Microwave under-light stopped working

I have a Sharp microwave (Model R1480) over-the-range model. Has the smooth touchpad style membrane buttons on the control panel. Anyway, the button that controls the Work Light (over the range top--it's mounted in the bottom of the microwave) no longer works. At first I thought the light bulbs (two of them) burnt out, but after replacing them, they still don't turn on. All the wiring between the bulbs and the control panel appear intact. I guess the button/switch in the control pad doesn't work. The strange thing is the button for the exhaust fan, which is right next to the light buttons, does still turn the fan on/off. Can a single control button go bad on these?
Anyone know if I can repair just this worklight switch/circuit (replace the wires?), or will I probably have to replace the whole control panel (I've seen it for ~$50 online--ouch)? At least if I do have to replace it, it looks like it just pops in and out, and the connectors do the same. Any advice on this is appreciated; thanks.
F
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Does your microwave normally beep when any buttons are pressed? If so, and the light is the only one which doesn't beep, you'll know it's the membrane assembly.
My guess is the triac or whatever solid state switch - or maybe even mechanical relay - is bad. Listen closely for a click inside the unit when you press it. Could be it has a relay with carbon loaded contacts.
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It does beep normally, and yes, the Light button still beeps...just no light. So it's probably the solid state switch? Hmm. I'll have to take another look to see what I can take apart. Thanks.
F
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Fr@nk wrote:

Hi,
*Might* be the key panal, but more likely something on the smart board let go....relay, burnt trace, etc.

The key panal is pinched between the plastic consol and the smart board, the whole consol would likely have to come off to access it. When ever working on a microwave the high voltage capacitor should be discharged.
I found these with your model#... http://www.repairclinic.com/referral.asp?R 3&N8501 Touch pad
http://www.repairclinic.com/referral.asp?R 3&N0993 Power control board
http://www.repairclinic.com/referral.asp?R 3&N5159 Touch control pad
Jeff. Appliance Repair Aid http://www.www.applianceaid.com /
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So it's like this?:
|o| | s | |u| K | m | |t | E | a | |e| Y | r | |r | | t | | | P | | |b| A | b | |u | N | o | |t | E | a | |t | L | r | |o| | d | |n | | | |s | | |
I can replace one, two, or all three of these separately? It's not just one unit?
And how do I discharge the high voltage capacitor?
Thanks for the tip on parts.
F

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Hi,

Sort of...the key panal and outer buttons are the same parts, the key panal is behind the plastic frame and the smart board and metal frame are screwed to the plastic frame holding it all together.

All one unit.

These should help... Use a metal ( not the shiny chrome type ) screw driver with a insulated handle to short across ( touch both at the same time ) the terminals of the high voltage capacitor to discharge it. With the microwave unplugged.
http://www.applianceaid.com/newimages/nuker101.JPG
jeff. Appliance Repair Aid http://www.applianceaid.com /
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(Wow, quick reply!)
OK, I guess I've narrowed it to either the front panel (with the buttons) or the power control panel. Looking at the links you gave me (thanks), the front panel is $60-ish and the power control panel is ~$150! Yipe! Heck, I can buy a new oven for $200.
I'd like to determine if just replacing the cheaper part (the front panel) will fix it. Does this narrow it down at all? The bottom row of buttons on the front are:
---------------------- ---------------------- ---------------------- | Work light | | Night light | | Fan | ---------------------- ---------------------- ----------------------
All three buttons beep. Only the far right one (Fan) actually work. The other two light buttons just beep; no light comes on or off.
From this can I tell if it's the front button panel OR the power control panel inside? Thanks very much.
F

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Fr@nk wrote:

Hi,
With a noise being made by pressing the key panal pad, that would be a good sign the key/touch pads are working and the problem is on the main control/smart board. I'd open it up ( power off first ) and remove the smart board and inspect front and back side of the board for any burnt traces first.
jeff. Appliance Repair Aid http://www.applianceaid.com /
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OK, I pulled the panel/board combination out and took it to a local appliance repair shop. They took it in back for a few minutes and told me they checked it, and the board is fine; the buttons are fine. They asked me, "What's wrong with the microwave?". I said (pointing to the light buttons) that the work light and night light buttons don't work anymore (but the fan button, right next to those, works). They told me I'd have to bring the whole microwave in. Ouch! It's an over-the-range model. I don't even know where I'd start to try to unmount the thing from the wall.
OK, I'm out of ideas now. I know it's not the bulbs; I swapped the good in-oven bulb with the work light one, and the work light still didn't come on. I pulled out each bulb's socket and examined the connections; they're all solid--not loose or broken. The only thing left I can think of would be a wire INSIDE the plastic casing has broken...but I can't believe that happened. There is a plain old fuse sitting there behind the control panel (inside the main microwave, not part of the panel board), but it doesn't seem like a little work light would use such a fuse (it's about an inch long, 1/4 inch in diameter).
Anyone have any other ideas as to what can be knocking out my microwave's worklight/nightlight? Again, the buttons still beep; they just don't do anything. Can I just get replacement wires (they have the little plastic connectors soldered to their ends)? Do they need to be "official" Sharp wires or can I just use some Radio Shack wires? Any help is appreciated; thanks.
F
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Fr@nk wrote:

Hi,
Glad to hear the board is not burnt, but it cannot be deemed "ok" outside of the microwave as power is needed to operate the relay(s) on the board for the lights.
Broken or open wire between the board and sockets is possible, each wire would have to be checked for continuity. Any "stove/range" style wire will do fine.
The sockets can be removed and a cheater cord attached to each socket to check the bulbs and sockets.
jeff. Appliance Repair Aid http://www.applianceaid.com /
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Jeff-
There's just no way I'm going to take the whole oven off the wall and bring it in to this place (or any place). Do you know if any of the "mail in" board repair places (I found at least one on the net) that supposedly specialize in these repairs can actually test and repair the board/relay? I'd consider that as an alternative. Otherwise I'll have to pay someone to come out and test it in my house.
I'll have to try to find some wires with these type connectors, and replace them to test. Thanks for your help.
F
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