On Wed, 19 Jan 2011 08:04:43 -0800 (PST), BSAKing
wrote:

I have one of these guys and it has served me very well for probably
15+ years, so I have no quarrel with it.

From the manual, the model number is a JVM 250 BVC or JVM 250 WVC
(probably a white or black model).

In any event, this morning old Betsy decided not to heat anything up.
All the bells and whistles are there, fan runs, etc, lights action,
keypad works, just no heat. So I suspect more than likely the
magnetron or xformer.

I was wondering if anyone knows if there is a secondary fuse I could
check on this model before I turf it? Obviously main one is good as
everything else powers on.

The second question is that I remember installing this thing and
having to adapt a hole in the wall to an outside vent etc to fit it. I
am hoping that maybe a new model of the same make would have roughly
the same vent location so I do not have to rebuild that part to put in
a new one.

Or maybe it is standard for all microwaves? Does anyone know?

Any clues or input appreciated.
You can go here and get started (It is the GE Microwave Section)
http://tinyurl.com/37d5fq3
If you change the parameters, it will change the models.
You will find that if you click on any particular model, you can get
to the insallation instructions, with dimensions, etc.
You can also go here http://www.geappliances.com/
scroll down to Contact Us and send them an email with your problems.
Personally, due the age, I would replace it. You can get the current
model from them. It will require a new bracket, but install looks
easy.
I am about to do it. Broke the handle. Super-glue has fixed it, but
the handwriting is on the wall.
HTH
Took a few days but they were very helpful