Bakelite 300 series with lamp

[wheresthetubes]

Hello, I have a bakelite 300 series telephone which has a small lamp fixed just above the dial. It isn't operating, I assume it used to light up to indicate an incoming call. I inquired through the internet to a company that restores these phones to working condition, and they advised that the lamp would be for 'curio' value now as they would not be able to get the lamp working again. The telephone works in all other respects rather well. Its an AEP in remarkably good condition, not something I'd usually buy (paid £65), but bought it with a view to getting the lamp working again. My question is; Is it possible to get the lamp working?? It seems odd that an engineer specialised in restroring vintage telephones isn't able to get the lamp working (though he never looked at the phone) or is this really impossible?

[russell_w_b]

Originally Posted by wheresthetubes

Hello, I have a bakelite 300 series telephone which has a small lamp fixed just above the dial. It isn't operating, I assume it used to light up to indicate an incoming call.

I wouldn't be so sure about your assumption. Is there a label under the lamp? What sort of bulb does it take? Are there any push-buttons on the telephone? What, exactly, is the type of telephone (numbers on a label on the base, hopefully)?

Any chance of a picture? That would help most of all! It sounds like you have either some sort of non-GPO telephone, or it has been modified in some way.

[Darren-UK]

I'm thinking along the same lines as Russell, in that it's non-GPO or has been modified. I've been searching the various telephone websites and found no 300 series instruments fitted with a lamp.

Backing Russell again, a few images would be great help. It may also be useful to know what markings there are beneath the grip of the handset - assuming the handset to be the original, of course.

[AndiiT]

Hi,
I am in agreement with others here in that the phone may have well been modified and I am guessing that it was possibly originally part of a secretary/manager "plan system" where the lamp was used to either indicate a call was waiting or, more likely, that the exchange line was in use.

It shouldn't be too difficult to arrange the lamp to light on an incoming call in conjunction with the bell although you may have to change the type of the lamp to a neon one (if it isn't already).

With current high impedance bell working lamp signaling can sometimes be a little tricky to get working but isn't impossible, once we know what type of phone it is I may be able to offer some pointers.

I have enclosed a picture of the only phone I have ever seen of this type with a lamp fitted.

Regards
Andrew

[davidw]

The only ones I've seen with lamps were in the underground control/plotting room at the old RAF Bawdsey where a desk full of phones all ringing at once would be a problem. They were simply neon lamps with series resistor wired accrosss the bell coils which in the dim light of the plotting room worked remarkably well. There was never as far as I recall a proper "N" diagram but most of us military station GPO staff were made aware of various local arrangements.

[Station X]

It would be a good idea to trace which terminals in the phone the wires from the lamp go to.

[russell_w_b]

Originally Posted by AndiiT

'I have enclosed a picture of the only phone I have ever seen of this type with a lamp fitted.'

Is that a modified 326? My limited knowledge tells me that plan-sets didn't have lamps fitted until the introduction of the 700 series telephone (A 710, for example, could be fitted with lamps).

Until the OP gets back with a photo and description, I shall continue to suspect that the lamp has been fitted in the hole left by a chrome push-button, like the 'recall' button on a type 330.

We really need a photograph!

[wheresthetubes]

Hello, here's the AEP. Appears to be a model 332 from the diagram inside the metal plate. Can I have some advice please on how to get the lamp working, haven't done this type of work before though sure I could get it done (if it's possible to get the lamp working in any case). I've never fully opened one of these phones before. There are three large screws holding the workings onto the bakelite case, with a further small screw going into the dial through the bakelite... is it a simple case of unscrewing the four screws and then lifting the bakelite case away from the workings?? Thought I'd ask first as there may be springs or some other complication etc. I'm assuming that even though this may be a modification, given that the lamp was fitted and presumably in use, it would follow that the lamp could be reactivated again??

Many thanks.

[russell_w_b]

Originally Posted by wheresthetubes

Hello, here's the AEP. Appears to be a model 332 from the diagram inside the metal plate.

Ah... It's not a UK model; Spanish? Portugese? Brazilian? Mexican?

It looks to me like the lamp (and a push-button light-switch) has been added as a modification, possibly as some sort of intercom unit. It certainly isn't shown on the diagram (assuming the diagram to be original).

I think the best thing you can do is examine the lamp-holder and see what sort of bulb is fitted. It may be possible to replace it with a neon bulb which, when connected to a suitable resistor, can be made to glow when the bell rings. As Station X says, it would help to see where your lamp is connected -and that push-switch...

Remove the three large screws holding the chassis (bells, capacitor, induction-coil) in place, and gently lift it out if the case. Trace the source of the wires from the lamp and extra switch, and report back.

[Tom_I]

The annotations on the diagram are in Portuguese.

I'd agree that the lamp and switch don't look original. The switch in particular looks as if it's not quite centrally mounted, compared to the logo on the top panel.

[Darren-UK]

I've lightened the first image from post #8 and attached it hereto.

I'm not sure if it's the switch that isn't centrally mounted or the logo. I presume the logo is a stick-on effort? The position of the lettering on the logo doesn't appear to be horizontal, suggesting it's either moved (post application) or was crudely applied from the start.

The lamp appears to be too big and thus overhangs the edge of the casing. I therefore can't see the lamp being factory fitted, be it in Portugal or wherever.

Even though the switch isn't in line with the two chromed buttons in the cradle, it's difficult to see how the handset can be replaced without it fouling the switch. I guess the handset can be correctly replaced though and it's just an illusion of the image.

Personally I'd de-eyesore the instrument and try to restore it by filling and disguising the holes, but then the modifications (which clearly aren't original) have removed most of the instrument's value - restored or as-is.

[russell_w_b]

Originally Posted by Tom_I

The annotations on the diagram are in Portuguese.

In that case, the instrument will have been manufactured by 'Automatica Electrica Portuguesa' (AEP). I rather thought the badge looked to be moulded into the bakelite, like the 'GEC' is on the back of my GECophone.

[wheresthetubes]

Hello,
carefully lifted the internals out to discover that the wires that should have lead from the bakelite switch and the lamp have been snipped at source. So I removed the lamp holder. There are 3 lugs; one central and the other two lugs are either side of this one.

My intention is to replace the old bulb with an led. The only problem I'd encounter here is finding an led that will fit into the old bulb holder as it takes the old style bulbs with the lugs that twist into place. Can anyone advise what rating the led would need to be??

Of course the second problem is figuring out how to re-wire the bulb back into the circuit. I've posted a pic of the circuit... could anyone advise which lugs on the bulb holder I'd have to solder the wire(s) to, I'm assuming its the central lug, though it looks like there were originally wires connected to all three lugs on the bulb holder. I'd also need to know where the wires would need to connect into the circuitry.

I'm content to leave the brown bakelite switch disconnected, I'd just like to get the lamp flashing to indicate internal calls.

I've not undertaken this type of challenge before, but I'm absolutely sure that with a bit of help from you chaps I'd get this done.

[davidw]

Does that bulb have any markings on it? It looks with like a neon to me, I can't enlarge it enough to see a filament but the two uprights resemble the electrodes of a neon.I stand to be corrected on this!

[wheresthetubes]

Yes, bulb has 'Hivac England 7L' written on it, have included two pics. Thanks.

[AndiiT]

Originally Posted by wheresthetubes

.......My intention is to replace the old bulb with an led......

Hi,
Personally I wouldn't replace the bulb with an LED as it would be a little more difficult to get this to flash on an incoming call.

The lamp in your phone certainly looks like a neon and should be able to be made to flash, in conjunction with the bell, in sympathy with the incoming ringing cadence by connecting the lamp, via a suitable series limiting resistor (something in the region of 100K to around 220K should suffice), in parallel with the bell coils .

Looking at the diagram for the 332 telephone your lamp (and resistor) should be wired between T12 and T2 on the phone terminal board.

Depending on the type of switch that is fitted (i.e. push to make or toggle on/off) you might want to utilize this to either switch the neon or bell in or out of circuit.

Regards
Andrew

[russell_w_b]

Originally Posted by wheresthetubes

'My intention is to replace the old bulb with an led.'

I don't know how far from the exchange you are, but the distance will affect your plan.

For a REN of just under 1 (3300R resistor in series with 1000R bell-coils), I get a ringing current of 9mA at 43V RMS. For a REN of 4 (original configuration, 3300R strapped OOC, I get a ringing current of 16mA at a voltage of 34V RMS.

So that's what you have to play with if, like me, you live over 6km from the exchange (as the wire goes). Of course, you'll need to run your own tests...

Telephone type 710.
AVO 9 II

I would stick with the neon and follow the advice offered in the threads on neon handsets.

[wheresthetubes]

Thanks Andrew, I've included pics of the terminals to bulb holder, telephone circuit board, and hand-drawn diagram including your instructions. Can you advise if I'm understanding you right according to the diagram I've made, in particular where I have placed the resistor (in line with the live terminal on the bulb holder from T12). I'm assuming this is where it should go, as opposed to being in line between T2 and the other lug on the bulb holder.

Also, I was going to start with a 220K resistor, and if the lamp does not light then I try a 150K, and if still no joy then a 100K, have I got this right??

Many thanks in advance for the advice, best regards.

[davidw]

Definately a neon so what you are suggesting in your diagram is exactly right. I can't recall what resistance we used to use (post 5 above) but you can't hurt anything by experimenting with values as suggested by Andrew.I have a feeling you may have to go to a lower value,but try it and see.
If you have a suitable variable resistor to hand you could try it at various settings to get the best results then substitute a fixed one of the measured value.Have fun.
Regards.

[AndiiT]

Hi,
As David has already mentioned your diagrams are correct although I wouldn't recommend using a variable resistor to determine the correct resistance value as if you accidentally set it to to lower "experimental" value you are at risk of damaging the neon and I suspect that a replacement bulb of that type might be a little difficult to source these days.

In practice it doesn't really matter whether the resistor is in series with the lamp and T12 or T2(1) as long as there is a series resistor fitted.

If you haven't already done so make sure that you have fitted a 3k3 resistor between straps T1 - T2; in this case you must connect one end of the neon to T1

Regards
Andrew