Whirlpool gas oven ps/control board burnt resistor

[greezmky]

Hello all,

I am attempting to repair a control board for a gas oven. The initial fault occurred after a lightning storm, the digital read out and all oven controls ceased to work. Upon inspection I found a resistor on the line side to be open. I replaced it with a 1/4watt as that is all I had at the time. I applied power to the board while on the bench and it worked (display lit and buttons functioned), however when my dad plugged it all back in it "sparked, crackled and shut off". I then purchased .5watt resistors and we tried again. Again it burned out the resistor. I have not been present either time when he hooked it up and plugged in the range, but each time I have bench tested it and the display comes on and buttons work. I am including some pictures and further information below.

I started to trace out the circuit, curious why there is so much draw causing the 10ohm resistor to open. I believe the power circuit is a switch mode power supply? Sorry still kind of a noob.

One 470uH inductor in series to and before the resistor on the line side seems to have a small crack but ohms out at 1.1ohms or so.

A few questions:

1. If I traced the circuit out correctly and the diodes make up a full wave rectifier, then why is one diode larger/different from the other three?

2. What seems to be the most likely failed component that would allow it to function on the bench but burn the resistor when installed in the range/oven?

3. Could the 470uH inductor be shorted? I read something about inductors in series on ac mains to reduce high inrush current on initial power up? Is that what this one is doing, and is this the correct function in this situation?

My circuit tracing efforts:


The two relevant pages from the service manual for the stove:



Board top and bottom:



R71 is the resistor that keeps burning up

D49 is the odd ball diode 1N5406, unable to read others while on board

I tested dc voltage after rectifier and it read approximately 160vdc as that is close to what I had in a simulator on my phone

L3 is the somewhat questionable inductor

Y3, MOV tested OL out of circuit


I apologize for the long post.
Thank you in advance for any help and feel free to ask any questions.
Robert

[petehall347]

Re: Whirlpool gas oven ps/control board burnt resistor

links open a blank page here

[greezmky]

Re: Whirlpool gas oven ps/control board burnt resistor

Thank you petejall347. Should be easier that way too.

[petehall347]

Re: Whirlpool gas oven ps/control board burnt resistor

bottom pic far left bottom . whats going on with the trace that looks missing ? appears to be under the yellow block thing

[stj]

Re: Whirlpool gas oven ps/control board burnt resistor

runs out of the oven, blows inside.
exposed to EMP,

i would be checking the relays for shorted coils or back-emf diodes.
any time you have EMP it gets into coils like recieving antenna.

[greezmky]

Re: Whirlpool gas oven ps/control board burnt resistor

bottom pic far left bottom . whats going on with the trace that looks missing ? appears to be under the yellow block thing

Just a mounting hole for a screw if that option was used here, it is not, and it has some coating that ran over on it. Looks funky in the pic but just verified physically on the board.

[greezmky]

Re: Whirlpool gas oven ps/control board burnt resistor

runs out of the oven, blows inside.
exposed to EMP,

i would be checking the relays for shorted coils or back-emf diodes.
any time you have EMP it gets into coils like recieving antenna.

Okay I can remove the relays and check them. They are all one legged on the hot trace, I did not consider that. I will try to test them tonight and report back.

I can still check But according to the connection figure for three of the four relays on digikey there is no back-emf diode: https://www.digikey.com/product-deta...BoCd9kQAvD_BwE

And it looks like all the coils are DC with the contacts controlling AC so that one leg of the relay is hot AC

[stj]

Re: Whirlpool gas oven ps/control board burnt resistor

yes, the diode will be on the board.
if the diode or coil are bad it will short the supply - but only when it activates.

[R_J]

Re: Whirlpool gas oven ps/control board burnt resistor

If the board works on the bench, and blew the resistor in the range, have you checked the a/c going to the board in the stove? Maybe there is a fault with the neutral and the board is seeing 220v

[stj]

Re: Whirlpool gas oven ps/control board burnt resistor

but was it just powered on the bench?
as opposed to someone actually selecting something involving the relays?

[redwire]

Re: Whirlpool gas oven ps/control board burnt resistor

The door switches are low voltage, so a short to chassis GND with them might be causing the problems.
Check their continuity to GND and inspect the door switches.

[greezmky]

Re: Whirlpool gas oven ps/control board burnt resistor

yes, the diode will be on the board.
if the diode or coil are bad it will short the supply - but only when it activates.

One relay actuated (sound) when plugged in on the bench I will have to trace it and see what I see.

The way my dad tells it is he hooks everything up then plugs in the power cord. It comes on for a second and burns the resistor. I checked some of the components with his crappy meter but will have to take my better meter over and verify no ground on light and door circuit.

This is the only board that deals with 120v the other board should not come into play until the buttons are pushed for bake or broil.

Thank you so far for your ideas thus far. I got caught up today and hope to look at the board a bit more tonight then maybe tomorrow go double check for grounds to chassis.

[CapLeaker]

Re: Whirlpool gas oven ps/control board burnt resistor

yes, the diode will be on the board.
if the diode or coil are bad it will short the supply - but only when it activates.

correct. However I don't think that this range is doing a "self check" as soon as it is plugged in. I mean the resistor in question is blowing after one second. So op hasn't even time to turn the cook top on.

My question is how does the op test this thing on the bench? With AC or inject DC? What is U13? I'd replace L2 and L3 inductors.

[greezmky]

Re: Whirlpool gas oven ps/control board burnt resistor

correct. However I don't think that this range is doing a "self check" as soon as it is plugged in. I mean the resistor in question is blowing after one second. So op hasn't even time to turn the cook top on.

My question is how does the op test this thing on the bench? With AC or inject DC? What is U13? I'd replace L2 and L3 inductors.

I test it with ac connected to L1 spade and Neutral spade U13 is the Viper12a

[petehall347]

Re: Whirlpool gas oven ps/control board burnt resistor

am thinking you could try just plugging in say door lock wires and seeing if it doesn't blow the resistor then . be best to use a series light bulb on the mains to try and save on resistors .

[redwire]

Re: Whirlpool gas oven ps/control board burnt resistor

With a lightning transient on mains, and the control board has no earth ground so the transient would jump across the easiest path to chassis ground.

I would check both the door switch and oven temperature sensor to make sure they are not shorted to oven chassis ground due to the lightning arc. Very important because if replacing the control board, a new board would keep roasting R71 and be expensive.
Everything else it seems to connect to the board through relays, so the arc may have hopped inside one but not likely IMHO.

If it's really hard to track down and a multimeter is not helpful, a night-light bulb in series can limit current or be used in place of R71.

double post https://www.eevblog.com/forum/repair...burnt-resistor if we don't hear back

[CapLeaker]

Re: Whirlpool gas oven ps/control board burnt resistor

redwire has a very valid point, but I'd still start on replacing that inductor first, then lift a leg on each of them 4 diodes and recheck those and repair R71 again. I did see the other post and your diagram. Looks like whenever you hook a certain thing up when someone installs that board, the little power supply draws too much power, smoking R71 like a fuse.

[R_J]

Re: Whirlpool gas oven ps/control board burnt resistor

The two coils on the input are not the problem, they are there to prevent noise from the switching power supply going back onto the ac line. Check the board on the bench, if it still works, install it in the stove with only the line & neutral connected and see if it still works, then connect the other plugs. Having something shorted on the relays output will have no effect on the relays coil so there will not effect the smps. You could have a problem with something connected to connector 3, check the wireing to the temp probe, door detecion,lock,position.

[greezmky]

Re: Whirlpool gas oven ps/control board burnt resistor

The two coils on the input are not the problem, they are there to prevent noise from the switching power supply going back onto the ac line. Check the board on the bench, if it still works, install it in the stove with only the line & neutral connected and see if it still works, then connect the other plugs. Having something shorted on the relays output will have no effect on the relays coil so there will not effect the smps. You could have a problem with something connected to connector 3, check the wireing to the temp probe, door detecion,lock,position.

That was my thought if nothing jumped out at me when others had a chance to examine my work so far. I did double post but only had one reply that said it may be a waste of time and to contact a pro. I want to learn so this is only a waste of time once I stop learning.

I am busier then I expected this weekend but figure tomorrow I am going to go to my dad's and test all the stove components and if they test good then do as you said and start with just line and neutral and see when the resistor pops as I plug stuff in. My only concern is that now the traces have started to lift but I can manage (time for a better soldering iron)

RJ you mentioned a possible issue with neutral and the other board but the other board, for the ignitors, gets power from a separate line and according to the lcc190(control board) documentation this is "Line Voltage Rated; 120V/220 + 10%-15%, 50/60 Hz line (auto detect); 120V AC" A coworker and I discussed the possibility of my dad's hose wiring being an issue as his house is quite old. My coworker had a house that killed a couple of pieces of equipment and come to find out the transformer was bad that fed the house. So I will check my dad's outlet voltage too but if it is auto sense for up to 220vac I doubt that is the issue?

I will report back when I have more info. I hate when people resolve issues, or don't resolve them, and just leave everyone hanging. I like to spread the knowledge as that is what I am looking for when I ask for help.

[R_J]

Re: Whirlpool gas oven ps/control board burnt resistor

I never said anything about the other board, I said to check the board out of the stove and if it still works, then reinstall it with only the line & neutral connected. But what I would do first is check the ac that is actually going to the board. check the voltage across connector1 neutral and connector2 line. If it is 120v THEN connect those two connectors and see if the board works. If it works, then connect the final plug for the door/temp probe.
What is the voltage rating on the main filter capacitor? or what is the number on the smps ic? that can tell you if it can handle 220v.