Bakelite 300 series with lamp

[wheresthetubes]

T1 and T2 are connected with a small metal connector as seen in the previous picture, therefore won't this bypass any resistor I place between T1 and T2..... won't I have to remove the connecting metal strap between T1 and T2 for the 3K3 resistor to be effective?

I've revised the sketch to include the wire that previously led from the bulb to T2, now going to T1. But there is now a 3K3 resistor between T1 and T2 and the connecting metal strap/joiner between T1 and T2 has been removed. Can you let me know if I have this right, many thanks.

[AndiiT]

Hi,
Whoops , yes T1 - T2 need to be removed and replaced by a 3K3 resistor this is to maintain the bell circuit as a high impedance one which is required using todays "modern" plug and socket wiring; this is providing that the bell coils in your telephone are still the original 1K ohm ones which they are most likely to be.

Your diagram looks fine to me, I would probably try a 150K resistor to begin with as the ringing voltage is around 75 Volts AC so a 220K series resistor in your circuit may be a little high as 270K is the resistor value for a neon operating at 250 Volts AC if that makes sense.

Regards
Andrew

[wheresthetubes]

Yes, I think Dave alluded to trying lower value resistor in an earlier post. Well, this is great, feel confident enough to have a go at getting the lamp working on this phone now. I guess a trip to Maplins to get these resistors in the next week is a must, as i have none at all, much less the ones I need. I realise the phone itself is of little value to collectors due to the lamp modification, but then AEP's generally arn't that collectable anyway. The lamp mod looks to be about as old as the phone, so I guess I'm restoring it.

I'll report back and let everyone know how I got, many thanks for the advice.

[wheresthetubes]

Hello, was about to have a go at this tonight, then it occured to me that perhaps the connecting strap between terminals T12 and T11 should also be removed?? as is the case with the connecting strap between T1 and T2, or should the strap stay in to keep T11 and T12 connected? Please see the earlier pic/diagram. Thanks, John.

[AndiiT]

Hi,
Strap T11 - T12 need to be fitted to maintain the bell circuit.
You could, however, replace it with a switch (the one already fitted to your phone may suffice) should you wish to fit a Bell On/Off facility; in this case the neon needs to be connected to T1 and T11 (via the series resistor) in order for it to continue to light on an incoming call when the bell is switched off.

You would also need to ensure that the BLUE lead of the line cord is connected to T11, as it is currently, and not T12.

Regards
Andrew

[wheresthetubes]

EUREKA!!! Lamp working, flashing in unison with bells. I tried a 133k resistor from terminal 12 to lamp, and bulb lit but only dimly. Exchanged resistor value for 100k and bulb flashed a little better, but still quite dim. So exchanged again for an 85k. Again a slight improvement, but I'm a little apprehensive of trying a lower value resistor for fear of frying the neon. As you say, they may be a little difficult to source. I'm not at all sure how bright these neons are supposed to be so I might even have it at optimum, but until I have replacements to hand I think I'd be better leaving the 85K in place for now.

Many many thanks for your help in getting the lamp working on this telephone. You know I had an engineer tell me it was impossible to get lamps working again on these old phones, and that they were very curiosity value only! And this guy worked on vintage telephones for a livving. Another guy didn't even get back to me.

I may have a go at utilising the switch to turn the bells off, this may even have an effect on the brightness of the lamp, but again I don't think I'll try anything further until I can get some spare neons that will fit the bulb holder.

Best regards, John.

[AndiiT]

Hi,
First of all congratulations on getting the lamp to operate.

Originally Posted by wheresthetubes

........ I'm not at all sure how bright these neons are supposed to be.......

Regarding the brightness of the neon, I am not too sure (and probably, unusually, also a little young for this type of phone/neon combination) how bright it should be.

The newer 700 type telephones which were fitted with a "Lamp signaling handset" had a small reflector underneath the neon to increase the brightness of the neon, you might want to try something similar with your set up if at all possible, perhaps not as easy with an upright mounted lamp.

I have enclosed a picture of one of my own Plansets with a lamp signaling handset so that you can see the reflector I mentioned.

It might be nice to see if you could get a picture of the lamp in operation and post it on here.

Regards
Andrew

[wheresthetubes]

Hello, yes, I will post a pic fairly soon. I was checking out the switch that supposedly turns of the bell circuit. I put my multi-meter to it but couldn't get any continuity reading, that is not until I pressed down the switch and held it down. I think this switch will only operate by keeping it continually pressed down, there isn't a 'click' when you press down so I think this is the case. The phone must have been in an office environment where a secretary had to use 2 or 3 phones at a time. I won't know for sure until I connect it up, as feeling bouyed by my earlier success I've decided to connect the switch.

I've posted a pic of the switch. It has two terminals (with remains of the old wiring still attached). I'm assuming one terminal has to be attached to T12 and the other to T11, whilst as you pointed out earlier, the connection between T12 and the lamp (with resistor in series) will have to be moved to T11?

If I got this right let me know. I'd rather put in a vintage period switch that would click off the bells without having to compress down continually, but I'm not likely to get one of those in a hurry so I'll just connect the one I have. I'll post a pic when I get this done.

Best regards, John.

[davidw]

You could try putting the 100k and 133k in parallel giving you about 60k which may get you a bit more brightness.( damage to your neon is unlikely..remember you have an extra 3k in circuit that we never had originally). If you get stuck I have a couple of these neons I liberated!
They were never very bright in the area I had them in use, as the room was kept in low light.
Well done for persevering.

[AndiiT]

Hi,
It sounds like the switch that you described is a "push to make release to break" type so would only be good for use as a recall button and not an on/off button - for on/off you need a torpedo switch similar to those used in some table lamps, these are still readily available from places such as Wilkinson's (if you have one close by) or B&Q.


The extra 3k in circuit that David mentions shouldn't cause a problem as it is only in series with the bell and not the lamp too; at least it is if you ensure that the lamp is connected direct to the white of the line cord on T1.

If fitting a locking switch to silence the bell remove strap T11 - T12 and connect the switch across these terminals instead, then connect your lamp across T1 and T11.

Regards
Andrew

[wheresthetubes]

Thanks, I'm going to have a little experiment running resistors in parallel as I've never done this before, relatively new to electronics so everything's a learning curve at the moment. However I do have a few lower value resistors to try first, but that will wait until I have the switch in place. I might be begging for a neon depending on how this goes.

I've had a look at the torpedo switches, problem with them though is they just look too modern and will look very odd on my old bakelite. I was thinking more in terms of a toggle switch, and I'm watching one on ebay at the moment; a vintage toggle switch with some bakelite and brass. It'll at least be more in keeping with the age of the phone.

Many thanks for the advice, I'll post a pic of the phone in action once I have all the work completed.

[russell_w_b]

Originally Posted by wheresthetubes

'I've had a look at the torpedo switches, problem with them though is they just look too modern and will look very odd on my old bakelite.'

The push-button switch on your telephone may have been used to momentarily sound a remote buzzer as part of an intercom system. Those sort of switches were very popular in desk and table light-fittings in the 1960s and 1970s, and all you need is a push-on-push-off switch body that is compatible with the retaining bezel you already have.

You may even come across one mounted without a bezel, inside an old lamp-base.

[AndiiT]

Originally Posted by wheresthetubes

..... I'm going to have a little experiment running resistors in parallel ..... relatively new to electronics so everything's a learning curve at the moment. ....

When wiring resistors in Parallel the first thing to remember is that the final total value will always be lower than the lowest value resistor of the pair that you are using.

For resistors in series you simply add together the values, which I am certain that you already knew. For resistors in parallel the basic formula is -

R total = (R1 x R2)/(R1 + R2) or "Product over Sum", for the mathematically minded

Regards
Andrew

[wheresthetubes]

Just back from my hols, and awaiting me on my door step is the two way switch I bought for £2.49 with postage. Its a switch that was removed from the cockpit of a WW2 Spitfire, so keeping in age/appearance with the phone. A bit stiff but the DW40 sorted that. Phone works like a dream, switch turns off the bells and lamp continues to glow to indicate incoming call. It was a bit fiddley wiring this up but we got there. Posted pics, they're a bit dark but unable to show the lamp in action without turning off the flash. Thanks to all of you who advised, and special thanks to Dave for the instructions. Very pleased with this phone. So on to my next project.... the roberts R77 or the Decca Junior Gramophone.... Best regards, John.

[wheresthetubes]

Blimey, sorry, I meant Andy, not Dave, .. thanks Andy.

[Dave Moll]

Here is an enhanced version of the final picture: