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Old 15th Feb 2011, 2:32 pm   #21
frglee21
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Default Re: 232L bakelite telephone and No 26 Bellset

Very well done Ivan!

It's a great feeling of achievement when you get something like that up and running properly - the first of many?

Is a collector of commercial radio equipment called a 19inch-o-rack ?

Best Wishes, Lee.
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Old 13th Jun 2013, 8:51 pm   #22
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Default Re: 232L bakelite telephone and No 26 Bellset

Hi to all, I have just joined the site and have read a number of posts relating to telephones, though I have a very basic grasp on the subject. However thanks to information posted on here and elsewhere I have successfully rewired my 706/L phone, installed a 3.3k ohm Resistor and an original No. 205 rectifier for it to fully work on a BT plug and socket, leaving just the on/off bell switch to wire up.

I have a few other phones yet to be converted, as regards the No. 205 rectifier my understanding from other posts is you can use two 1N4001 diodes back to back with one reversed to serve the same purpose, is there a specific type as I require?

If anyone can point me in the right direction, as it would be greatly appreciated many thanks in advance :- )

Last edited by Station X; 13th Jun 2013 at 10:23 pm. Reason: Forum rule compliance.
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Old 14th Jun 2013, 10:33 am   #23
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Default Re: 232L bakelite telephone and No 26 Bellset

Quote:
Originally Posted by kevcurr63 View Post
'...my understanding from other posts is you can use two 1N4001 diodes back to back with one reversed to serve the same purpose, is there a specific type as I require?

If anyone can point me in the right direction, as it would be greatly appreciated many thanks in advance...'
Any diode with a drop of 0.6V or thereabouts will do. All they're for is for clipping sudden clicks that may cause acoustic shock on the more sensitive rocking armature receivers as found in 7XX series telephones.

Don't use them as a 'sticking plaster solution' for clicky dials! If you get rat-a-tat-a-tat-a-tatting when your dial rotates, it's the dial-off-normal contacts that require cleaning: the ones that shunt the receiver.
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Old 14th Jun 2013, 12:46 pm   #24
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Default Re: 232L bakelite telephone and No 26 Bellset

Hi,
Thanks very much for taking time to reply, itís most appreciated, being new to this I am not entirely sure what to look for when it comes to diodes, and do forgive my complete lack of knowledge of electronic components, I donít know what a diode with a drop of 0.6V means, my apologies I need an idiot proof guide! Is 1N4001 Silicon Bridge Rectifier Diodes RoHS, Maximum Current: 1A Maximum Voltage: 50V the kind of thing I would need or I am way off the mark?

I will definitely clean contacts before proceeding further with the other phones, I also have 232/L phone which I wired to a cable with BT plug and it works perfectly when I tried it, both dialling out and receiving calls. Though, lacking a bellset, I have been looking high and low for a matching No 26 bell set, the small number I have seen do seem quite pricey being on a tight budget [arenít we all these days!].

However it did occur to me that perhaps it would be possible to construct a bellset from component parts then house it on a suitable baseplate. I have a working BT Indoor Bell - Bell 50E which I think would probably be about right for the bell ringer component then if correctly wired with a bell capacitor between bellset and phone it might be ideal [Would a Bell Capacitor 1.8mf micro farad 250v in series with the bell be suitable?]. I might be a bit optimistic but I would like to give this a go in the future and if it works then perhaps add a reproduction No 26 casing.

My apologies for asking a lot of questions due to my lack of knowledge, though I would greatly appreciate any input on all or any of the above, again many thanks in advance

Regards

Kev
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Old 14th Jun 2013, 4:45 pm   #25
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Default Re: 232L bakelite telephone and No 26 Bellset

Other options, if you just want a ringing facility on it rather than maintaining originality, would be either to use a bell (set) comletely external to the 'phone itself or to purchase one of the miniature bells that can be fitted inside the telephone.

I have no personal experience of the latter, but I suspect that they would sound fairly "tinny" compared with a proper bell of the era.
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Old 14th Jun 2013, 8:15 pm   #26
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Default Re: 232L bakelite telephone and No 26 Bellset

Hi, I tried the BT Indoor Bell - Bell 50E and telephone both plugged into a double socket and that works great, you definitely cannot miss it ringing. I opened the plastic bell casing and I think it looks identical to the set of bells, etc youíd find in a newer 746 telephone, given I paid £2 for the indoor bell at a car boot sale I canít complain.

Before I bought that I did think about the miniature bells that can fit inside the phone but after looking at them online I agree I think it would be probably pretty tinny and feeble in comparison to a proper bell set, and thanks for the suggestions they always appreciated by me.
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Old 14th Jun 2013, 9:46 pm   #27
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Default Re: 232L bakelite telephone and No 26 Bellset

Those diodes would do fine. They're not essential, but a 'nice-to-have' and reflect the GPO's improvements to the circuit.

As for your 232, you don't need a bell capacitor, as the cap is in the master LJU (see attached diagram). If you get yourself a tatty old 700 series telephone cheap, you could gut it, apart from the bell-motor, gongs and terminal strip (or PCB), as the 7XX contemporary bellsets were, effectively, but with a plastic cover over them for wall-mounting.
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Old 17th Jun 2013, 8:28 am   #28
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Default Re: 232L bakelite telephone and No 26 Bellset

Thanks again, I have ordered some diodes and once they arrive I will find some time to use them. I was not sure about a bell capacitor but again thanks for the information, I will have a look for a cheap 700 series and if I find one I may do as you have suggested, many thanks for the diagram also.
Regards
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Old 17th Jun 2013, 2:18 pm   #29
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Default Re: 232L bakelite telephone and No 26 Bellset

Quote:
Originally Posted by kevcurr63 View Post
....I tried the BT Indoor Bell - Bell 50E ....
Hi, Bell 50E is a high impedance (4KOhms) bell and will not require the additional 3k3 resistor to be fitted in series as shown in Russel's diagram.

Regards

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Old 17th Jun 2013, 7:51 pm   #30
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Default Re: 232L bakelite telephone and No 26 Bellset

Hi Andrew,
Thanks very much for the info, Iíve have to say this is an excellent site for people like me looking to learn, pick up handy tips and receive good advice.
Regards
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Old 17th Jun 2013, 10:29 pm   #31
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Default Re: 232L bakelite telephone and No 26 Bellset

The resistor may not be necessary with a 1 kilohm (d.c. resistance) type 59A bell motor. Depends on what else is hanging on your line and how far you are from the exchange. I showed the resistor in case it was required, otherwise a link may be fitted.

It's a case of 'suck it and see'!
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Old 20th Jun 2013, 1:29 am   #32
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Default Re: 232L bakelite telephone and No 26 Bellset

A 3.3K resistor does not make things correct anyway. A bell is inductive and the 1K resistance is only part of the impedance.
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Old 20th Jun 2013, 9:01 am   #33
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Default Re: 232L bakelite telephone and No 26 Bellset

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A 3.3K resistor does not make things correct anyway. A bell is inductive and the 1K resistance is only part of the impedance.
Quite. Approximately half the ringing voltage is dropped across the 3k3 resistor. The 59A bell-motor has an impedance (they vary, slightly) of 1600 + j1928 (or Z = 2505 Ohms).
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