Opinions wanted : Removing the need for a battery on a 764/1 - UK Vintage Radio Repair and Restoration Discussion Forum

richwk1 · 14th Apr 2010, 12:56 am

I have several 764/1 which have batteries in various states of uselessness. I have been toying with the idea or removing the batteries completely and wiring the touch pad directly to the board to negate the use of the battery.

I would value opinions as to the feasibility of my idea and some pointers in the right direction would also be appreciated.

I know on later models the 764/2 and the 755 the batteries were removed in favor taking power directly from the line for the touch pads could i do something similar.

I have used a separate dc transformer to power the touch pads to make sure they are functioning so i know using a source of power other than the battery is possible but i don't want the phones to need an external power supply.

Thanks Rich

Station X · 14th Apr 2010, 8:35 am

Quote:

dc transformer

richwk1 · 14th Apr 2010, 10:44 am

Multi Voltage ac/dc adapter as used on electronic keyboards and the like to be more specific ( not a dc transformer !!)

Rich

Station X · 14th Apr 2010, 12:31 pm

To me a transformer in the electrical sense, will always be a wire wound device for converting one AC voltage to another. Hence my querying dc (sic).

AndiiT · 14th Apr 2010, 7:59 pm

Hi,
There was an option for powering the keypad on a 764 and similar using a Power supply type 53B which is a 10 Volt unit of the type used to power plansets and suchlike, this was usually done if the telephone was connected via a PMBX as the line voltage would not be present all the time so the battery would lose charge.

A point to beware of is by modifying the phone in this way it may then not be "officially" approved, I doubt that BT would come knocking on your door regarding this though.

An N Diagram and some useful information about different charging methods can be seen Here

Regards
Andrew

richwk1 · 14th Apr 2010, 8:52 pm

Andrew, thanks very much for some useful comments!!! The diagram provided is just what i have been looking for, allowing me to work out which terminal and wire combination's do what.

The phones work perfectly when connected to my mains adapter but on battery power only, the buttons make no clicks at all.

I have left he battery charging on the line (with correct strap and wire combination) for five days and while the battery is showing 8.2v (blue battery) it will not power the buttons.

As soon as i connect the mains adapter set to 7.5v ( as 8.2v isn't available, lower is better than higher to be on the safe side) the touch pad works correctly.

Something else i have been looking at is a replacement battery pack, possible make one or buy a NIMH battery pack already made ( they do some on ebay) but not sure they do 8.2v or close to it

Rich

AndiiT · 14th Apr 2010, 10:08 pm

Hi,
Regarding replacement batteries I seem to recall, either seeing somewhere or by word of mouth, that a PP3 9 Volt battery could be used to power the keypads on these phones; It would of course have to be of the rechargeable variety and may even possibly trickle charge from the line.

Regards
Andrew

richwk1 · 14th Apr 2010, 10:26 pm

Andrew, i think you may have just saved me a lot of time trouble and expense.

Why didn't i think of that, i have a couple of pp3 rechargeable batteries left over from my old smoke alarms when i rewired the house and put mains units in.

I appreciate your help, it's always good to get a fresh perspective.

I will rig something up with one of the phones and post how it goes.

Regards Rich

Dave Moll · 16th Apr 2010, 7:07 pm

There is also advice about replacing the batteries here.

14th Apr 2010, 12:56 am	#1
richwk1 Retired Dormant Member Join Date: Aug 2009 Location: Birmingham, West Midlands, UK. Posts: 80	Opinions wanted : Removing the need for a battery on a 764/1 I have several 764/1 which have batteries in various states of uselessness. I have been toying with the idea or removing the batteries completely and wiring the touch pad directly to the board to negate the use of the battery. I would value opinions as to the feasibility of my idea and some pointers in the right direction would also be appreciated. I know on later models the 764/2 and the 755 the batteries were removed in favor taking power directly from the line for the touch pads could i do something similar. I have used a separate dc transformer to power the touch pads to make sure they are functioning so i know using a source of power other than the battery is possible but i don't want the phones to need an external power supply. Thanks Rich

14th Apr 2010, 10:44 am	#3
richwk1 Retired Dormant Member Join Date: Aug 2009 Location: Birmingham, West Midlands, UK. Posts: 80	Re: Opinions wanted : Removing the need for a battery on a 764/1 Multi Voltage ac/dc adapter as used on electronic keyboards and the like to be more specific ( not a dc transformer !!) Rich

14th Apr 2010, 12:31 pm	#4
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Opinions wanted : Removing the need for a battery on a 764/1 To me a transformer in the electrical sense, will always be a wire wound device for converting one AC voltage to another. Hence my querying dc (sic). __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

14th Apr 2010, 7:59 pm	#5
AndiiT Octode Join Date: Aug 2005 Location: Saltburn-East, Cleveland, UK. Posts: 1,786	Re: Opinions wanted : Removing the need for a battery on a 764/1 Hi, There was an option for powering the keypad on a 764 and similar using a Power supply type 53B which is a 10 Volt unit of the type used to power plansets and suchlike, this was usually done if the telephone was connected via a PMBX as the line voltage would not be present all the time so the battery would lose charge. A point to beware of is by modifying the phone in this way it may then not be "officially" approved, I doubt that BT would come knocking on your door regarding this though. An N Diagram and some useful information about different charging methods can be seen Here Regards Andrew

14th Apr 2010, 8:52 pm	#6
richwk1 Retired Dormant Member Join Date: Aug 2009 Location: Birmingham, West Midlands, UK. Posts: 80	Re: Opinions wanted : Removing the need for a battery on a 764/1 Andrew, thanks very much for some useful comments!!! The diagram provided is just what i have been looking for, allowing me to work out which terminal and wire combination's do what. The phones work perfectly when connected to my mains adapter but on battery power only, the buttons make no clicks at all. I have left he battery charging on the line (with correct strap and wire combination) for five days and while the battery is showing 8.2v (blue battery) it will not power the buttons. As soon as i connect the mains adapter set to 7.5v ( as 8.2v isn't available, lower is better than higher to be on the safe side) the touch pad works correctly. Something else i have been looking at is a replacement battery pack, possible make one or buy a NIMH battery pack already made ( they do some on ebay) but not sure they do 8.2v or close to it Rich

14th Apr 2010, 10:08 pm	#7
AndiiT Octode Join Date: Aug 2005 Location: Saltburn-East, Cleveland, UK. Posts: 1,786	Re: Opinions wanted : Removing the need for a battery on a 764/1 Hi, Regarding replacement batteries I seem to recall, either seeing somewhere or by word of mouth, that a PP3 9 Volt battery could be used to power the keypads on these phones; It would of course have to be of the rechargeable variety and may even possibly trickle charge from the line. Regards Andrew

14th Apr 2010, 10:26 pm	#8
richwk1 Retired Dormant Member Join Date: Aug 2009 Location: Birmingham, West Midlands, UK. Posts: 80	Re: Opinions wanted : Removing the need for a battery on a 764/1 Andrew, i think you may have just saved me a lot of time trouble and expense. Why didn't i think of that, i have a couple of pp3 rechargeable batteries left over from my old smoke alarms when i rewired the house and put mains units in. I appreciate your help, it's always good to get a fresh perspective. I will rig something up with one of the phones and post how it goes. Regards Rich

16th Apr 2010, 7:07 pm	#9
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,130	Re: Opinions wanted : Removing the need for a battery on a 764/1 There is also advice about replacing the batteries here. __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)