Microwave oven troubleshooting
 

We got this oven in for repair Its a GE model JE2160SF-03. The name
plate reads 120V 1.65KW (MW). I don't know what the MW stands for
however the 1,65 KW would seem to translate into 13.75A. The line fuse
is 20A. The customer tried to use this with a generator during a
recent power failure. He said that the microwave made some odd noises
as the generator surged a few times and so he disconnected it.

On full power mode the unit draws about 7.0 amps and does not heat the
food. An ohm meter test on the capacitor seems to indicate that it has
a good bleeder and that it does charge. I ran the transformer primary
at 12 volts, (10 percent line voltage), and noted that it puts out
about 260V between chassis and the HV lead. There was a small voltage
present on the filament terminals as well. There are no shorts or
leakage to ground on any components. The diode tests good as well.
With a 10 ohm resistor in series with the diode during full power mode
the voltage drop according to Sam's notes should be between 3 and 4
volts. The reading I got was about .200V.

During brief tests of the unit the Magnetron seems to get ever so
slightly warm so that is the only indication that something is getting
to it. I haven't tried to make any HV measurements. I really don't
have a safe way to do that. I'm ready to condemn the Magnetron however
I would hate to think that I'm overlooking anything. Does it seem
possible that power surges might harm only a Magnetron while at the
same time spare all the delicate electronics? Does anyone have any
further thoughts on this? Thanks, Lenny.

Microwave oven troubleshooting
 

klem kedidelhopper writes:

We got this oven in for repair Its a GE model JE2160SF-03. The name
plate reads 120V 1.65KW (MW). I don't know what the MW stands for
however the 1,65 KW would seem to translate into 13.75A. The line fuse
is 20A. The customer tried to use this with a generator during a
recent power failure. He said that the microwave made some odd noises
as the generator surged a few times and so he disconnected it.

On full power mode the unit draws about 7.0 amps and does not heat the
food. An ohm meter test on the capacitor seems to indicate that it has
a good bleeder and that it does charge. I ran the transformer primary
at 12 volts, (10 percent line voltage), and noted that it puts out
about 260V between chassis and the HV lead. There was a small voltage
present on the filament terminals as well. There are no shorts or
leakage to ground on any components. The diode tests good as well.
With a 10 ohm resistor in series with the diode during full power mode
the voltage drop according to Sam's notes should be between 3 and 4
volts. The reading I got was about .200V.

During brief tests of the unit the Magnetron seems to get ever so
slightly warm so that is the only indication that something is getting
to it. I haven't tried to make any HV measurements. I really don't
have a safe way to do that. I'm ready to condemn the Magnetron however
I would hate to think that I'm overlooking anything. Does it seem
possible that power surges might harm only a Magnetron while at the
same time spare all the delicate electronics? Does anyone have any
further thoughts on this? Thanks, Lenny.

You could power the HV transformer from 12 VAC with it connected and
see if you get several hundred V.

Check the magnetron filament. If it's possible to disconnect the HV
from the filament winding, see if the filament lights up and the tube should
get fairly warm from that alone.

Since you're only drawing 7 A - which could be the no load current for
these very lossy transformers, it sounds like either the magnetron is
bad and not drawing any current or its filament isn't lit.

Any shorted component would result in higher current.

But how running on a generator killed the magnetron might be a mystery.

--
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Microwave oven troubleshooting
 

On Thu, 1 Apr 2010 12:18:38 -0700 (PDT), klem kedidelhopper
put finger to keyboard and composed:

We got this oven in for repair Its a GE model JE2160SF-03. The name
plate reads 120V 1.65KW (MW). I don't know what the MW stands for ...

MicroWave???

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Microwave oven troubleshooting
 

"klem kedidelhopper"


** Gotta be a leg pull ???


We got this oven in for repair Its a GE model JE2160SF-03. The name
plate reads 120V 1.65KW (MW). I don't know what the MW stands for
however the 1,65 KW would seem to translate into 13.75A. The line fuse
is 20A. The customer tried to use this with a generator during a
recent power failure. He said that the microwave made some odd noises
as the generator surged a few times and so he disconnected it.

On full power mode the unit draws about 7.0 amps and does not heat the
food.


** OK - so the magnetron is not operating and you are seeing only the
usual, rather high magnetising current for the transformer. Attempted use
with a "generator" is the likely cause of the failure cos many small
generators are voltage controlled but not frequency controlled.

The PSU in a typical microwave oven IS sensitive to the AC supply
frequency - cos it is resonant at 60Hz (or 50 Hz as the case may be).

Operating at a higher or lower frequency then intended will cause serious
misbehaviour of the PSU and in your example this has caused failure of the
magnetron, likely by over-voltaging the heater.


..... Phil

Microwave oven troubleshooting
 

On Apr 1, 8:27*pm, "Phil Allison" wrote:
"klem kedidelhopper"

** *Gotta be a leg pull ???

We got this oven in for repair Its a GE model JE2160SF-03. The name
plate reads 120V 1.65KW (MW). I don't know what the MW stands for
however the 1,65 KW would seem to translate into 13.75A. The line fuse
is 20A. The customer tried to use this with a generator during a
recent power failure. He said that the microwave made some odd noises
as the generator surged a few times and so he disconnected it.

On full power mode the unit draws about 7.0 amps and does not heat the
food.

** OK - *so the magnetron is not operating and you are seeing only the
usual, rather high magnetising current for the transformer. *Attempted use
with a "generator" is the likely cause of the failure cos many small
generators are voltage controlled but not frequency controlled.

The PSU in a typical microwave oven IS sensitive to the AC supply
frequency - *cos it is resonant at 60Hz (or 50 Hz as the case may be).

Operating at a higher or lower frequency then intended will cause serious
misbehaviour of the PSU and in your example this has caused failure of the
magnetron, *likely by over-voltaging the heater.

.... *Phil

But the filament is not open. Lenny

Microwave oven troubleshooting
 

"klem kedidelhopper"

** Gotta be a leg pull ???

We got this oven in for repair Its a GE model JE2160SF-03. The name
plate reads 120V 1.65KW (MW). I don't know what the MW stands for
however the 1,65 KW would seem to translate into 13.75A. The line fuse
is 20A. The customer tried to use this with a generator during a
recent power failure. He said that the microwave made some odd noises
as the generator surged a few times and so he disconnected it.

On full power mode the unit draws about 7.0 amps and does not heat the
food.

** OK - so the magnetron is not operating and you are seeing only the
usual, rather high magnetising current for the transformer. Attempted use
with a "generator" is the likely cause of the failure cos many small
generators are voltage controlled but not frequency controlled.

The PSU in a typical microwave oven IS sensitive to the AC supply
frequency - cos it is resonant at 60Hz (or 50 Hz as the case may be).

Operating at a higher or lower frequency then intended will cause serious
misbehaviour of the PSU and in your example this has caused failure of the
magnetron, likely by over-voltaging the heater.



But the filament is not open. Lenny


** Never said it was - ****.



..... Phil