Fixing the electrics in my old German mill Ruhla 250/710

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liveaboard
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by liveaboard »

I have German and English manuals; the German is poor scans of an original, the English in my translation.

I also have wiring diagrams.

My advice is to do what I did, and change all the control relays.
But you need to be a good electrician, because the new ones you get will have the contacts in different locations.
Are you Russian?
I know many were sold there.
SERHII
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by SERHII »

Hello! Thanks for writing! Everything is correct, it is possible in Russian. (but I'm in Ukraine - Zhytomyr) I brought this machine from Germany in August, unfortunately there are no schemes. Your diagram in the forum cannot be enlarged because the wire numbers are not visible. If there is a clearer picture, please PM it. Best regards, Serhii.
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liveaboard
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by liveaboard »

I sent you a private message.
I would like to have pictures of your machine, especially close ups of the tops and bottom of each relay, showing the wiring and any jumper wires.
SERHII
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by SERHII »

Good evening. Thank you, everything has come. But the image is not quite clear.
Tomorrow I will take a photo of my milling machine and send it to you.
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liveaboard
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by liveaboard »

In other news...
The feed circuit apparently shorted, all the breakers tripped back to the distribution box at the house.
After resetting, the feed motor seemed to labor for a few seconds before the machine switched it off (the overload heat relays cut the control circuit instead of the power to the motor, so it's difficult to tell what happened).

The 1HP feed motor is controlled with 5 power contactor relays. 2 were still original. they both tested good on the bench but I replaced them anyway. To my surprise, the machine works again.

These Siemens relays with aux contacts were lost in the mail and I only received them months after I needed them.

I'm not completely convinced, but there's no way to fix it if it ain't broke so I'll just use it until it does.

2 of the power contactors I replaced earlier are ganged with miniature control relays that act as the aux NC contacts, that might cause trouble. So if it happens again I'll swap them out for the Siemens relays.

The 2 HP cutting motor still runs though identical original 50 year old east German contactors without problem.
Ruhla original relays and replacement.jpg
Ruhla 250-710 new relays 2022.jpg
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liveaboard
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by liveaboard »

The problem with my feed motor came back, this time I was able to trace the fault.
At first I thought it was mechanical, then I realized the motor was missing a phase.
After some investigation, I figured out that one of the motor power wires between relays (there are 5 power relays and 2 overheat cutouts for the feed motor) failed somewhere behind the relay mounting plate. There has to be a junction between several wires hidden in there.

I added a jumper wire between the relays and the problem went away.

Ruhla 250-710 jumper wire.jpg
Ruhla 250-710 jumper wire.jpg (152.67 KiB) Viewed 62825 times
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NP317
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by NP317 »

Wow! Good troubleshooting.
RussN
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liveaboard
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by liveaboard »

Thanks; I feel quite pleased with myself.
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by Bill Shields »

Now to find it without creating another problem ..
Too many things going on to bother listing them.
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liveaboard
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by liveaboard »

Some trouble with the milling machine; the fast traverse stopped working, and whenever I pressed the button the feed would stop instead.
Other strange symptoms too, relays energised that shouldn't have been, lights on that should be off and off that should be on; some diabolical wiring or switching error.

So I got the wiring diagram, a test light, and a voltmeter and went at trying to work it out.

Then there was a crackling pop of a short circuit or something, and it went silent.

Well, we're all thinking that this is really bad right?

Not so! Actually, after that it went back to working as it should.
I assume some connection was crossed by a chip or something.
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by LIALLEGHENY »

Check your ground points .......sounds like something is searching for a ground and is trying to pull a ground circuit anyway it can , including through the relay coils, lights, etc, inadvertently energizing them.
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liveaboard
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by liveaboard »

Thanks for the thought;

The control circuits are powered by a dedicated isolation transformer; the machine chassis is solidly grounded.
In addition, the power runs through a sensitive GFI, so if any power goes to ground it will be pretty obvious.

Anyway, right now it works, and fault finding is pretty much impossible when there is no fault to find.
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