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Whirlpool double oven dead display, but want to confirm control power transformer ok first, Whirlpool RBD305PRS00

steveg_nh

Premium Member
Joined
Jun 10, 2013
Messages
47
Location
Southern NH
Model Number
RBD305PRS00
Brand
Whirlpool
Age
More than 10 years
I have a dead display on my Whirlpool double ovens, model RBD305PRS00. This happened before, and I sent the control board to a repair place and they fixed it up and it's been working for 3 years. So maybe it's not the control board again, or maybe it is, but I'd like to be sure before I send it in again for another $149. When power is on, the display is blank. The only thing that works is the oven light, either by the switch or by opening the doors. If you try to do anything else you get a quick short beep, a long beep, and then 3 short beeps.

I removed the top control touchpad and control board and tested the control power transformer per the spec sheet. I get 57 ohms across the primary (spec is 75-95) and I get 2.2 ohms across the secondary (spec is <1 ohm). But I read sometimes that's ok and you should measure voltage across the two reds to the transformer from the control board, and across the 2 blues from the transformer back to the control board. But I'm not sure of the proper testing procedure. Do I have to have the entire panel connected to do this test? I would think so, as the wires to the transformer won't be getting any power with all the wires unhooked unless I'm missing something. Is that the right next step? Plug everything back in and turn the power on and test across those again? Am I literally testing red to red, and blue to blue? Not red to neutral or blue to neutral?

Thanks.
 

rickgburton

Appliance Tech - Moderator
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Messages
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Location
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Here's the part you need:
whirlpool-transformer-120vac-60hz-wp9760587-ap6014062_01_l.jpg
 

steveg_nh

Premium Member
Joined
Jun 10, 2013
Messages
47
Location
Southern NH
Thank you Rick. Based on the symptoms, is this obvious that it's the transformer, with those resistance readings? Is it not necessary to get the transformer output voltage to confirm?
 

steveg_nh

Premium Member
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Messages
47
Location
Southern NH
I actually did a bit more troubleshooting, seeing the transfomer is $120, I don't want to throw parts at it. I put the control panel/board back into the oven and turned on the power. I do get 122vac across the two red wires to the transformer, and 25vac back to the board across the two blue wires FROM the transformer. This shows a good transformer, as well as a good thermal fuse, correct? Given this, is it in fact the control board again as the likely issue?
 

rickgburton

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is this obvious that it's the transformer, with those resistance readings?
I get 57 ohms across the primary (spec is 75-95) and I get 2.2 ohms across the secondary
That's what I'm going by. It's out of range on both sides. I understand you don't want to throw parts at it, and the board might be bad again, However with those resistance readings, so is the transformer. Whirlpool says check the transformer by resistance not voltage output.
 

rickgburton

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Are you checking the output voltage with the connector connected or disconnected?
 

steveg_nh

Premium Member
Joined
Jun 10, 2013
Messages
47
Location
Southern NH
Connected. If it wasn't connected, the transformer would have no voltage at all. Unless I'm totally misunderstanding the wiring. The transformer gets fed from the control board via the red wires, and then returns the lower voltage back to the control board for other functions, via the blue wires.
 

rickgburton

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Output voltage is the blue wires. It should be 24 VAC. Was it connected?
 

steveg_nh

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Messages
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Yes, I mentioned that above, I actually get 25 volts AC. It was 24.6 - 25, and stabilized at 25. I consirdered that acceptable if transformer output is rated at 24vac.
 

rickgburton

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I'm not an electronics tech but I can't see how a transformer can be so far out of specs and still work. That blows my mind. Not so much the 20 Ω out of range on the primary side but 2.2 Ω on a circuit that should measure less than one ohm. Anywhere else that would be considered an open circuit. Maybe it is OK. I'm going to need to look into this. At this point, if you have the correct output voltage, it must be working.
 

steveg_nh

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Messages
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Location
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Agreed, but as long as I'm told the control board can be fixed, or if it's ok in fact, I plan on swapping the transformer anyway. But I hear you! It was on this board that I read another tech advising that being slightly out of spec, if the voltages are ok, isn't an issue.
 

rickgburton

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My apologies Steve. It wasn't meant that way. Just a general sarcastic statement.:)
 

steveg_nh

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So you will find this interesting Rick. I got the new transformer today, and it didn't test any better than the one I have. A bit worse actually on the secondary side. 59.8 ohms on the primary side and 2.5 on the secondary. Both technically out of spec, but the same as the one in my oven. Defective new part? Leave it in, or stay with the old one? Keep the old one as a spare perhaps.
 

rickgburton

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That's crazy. When was the last time you checked the batteries in your meter. Just a thought.
 

steveg_nh

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Messages
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Location
Southern NH
Meter is working fine, for everything else at least. But not to be one of those guys, I changed the batteries to new ones, with the same result. Same resistance on each transformer, with the new one being slightly better on the primary, and slightly worse on the secondary. And both have continuity across the secondary terminals, and not the primary. So unless my transformer was failing, or overheating, it was fine. But I'll just leave the new one in, and keep the old one as a backup. At 15 years old, that $80 part owes me nothing.
 
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