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Old 15th Dec 2017, 11:43 am   #1
scalpel
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Default Help needed to restore 70's phone

Hi everyone, I'm Dan and have joined for help and advice on repairing / restoring my girlfriend's old eBay find...

On to the crux of the issue; I need help in a positive identification of the phone and then help in modifying for use on the current telephony system here in the UK.
At this point I believe the phone may be a hodge-podge of parts as I cannot find a wiring diagram relating to the phone circuit board, as the exterior looks like a 746 (I think) but the wiring is significantly different.

Anyway any help is appreciated and if someone can list the required work in steps I would be eternally grateful (the girlfriend brownie points would be epic)...

Thanks
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Old 15th Dec 2017, 12:47 pm   #2
Nickthedentist
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Default Re: Help needed to restore 70's phone

Hello and welcome.

It's a 746-type phone, but is not a GPO version. It looks like cut-down (cheapened) version made for use on private internal phone systems. As well as deleted terminals, it has no ASTIC (a coil which looks like a little transformer, designed to help reduce the loudness of your own voice in the earpiece when talking into the phone). It will still work OK though.

Could you post a pic of any identifiying marks underneath?

N.
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Old 15th Dec 2017, 1:18 pm   #3
Station X
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Default Re: Help needed to restore 70's phone

I came across something similar with a 706 look-a-like.

From what I remember the connection to the line cord wasn't standard.
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Old 15th Dec 2017, 1:22 pm   #4
ThePillenwerfer
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Default Re: Help needed to restore 70's phone

You could get a proper GPO circuit board for it from a company called Telephone Lines for a fiver. See: http://telephonelines.net/index.php?...roducts_id=774

I'm only in Sheffield so if you get stuck give me a shout.
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Old 15th Dec 2017, 1:24 pm   #5
Nickthedentist
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Default Re: Help needed to restore 70's phone

It's also not got one of those green metal rectifier stacks or the double lamp block thermistor either.

Joe's idea is excellent if you can't get it working well enough. Very reasonably-priced too, assuming p&p not too exhorbitant.
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Old 15th Dec 2017, 1:34 pm   #6
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Default Re: Help needed to restore 70's phone

P&P is included, Nick.
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Old 15th Dec 2017, 1:35 pm   #7
Nickthedentist
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Default Re: Help needed to restore 70's phone

Cor!
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Old 15th Dec 2017, 5:59 pm   #8
Oldcodger
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Default Re: Help needed to restore 70's phone

For the OP- ( REF POST # 2), the ASTIC coil ( without getting too technical), sends back a portion of the transmitted speech to the caller. The result is that with sent speak returned, caller lowers their speech level. All dependant on the regulator ( missing ) regulating the length/ impedance of line ( again if memory serves - been a long time since my A/B TTA courses).
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Old 15th Dec 2017, 8:30 pm   #9
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Default Re: Help needed to restore 70's phone

Hi, I have seen similar phones to this pass through my collection in the past. This phone was probably originally used on a PAX and not a PSTN exchange line.
For what its worth you could try wiring it in the following way and see what happens.

RED of line cord to T8 (orange wire to dial)
WHITE of line cord to T18
BLUE of line cord to T4
GREEN of line cord needs to be insulated and tucked away as there are no spare terminals to park it on.

If you have no outgoing speech or dial tone upon lifting the receiver experiment with a resistor of between 150 ohms and perhaps 1K Ohm between T10 and T11 (pink of dial and white of handset) till an acceptable volume is achieved on an outgoing call.

If ringing problems are experienced remove strap T16 - T17 and put a 3k3 resistor in its place.

Regards

Andrew
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Old 15th Dec 2017, 10:33 pm   #10
scalpel
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Default Re: Help needed to restore 70's phone

Used AndiiT's steps and phone is restored to working order. Thanks all!!!

Not told girlfriend yet... going to surprise her with the first call tomorrow.
If the dialler is disabled would it affect the ablity to converse of the inbound?
No call package and the internet so we intended this as inbound only.
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Old 16th Dec 2017, 4:29 am   #11
ThePillenwerfer
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Default Re: Help needed to restore 70's phone

If you want to disable the dial you need to move the Red wire going in from the socket from T8 to T10, ie from the terminal with the Orange wire going to the dial to the one with the Pink wire.

I can't see any advantage to doing so though, apart from preventing anybody from using it and upping your bill.
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Old 16th Dec 2017, 8:51 am   #12
scalpel
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Default Re: Help needed to restore 70's phone

Quote:
Originally Posted by ThePillenwerfer View Post
I can't see any advantage to doing so though, apart from preventing anybody from using it and upping your bill.
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