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

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

Post by liveaboard »

I took care of some gearbox trouble months ago when I got the machine, but then I had to do other work.

Now finally about to get back into it and work on the crazy relay box.
electric box full.jpg
several of the original East German relays were swapped out for relays that were discontinued 30 years ago; I assume the failures were 30 years ago too.
One I took out for a bad coil also had a bad contact.
esgo DDR relay 1.jpg
So I'm going to change out all the old relays, and hopefully the problem will be solved. If not, it had to be dome anyway.
The old relays are diabolical, with mixed NO or NC contacts that are difficult to see until the wires are out of the way.
old relay with NO NC symbols.jpg
The wire routing is hidden.
I do not have a complete wiring diagram, only block type.
I'll use these inexpensive ABB CR-M230AC4 4PDT relays; some of the old ones will be replaced by 2 new ones.
relays new type ABB CR-M230AC4.jpg
I lifted the mill up onto my small workbench so I don't have to crawl around on the floor while I work.
I bought a label maker, to label all the wires before disconnecting.
Ruhla 250 710 on workbench.jpg
I just hope this works!

Oh yeah, I got a new rectifier too. The clutches are supposed to get 24VDC but they only get 18 now.
new and old rectifier.jpg
kl7sg
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by kl7sg »

Those old "Selenium" type rectifiers would fail over time.
The new bridge rectifier will work much better.
Also, wear gloves when touching the selenium rectifiers. They are considered to be toxic.
Have a nice day,

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

Post by armscor 1 »

Wow, relay logic from days gone past, have not seen selenium rectifiers since I was an apprentice in the late sixties, going to be a difficult task without a wiring diagram, good luck.
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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'm just going to copy the existing wiring, and hope it works.
If it doesn't work, then I'll need to get into it.

My main worry is the relays that have been changed in the past, I hope whoever did the electrical work was clever enough to get it right.

There was an idiot in the gear change box, and I'm very pleased with myself that I was able to figure it out and fix it.
The rectifier is $1.50 of preventive maintenance while I have it on the bench.
John Hasler
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by John Hasler »

kl7sg wrote: Sun May 23, 2021 1:12 pm Those old "Selenium" type rectifiers would fail over time.
The new bridge rectifier will work much better.
Also, wear gloves when touching the selenium rectifiers. They are considered to be toxic.
There's no hazard in touching elemental selenium (besides, the plates you can touch are just heat sinks). Just don't eat too many of the selenium disks from between the plates.

What can be toxic is the fumes from a selenium rectifier that is in the process of burning out.
kl7sg
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by kl7sg »

In training over the years we were taught to avoid it.
See the following link

https://www.parduebrothers.com/ct90/sel ... esting.pdf

Cheers
Have a nice day,

Mike
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Bill Shields
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by Bill Shields »

What is the contact current rating on the new vs old relays?
Too many things going on to bother listing them.
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GlennW
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by GlennW »

I ws wondering that as well, as it seems you are replacing what I would call a contactors with relays.

Load carrying capacity may differ.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
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Bill Shields
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by Bill Shields »

Exactly....
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 »

New and old relays are 6A.
Actually, the old ones show 4.5A for the NC contacts and 6A for the NO contacts.
They're just physically huge East block lumps from the 50's.

The contactors are the even bigger units above; they seem to be ok. The relays I'm changing only handle the control current, switching the contactors and each other.
With the lower current coils, that control current will be lower than before; the new relay coils are just 1.5w. I didn't measure the old ones, but the coils are thumb sized.

I believe the machine was built in the 70's, pretty late to still have that selenium rectifier instead of a silicon one. And it has mercury filled glass tube mechanical delay relays!
The little actuators whir and the plate holding the 3 tubes tilt until the mercury slides across and makes the contacts.
They seem to still work, so I'm leaving them in. Delay relays are actually a bit expensive.
And besides, they're sort of cool.
`
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NP317
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Re: Fixing the electrics in my old German mill Ruhla 250/710

Post by NP317 »

I read your reports with interest!

Having retired from the job as Maintenance Manager for the 1960-vintage Seattle ALWEG Monorail Trains, I became well aware of relay logic used in machines. During my tenure, both Monorails were restored and rebuilt to make them reliable again. That involved restoration to some of the brilliant original functions, plus replacing original relay logic with modern programmable electronic controllers and 2-wire communications throughout each 4-car train. We reduced the flexing and failing intercar wire bundles by at least 90%!
All this for their 50th anniversary in 2012. They are still operating as the only money-making public transit in the USA. Stories there...

So keep plugging away and providing the entertainment for us, and the progress for yourself.
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;
Today I had a few hours to work on it (Happy!).
I bought a Dymo labeler to make a tag for each wire as I remove it.
As each relay is removed, I make notes and check it's contacts for NO, NC, and faults.
first 3 relays out and found 6 faults! 3 no contact and 3 intermittent.
So that's nice.

In tiny little microscopic letters on the new relays, I read "6A resistive, 1A inductive".
Not so nice.

I can tell by the wires that the inner NO contacts on 3 relays are used for motor power. Reversing I think, not sure. I can use regular contactors for those, I have 2 on hand and NO contactors are available locally.
Not cheap, but ok I only need to buy 1. I need to go to the electric supply anyway to get DIN rail for the relay mounting.

The other relays are used only for control switching so 1A should be just fine.
The old relay coils dray 35W, the new ones draw 1.5W.

I have to do other things tomorrow, Wednesday too, but hopefully I'll have my head full of wires again on Thursday.
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