UK Vintage Radio Repair and Restoration Discussion Forum

UK Vintage Radio Repair and Restoration Discussion Forum (https://www.vintage-radio.net/forum/index.php)
-   Vintage Telephony and Telecomms (https://www.vintage-radio.net/forum/forumdisplay.php?f=111)
-   -   Sterdy door phone handset/cradle (https://www.vintage-radio.net/forum/showthread.php?t=141940)

Sparks 5th Dec 2017 9:37 am

Sterdy door phone handset/cradle
 
2 Attachment(s)
Quick question. Can anyone please tell me what this component is inside the cradle body ? Is it a transformer, buzzer or something else ? I haven't a clue. Thankyou.

rambo1152 5th Dec 2017 5:42 pm

Re: Sterdy door phone handset/cradle
 
I think it is the buzzer that announces someone at the front door.

Sparks 5th Dec 2017 5:58 pm

Re: Sterdy door phone handset/cradle
 
Thankyou Rambo. If so, any idea how I can test it ? The unit isn't active, it's purely decorative so it doesn't matter too much if it doesn't work. Thankyou.

Sparks 6th Dec 2017 7:12 pm

Re: Sterdy door phone handset/cradle
 
I guess it's just a question of applying a voltage of sorts across the terminals to see if the buzzer works. What would be a suitable value ? I don't want to overdo it and risk damaging the unit. Ta.

Station X 6th Dec 2017 9:39 pm

Re: Sterdy door phone handset/cradle
 
If it is a buzzer, I can't see any interrupter contacts, suggesting that it works on AC.

What is the resistance of the coil? I can't see how many noughts there are.

Is there a gap between the coil cheek and what looks like a piece of flexible magnetic metal?

dagskarlsen 7th Dec 2017 7:42 am

Re: Sterdy door phone handset/cradle
 
Not easy to guess on such voltage, but other buzzers for 10-12 V AC I have seen has had around 100 ohms resistance, so I would take the chance of try for 1 second.

Sparks 7th Dec 2017 9:58 am

Re: Sterdy door phone handset/cradle
 
4 Attachment(s)
Some more pictures in the hope they help. The coil thing says 100 ohms. The flat piece of metal at the bottom of the coil is quite thin and flexible. There are also a red wire and a black wire attached to either end. A hook switch is attached to the top - it breaks a circuit when the handset is in place and makes it when it is lifted.

Thankyou for your replies folks.

Station X 7th Dec 2017 10:19 am

Re: Sterdy door phone handset/cradle
 
Definitely an AC Buzzer.

Try powering it from the output of a bell transformer, starting with the lowest available voltage. It would be advisable to check the continuity of the coil first.

Sparks 7th Dec 2017 10:21 am

Re: Sterdy door phone handset/cradle
 
Thanks Graham. I don't know if it's significant but the handset has a No.16 carbon mic so obviously some sort of voltage is supplied to the unit.

Station X 7th Dec 2017 10:23 am

Re: Sterdy door phone handset/cradle
 
The supply to the telephony parts of this will be DC, possibly 6V or lower.


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