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Old 11th Apr 2021, 12:06 pm   #1
dagskarlsen
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Default "New exchange" from Norwegian STK (=STC)

Thinking about some modernizing so I got a "new" exchange Marked STK (Norwegian STC) but I have not a clue how to get it working. I just guess on 48V and this need help to learn how to wire it up. I'll probably need a ring voltage source, and a dial tone source, but where to connect it? The back board is wood painted slate as the exchange.
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Old 15th Apr 2021, 11:24 am   #2
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Default Re: "New exchange" from Norwegian STK (=STC)

the wooden strip has all the connections. start with 24v. its not very clear in the photos i guess the exchange line connections start at the left followed by the extensions . is it a swedish item .does the name or designation plate give any clue ie the number of exchange lines , then the number of extensions the last connections on the right woiuld appear to be the power input.
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Old 15th Apr 2021, 11:55 am   #3
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Default Re: "New exchange" from Norwegian STK (=STC)

I assume that TB and TE toward the right-hand end will be battery and earth respectively.

The left-hand twelve appear to be six pairs for "subscriber lines" (presumably extensions).

The next four ("centre lines") are presumably exchange line pairs, and possibly the next pair (labelled BB and BB1), though this is less clear.

As to how the six "control board" connections and the one marked "FA" are used, I've no idea.

Owing to reflection, I can't see the labels on the pair at the far right.

(Thanks to Google for translations from Norwegian to English.)
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Old 15th Apr 2021, 6:22 pm   #4
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Default Re: "New exchange" from Norwegian STK (=STC)

Thank you, I have tried 24V ont the 2 right terminals, and phones from the left, but when I go off hook the relay turns on and off like flash-light. If I hold the relay engaged by my finger, the phone is dead.
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Old 15th Apr 2021, 6:36 pm   #5
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Default Re: "New exchange" from Norwegian STK (=STC)

At least you know that power is getting in OK. Presumably, something (goodness only knows what, though) needs to be happening in the "control board" section.

Is this a manual exchange requiring an operator or is it an electro-mechanical automatic?

How feasible is it to trace the wiring of the unit?

As a matter of interest what say the labels of the pair at the far right?
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Old 17th Apr 2021, 6:07 am   #6
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Default Re: "New exchange" from Norwegian STK (=STC)

It is extremely difficult to follow the wires, but here may be some more help.
I tried to translate the text..

Measuring on the lines to Operators... no voltage between the terminals.

dsk
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Old 18th Apr 2021, 2:59 pm   #7
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Default Re: "New exchange" from Norwegian STK (=STC)

Can I ask some questions,
1 Do the relays have letters on them eg L,K A etc. Perhaps the STC engineers followed common practise and clues can be found in Atkinson.
2 What are the coil resistances ?
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Old 18th Apr 2021, 7:56 pm   #8
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Default Re: "New exchange" from Norwegian STK (=STC)

I have to measure some of the coils, and take some photos of the markings.
The previous owner, a retired telco man claims it is made for 24V.
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Old 19th Apr 2021, 2:12 pm   #9
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Default Re: "New exchange" from Norwegian STK (=STC)

Here you may see some of the relays with handwritten markings
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Last edited by dagskarlsen; 19th Apr 2021 at 2:18 pm. Reason: Pictures missing
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Old 21st Apr 2021, 7:53 am   #10
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Default Re: "New exchange" from Norwegian STK (=STC)

Hi
Thanks for the photos.
Do any of the relays have a stepping mechanism?
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Old 21st Apr 2021, 9:18 am   #11
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Default Re: "New exchange" from Norwegian STK (=STC)

Relays with 'L' in the designation are generally Line relays which operate when a line goes Off Hook. Does this tie up with the extension line numbering?

With no sign of any strowger or crossbar mechanism, if this unit is automatic, it must use some kind of relay matrix switching
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Old 21st Apr 2021, 7:25 pm   #12
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Default Re: "New exchange" from Norwegian STK (=STC)

No stepping mechanism, but I have used some hours to clean most the relay contacts and adjusted some who had visible deformations, now it is possible to call from some of the extensions. (only tested 1-4 so far) when I go off hook and dials the relay is acting from left to right one for each pulse. (2 rows and possible to have 2 calls at the same time)

So far no connections working to the central office so I guess I have to keep on cleaning and tuning.
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Old 27th Apr 2021, 3:44 pm   #13
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Default Re: "New exchange" from Norwegian STK (=STC)

Thank you for the hints and help, now all 6 lines works. Have not been able to get any trunk line, but that may be depending of the operators unit that are missing. It has been fun to get it working, but now I do not know what to do with it. (I already has a 1946 step by step exchange working well)
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Old 29th Apr 2021, 7:13 pm   #14
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Default Re: "New exchange" from Norwegian STK (=STC)

Now I got the C.O. line working to.
Grounding button needed on the phone, and that connects to C.O. line. (both incoming and outgoing calls)
The 2 B connections are for a DC 24V ringer.
(The only one I have is a fire alarm ringer so that was loud )
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Old 29th Apr 2021, 7:39 pm   #15
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Default Re: "New exchange" from Norwegian STK (=STC)

Aren't the a2 and b2 that you have queried a second "C.O. line"?
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Old 29th Apr 2021, 8:07 pm   #16
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Default Re: "New exchange" from Norwegian STK (=STC)

It may probably be, but I have not got any result of testing by moving my city line to those 2 terminals. Maybe I have to test more.
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