Telephone Switching > General PAX & Intercom Systems

Got a "new" STK (=STC) exchange, need help

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dsk:
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.  :-)

RB:
Hi DSK!
Wow, you don't pick the easy stuff for a project. :)
That's quite the board!
Well, lets start by saying, I don't know much about multi line exchanges.
Only that once you find the first connection, the rest work the same.
My guess would be...
Extensions,Incoming lines, Lites...Fairly certain about these.
 Ring, Tone, ?, power... The order, not sure about. can't read that language.
And the power connections at the end.
Once you get the extensions, incoming lines, lites, and power wired, you can take the audio from a radio, and connect it to one of the unknown inputs, and be able to hear it when off hook. "low volume".
That will be the "TONE" input.
The ringer I am not sure of???
Start there, and I bet you will have about 70% of it wired.
You can try it with a 24 volt power supply.
If it is too low, once you start selecting lines, etc... you will notice that the relays get slower to react.
And then will fail to lock.
That will be an indicator that you need to go to 48 volts power. "Which is probably what it needs".
The lites in the phones may also lead you to the correct input power needed.
Well, that's about all the initial help I can be.
Good luck with the project, and keep us updated  :)

dsk:
Seems like 24V is OK but it may be a capacitor or something making a problem of holding the line. 
When I press one relay I can hear a buzzer making a sort of dial tone, and generating an AV ringing current

Enclosed 2 bad 5 sec mp4 films. (not easy to film with 1 hand and press on the relay with the other hand.  :P

I actually do not know what the next step will be.
dsk

RB:
Thanks for the vids.
The tone seems almost ok.
The off hook, bothers me.
IMHO, The set is experiencing a voltage starvation.
Going off hook, closes the line.
Included in the line is the OFF HOOK relay.
That's not what it is called, just my version.
There are at least 2 relays assoc with that off hook sample.
When you close relay 1, it powers relays 2 and 3.
As soon as that happens, you have 3 relays fighting for power.
If it is not supplied, the relays will collapse and release, only to see OFF HOOK, and lock on again
That is why it is "Buzzing", or chattering.
Bump it up to 48 volts, and give it a "QUICK" check.
Before that tho, check the CAPS for operating voltage.
That may tell you more.  :)

Key2871:
Yes I think it's going to want 48 volts to run right.
It seems things are acting voltage starved.
I saw a you tube vid of a British switch the guy got and didn't start of with enough voltage so it too didn't work right.

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