Whirlpool Combi-oven blows fuse, please help.

[Pier]

Re: Whirlpool Combi-oven blows fuse, please help.

I've desoldered the relays and #3 indeed has been welded short.
The other ones look okay apart from some burn marks.

On a scale of minor electrocution to house on fire, how likely is the device to work by just replacing the relays?

I've looked for the same relays (Omron G2R-1A-H 24VDC), but i can only find them in 100pc package, which isn't gonna happen.

It looks like Tianbo TRA1 L-24VDC-S-Z 5 has the same specifications, no?

[Pier]

Re: Whirlpool Combi-oven blows fuse, please help.

So, i was thinking.. if i were to replace the bad relay with one of the working ones (i rarely use the grill feature), put back together the device and power it, shouldn't everything besides the grill work? (assuming only the relay is bad)

Or is this a bad idea?
I mean, the worst thing that can happen is that the relay will short again?

[stj]

Re: Whirlpool Combi-oven blows fuse, please help.

the other 2 relays need cleaning or replacing, once they start arcing the contacts dont work well anymore.

you also need to deal with the cracked soldering on the board - and the arcing.

[Pier]

Re: Whirlpool Combi-oven blows fuse, please help.

the other 2 relays need cleaning or replacing, once they start arcing the contacts dont work well anymore.

you also need to deal with the cracked soldering on the board - and the arcing.

I can't see where the cracked soldering on the board is, any chance you can point it out?

You think if i were to replace the bad relays with new ones, the arc like in the video will probably still be there?
If so, i guess it's no use to switch the relays and do a test?


The markings on the PCB say "FC" "GR" "FCFAN" "MW" for the relays, the shorted one is FCFAN. (the fan for hot air?)

[stj]

Re: Whirlpool Combi-oven blows fuse, please help.

can you upload the video?
youtube is useless because it cant be paused or stepped through.

[Pier]

Re: Whirlpool Combi-oven blows fuse, please help.

can you upload the video?
youtube is useless because it cant be paused or stepped through.

This site doesn't accept .mp4 and compressed is too big filesize but i took some screenshots of the video.

To me it looks like an arc between the thermoactuator and the waveguide for the magnetron.

[stj]

Re: Whirlpool Combi-oven blows fuse, please help.

hmm - you really need to get to that!

btw, wondering what trashed the relays - make sure none of the fans including any hidden motor for rf-scatter arent stalled.

[Pier]

Re: Whirlpool Combi-oven blows fuse, please help.

hmm - you really need to get to that!

btw, wondering what trashed the relays - make sure none of the fans including any hidden motor for rf-scatter arent stalled.

I've put back the relays for FCFAN, FC and MW and provided power to the device.
Microwave alone works fine, but if i switch to hot air the fuse blows just like before.

Both motors spin freely.

The biggest reason for me to fix this machine is so i can microwave rice which i can now, so for the time being i'm satisfied but if i have more time i'm gonna look for what's wrong with the hot air.

Maybe if i have time this week i'll switch the relay for the grill and hot air to see if i can use the grill.

I've also tried to make a schematic by looking at the pcb / wires and to me it looks like the relays for FCFAN, GR & FC are all part of the same circuit and the microwave has it's own.
The thermoactuator where the spark occurs is also on this circuit.

[goontron]

Re: Whirlpool Combi-oven blows fuse, please help.

^ for sake of curiosity, can we get shots of just the thermo-actuator?

[tvsteve2]

Re: Whirlpool Combi-oven blows fuse, please help.

The most important thing I saw in your pics is the arced out hole in the waveguide mica in pic 3 the magnetron is probably shorted and that's why the relays are arced (they may still be useable) remove the two HIGH Voltage wires from the magnetron and the HV single wire from the secondary winding of the transformer to the Cap with the rectangular diode on it (check to see if either the cap or diode are shorted) With the three connections unhooked the unit should be able to turn on and not blow fuses (that method unloads any magnetron loads and kills the HV) The Mica HAS TO BE REPLACED and the tube's hole in the waveguide checked for burning and replace the magnetron if no shorts on the diode or cap also the 2 contacts on the magnetron should show continuity (short) but not to the metel housing of the tube.

[Pier]

Re: Whirlpool Combi-oven blows fuse, please help.

^ for sake of curiosity, can we get shots of just the thermo-actuator?

It's the red/brown servo-looking thing.

I've put the machine back together for the time being so that's all i've got for now.

[Pier]

Re: Whirlpool Combi-oven blows fuse, please help.

The most important thing I saw in your pics is the arced out hole in the waveguide mica in pic 3
the magnetron is probably shorted and that's why the relays are arced (they may still be useable)
remove the two HIGH Voltage wires from the magnetron and the HV single wire from the secondary winding of the transformer to the Cap with the rectangular diode on it (check to see if either the cap or diode are shorted)
With the three connections unhooked the unit should be able to turn on and not blow fuses (that method unloads any magnetron loads and kills the HV)
The Mica HAS TO BE REPLACED and the tube's hole in the waveguide checked for burning and replace the magnetron if no shorts on the diode or cap
also the 2 contacts on the magnetron should show continuity (short) but not to the metel housing of the tube.

Thanks, i will try this the next time i open it up.

The microwave alone runs fine now that i've took out the bad relay, if i can figure out what exactly the problem is with the rest i'll buy new mica with the other parts i'll need.

I took out the magnetron before and it was very clean, didn't check for continuity though.

[jazzie366]

Re: Whirlpool Combi-oven blows fuse, please help.

I don't know why you can't access imgur but i've added some pics as attachment.

This is the cap, this probably has about 270v on it DO NOT TOUCH THIS UNTIL YOU HAVE CHECKED WITH A PROPERLY RATED MUTLIMETER THAT THERE IS NO HIGH VOLTAGE ON THE UNIT!

If you can verify that there is no voltage present SAFELY, then it's alright to touch the inside of this unit.

That cap should be a suspect, when they fail they can cause things like that relay to blow. The reason being is because the current that will be drawn will be much higher if that cap is bad. This could also explain the relay going bad, it literally looks as if the internals have imploded.

Also keep in mind what stj said, there's water damage that needs to be investigated.

If it were me, I'd personally replace the entire board with a new one to be safe, as well as the main capacitor.

Also if I'm not mistaken, those caps have mutliple taps, and one of those is extremely high voltage (2000V)? My microwave has a 2kv run cap in it.

[TechGeek]

Re: Whirlpool Combi-oven blows fuse, please help.

2kV RUN!?

[goontron]

Re: Whirlpool Combi-oven blows fuse, please help.

^ no. nono. no. (not you TG, the post above it)

That is the main filter for the line. See the scmatic on the side of whats inside of it? And if you look at the rest of the pics you will the that it is between the mains and the rest of the unit. Thats an EMI filter in a can.

[Pier]

Re: Whirlpool Combi-oven blows fuse, please help.

This is the cap, this probably has about 270v on it DO NOT TOUCH THIS UNTIL YOU HAVE CHECKED WITH A PROPERLY RATED MUTLIMETER THAT THERE IS NO HIGH VOLTAGE ON THE UNIT!

If you can verify that there is no voltage present SAFELY, then it's alright to touch the inside of this unit.

That cap should be a suspect, when they fail they can cause things like that relay to blow. The reason being is because the current that will be drawn will be much higher if that cap is bad. This could also explain the relay going bad, it literally looks as if the internals have imploded.

Also keep in mind what stj said, there's water damage that needs to be investigated.

If it were me, I'd personally replace the entire board with a new one to be safe, as well as the main capacitor.

Also if I'm not mistaken, those caps have mutliple taps, and one of those is extremely high voltage (2000V)? My microwave has a 2kv run cap in it.

Thanks for your insight, after watching some youtube on the subject i have decided to build a capacitor discharge tool and High Voltage Probe with parts i can possibly salvage from dead electronics i have collecting dust.
So i can safely discharge both caps and do some measurements on them the next time i open it up.

I'm having difficulties spotting the water damage, other than some minor oxidation on the solder, but that's to be expected for a machine this age, no?
(the plastic parts inside say 1995, so i'm guessing it's at least 20 years old)
My guess is the relay shorted because steam has entered it's enclosure. (they're definately not water/air-tight)

I've looked on ebay for a replacement board but no luck so far and even if i'd find one i doubt i will pay ~40 EU for a board that's likely as old as the one i have.
Considering new ovens like this one can be had for as "little" as 100EU i'll try my luck with some new relays (~1.50EU/pc) if i can't find anything wrong with the parts not on the board.

As Goontron already pointed out, the cap in the pic isn't the one for the microwave. I think the highest voltage coming out of that cap is 240VAC (275 peak?)

Also, i have been looking for a guide on how to test the thermoctuator but couldn't find anything so if anyone can point me to one, that'd be great.

[budm]

Re: Whirlpool Combi-oven blows fuse, please help.

BTW, that picture in post 33 is the L-C line filter as goontron has pointed out, you can see the 680K bleeder resistor 'R' to discharge the caps. Peak Voltage of 240vAC R.M.S is 339V.

[Pier]

Re: Whirlpool Combi-oven blows fuse, please help.

I haven't opened up the machine after i was able to get the microwave running, so i didn't actually check it but i can't recall seeing a high voltage fuse in there.
All the video's i've seen explaining microwave repair do have one of those, any way i can find out if one should be present and if so, what rating should it have and where in the circuit it should be?

Anyways, here's my checklist for when i next open it up:

-discharge capacitors
-check if there actually is a high voltage fuse present and if not figure out which/where there should be one
-check capacitors for short to ground
-check capacitors for resistance (taking bleeder resistor into account)
-check rectifier diodes
-check magnetron for short to ground
-check magnetron for resistance
-solder in new relays
-cross fingers & power up the device


Stuff i'm not sure if i should and/or how to:

-check HV transformer (need an oscilloscope for that?)
-check quartz heating element for resistance?
-check temperature switches and thermistors?
-check thermocouple
-check thermoactuator and/or remove from circuit but adding a jumper?


I was already happy that the microwave works but gaining some more knowledge on electr(on)ics was pretty satisfying aswell. Up untill now i had some basic knowledge from jailbreaking and attempted repair on PS3's, but never checked anything besides the fuses with a multimeter.
Now i'm starting to understand how i can find bad SMD caps in a pcb with my multimeter, yay!
The microwave is quite old and because i'm a bit short on cash i won't be buying a new one anytime soon but this troubleshooting is clearing up alot for me on how exactly power is supplied to electr(on)ic devices.
I guess it's of more importance to me to actually understand how it should work and subsequently why it isn't now.

So, thanks for that, guys 'n girls. <3

[stj]

Re: Whirlpool Combi-oven blows fuse, please help.

check the bleed resistors too - i'v seen them change value or go open-circuit.