MemberJanuary 13, 2020 at 1:26 pm
Checked fuses F1 and F2 as well as thermal safeties, LWCO for boiler.
Absolutely nothing is happening on the display, I hear relays clicking however screen is dead and cooling fan not turning on.
MemberJanuary 13, 2020 at 4:26 pm
I’ll just proceed with some possibilities by assuming you have a version E or G oven and are located in the U.S.:
- If the main contactor K1 is NOT pulling in, then check F7. It’s an in-line fuse located in the wiring from the round “special” transformer.
- If the main contactor IS pulling in, then I suggest unplugging the bus cable connections (the telephone jack-looking ones) for inspection. If there’s corrosion, the that’s probably your problem.
MemberJanuary 13, 2020 at 5:30 pm
The model is a G. And I am based in the US.
The main contactor is pulling in and I checked the special transformer fuses and those are not blown.
From what I could tell it appears that the PCB has failed.
MemberJanuary 13, 2020 at 8:35 pm
I worked with him on this to try and figure out what happened.
The cooling fan doesen’t run but it’s possible it’s still good.
I also measured power at the main contactor and it’s good, 120V on both legs which is what I’m assuming is correct.
There’s LED lights that come on, one on the board mounted on the oven, can’t tell on the screen board itself. When you turn it on you can hear things clicking, not sure what’s clicking.
MemberJanuary 14, 2020 at 5:33 am
I think you’ll find three poles of the contactor in use. TWO poles are the 120v in, which supplies power to the main blower motor.
The THIRD pole of the contactor is 230v from the special transformer, serving as the latching circuit to keep the contactor energized…and to power everything else.
How about fuse F5 on the control transformer?
And…I hate to sound like a broken record, but – how do the BUS cable connections look?
MemberJanuary 14, 2020 at 7:08 am
Push all the buttons twice, if nothing happens then replace it….. 🤪
MemberJanuary 14, 2020 at 11:49 am
The 120V is present at the contactor, coil is energized.
Didn’t see an F5 on the control transformer but I’m assuming it works since the 120V is present.
Would it at this point be the control PCB?
MemberJanuary 14, 2020 at 12:28 pm
Is the relay latching in? and reread Ectofix’s post:
How about fuse F5 on the control transformer?
MemberJanuary 14, 2020 at 12:41 pm
It’s inline? I think I see it.
There is 230V present at the 3rd connection on the contactor, I measured it, it’s there.
There’s 120V on the first 2 and then 220-230V on the third one. The K1 is pulling in.
Don’t know about the fuse
MemberJanuary 14, 2020 at 4:35 pm
Here’s the control transformer:
Input is 230v and is a multi-tap secondary for 2.5v, 11.5v and 12v.
If the 2.5v isn’t present at the operator PCB, then it won’t light up (dead).
@fixbear, the one you linked is the “special” transformer.
Since the oven is made in Germany, they use 230v components throughout. That torroidal transformer added in there allows the 230v oven to work from 120v here in the U.S.
Amazingly enough, ALL through a .8a in-line fuse.
MemberJanuary 14, 2020 at 4:38 pm
Okay, so if you have the 120V present, then the control transformer is working?
MemberJanuary 14, 2020 at 5:16 pm
No. Two totally separate circuits.
The only components that see 120v are:
- the special (torroidal) transformer – directly from the power cord
- the main blower motor – through two poles of K1 contactor.
That’s the extent of the 120v usage.
Everything else receives 230v from the torriodal transformer, primarily via K1’s third set of contacts:
- the cooling fan
- the gas train components
- the solenoid valves
- the three water pumps.
The control transformer also receives 230v. It’s secondary output supplies:
- the operator board
- the I/O board
- various control circuitry at an electronics level of input…
- and things like the cabinet lights and buzzer.
MemberJanuary 14, 2020 at 5:19 pm
Okay, so if I saw 120V at the contactor on the first 2 terminals, K1 and it was engaged, why wouldn’t the cooling fan be on?
I saw 220-230V at the last terminal on K1.
MemberJanuary 14, 2020 at 5:36 pm
Ya got me there, so I had to look. I made a mistake. First one this year. My apologies for the misleading information about that.
The cooling fan is 230v too.
K1 first two sets of contacts routes the 120v to the main blower motor.
Sheesh! I rushed through six pages of the schematic on my computer screen and got a little little twisted, I guess. I MUCH prefer hard-copies.
I’ll go back and revise my posts.
MemberJanuary 14, 2020 at 6:50 pm
I MUCH prefer hard-copies.
Your not alone on that one. Wait till your eyes get older.
MemberJanuary 14, 2020 at 7:35 pm
It’s sad that they don’t make the schematics like Hiedelburg, Miller, Man/Roland or Polar. The “books” are about 4 to 5 hundred pages long, but due to the complexity of the machines are easy to read once you understand their system. Two to three electrical Cabinets, One on the feeder and one on the delivery and sometimes one Mid. Often with over a hundred contactors and relays. But the system was easy to understand.
MemberJanuary 14, 2020 at 6:00 pm
Also forgive my delay about why the cooling fan might not be working. I’m juggling thoughts on this while trying to get dinner in the oven.
The THIRD set of K1 contacts supplies 230v to the cooling fan and an input to the I/O board.
Maybe the fan is bad or maybe there’s a bad connection somewhere.
MemberJanuary 14, 2020 at 8:26 pm
Okay, well that makes it a bit more confusing.
There was 230V at the contactor on the third leg, 120V on the first 2, if that cooling fan is powered at 220-230V, then why wouldn’t it work?
The thing we’re trying to solve is the main screen not coming on and nothing’s happening, now a $1300 board got overnighted so hopefully it’s the right one.
I was just trying to verify that it WAS the part to replace before buying it.
MemberJanuary 14, 2020 at 6:41 pm
I link’d both so he realized what he was seeing.
MemberJanuary 14, 2020 at 7:39 pm
I thought you said “LICKED”.
I couldn’t picture that. Thanks for the correction.
MemberJanuary 14, 2020 at 3:13 pm
Thanks for the response to my question. I checked the connections and the looks good, no damage or build up and like Olivero was saying it is pulling the correct voltage.
Each fuse that is on the diagram provided by Rational is good. After going through some data tree I found on their site it looked like the PCB was bad so I ended up ordering the PCB.
Hopefully that fixes the issue.
MemberJanuary 16, 2020 at 10:55 am
So the PCB was replaced and that was a bust. If the unit has power coming in, the fuses are functioning the contactor “pulls in” and provides power but yet the fan does not turn on – would that be the contactor?
MemberJanuary 16, 2020 at 1:18 pm
Just got off the phone with Rational “tech support” very adamant that a local service provider should handle it.
He did tell me however there are a total of 5 fuses on the machine, checked all 5 and they are good per a multimeter.
Voltage on the transformers is good per the data provided by etcofix and fixbear.
What else could be the issue? like I said earlier the fan is not turning on so it would appear that there is an issue earlier but the voltage is all reading correct.
MemberJanuary 16, 2020 at 2:09 pm
Nafets47, I thought this is what you would find. I am not a Rational tech, and therefor don’t have drawings for your individual model. But I did manage to find the training drawings that come close for your input voltage. They are not as accurate as the ones on the machine Also I don’t know how you measured the contactor output voltages nor do I know your line voltage. The information I provide below is for single phase.
On the special transformer output there is a fuse (F7). Your incoming power has to go through that to the cooling fan. as well as the control transformer.This transformer has multiple taps on the input for your line voltage from 100V to 240V to make your required 230 that the machine is designed for. So you need to measure if you have the 230V output from that transformer. The K1 relay 13 and 14 supply the fan from the special transformer. and the control transformer also gets it’s power from the same, but not through that pole of the relay.
Now the blower fan is direct off K1 pole 1 and pole 2 On the back of the motor are 2 fuses, F20 and F21
There are several methods of using a voltmeter to test the relay contacts. The fastest in this application is to just measure across the pole your checking powered for 0 volts. anything other than 0 the pole is open. This is how we determine what pole is open or has resistance. A relay that has a high resistance contact from arcing or wear will often show 5 to 10 volts under load.
MemberJanuary 16, 2020 at 4:18 pm
When I measured it with him, we were getting on K1, the contactor, 120V on the 1st and 2nd leg, measured top and bottom to ground and top to bottom read 0V so it’s good. Then the 3rd pole is empty, the 4th has another set of wires which was reading 220V to ground.
Nafets says he checked the fuses, so what would the next thing be to check? The transformers? It seems the 120V and 220V are both present, so what has to actuate to get power to the cooling fan to go?
MemberJanuary 16, 2020 at 4:26 pm
Using ground as a reference for the second side of a circuit is NEVER proper troubleshooting.
In this oven, ground is NOT part of the 120v circuit at ALL. AND…although half of the 230v circuit IS bonded to ground, you’re completely skipping over that second side by using ground as a test point.
All wiring and connections for BOTH sides of the circuit are equally important.
Make your voltage readings how the component(s) receives it. Make both sides of your voltage readings AT THE COMPONENT that’s supposed to received it.
MemberJanuary 16, 2020 at 4:57 pm
Okay cool, I got you.
There is 220V on the inlet of A2 board, the brown and blue wire, across the 2 is 220V.
So there is power to the CPU board but it’s not giving power to the cooling fan.
MemberJanuary 16, 2020 at 4:22 pm
Correction, the model is SCCWE62G
Page 60 or so, the wiring diagram begins.
MemberJanuary 16, 2020 at 4:29 pm
So you’re saying this is a version H oven instead of a version G?
If you don’t understand where I’ve getting that distinction, the oven’s version is the FIFTH digit in the serial number.
MemberJanuary 16, 2020 at 4:40 pm
Whatever I wrote above is what it’s saying on the label.
I don’t know how they configure it.
MemberJanuary 16, 2020 at 4:39 pm
BTW: I’m glad you found a schematic. I was going to email one (albeit, for the wrong oven…we now know) to your friend, so I requested we CONNECT here in this forum platform. That way we could trade emails. He never responded.
I asked if he HAD a schematic. He never responded.
I asked several OTHER relevant questions to which he never responded.
I don’t mind helping another tech, but communication is a two way street. Up to now I just about threw my arms up and walked away.
MemberJanuary 16, 2020 at 4:44 pm
Yeah, no worries. It can be a bit tricky, I’ve been on a lot of Forums for help so I understand, give him some time to get used to it, I’m sure we can make it work 🙂
MemberJanuary 16, 2020 at 4:36 pm
The model is a SCC WE 62G
MemberJanuary 16, 2020 at 5:12 pm
So now that we know we’ve been talking about the wrong oven all this time, let’s take another look.
Now we’re talking about a White Efficiency (WE) oven. A version H.
The cooling fan in that oven is NOT powered by the special transformer’s output as it was in the version G oven. Instead, it is powered through your control board, to a DC converter. The fan is designed to run from a variable range of 18 to 28vdc. Therefore, let’s stop worrying about the fan anymore. The fan isn’t working because the board isn’t.
Make an input voltage reading at your control board. Plug X14. That’s power in supplied from the control transformer. You should read 18vac between pins 1 and 2, then 11.5vac between pins 3 and 4.
DON’T use GROUND in your voltage readings.
MemberJanuary 16, 2020 at 5:27 pm
Okay, so he’s got 1-2 is 18.5V and 3-4 is 16.5V
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