safety switches
which seems to be a common point of failure on these, it's got to be either
the magnetron or the inverter. Anyway to tell which? I doubt either is
worth bothering with but I'd still be curious.
Can't help with the 3 second shutoff, but ours has to have the door
slammed shut just right to get the interlock mechanism to work.

Paul

Steve Kraus wrote:
...shuts off after 3 seconds. I understand it automatically does this if
it detects that it's not working. So if it's not the door safety switches
which seems to be a common point of failure on these, it's got to be either
the magnetron or the inverter. Anyway to tell which? I doubt either is
worth bothering with but I'd still be curious.

Should get some radiated pulses from the coils at some distance on scope,
if it's making hv. Cover off. I've seen schematic somewhere on web.

Don't mess around if you don't know what your doing.

Greg

Don't mess around if you don't know what you're doing.

I checked that the magetron filament is not open nor is it shorted go
ground so all things point to the inverter. I may check for bad HV diodes
and a few other things. I found a good resource he

http://www.epanorama.net/sff/Misc/Ap...ens/Panasonic%
20A606Y4A00AP%20Microwave%20Oven.pdf

In the end I will just get another oven. I'm disappointed though at how
few of the mid-size units have a door that simply pulls open. (The broken
unit has this.) Pushing a button to pop the door open may seem a trivial
difference but why go through two motions when you can do one?

Steve Kraus wrote:
I found a good resource he

http://www.epanorama.net/sff/Misc/Ap...ave%20Oven.pdf

If you haven't already, also read
http://www.repairfaq.org/sam/micfaq.htm#micsaf for important safety
advice.

"Classic" (non-inverter) microwave ovens often have a thermal cutout
bolted to the side of the magnetron - usually a small plastic cylinder,
about 1/2" (13 mm) diameter by 1/2" high, with a metal flange on one end
and two wires on the other. It's wired into the line voltage input (120
or 240 V) to the high voltage supply. If you have one of these, you
might check that it's not open, and doesn't open when heated a small
amount.

The schematic above doesn't show a thermal cutout, but it looks like
the "DPC" (which I assume is the keypad and display) can request varying
power levels from the inverter - the thermal cutout could be plugged
into the DPC, and when the DPC is unhappy, it may command a shutdown.
The DPC could also use a thermistor - which sometimes looks like a
little epoxy bead on the end of two wires - to sense this.

If there is a cooling fan, make sure it is spinning freely, and not
blocked by dust and junk.

"Classic" microwave ovens also often have three door switches. One
of them opens the 120 V line if the door is open. One of them *shorts*
the 120 V line after the fuse (which blows the fuse) if the door is not
closed correctly. One of them switches low voltage to the control
panel. With the oven unplugged from the wall and left to discharge for
several minutes, you can at least check that the switches are not stuck
open or closed by operating the door.

With the oven unplugged from the wall and left to discharge for several
minutes, it should also be relatively safe to check the inverter side of
the magnetron filament connector to see if the filament winding on the
big transformer is open. You could also check the current transformers
for continuity, and check all four diodes on the main input bridge.

With the oven running (or on and ready to run), there should probably
be some kind of pulses on the two I/O lines connected to the DPC - one
appears to be transmit and the other appears to be receive. Measure
relative to the "0 V" pin on the DPC connector and not anything else.

DANGER! There should be about 340 V DC on the output of the main diode
bridge when the oven is ready to run, and something less than that when
it's actually trying to make power - I don't know how much less, but a
guess would be more than 170 V (half). The only safer way to measure
this is to clip the meter leads into the circuit with the oven
unplugged, and then plug the oven in and see what you get. DANGER!

Matt Roberds

Steve Kraus formulerede Monday:
Don't mess around if you don't know what you're doing.

I checked that the magetron filament is not open nor is it shorted go
ground so all things point to the inverter. I may check for bad HV diodes
and a few other things. I found a good resource he

http://www.epanorama.net/sff/Misc/Ap...ens/Panasonic%
20A606Y4A00AP%20Microwave%20Oven.pdf

In the end I will just get another oven. I'm disappointed though at how
few of the mid-size units have a door that simply pulls open. (The broken
unit has this.) Pushing a button to pop the door open may seem a trivial
difference but why go through two motions when you can do one?

Many reasons advocate a pushputton lock.

With a pushbutton lock, you can get more force keeping the door locked.

The pushbutton can turn off the microwaves before the door opens.

If you pull the door open, a door switch have to turn off the
microwaves, and it might be possible to just opening the door a few
millimeters without turning off the oven, so microwaves can escape.

A push on the button can only push the oven "inwards", while a pull in
a handle can pull the oven on the floor, especially when microwave
ovens doors have to be kept closed with a comparatively large force.

When I press the open-button, the door swings completely open, I don't
need to also open the door manually.

Leif

--
Husk kørelys bagpå, hvis din bilfabrikant har taget den idiotiske
beslutning at undlade det.

Leif Neland wrote:
Steve Kraus formulerede Monday:
Don't mess around if you don't know what you're doing.

I checked that the magetron filament is not open nor is it shorted go
ground so all things point to the inverter. I may check for bad HV diodes
and a few other things. I found a good resource he

http://www.epanorama.net/sff/Misc/Ap...ens/Panasonic%
20A606Y4A00AP%20Microwave%20Oven.pdf

In the end I will just get another oven. I'm disappointed though at how
few of the mid-size units have a door that simply pulls open. (The broken
unit has this.) Pushing a button to pop the door open may seem a trivial
difference but why go through two motions when you can do one?

Many reasons advocate a pushputton lock.

there's only one, it's cheaper and you can use more plastic.

With a pushbutton lock, you can get more force keeping the door locked.

The pushbutton can turn off the microwaves before the door opens.

If you pull the door open, a door switch have to turn off the
microwaves, and it might be possible to just opening the door a few
millimeters without turning off the oven, so microwaves can escape.

A push on the button can only push the oven "inwards", while a pull in
a handle can pull the oven on the floor, especially when microwave
ovens doors have to be kept closed with a comparatively large force.

Tappan had some good doors. There was a handle you'd pull and a pushbutton
to unlock the door on the handle. The latch was metal and pressing the
button would shut off the microwave and opening the door once it was
unlatched would activate the shorting switch.

The all plastic doors scare me.

It's also interesting the older microwaves had dozens of screws and so
much shielding it was hard to even see inside. I'm suprised the shock from
popping popcorn doesn't blow the doors off new microwave ovens.