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Rational SCCWE62G dead
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If you don’t have any output on the gray pair and the white pair, ohm the primary winding (your 240 in) If you have lost or have a low voltage on the secondary (which the drawing shows as independent winding’s) Check for it at the fuse and output terminal. F1 is the gray pair and F2 is the white pair. The center two terminals are the unfused ones, The control board (A2) also has a single 8 amp fuse on both supply’s. (Gray and White are linked on the board). That may be your problem if it isn’t the transformer
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So Nafets is out of the office for a couple of days, feeling under the weather so to speak.
I could go over there and take a look at it, what is it you guys want me to look at?
I haven’t spent as much time in this thing as Nafets so I’m not sure exactly where everything is but I’m willing to give it a shot.
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This has been an incredible thread to follow. I’m so impressed at the skill level here, but even more impressed with the generosity of others with their time and knowledge.
This thread is a perfect example of what techtown is for – my hats off to all of you!
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I’m just happy it’s here or we’d be so utterly lost, lol.
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I read through some of the posts and I think you all just need to go back to the beginning and basics. Check safety circuit from troubleshooter. Then go from there. https://www.heritageparts.com/medias/RAG0168.pdf?context=bWFzdGVyfHBkZi1tYW51YWxzfDM1MTM5MjJ8YXBwbGljYXRpb24vcGRmfHBkZi1tYW51YWxzL2g1YS9oMGUvODk4MTcyNTYxMDAxNC5wZGZ8MDc0ZWYzNGM4YTBjZmM5OWMzNzA3MjIzNzY5ZTI0ZjQ0N2MyZDUyMjAxZTk4Y2RlYWRjMTM3MjkxYWUwNmMwZA
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It’s very possible, we’re still learning how to SOP is on this unit and where everything is so I think you’r right.
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I agree with NoJali on this. Go to page 167 and down the check list. I don’t think you ever checked the fuse on the special transformer.
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I came back into the office for a couple hours today and went to check on this Rational.
So I double checked the voltage on my transformer:
When I check the two greys I get 5 volts, if I check the bottom two whites I get 9 volts.
When I check the grey and white that are closest I get 18v, and when I check the grey and white farthest from each other I get 0v
Then when I check the connector end before it connects to the PCB I get 14v.
I was checking ohms and I got 13.8 when checking the 240V connection but got nothing on any of the grey and white connections with any alteration of sequence.
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Separately, thank you for answering my question about the transformer that was great data.
And also thanks for explaining with a real life scenario how checking ground could leave you clueless.
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so either a fuse is open or the winding is. on the secondary. Meter is in AC volts mode, right.
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Correct AC volts
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So with the data to hand that when I check the voltage on both greys and both whites and it adds up to 14V and when I check the cable before it goes into the PCB and it reads 14V not 18V and per the data tree from the manual stating it should be 18V.
Is it safe to say the transformer is the issue?
The only reason I am hesitating on this as the issue is because of the point that when I checked the grey and white closest together I get 18V
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Nafets47 replied:
So with the data to hand that when I check the voltage on both greys and both whites and it adds up to 14V and when I check the cable before it goes into the PCB and it reads 14V not 18V and per the data tree from the manual stating it should be 18V.
Is it safe to say the transformer is the issue?
The only reason I am hesitating on this as the issue is because of the point that when I checked the grey and white closest together I get 18V
You’re not understanding the transformer’s configuration. That transformer has two separate and distinct secondary outputs because there are two separate secondary windings (look at the schematic). The two gray wires supply output from one winding to the PCB and the two white wires supply the OTHER winding’s output ALSO to the PCB.
You DO NOT add them up. You DO NOT need to read from one secondary winding to the other. They are two SEPARATE secondary windings in that transformer. They have NOTHING electrically in common with each other except for they’re each creating their own, separate induced voltages from a common magnetic field off the SAME PRIMARY WINDING.You said you only read 5 volts from one winding’s output (via the two gray wires) and and 9 volts from the other (via the two white wires).
THAT’S the problem. They should be reading 11.5 volts and 18 volt, respectively, but they’re NOT.
If I was there, I’d be tempted to isolate the transformer (disconnect the PCB) to see what the transformer’s output would be under those conditions.
Then again, if there was something wrong with the PCB that’d pull the transformer’s output down so dramatically, then the fuses should blow.
Sitting here studying your readings on my computer screen, I’d say you have a bad control transformer. Possibly a shorted primary winding, but only to a point that it’s not overloading the 240 volt circuit enough to blow the .8a in-line fuse between it and the big toroidal (excuse me…SPECIAL) transformer.
What I’m saying is that not ALL of the control transformer’s turns of the PRIMARY winding are in the game anymore because, somewhere in it, two of the MANY turns of that primary winding haveshorted together for some reason. As such, the transformer is no longer creating a strong enough magnetic field to induce the specified output voltages.
I don’t ever recall seeing a transformer do that, but it seems plausible…so, THAT’S MY theory.
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Watch this video about transformers:
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I linked wrong manual haha, but in any case need to just go down the list and re-affirm that the components check out good. Don’t assume anything is good.
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This control transformer has multiple taps on the input / primary side. To make a multiple tap primary one has to solder each tap onto the winding as it is wound at specific number of winds. Also in a certain area for the taps to come out. It’s not a easy thing to scrape off the varnish, flux, and solder on a wire. Re varnish the joint. Continue to the next one and do it again. All without nicking the winding wire. The taps are usually on the same side where the armature isn’t. With heat expansion and contraction you can bet there will be some joint rubbing of the taps. Two taps on top of each other like the 110 and 240 that shorted would definitely do this. 13.8 ohms on the primary seems near normal, but I don’t have any way to verify that. Somebody have one they can check?
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fixbear replied:
13.8 ohms on the primary seems near normal, but I don’t have any way to verify that. Somebody have one they can check?
Well, you made me look. We had one in stock, so checked the windings’ resistances with my Fluke.
13.3Ω between the 0v & 240v terminals:
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I’m gonna ask him to check this, pretty funny you had one on hand.
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How can we have any certainty the the primary coil has a tap short. Simple, our Ohm meter. Making sue you have quality leads that are sharp, measure the taps starting at the lowest and working up to the highest. If you have a tap rated at 100V and the next one is 120V, your Ohm valve should increase 20%. If the base tap is 120V and you have a 240, The value will double..
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So I got the transformer in from PartsTown and replaced it. I checked the voltage on the grey wires and the white wires and they are 12V and 19V which is completely different than the transformer that I had replaced.
Now the PCB has a light on the bottom of the card, however per the “trouble shooting tree” I attached if the light above the card is not lit that means the PCB is bad.
Well I guess that was good to know the transformer was bad, unfortunate the PCB is also not working.
Any idea why the transformer would “kick it” and also take the PCB with it? I mean its only 18V of electricity and none of the fuses were bad on the machine.
Just seems odd, however the board could just be that sensitive.
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Which board do you have in the machine, the original or the replacement you bought?
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