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Thanks gene. I ordered a diode today. I will let you know the outcome whe I get the part.
Joe
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Hi Gene
I received the diode and the Magnatron yesterday. I replaced the diode first, powered up the microwave and attempted to heat a small amount of water. Smoke came out of the transfomer area. I then replaced the magnatron keeping the new doide. MORE SMOKE. Next I put the old diode back in an left the new magnatron in place. More smoke.
In each instance the capacitor did not have any charge.The new dioded (using the battery test now measures 8.57V one way and 12.56V the other.
I did not check it before installation. Could the capacitor be the problem? I mesured it as stated in previouse a message and it seemed to check OK.
I am baffeled!
Joe
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Originally Posted by: soundj  ... Smoke came out of the transformer area... Joe, This is very bad sign, especially if it did not smoke before. Do you have the wiring diagram for the microwave? If you do, then double check all wires connections (the transformer to the capacitor and magnetron "F" & "FA" terminals and the diode) in accordance with the diagram. The new diode is now damaged. Gene.
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There are no wiring shorts. I think the diode was defective and caused the transformer to overheat thus destroying trhe transformer.This is the circuit I used to check wiring ( The Voltage Doubler Circuit Used In Microwave Oven High Voltage Systems). The capacitor has never had a charge. At this point I don't know if anything in the HV circuit is any good! Joe
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Joe, I did not mean any wires shorted. The transformer has two secondary windings - high voltage and filament (low voltage). It is very important how they are connected to the capacitor and the magnetron. As you can see from the diagram (attached to the reply) the wire from the high voltage winding connected to one of the capacitors terminals while the one of the filament winding wire together with the diode and "FA" magnetron terminal are connected to the second capacitors terminal. The second filament filament winding wire should be connected to the "F" magnetron terminal. The capacitor had no charge most likely because of a bad diode. Gene.
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The small secondary has about 0.4 ohms, The high voltage large secondary shows open from one side to ground and ashort from the other side to ground. All wires disconnected when taking resistance measurements.
Joe
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Joe,
Looks like the high voltage winding is bad because its normal resistance reading should be about 70 Ohms. In the other word the transformer has gone bad.
Did you check the wires connections on the high voltage side of the microwave?
Gene.
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All wires seem ok, That is no damage or opens. The only visable sign is the secondary part of the transformer (where the white lead connects. The tape holding the white lead to the Xformer is brown and has dislodged from the xformer. the area around the connection is dark brown as well.
Joe
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Rank: Advanced Member
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Joe, I did not mean wires conditions. I meant wires connections. Quote:...The tape holding the white lead to the Xformer is brown and has dislodged from the xformer. the area around the connection is dark brown as well... It proves a bad transformer. Gene.
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Rank: Member
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I am not sure where you are leading to. All connections are in good condition.All wire connections leading to the transformer check good. I hope thats what you meant. Thge fact remains that the transformer smoked after replacing the diode. The wires were replaced in the same order they were removed. there aren't any wires connecting to any spot they aren't suppose to.
The question to me is what took out the transformer. and what else in the HV circut is damaged.
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