I've got an old convection microwave that's probably seen it's better
days, but I thought I'd throw this out here and see if there are any
ideas. It's actually on it's second magnetron tube, which I replaced
like 8 years ago. The symptoms (way back 8 years ago) were when you
tried to nuke something, it made a loud hum (loud enough to say "oh
sh*t" and turn it off).

This time, the controls seem to work fine (set it to nuke or to
"convect" something, the timer counts down as long as the door is
shut... just exactly like it's working), but the fan motor doesn't
start, there's no gentle hum of nuking. Set to convection, the fan
motor doesn't start (I didn't leave it on long enough to see if the
heating element heated).

Anyway, it sounds like maybe the momma transformer has given up the
ghost. Yes? The baby transformer is putting out it's 13, 3, and 8,
like it should, which is why the control panel is so happy.

It's a 1993 GE, so, yeah, I got my money's worth out of it, but new
ones are like $600 (over the range version), and it ticks me off that
you can get one just like it, but without convection for $200.

So do folks here have a theory? Something for me to try?

On Dec 3, 10:00 pm, sengsational wrote:
This time, the controls seem to work fine (set it to nuke or to
"convect" something, the timer counts down as long as the door is
shut... just exactly like it's working), but the fan motor doesn't
start, there's no gentle hum of nuking. Set to convection, the fan
motor doesn't start (I didn't leave it on long enough to see if the
heating element heated).
(snip)
So do folks here have a theory? Something for me to try?

Anybody? The ohmmeter over the internal 15A fuse shows continuity.

sengsational wrote:

I've got an old convection microwave that's probably seen it's better
days, but I thought I'd throw this out here and see if there are any
ideas. It's actually on it's second magnetron tube, which I replaced
like 8 years ago. The symptoms (way back 8 years ago) were when you
tried to nuke something, it made a loud hum (loud enough to say "oh
sh*t" and turn it off).

This time, the controls seem to work fine (set it to nuke or to
"convect" something, the timer counts down as long as the door is
shut... just exactly like it's working), but the fan motor doesn't
start, there's no gentle hum of nuking. Set to convection, the fan
motor doesn't start (I didn't leave it on long enough to see if the
heating element heated).

Anyway, it sounds like maybe the momma transformer has given up the
ghost. Yes? The baby transformer is putting out it's 13, 3, and 8,
like it should, which is why the control panel is so happy.

www.repairfaq.org has lots o' information about microwave ovens.

Is there some kind of interlock that prevents the magnetron from
nuking if its cooling fan doesn't spin? I think I saw a sail switch
for this in ours.

www.microwavedisplays.com has lots of oven repair manuals available
online at no charge.

On Dec 7, 1:34 am, "larry moe 'n curly"
wrote:
sengsational wrote:
.... controls seem to work fine (set it to nuke or to
"convect" something, the timer counts down as long as the door is
shut... just exactly like it's working), but the fan motor doesn't
start, there's no gentle hum of nuking. Set to convection, the fan
motor doesn't start (I didn't leave it on long enough to see if the
heating element heated).

Anyway, it sounds like maybe the momma transformer has given up the
ghost. Yes? The baby transformer is putting out it's 13, 3, and 8,
like it should, which is why the control panel is so happy.

www.repairfaq.org has lots o' information about microwave ovens.

Thanks for the reply. That site is going to take some serious time to
pick through!

Is there some kind of interlock that prevents the magnetron from
nuking if its cooling fan doesn't spin? I think I saw a sail switch
for this in ours.

Yeah, the interlocks seem to be working, but I'll double check. There
are two on the door. Opening the door stops the count-down clock, so
at least one of them is working. I tested both, and they both change
from open to closed (or closed to open) when the door is open and
shut. Might there be some other interlock besides the door? I have
the schematic, so I'll have another look.

www.microwavedisplays.com has lots of oven repair manuals available
online at no charge.

The site that used to be there must have moved....there's just one of
those "junk" sites there now...parked on that site, trying to sell it
for $500.

--Dale--