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BE CAREFUL BEFORE TOUCHING THE MAGNETRON AND BE SURE THE MAINS IS DISCONNECTED AND ALL CAPACITORS DISCHARGED
Unplug all the wires from magnetron carefully and take note for the connections (as the wiring is critical).
1. Now with the multimeter set on LOWEST resistance range check both terminals resistance, should be less than ONE Ohm (Ω).
2. Now select the meter's HIGHEST resistance range and check from any terminal (infact the filament connections) to the metal housing resistance , DO NOT TOUCH any probe test terminals at this point. No resistance should be shown, if there is any, the Magnetron is BAD.
Hope it is helpful.
BE CAREFUL BEFORE TOUCHING THE MAGNETRON AND BE SURE THE MAINS IS DISCONNECTED AND ALL CAPACITORS DISCHARGED
Unplug all the wires from magnetron carefully and take note for the connections (as the wiring is critical).
1. Now with the multimeter set on LOWEST resistance range check both terminals resistance, should be less than ONE Ohm (Ω).
2. Now select the meter's HIGHEST resistance range and check from any terminal (infact the filament connections) to the metal housing resistance , DO NOT TOUCH any probe test terminals at this point. No resistance should be shown, if there is any, the Magnetron is BAD.
Hope it is helpful.
Raza's tests are for the filament and leakage and are good. However, if you want to test it for efficiency there is no way other than to power it up and detect the RF leaving the antenna port. This is a highly specialized job and unless you have the equipment to do it, I strongly suggest you do not try. The voltages and RF radiation from a magnetron are absolutely lethal and both can result in instant death.
Also beware that they MUST be force cooled while operating and they contain strong magnets.
Raza's tests are for the filament and leakage and are good. However, if you want to test it for efficiency there is no way other than to power it up and detect the RF leaving the antenna port. This is a highly specialized job and unless you have the equipment to do it, I strongly suggest you do not try. The voltages and RF radiation from a magnetron are absolutely lethal and both can result in instant death.
Also beware that they MUST be force cooled while operating and they contain strong magnets.
To test the magnetron RF power requires very specialized test equipment but it sounds like you are trying to repair a microwave oven. The RF testing kit would cost about as much as 500 new ovens so unless you are doing this as a business I would stop right now!
What exactly are you trying to do? If you have a microwave oven with a non-functioning keypad it is very unlikely to be anything to do with the magnetron. What fault symptoms do you see.
To test the magnetron RF power requires very specialized test equipment but it sounds like you are trying to repair a microwave oven. The RF testing kit would cost about as much as 500 new ovens so unless you are doing this as a business I would stop right now!
What exactly are you trying to do? If you have a microwave oven with a non-functioning keypad it is very unlikely to be anything to do with the magnetron. What fault symptoms do you see.
RF testing kit is real expensive tool and needs special skill to use without getting harmed from the High Voltage or the RF power, as both are dangerous to the life.
On the keyboard question, there are many possibilities to this defect. You are needed to put here some symptoms to guess the fault.
May be just DC supply Bad (5 volts to MC) or may be some gating circuit integrated with microcontroller or some ROW and COLUMN generator (still a lot of possibilities)
My test procedure in post #2 was just for a beginner. As to test Magnetron in Live Circuit is a specialized job.
RF testing kit is real expensive tool and needs special skill to use without getting harmed from the High Voltage or the RF power, as both are dangerous to the life.
On the keyboard question, there are many possibilities to this defect. You are needed to put here some symptoms to guess the fault.
May be just DC supply Bad (5 volts to MC) or may be some gating circuit integrated with microcontroller or some ROW and COLUMN generator (still a lot of possibilities)
My test procedure in post #2 was just for a beginner. As to test Magnetron in Live Circuit is a specialized job.
Would you explain these faults & their remedies ? please
As you said in your above mentioned beautiful post :
" May be just DC supply Bad (5 volts to MC) or may be some gating circuit integrated with microcontroller or some ROW and COLUMN generator (still a lot of possibilities)."
1) If DC supply gone bad, then, what are the symptoms of it & how to resolve the issue ? From where the DC supply is originating & where its terminating ?
2) What about ROW & Column Generator ? what are the symptoms of bad ROW & Column Generator & how to resolve the issue ?
3) Gating circuit integrated with microcontroller, if its gone bad then, what are the symptoms of it & how to resolve the issue ?
Symptom 1. Check the supply voltage for their proper limits and if not correct them.
Symptom 2. Any gating circuit can be tested for proper working with a Logic gates IC tester.
Symptom 3. For testing Digital special circuits a Skilled person must have the knowledge of those.
If the supply is gone bad has different effects of different situation. If regulated supply is BAD and gone to its highest level caused by a short circuited series regulator, the all ICs may had (repeat may had gone) bad but if gone bad to no supply voltage then you have to check the culprit of failure.
let us be very clear on this subject.....as far as testing the mag in a mw goes-the check of continuity between filament pins to case(sc mag-scrap buy a replacement magnetron) will isolate a faulty mag....be very careful about removing the filament wires as the hi voltage capacitor may still be charged...another way to locate a faulty mag is to listen to the mw as you start a cook cycle and if there is no buzz as the mag cuts in (which quickly dissappears)or a constant growl the mag is faulty and needs changing(can also be caused by a sc diode followed by fuse blowing or smoking ht transformer-or sc capacitor or the asm rectifier sc which usually blows fuses straight away.Other faults ,capacitor oc or lo in value can affect the mag as well.most capacitors have an internal bleed resistor fitted which is meant to discharge it but you cant rely on it-safety first-manually discharge the cap...as far as keypads go if they dont work it may simply be an interlock fault or cleaning of the ribbon cable where it enters the display board ...if the membrane keypad has failed throw it away and buy a new one.
do not carry out repairs to any microwave unless you know exactly what you are doing............ just as an example heres a service manual for one ......
Symptom 1. Check the supply voltage for their proper limits and if not correct them.
Symptom 2. Any gating circuit can be tested for proper working with a Logic gates IC tester.
Symptom 3. For testing Digital special circuits a Skilled person must have the knowledge of those.
If the supply is gone bad has different effects of different situation. If regulated supply is BAD and gone to its highest level caused by a short circuited series regulator, the all ICs may had (repeat may had gone) bad but if gone bad to no supply voltage then you have to check the culprit of failure.
Munzir, these are basic things that you must fully understand if you are to attempt repairs on electronic equipment. I am sorry if we seem to insult you but the questions you ask suggest to us that you are not yet ready to handle such dangerous equipment. We do not mean you harm but it seems you could put your life at risk by not heeding our warnings and none of us want that responsibility.
Magnetron radiation is invisible but extremely dangerous, simply pointing the waveguide at someone can kill them. They can also be seriously and irreversibly injured by waves reflecting off other objects. There is also the more obvious danger of the very high voltages and sufficient currents to casue serious burns or fibrilation. Before considering repairs on this kind of equipment you should have a thorough understanding of electronics, control systems and RF.
Almost certainly there is a microprocessor driving the display and keys to enter the time/power/start/stop and so on. The microprocessor requires a power source and this is one of the first things to suspect as being faulty if the unit doesn't work. The microprocessor is probably a generic type but programmed at the factory and stamped with a custom part number, without knowing what it's real part number is you can't tell what the supply to it should be. Typically the supply voltage is 3.3V or 5V but if the display is flourescent it may also need a low AC voltage for the filament and a high voltage (> 20V) for the display segments. Without a service manual it is almost impossible to say what the voltage should be and one model will be different to the next.
Munzir,
Testing for the supply limit means if the supply for a Microcontroller you must know whether it is 5 volts or what. If it is 5 volts, it must be be in the limit from 4.75 volts to 5.25 volts. If it is low the MC will not work and if it is more than 5.25 it may damage the MC. So is the case in other supplies like 12 volts and so on.
I hope these basic things are in your knowledge.
Almost certainly there is a microprocessor driving the display and keys to enter the time/power/start/stop and so on. The microprocessor requires a power source and this is one of the first things to suspect as being faulty if the unit doesn't work. The microprocessor is probably a generic type but programmed at the factory and stamped with a custom part number, without knowing what it's real part number is you can't tell what the supply to it should be. Typically the supply voltage is 3.3V or 5V but if the display is flourescent it may also need a low AC voltage for the filament and a high voltage (> 20V) for the display segments. Without a service manual it is almost impossible to say what the voltage should be and one model will be different to the next.
It depends upon the Keyboard style and availability at the same time. There are still many things to make sure for proper working. If there are coders and decoders for the Row_Column circuitry, you have to be sure about them for proper working.
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