Have been given a disassembled Whirlpool grill-microwave oven with missing decals & fuses?

[Benny7440]

Have tried in 2 days & more than 4 hrs to stumble with that model & even chated with someone at Whirlpool but got out empty hands.

This unit was bought about 1 yr ago probably at Walmart. It suddenly stopped working but appeared to be on. The son of the owner openned it & took out "2" fuses out & tried to find them locally without any luck. They decided to throw it away: that's the reason a sister of mine told her neihgbor not to throw it but instead give it to me for a re-check. So, I've no owners manual, there's no sticker with model info anywhere. The main fuse is missing AWA what appears to be another fuse enclosed at a separate plastic enclosure (see attachements).

There's a simplified schematic included at an inner side of cover but no troubleshooting scheme.

After finding & connecting the said fuses I'm intending to give it try: do any of you have any advise as to how to proceed before any other fuse gets blown out? Thanks in advanced for any info on this!

 

[kellys_eye]

Show the schematic.

Usual problems with such devices are faulty heating elements. An insulation test between mains live-to-earth and neutral-to-earth would be the first check to make (fuses IN, device UNPOWERED).

 

[Benny7440]

Thanks for replying, kellys_eye!

The schematic is at the attachement.

 

[Minder]

Show the schematic.

Usual problems with such devices are faulty heating elements. An insulation test between mains live-to-earth and neutral-to-earth would be the first check to make (fuses IN, device UNPOWERED).

Its also a microwave!
Usually the cap or even the transformer.
There are exceptionally high voltages present, so care is needed.
If it doesn't grill or M.W. then it could be the thermal sensors.
M.

 

[Benny7440]

Have re-checked all those points that you mentioned & everything seems to be ok. If it's needed, I can send you another photo with more details from the inside of the unit.

 

[kellys_eye]

Without recourse to a test meter......

Grab a few spare fuses!

Replace the standard fuse but leave the high voltage fuse out of circuit.

Power the unit up and check for all operations. If the main fuse blows again you should disconnect or remove the heating elements and try again (new fuse of course).

If it blows with the heating elements out of circuit then the transformer is probably shorted and not worth fixing.

If it powers up and the fuse is ok then the heating element(s) are shorted and require replacement.

If the grill side all works then fit the HV fuse. Power up again. If the fuse(s) blow then either the magnetron or the diode could be faulty (so could the capacitor).

Try these tests first and report your findings.

Note - as already mentioned there are LETHAL VOLTAGES PRESENT in this unit. Take all appropriate precautions when working with high voltages. If you don't know what these precautions are then DON'T MESS WITH THE UNIT!

 

[Benny7440]

Sorry kellys_eye to reply today but we had a blackout yesterday, almost all day.


Important points: relevant measurements below...

...0.7 ohms primary of power xformer both, attached & disconnected to control board & magnetron; ...infinity to gnd;

...0.3 ohms at magnetron contacts; ...3.3 ohms to gnd (all with one side disconnected);

...infinity between terminals; ...going down from ~40 Mohms with positive meter lead at chassis, with reverse polarity infinity.


All measurements were made with door closed & no fuses in.


Note: Was about to upload another photo but have received 3 cosecutive security error alerts & asking for refreshing & going back & to try again. 3 times tried but the attaching process failed an equal amount of trials. I'm posting now just the data gathered, then I'm going to logout & then login back again & try the attachement again... below.


Note: The same error ocurred without an attachement???

 

[ramussons]

As long as the Hi Voltage fuse is not in circuit, you can connect a 100/250 watt incandescent bulb in place of the main fuse to do the testing. Saves on Fuse replacements.

 

[Benny7440]

Thanks to you too, ramussons, for replying!

Finally stumbled with the model # (wmg09sae). Other info found is Power = 1350 W, grill power = 1000 W & microwave power output = 900 W.

I found a 25 A fuse & used it with the primary of power xformer disconnected and all functions well (the needed fuse should be 20 A). Have not tried the grill part of it, yet.

Planning to test the grill tomorrow and, if all goes well, then the microwave part. The only part that still doesn't convince me is that measurement at the magnetron to gnd..., I'll put my old brain fixed into this before trying to use the microwave.

If anything new or extra in relation to this from you is posted will be appreciated!

 

[Benny7440]

Have a specific question in relation to the magnetron of this unit (in the case you can't read it clearly, the magnetron shows Galantz M24FB-610A & under this the following string G0316503 GAL03 GEMCS1, the last digit is a small '1' like a subscript but aligned as a regular digit).

As mentioned above, the ohmic resistance between leads is 0.4 ohms & each lead to chassis is 32.8-9 ohms, both polarities. These measurements were made with magnetron disconnected completely from the circuit but still attached physically to the unit with door closed & the main fuse on.

My question is in relation to the leads to chassis resistance, is it in the expected range?

 

[Alec_t]

Could that leads-to-chassis resistance be the forward resistance of the high voltage diode, assuming your microwave is similar to this ?

 

[Benny7440]

Could that leads-to-chassis resistance be the forward resistance of the high voltage diode, assuming your microwave is similar to this ?

The magnetron was not connected to anything except by way of been in contact to the chassis (Grounded).

Need help finding the owners manual for this unit, could anyone knows a way of finding it? It might prove useful to know that the unit was probably bought at Walmart in Puerto Rico.

 

[Benny7440]

Deleted a duplicate post (previous)!

 

[Benny7440]

At the fourth chat with Whirlpool services was given an unuseful email for contacting them so receved an appropriate mailer message.

Did another test with the unit & found something that caught my attention, the circumstances for the test were as follows:
---> main fuse connected,
---> one cable from power xformer disconnected,
---> high voltage fuse out (the one attached to the magnetron),

Door is closed: the display seems to work well & all functions too. When the door is openned the light goes on & when closed the light goes off BUT the ventilation fan tries to start spinning for an instant. This suggests to me that there might be something wrong in the synchronism of the 3 door switches. Are you in accordance with me at this?

Thanks for any help on this last issue! Right now I'm going to have a long examination of the schematic to see if it is what I'm afraid of...

 

[Benny7440]

At a test I've found that one of the swithes goes from off to on twice after the door arm start touching its little protution when I'm closing the door. Think, but not verified yet, tbat this short span of time is not only enough for trying to start the fan but also to cause a serious enough short circuit condition to blow the fuses.

Do you agree?

 

[debe]

On your original circuit posted there is a Monitor switch on the door latch setup. This should be open circuit when the door is shut, its a safety switch. Its designed to blow the main fuse. All microwave ovens have this safety switch.

 

[Benny7440]

Have successfully tested the 'Broiler' function today with the primary of the power xformer disconnected. It remains to try to find another Monitor switch & adecuate power fuse for the last test as a microwave, per se...

 

[Benny7440]

Yesterday I put another good switch as a monitor switch & put a little oversize fuse at the magnetron circuit but after ~45 secs it didn't even warmed up the little liquid but it made a train-like noise &, after a little over half a minute it started to give off a burning odor: you know, over-heating electric smell.


I reopenned the unit but only after heating up the cup of coffee at another microwave & drinking it & rinsing the cup. It was too late, by touching the various parts (xformer, magnetron, condenser & high-voltage diode) I thought of discovering the culprit but I haven't found even a warm component.


Is there a way of testing these components out of the circuit (independently) instead of repeating the test I already performed? Also, it would be important to find a source of GOOD info on the theoretical function of a microwave oven.

 

[Alec_t]

Also, it would be important to find a source of GOOD info on the theoretical function of a microwave oven.

Electrical power is applied to a magnetron to generate microwave radiation, This is then guided to the oven cavity where it heats the contents. The power supply is switched on and off repeatedly to control the average microwave power. This explains the magnetron operation.

 

[debe]

What you describe is a short circuit in the Magnetron or the Diode or the Capacitor. These are the only 3 components that are likely to cause an overload of the transformer, which is the noise you describe.