UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Telephony and Telecomms

Notices

Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment

Closed Thread
 
Thread Tools
Old 31st Dec 2020, 10:58 am   #1
Xyience
Tetrode
 
Join Date: Dec 2020
Location: Chelmsford, Essex, UK
Posts: 57
Default Connecting U43 to an Electric Bell

I have just restored and converted a French U43 Ericsson dated 1964.

I was amazed at just how little I needed to do to get this working on our phone line - a BT line cord, two diodes and a quick clean up of some oxidised contacts.

The sound from the earpiece is a bit quiet and the sound from the Mother-In-Law speaker is about 50% too quiet (any ideas? I might remove the added rectifier to see if this helps - I chose random diodes!)
Apart from this the phone looks and performs really well.

But to the main question - I have a vintage electric bell (see attached) that I would like to use as a bellset for the phone. I know it will not give a traditional twin-bell tone, but this car boot find deserves a purpose in life.

I cannot find much in English on the U43, and nothing about bellsets for the model.
Can anyone suggest a circuit that can connect the two?

[The bell dings nicely with a tired 12V battery, but too aggressively with a 12V 2.5A smoothflow model train supply]

HAPPY NEW YEAR TO US ALL
Attached Thumbnails
Click image for larger version

Name:	IMAG2088.jpg
Views:	109
Size:	59.5 KB
ID:	223557  

Last edited by Xyience; 31st Dec 2020 at 11:05 am. Reason: attach photo
Xyience is offline  
Old 31st Dec 2020, 11:41 am   #2
Dave Moll
Dekatron
 
Dave Moll's Avatar
 
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 5,423
Default Re: Connecting U43 to an Electric Bell

The problem is that the bell shown is a DC trembler bell (rated, as you say, at 12V), whereas the ringing current from a telephone line is 25Hz AC at around 75V or so.

Incidentally, I am unclear what the diodes described are for.
__________________
Mending is better than Ending (cf Brave New World by Aldous Huxley)
Dave Moll is offline  
Old 31st Dec 2020, 11:52 am   #3
Xyience
Tetrode
 
Join Date: Dec 2020
Location: Chelmsford, Essex, UK
Posts: 57
Default Re: Connecting U43 to an Electric Bell

That is an issue. It doesn't sound like compatibility would be easy or cost-effective.

Would the bellset/bell from a junked GPO phone work with the U43? These seem easy to come by.

The diodes are instead of a No 205 rectifier as suggested by https://www.britishtelephones.com/tranchan.htm

Phones are entirely new to me, and I didn't want to blast my families hearing, so I went with the instruction.
Xyience is offline  
Old 31st Dec 2020, 12:05 pm   #4
Dave Moll
Dekatron
 
Dave Moll's Avatar
 
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 5,423
Default Re: Connecting U43 to an Electric Bell

Quote:
Originally Posted by Xyience View Post
Would the bellset/bell from a junked GPO phone work with the U43? These seem easy to come by.
That sounds like a much better option. You could always use the DC bell as a doorbell.

Quote:
Originally Posted by Xyience View Post
The diodes are instead of a No 205 rectifier as suggested by https://www.britishtelephones.com/tranchan.htm

Phones are entirely new to me, and I didn't want to blast my families hearing, so I went with the instruction.
After posting, I did wonder whether this was what you meant. The way these work is by only conducting above a certain level of signal so that they don't conduct at speech level but the higher-voltage spikes caused by switching are shorted out to prevent "acoustic shock" (loud clicks in the earpiece).
__________________
Mending is better than Ending (cf Brave New World by Aldous Huxley)
Dave Moll is offline  
Old 13th Jan 2021, 10:52 am   #5
Xyience
Tetrode
 
Join Date: Dec 2020
Location: Chelmsford, Essex, UK
Posts: 57
Default Re: Connecting U43 to an Electric Bell

I found a perfect donor telephone for my purposes. A stinky, discoloured cream 706. The smell off this phone actually made me gag once or twice!

I stripped off all of the components and mechanical items one by one until I was assured that I had just enough left to operate the bell. This left the metal chassis, the circuit board, but only to mount the striker mechanism, and the two gongs.
I added a resistor to correct the REN and wired up directly to the U43.

This works perfectly. When I get some more time I will give the bellset its own BT plug and add a nice cover to keep fingers away from the exposed terminals. This is hung high up on a wall so it is safe enough for now.
Everyone in the house loves the sound of the metal bells. Takes me right back to the 70's.

I experimented with the phone by taking out the DIY 205 rectifier. This does allow some unpleasant transients to reach the receiver, so the diodes stay.

Thanks for the tips Dave
Xyience is offline  
Closed Thread

Thread Tools



All times are GMT. The time now is 6:45 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Copyright ©2002 - 2021, Paul Stenning.