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Rational SCCWE62G dead
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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.
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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.
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Fixbear,
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?
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Olivero,
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.
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Ectofix,
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.
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Correction, the model is SCCWE62G
https://www.partstown.com/modelManual/RATL-SCCWE-62G_pm.pdf
Page 60 or so, the wiring diagram begins.
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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.
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Whatever I wrote above is what it’s saying on the label.
I don’t know how they configure it.
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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.
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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 🙂
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The model is a SCC WE 62G
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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.
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Okay, so he’s got 1-2 is 18.5V and 3-4 is 16.5V
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There was an SD card in the old board…assuming the board he replaced was this one:
Rational 42.00.080P CONTROL PCB
Did he transfer the SD card to the new board?
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I’ve sent you a connection request. Approve it and we can swap email addresses so I can send you something.
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I accepted you.
I think he put the old board back in since the new one didn’t fix it.
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also the cooling fan in a WE unit only runs if the unit
is in a cooking mode or if the temperature in the cabinet reaches a certain point. just turning the oven on wont neccessarily make the fan run
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Good to know, on Convotherm’s the cooling fans in the electrical compartment run regardless, as soon as the unit gets power, those fans run.
That’s what I based it off of, so good to know I was wrong on that.
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@etcofix
The PCB I replaced was not the 42.00.080P but the 42.00.112P so no SD card was removed.
However looking over the Training Manual it goes over the point on pg 21 that LEDs above and below the SD card should be on, and that if the LED above the SD card is not on this PCB has failed and if the one below the SD card is off there is an issue with the power supply.
However I found both to be not on, with the unit powered and the switch turned on.
So it would appear that the power supply is the issue. I am going to test this a bit later today.
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So I checked the transformer and it is only providing 7 volts AC to the board when the manual says it should be providing 18V, additionally the transformer states on its casing it should provide 11.5-18V
The correct voltage is coming into the the transformer 240V, so it would appear this is the reason for my issues.
Does that seem accurate?
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Sounds like a problem. However, could you please tell me EXACTLY where you’re connecting your two voltmeter test leads so I can see it on the schematic?
Remember that the control transformer has TWO secondary outputs. So, explain your testpoints when you read BOTH voltages.
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See attached picture
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I don’t understand what test points you used in your picture.
Did you do it like how I’ve illustrated in MY attached picture?
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See attached picture
The connector running off the port that I circled goes to X14 and I put my leads into that connector to test the voltage and when I leave just one lead in the connector and touch ground I get 7V and when I put one lead across 3 of the 4 wire terminals and the other across the last terminal I get 4V
And when I tested 240, I put a lead on the terminal I “Xed” and the other on ground and got 240
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DO…NOT…USE…GROUND!
Ground is NOT a proper test point.
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Connect your test leads like I showed in my photo.
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I’ll point out that you read 240v referencing ground because the special transformer’s secondary is bonded to ground for safety reasons. However, there’s allotta wires and connections between that ground and that side of the 240v going to each component. By using ground as a test point, you’re essentially COMPLETELY overlooking all those wires and connections in your troubleshooting. What if there was a faulty connection in that leg….and you don’t find it because you overlooked it…by assuming that it’s all the SAME?
As for the CONTROL transformer’s outputs, there’s NOTHING on the schematic indicating that ITS secondaries are bonded to ground. So, ground IS NOT part of the circuit!
Actually, GROUND is NOT part of ANY circuit in this oven other than the ignition electrodes…which is another topic.
I’ve alluded to this already in this same thread.
To use a voltmeter as a troubleshooting tool, you MUST look at the supply voltage the same way the component receives it. The voltmeter is your EYES looking in to see what the component is seeing…and getting as an input.
GROUND is not a part of ANY of that.
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Didn’t we rant and rave about using ground about a year ago. on a cooler?
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More times than that, I think.
It’s a learning curve, I guess, to listen to those of US who’ve been “troubleshooters” of equipment for DECADES.
Maybe using ground stems from old habits used for troubleshooting DC circuits in automobiles.
Yet, I’ve found that even some electricians will do it.
I just shake my head and TRY to explain why you should NOT do it.
I don’t know why it’s so hard for people to understand that GROUND r-a-r-e-l-y plays a part in a circuit. On those rare occasions, then:
They STILL must scrutinize all…ALL wiring/connections between the power source and the component. They must troubleshoot BOTH sides to the component. They must LEARN the ENTIRE circuit as they go to look for any possible or plausible potential problems.All of that is logical to ME (and YOU), but it takes some time and experience of learning that logic to TRULY and effectively troubleshoot electricity. Some folks “get it” quickly. Others (like myself) require MUCH more to finally get it.
In MY case, I had to actually be assigned as an instructor in order to force me to REALLY school up on the trade. Those four years in that job was a major turning point….and has served me well in these subsequent 35+ years back at it in the field of troubleshooting stuff.
One thing’s for certain. Attempting to “mentor” someone at the task of troubleshooting electricity… through pounding away at a computer keyboard as my only way to convey the logic….is EXTREMELY frustrating when compared to my actually being there in person to oversee its execution.
FWIW: I think I’ve gone “above and beyond” in THIS particular thread.
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Definetley a learning curve, some of us were taught to measure to ground but what you are saying makes sense.
Nafets and I are both not nearly as advanced as you guys are, no doubt about it and I definetley appreciate the time you are taking to help us figure it out.
I plan on going over there tomorrow and taking another look know that I have a better idea of what I’m looking for.
When he checked pin 1-2 and 3-4 on the connector, the voltage was lower than it should be, 1-2 was 18.5V and 3-4 was 16.5V between the pins, not reading to ground.
It seems that board is not getting the power it needs and as a result, no LED’s are lit on that board.
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ectofix, got it on the not using ground.
Like olivero was stating, was the way we were taught.
Regardless, I went back and tested it again like you pointed out in your drawing and I was getting 240 where I was supposed to get 240, but was not getting 18v where I was supposed to get 18V.
I am going to double check in the morning and try another volt meter to ensure that mine is not being finicky.
One thing I wanted to know kinda separate to this, is the transformer has two fuses mounted to the device. Neither of these were bad/blown, is that peculiar that the voltage would not be correct coming out of it with the fuses still intact?
The main reason I am asking is because that device was the second thing I checked (its fuses) and because they were good I skipped it and went on down the line looking for other things wrong. In your experience is this common?
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There are occasions that transformers get a open or short internally. This will throw them out of spec. Or total failure. They are also built different ways. Simple ones will just multiply the input by the ratio for a output. But they can be built to regulate so the a input will create a more constant output.
One thing I learned about most German and Swiss machines over the years is that they have taps on the power transformers to compensate for distribution variations. Most European machines want to see 230v. I don’t have drawings or installation manuals for your particular machine, but if it has a over-voltage to the control transformer, you’ll have a high output And increased voltages can damage components. Small differences take a long time to cause a problem, but larger ones show up quicker. I know in my state the power company public service rules allows them to provide as little as 194 volts to 250 on a 230V service. That’s a big range, so we also always measure the service power at a install. I’ve actually seen a power company’s regulator send a high enough voltage to a service panel that it arced through the back of the panel and started a house on fire. Service was only a few weeks old. The power regulator on the pole is a floating core transformer. The output low voltage it designed to pull the core to a proper voltage. If it hangs, you have problems. I always liked to leave my Fluke 87 on record for a bit to see whats happening.
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Fixbear covered that better than I could’ve.
* * * * * *
Let me relate my OWN troubleshooting story from this past week:
A steam table wasn’t heating. A two-pan well using a 120v, 3000w Chromalox element like in my attached picture.
For troubleshooting this problem, I was limited in what I could do since the staff were serving food right above me. I needed to reach a resolution quickly.
I knew the thermostat was energizing its two-pole contactor since I could hear it pulling in within the control box enclosure. Flex, liquid-tight conduit led the line and neutral wires from it to the element’s box. The element connections inside that box were horrible to access. An initial test with my voltage detector stick made it chirp and light up – indicating there was some semblance of line voltage in there.
I managed to get me (with a flashlight in my mouth) and a voltmeter under there to get some readings from the element’s threaded terminal lugs. I got 0v.
So, the question at this point was “What am I loosing…and where at?”
Well, I don’t just guess at such things. I therefore took a minute at being a bit more methodical with my test leads. I reoriented my test points a few times.
I took readings from the TWO incoming wire’s strands:
120v.
I took readings at the BOTH wire’s crimped terminals:
120v.
So far, so good…
From there, I alternately moved ONE test lead off the wire terminal and onto its respective element threaded stud it was connected to.
Through that brief dance with my test leads, I found I had the lost neutral connection between its wire terminal and the very threaded stud that it was plainly & securely connected to! I was dropping all 120v at an invisible, bad NEUTRAL connection DIRECTLY AT THE ELEMENT…simply due to a MICRO-thin layer of oxidation that had formed between the wire terminal where it sat FLAT against the landing of the element’s terminal.
That’s all it was! I subsequently took BOTH connections apart (line side too), cleaned them up with a brass brush and securely reconnected them. THAT got it going again.
Easy peasy lemon squeezy!
SO, how is this overly simple story relevant to this thread?
WELL…WHAT IF… I’d used GROUND as a test point in this situation?
I would’ve been seeing 120v to the element ALL DAY LONG…and been scratching my head over what the heck was going on here and possibly would’ve concluded that the element was bad.
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That is a very good point.
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So, I’m curious of the outcome of this.
It’s Saturday. Did you go back and look at this today?
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Your not alone on this. Funny how we get invested in a problem.
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No, I did not but it’s possible Nafets did.
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