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jgbena  
#1 Posted : Thursday, December 11, 2014 8:45:34 AM(UTC)
jgbena

Rank: Member

Groups: Registered
Joined: 12/11/2014(UTC)
Posts: 3

Greetings (first time poster here)

I have an older Magic Chef electronically controlled stove.

Recently the oven stopped working. No flame.

I press "Bake", Dial the temperature I wish then press "bake" once more.
The oven "On" annunciator lights up. and I hear an audible click as normal.
The igniter bar does not heat up at all.

Steps I have taken,
removed old igniter
measured the resistance accross the leads. 255 Ohms (means its good)
Replaced the igniter anyway with a new part keeping the old as a spare.

Result: No change in performance.. oven still will not light.

I do not have a schematic for this stove. does anyone know where I can get a service manual and/or schematic for this model? Also does anyone know the correct procedure for oven temperature calibration?

Thanks
Jon
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jgbena  
#2 Posted : Monday, December 15, 2014 6:11:07 AM(UTC)
jgbena

Rank: Member

Groups: Registered
Joined: 12/11/2014(UTC)
Posts: 3

As usual whenever I have to fix something of mine its never anything typical. After a while of troubleshooting this weekend. I determined the problem with the oven.

Steps I took initially:
-Measured Resistance on Igniter @950 ohms (OK)
-Measured resistance across Temperature Probe @ 1K ohms (OK)
-This unit is equipped with a dual gas valve with two coils so I measured the resistance across each of the coils and compared them. both were in a few ohms of each other so that was fine.
-Checked the overtemp switch and It was closed (normal)

Finally I knew that the broiler works and the and bake did not and I knew the controller was working as I was hearing the relays click. I decided to switch the wires on the broil and bake outputs on the controller board. Fired up the broiler, and it sure enough the bake glowbar lights and the flame came on. Success..

Now that I knew this information I began to diagnose the controller board. Checking the output of the bake relay with a volt meter to Neutral I was reading zero volts. So either the relay terminals weren't getting power or the relay was bad. Upon closer examination after I took the unit out i saw that the foil trace around the output pin of the relay was black and looked burned. Sure enough the foil had been burned away over the years.

The controller has three circuit board stacked on top of one another and they are held together with heat staked plastic standoffs and a couple of the snap in variety. I had to drill out the plastic on the four that were staked and snap the boards apart.

The actual problem was caused by a burnt foil trace on the circuit board which was actually a result of a a factory defect in the board. There was not enough foil around the hole to deal with the current that is drawn off that circuit. Over the years it slowly disintegrated until recently.

The fix required me to scratch off the green solder mask covering the foil trace and lay in a piece of wire (I used 12 ga THHN) and solder along the whole thing.

To reassembly i had to use some 5 minute epoxy as I snipped off the excess plastic from the original heat stakes.

Reassembled the board, powered it up and set the oven on bake. It lit just fine. Finished assembling the rest of the range and gave it a final test.

What i noticed was that not only did i fix the oven lighting problem, it also seems to have solved my 30 degree low temperature problem as well!
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