GPO 248 with Bellset 44 Conversion Problem!

[Gavcr999]

Hello everyone, I'm a newbie on here and have over the last year and a half started collecting and converting, vintage, mainly GPO phones.

I am currently trying to convert a GPO 248 mounted on a`Bellset 44 which I am having problems with. I have wired it as per the guide here: http://www.britishtelephones.com/pstconv1.htm

It did briefly work although the contacts under the handset plunger were a little tempremental. But then the dial tone disappeared, and there is just a click when the handset is lifted or put back down.

I did discover that I can get the dial tone back by moving the green wire of the connecting cord to either terminals 1 or 5 of the bellset but with it wired like this it does not cut off the dialtone when the handset plunger is depressed.

It does not mention on the wiring guide where the green and white wires of the connecting cord should be wired to. These are wired as they were when I received the phone, Green T5 to B35 and White T6 to B33.

I've reached a dead end now with this so would very much appreciate any help or suggestions as I know there are people with a lot of knowledge of GPO phones on this forum.

Many Thanks!

[Darren-UK]

Extract from britishtelephones:

1. White of the line cord to B1 and B2.
2. Red of the line cord to B3 and B4.
3. Green of the line cord - insulate - not used.

[Gavcr999]

Sorry probably didnt make that very clear!
I meant the connecting cord between the phone and bellset.

[Darren-UK]

Ah right, sorry about that. Without studying the circuit, that section of britishtelephones isn't too clear really. It's headed "Telephone and bellset" which I took to mean the connections between the two.

[AndiiT]

Hi,
It may not be too clear on the British thelephones web site that the terminals marked B1, B2 etc are those of the bellset and the ones marked T1, T2 etc. are that of the telephone itself - this may cause some initial confusion.

Additionally neither the Bellset 44 or the 248 telephone have internal bell fitted so if you wish to recive incoming calls you will have to also obtain a bell of some sort, originally I think Bellset 26 was used but a 50C type or even a seperate tone caller (whislt not being as authentic) should suffice.

Once the bellset 44 and telephone 248 are connected together you should be able to obtain an operational phone by connecting the Red (B leg) of your line cord to B4 and the White of the line cord (A leg) to B2, ensuring that straps are fitted between B3-B4 and B1-B2 (NOT B1-B2-B3-B4)

A device for signalling incoming calls can be connected between bellset terminals B8 and B2.

Wired in this way transmission should be possible as long as the lever on the Bellset is in the 'SPEAK TO EXCH' position.

Regards
Andrew

[Gavcr999]

Thanks for your responses. The phone is wired as above and the lever in the correct position but still no dialtone.
Does anyone know if it is possible to wire the line cord directly to the phone terminals? I have tried wiring to terminals 1 to 3 as a 232 phone but this doesnt work. As the bellset buzzer doesnt work on external calls if it is possible to wire straight to the phone this would work just as well.

[AndiiT]

Hi,
I'll try and take a look at the n diagram later and see if I can guide you through connecting your phone and bellset together in order to achieve suitable operation.

On the subject of using the buzzer as a signalling device for incoming calls the short answer is that this isn't possible as the buzzer is a DC device and the current coming from the exchange to ring the calling device in a telephone is AC.

Originally the buzzer in the bellset would be used to alert the 'Main' station of a call from the extension(s) telephone(s).

The facility diagram shows how the Bellset 44 would have been set up in normal use.

Regards
Andrew

[AndiiT]

Hi,
Looking at the n diagrams it would appear that the telephone 248 was specifically intended for use with a Bellset 44 (or 39, which is similar)

Try connecting up the phone, bellset and line cord as follows and see if you manage to achieve speech transmission with the lever in the 'Speak to Exch' position then.

In the telephone

Strap T3-T4

In the Bellset base

Strap
B1-B2

B3-B4
B5-B6
B19-B20-B21
B17-B18-B23-B22
B31-B32
B34-B35

Then connect the telephone to the Bellset as follows -

T1-B21
T2-B27
T3-B34
T9-B31
T10-B26
T11-B25

Connect the line cord RED to B4, WHITE to B2

Test.

Once transmission is sorted then a suitable means of signalling an incoming call can be considered.

Regards
Andrew

[Gavcr999]

Thats for that, I'll give it a try and will let you know how I get on.

[Gavcr999]

Originally Posted by AndiiT

Hi,
Looking at the n diagrams it would appear that the telephone 248 was specifically intended for use with a Bellset 44 (or 39, which is similar)

Try connecting up the phone, bellset and line cord as follows and see if you manage to achieve speech transmission with the lever in the 'Speak to Exch' position then.

In the telephone

Strap T3-T4

In the Bellset base

Strap
B1-B2

B3-B4
B5-B6
B19-B20-B21
B17-B18-B23-B22
B31-B32
B34-B35

Then connect the telephone to the Bellset as follows -

T1-B21
T2-B27
T3-B34
T9-B31
T10-B26
T11-B25

Connect the line cord RED to B4, WHITE to B2

Test.

Once transmission is sorted then a suitable means of signalling an incoming call can be considered.

Regards
Andrew

Hi,
I tried wiring as above but still not working. As before I can still get a dialtone by wiring B5 to T5 but it does not cut off when the plunger is down.

I'm thinking now maybe there is a problem with a component in either the bellset or the phone rather than with the wiring?

I have another 248 here with a bellset 39 (both at present untested and yet to be conveted) so I will try swapping the 248's and I should at least be able to establish if the problem is with the phone or the bellset.

[AndiiT]

Hi,
If you have access to a multimeter forget the phone for a moment and try the following test(s) on the Bellset base.

With the lever in the 'SPK to EXCH' Position and the line cord connected to RED to B4-B3 and WHITE to B1-B2 check for between 42 to 50 Volts across B34 and B21, ensuring that strap B20-B21 is definitely in place.

Alternatively you could connect a spare line jack, terminal 2 to B34 and Terminal 5 to B21; plugging a known working telephone into this would at least prove that the Bellset exchange switching is operating correctly.

regards
Andrew

[Gavcr999]

Tried testing with multimeter as above and got a reading of 109 volts.
This is a high reading if it should be between 42 and 50v
regards
Gavin

[AndiiT]

Hi,
Did you have the meter set to AC or DC? It should be set to DC, check again with the meter definitely set to DC and let us know.

Regards
Andrew

[Gavcr999]

Originally Posted by AndiiT

Hi,
Did you have the meter set to AC or DC? It should be set to DC, check again with the meter definitely set to DC and let us know.

Regards
Andrew

Yes I had it set to AC, the reading with it set to DC is just under 50 V, so I guess this rules out any problems with the bellset

[russell_w_b]

You'll get that sort of voltage (90 - 120V typically) if you're measuring a.c. directly across the capacitor in the master LJU.

Don't know if this helps matters or confuses things, but I just thought I'd mention it...

[AndiiT]

Originally Posted by Gavcr999

Yes I had it set to AC, the reading with it set to DC is just under 50 V, so I guess this rules out any problems with the bellset

Hi,
That sounds right, I am not sure if the next suggestion will work but it's worth a try, connect your line cord as follows to the Telephone direct,

RED to T3
WHITE to T1
BLUE to T2

It is essential that the Blue lead is connected as the capacitor in the master socket/line jack forms part of the transmission circuitry and is substituted when the phone is connected via the Bellset across B34(T3) B27(T2)

Then try the phone pugged direct in to the main socket (if you have more than one socket that is) of your phone line.
Wired this way you should receive dial tone and the switch hooks should operate correctly. You won't be able to dial out unless the strap T3 - T4 is removed though.

Just for interest/information you should measure approximately 48 Volts DC if a BT line and 42 Volts DC if a Virgin Media (Ex-ntl etc.) line.

Regards
Andrew

[Gavcr999]

Hi, I've tried wiring direct to the telephone as above but still no dial tone!
Regards
Gavin