764 Push Button Phone - no pulse - UK Vintage Radio Repair and Restoration Discussion Forum

SeanStevens · 16th May 2011, 7:15 pm

I have acquired a 2/764. I left it plugged into a BT socket to charge the internal battery for an hour. It doesn't dial out (no pulse).

I've checked the ni-cad. It is putting out 1.8v. There is no mention of what voltage the beast runs on here: http://www.britishtelephones.com/t764.htm

HELP!

SEAN

BGmidsUK · 16th May 2011, 7:53 pm

How many cells? Should be a nominal 1.25V or thereabouts per cell. 1.8v doesn't sound right!

Brian

Darren-UK · 16th May 2011, 8:16 pm

There's a link via that given if post #1 in which 7.2V is stated.

SeanStevens · 17th May 2011, 7:26 am

Thanks - possibly it isn't charging properly - the voltage going to the battery is very low indeed. From the looks of things it should charge directly from BT socket.

SEAN

davidw · 17th May 2011, 7:56 am

What colour is the battery?
Battery secondary No 22 (RED) = 4.8v 150mA.
Battery secondary No 23 (BLUE) = 7.2v 150mA.
Both were used during the life of this phone.
Connecting a battery of the appropriate voltage should prove your battery or another fault.

BGmidsUK · 17th May 2011, 8:55 am

The cells could well have dendrites and therefore be pulling the charging voltage down

have you measured the charging voltage with it out of circuit?

Brian

SeanStevens · 17th May 2011, 9:02 am

I measured the voltage at the socket that charges the battery with the blue battery removed. It was measuring about 1 volt. I was shocked as the ni-cad had more voltage than that.

I could try stuffing 7.2 volts down the socket to see if the phone starts dialling out......

thanks again

SEAN

16th May 2011, 7:53 pm	#2
BGmidsUK Retired Dormant Member Join Date: Oct 2007 Location: Leicester, UK. Posts: 809	Re: 764 Push Button Phone - no pulse How many cells? Should be a nominal 1.25V or thereabouts per cell. 1.8v doesn't sound right! Brian

16th May 2011, 8:16 pm	#3
Darren-UK Retired Dormant Member Join Date: Apr 2003 Location: Blackpool, Lancashire, UK. Posts: 4,061	Re: 764 Push Button Phone - no pulse There's a link via that given if post #1 in which 7.2V is stated.

17th May 2011, 7:26 am	#4
SeanStevens Octode Join Date: Sep 2009 Location: Bath, Somerset, UK. Posts: 1,033	Re: 764 Push Button Phone - no pulse Thanks - possibly it isn't charging properly - the voltage going to the battery is very low indeed. From the looks of things it should charge directly from BT socket. SEAN __________________ There are only 10 types of people, those who understand the binary system, and those who don't.

17th May 2011, 7:56 am	#5
davidw Heptode Join Date: Sep 2006 Location: Woodbridge, Suffolk, UK. Posts: 643	Re: 764 Push Button Phone - no pulse What colour is the battery? Battery secondary No 22 (RED) = 4.8v 150mA. Battery secondary No 23 (BLUE) = 7.2v 150mA. Both were used during the life of this phone. Connecting a battery of the appropriate voltage should prove your battery or another fault. __________________ Dave G1AGK. My perception is my reality! Last edited by davidw; 17th May 2011 at 7:59 am. Reason: extra data

17th May 2011, 8:55 am	#6
BGmidsUK Retired Dormant Member Join Date: Oct 2007 Location: Leicester, UK. Posts: 809	Re: 764 Push Button Phone - no pulse The cells could well have dendrites and therefore be pulling the charging voltage down have you measured the charging voltage with it out of circuit? Brian

16th May 2011, 7:15 pm	#1
SeanStevens Octode Join Date: Sep 2009 Location: Bath, Somerset, UK. Posts: 1,033	764 Push Button Phone - no pulse I have acquired a 2/764. I left it plugged into a BT socket to charge the internal battery for an hour. It doesn't dial out (no pulse). I've checked the ni-cad. It is putting out 1.8v. There is no mention of what voltage the beast runs on here: http://www.britishtelephones.com/t764.htm HELP! SEAN __________________ There are only 10 types of people, those who understand the binary system, and those who don't.

17th May 2011, 9:02 am	#7
SeanStevens Octode Join Date: Sep 2009 Location: Bath, Somerset, UK. Posts: 1,033	Re: 764 Push Button Phone - no pulse I measured the voltage at the socket that charges the battery with the blue battery removed. It was measuring about 1 volt. I was shocked as the ni-cad had more voltage than that. I could try stuffing 7.2 volts down the socket to see if the phone starts dialling out...... thanks again SEAN __________________ There are only 10 types of people, those who understand the binary system, and those who don't.