Noticed something peculiar while wrestling with the microwave this evening.
My assumption is that the digital display is a vacuum fluorescent type.
With the board dismounted for close visual inspection I can see two little
metallic fingers connected to a one of the display's "pads" on the right
side. The fingers seem to be touching the inner surface of the glass.
There appears to be an identical arrangement on the left side of the
display; however, there is a circular blackened area on the inside of the
window where the left side fingers make contact.
Would this indicate a problem with the display, perhaps an internal
flashover, that could be causing the microwave to act as it does?
"Silver Surfer" wrote in message
...
One thing I've found very interesting about this problem. During my
Googling I came across more than a few posts on various sites mentioning
that their same model microwave was acting the same way as mine but would
work flawlessly when the screw is removed from the top of the control
panel and it is kind of cantilevered outward being supported by the two
plastic tangs at the bottom. All the wiring is still connected, but the
panel is tilted out at about a 45 degree angle from the case if you can
picture this. My microwave behaves exactly the same way. It does not fail
to work in this position.
Some have posited that a bad magnetron causes this behavior.
That brings a few questions to mind.
If it is a bad magnetron, what is bad about it? Does it leak microwaves
onto the board which then disrupt the operation of the solid state
components, but only when the board is in its normal position?
Is the "bad" magnetron causing a disturbance in the power supply which
gets conducted back into the board and disrupts the functions?
Are the wires acting as some kind of microwave antenna when the board is
in the normal position?
If there is stray microwave energy bombarding the board is there a simple
way to shield it?
What explanations do you have for the observed behavior?
"Sam Goldwasser" wrote in message
...
"Silver Surfer" writes:
I've looked at just about every conceivable location inside and outside
the
cabinet but have not located a schematic.
It's my daughter's microwave. Complaint was that it keeps shutting down
shortly after starting to heat something. Problem has been around
awhile
but kept getting progressively worse until now it's just about useless
to
cook something.
Brought it home with me. Tried it out. Worked perfectly quite a number
of
times. Took it apart just to look for something that could be causing
an
intermittent. Found nothing. Put it back together. Oops. Problem
back
with a vengeance.
Tore it apart again. Checked lots of connections and TCOs with my
ohmmeter.
Examined circuit board with a high intensity light and a magnifying
glass.
Underneath I assume? It does sound like an intermitten connection but
an ohmmeter probably won't find it. Only a really close examination.
While highly unlikely, check or replace the fuse as well.
Nothing turned up.
Unplugged the HV transformer primary and put it through its paces.
Everything worked flawlessly(except the heat of course).
Connected the HV transformer again. Voila. It's working normally
again!
My concern is that it will go back into the failure mode sooner or
later,
because no smoking gun has shown up.
When it was acting up it made me suspect that the board was losing power
because when it shut off the digital display required me to enter the
time
and date just like it does after it's unplugged.
An aside to Mr. Goldwasser:
Your excellent article on microwave repair has been an enormous help to
me.
Thanks for sharing your extensive knowledge with the rest of us.
Thanks. 
--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
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"Silver Surfer" wrote in message
...
Folks,
My searching on Google has come up empty. Do service manuals and
schematics actually exist for a GE microwave oven JVM1650BH03? If so
where might I acquire such material?