GE Microwave repair help
 

My trusty 18 year old GE just shot craps. It beeps and junk on the display
and I also found a reference to my problem in the EURAS database, but they
want me to pay for the info. It beeps and kinda freaks out. The boards in it
appear fine, no cold solder joints or burned components. I found a small
sheet of diagnostics inside the case, and the only thing I tested was the
TRIAC, and it reads 50ohms not the 70 listed on the sheet. Other than that,
I don't know much! What I found was this:

http://www.service-werkstatt.de/repa...2800001_Ge.htm

It's a Model JE2800-001, any help appreciated. Please copy me via email if
you have an idea of what to try.

Todd

Toddy wrote:
My trusty 18 year old GE just shot craps. [...] It beeps and kinda freaks
out.

Try unplugging it for a while, then plugging it back in. Maybe the
microprocessor is confused.

You might check the fuse, but it probably isn't blown if you can get
some action out of the oven.

Check the interlock switches. There will be at least one that is
designed to open with the door unlatched - it will either interrupt the
line voltage or serve as an input to the controller board. Usually,
there is also a switch that is designed to "crowbar" directly across
the hot and neutral lines and blow the fuse.

There should be a small power transformer on the circuit board; check
the AC voltage(s) on its secondary. Typically these have a pretty
simple linear power supply on the board and you may be able to tell if
the DC output is low. If you have a scope, look for excessive ripple
(bad filter cap) on the DC output.

Also see http://repairfaq.ece.drexel.edu/sam/micfaq.htm .

Please copy me via email if you have an idea of what to try.

Post on Usenet, get an answer on Usenet.
http://www.catb.org/~esr/faqs/smart-...html#noprivate

Matt Roberds

"Toddy" wrote in message
ink.net...

the only thing I tested was the
TRIAC, and it reads 50ohms not the 70 listed on the sheet

Close enough.

N

Been unplugged for over a day, was hoping that was it myself. I'm getting
garbage sometimes, so thinking voltage may be screwed up, I'll check the
transformer.


wrote in message
news:am2ve.68371$gc6.8217@okepread04...
Toddy wrote:
My trusty 18 year old GE just shot craps. [...] It beeps and kinda freaks
out.

Try unplugging it for a while, then plugging it back in. Maybe the
microprocessor is confused.

You might check the fuse, but it probably isn't blown if you can get
some action out of the oven.

Check the interlock switches. There will be at least one that is
designed to open with the door unlatched - it will either interrupt the
line voltage or serve as an input to the controller board. Usually,
there is also a switch that is designed to "crowbar" directly across
the hot and neutral lines and blow the fuse.

There should be a small power transformer on the circuit board; check
the AC voltage(s) on its secondary. Typically these have a pretty
simple linear power supply on the board and you may be able to tell if
the DC output is low. If you have a scope, look for excessive ripple
(bad filter cap) on the DC output.

Also see http://repairfaq.ece.drexel.edu/sam/micfaq.htm .

Please copy me via email if you have an idea of what to try.

Post on Usenet, get an answer on Usenet.
http://www.catb.org/~esr/faqs/smart-...html#noprivate

Matt Roberds

I testing the transformer that supplies the PCB, output is 2.5V and 14V AC,
close enough to match what's posted. With that and that alone plugged in, it
gives me a beeping and garbage on the display, so I'm down to narrowing
something down on the so called "Smart board" or replacing.


wrote in message
news:am2ve.68371$gc6.8217@okepread04...
Toddy wrote:
My trusty 18 year old GE just shot craps. [...] It beeps and kinda freaks
out.

Try unplugging it for a while, then plugging it back in. Maybe the
microprocessor is confused.

You might check the fuse, but it probably isn't blown if you can get
some action out of the oven.

Check the interlock switches. There will be at least one that is
designed to open with the door unlatched - it will either interrupt the
line voltage or serve as an input to the controller board. Usually,
there is also a switch that is designed to "crowbar" directly across
the hot and neutral lines and blow the fuse.

There should be a small power transformer on the circuit board; check
the AC voltage(s) on its secondary. Typically these have a pretty
simple linear power supply on the board and you may be able to tell if
the DC output is low. If you have a scope, look for excessive ripple
(bad filter cap) on the DC output.

Also see http://repairfaq.ece.drexel.edu/sam/micfaq.htm .

Please copy me via email if you have an idea of what to try.

Post on Usenet, get an answer on Usenet.
http://www.catb.org/~esr/faqs/smart-...html#noprivate

Matt Roberds

Toddy wrote:
I testing the transformer that supplies the PCB, output is 2.5V and 14V AC,
close enough to match what's posted. With that and that alone plugged in, it
gives me a beeping and garbage on the display, so I'm down to narrowing
something down on the so called "Smart board" or replacing.

Maybe there's bad electrolytics on that board. Seen it happen in some
other brands.

---
Met vriendelijke groet,

Maarten Bakker.

Toddy wrote:
My trusty 18 year old GE just shot craps. It beeps and junk on the display
and I also found a reference to my problem in the EURAS database, but they
want me to pay for the info. It beeps and kinda freaks out. The boards in it
appear fine, no cold solder joints or burned components. I found a small
sheet of diagnostics inside the case, and the only thing I tested was the
TRIAC, and it reads 50ohms not the 70 listed on the sheet. Other than that,
I don't know much! What I found was this:

http://www.service-werkstatt.de/repa...2800001_Ge.htm

It's a Model JE2800-001, any help appreciated. Please copy me via email if
you have an idea of what to try.

Todd

What I would suggest first is to replace all of the electrolytic
capacitors on the smart board. They may be black, green, blue, etc.,
and look like those seen in the photo he
http://www.sparkfun.com/shop/images/163.jpg

What happens is that the electrolytic (liquid) wears out, changes pH
level, or dries out over time, and they stop filtering the rectified DC
voltage from the power supply. The fluctuations (noise) that get
through will drive ICs crazy! New caps may fix this for you.

To get the replacements needed, you can visit Tritronics at
http://www.wehaveparts.com/index.cgi...ectrolytic.htm

Be sure the value of the caps you order is the same. Voltage can be a
step higher. These are all 105-degree caps, and very good, too. Be sure
the plus-minus polarity is the same when you install the new ones or
they can actually pop and take off like little rockets! Safety first!

Also, I would recommend resoldering and if possible actually testing
any parts which are burned or which have darkened spots under them on
the circuit board. Big transistors and resistors are your first
suspects. They can desolder themselves over time as the solder
experiences metal fatigue from the heat.

Lastly, look for brown glue (goo) used to hold components down before
they were machine soldered during manufacturing. This glue can become
conductive over the years, causing odd and aggrivating problems.

Still need help? I fix microwave control panels for only $32.50 in most
cases. See http://www.MicrowaveDisplay.com for details.

Good luck, and observe safety rules (such as those at
http://www.gallawa.com/microtech/safety.html)!