Help In Identifing These Bulbs

[xxxxxxxxxxxxxx]

Hi, just got an old radiogram and fixed it up so its working again. But, the thing is I have these (attached) bulbs from the power indicator and illumination for the front panel. Now, the odd thing is that they seem to be coated in a metalic-looking substance which is not conductive from the OUTSIDE. It would make sense to coat it from the inside anyway. The substance that coats the tops of them is visually identical to the stuff that coats the tops of the old electronics valves. These bulbs are rated at 6.3v at 0.32A and made by Philips. They are not currently functional, so I cant say wether or not the substance it to change the colour of the light.

Any help her would be appriciated. Thanks

 

[things]

they could just be normal bulbs. some bulbs have that "black" stuff on them. is it on the inside or outside? why not try powering one and see?

 

[mvs sarma]

they very much appear trnformer night lamps that work off 6 to 8 volts ac or dc with say 0.3to 0.5 amps current.
these were used in rdaios as dial illumination lamps in the days of valve radios.

witha 230 to 6 or 8 volts stepdown trnsformer, these bulbs were also used a panel mounted night lamps in olden days. Edison was a company supplying such assenblies.

Sarma

 

[xxxxxxxxxxxxxx]

Sarma, thats right they are from old valve radio illumination, what do you mean by "trnformer night lamps"?

Things- the black stuff appears to be metalic and is on the inside, im pretty sure. I would power one but both are blown. If you have ever seen the coating on the top of valves (like ones from an old radio) it is most definently that stuff.

 

[ThermalRunaway]

My feeling is that "the black stuff" is merely a result of use. In other words, the bulb went black over a period of time due to use of the bulb - perhaps it was getting very hot or maybe it went black after the bulb finally blew. If you were to buy new ones, they'd be completely clear.

If you're looking to replace the bulbs, you just need to buy ones that match the electrical characteristics printed on the bulbs you have. Any 6.3V, 0.32A bulb will work and your only consideration after that should be the physical size of the replacement bulb and it's fitting type. You don't have to stick EXACTLY to the electrical characteristics of your bulbs but obviously it's not recommended to use bulbs whose electrical characteristics are exceeded when in use. In other words, if you can't find a 6.3V bulb a 6.5V one would be fine but it's probably not recommended to use a 6.0V one. Same story with the current rating.

You could go a step further and mount white LEDs with a suitable current limiting resistor? Depends how original you want to keep the unit they came out of?

Brian

 

[xxxxxxxxxxxxxx]

Ok thanks, I want top replace them with something original, but I was considering some nice blue LEDs but that kindof spoils the old-ness of a set like Ive got. BTW, anyone who is seriously interested in buying it? If you are, Ill post some pictures..

 

[Hero999]

Now, the odd thing is that they seem to be coated in a metalic-looking substance which is not conductive from the OUTSIDE. It would make sense to coat it from the inside anyway. The substance that coats the tops of them is visually identical to the stuff that coats the tops of the old electronics valves.

Lol, that coating is formed by the filament evaporating and condensing on the inner surface of the bulb,

These bulbs are rated at 6.3v at 0.32A and made by Philips. They are not currently functional, so I cant say wether or not the substance it to change the colour of the light.

They aren't functional because the fillament is burnt out - it's coating the inside of the bulb.

Just buy an ordinary 6V 0.32A bulb or alternatively you might be able to replace them with LEDs which will only draw 25mA but that will depend on the design.

 

[mvs sarma]

Both Thermasl run away and Hero999 are verymuch right.
it is nothing more than carbom deposited after prolonged use.
vacuum failure can trun this back into whit ash color. so vaccuum is still holding. dirctly apply 6V or 5V from a batter or Power pack it will glow.

it was a typo In INdia we call it Transformer based low voltage bed light. Presently not being used nuch except in rural areas. it is an Edison tranformer 230 to around 6 or 8 volts with a current apability of .5 amps. and this bulb sits directly in a holder and connected to the Transformer and with a switch on the primary(Phase wire)
In fact the one with pin type holder is the so called bed light and the screw type is what is used in Valve radio receivers a s dial lamp and also you find this type bulb in lead-acid battery based hand torches with charging arrangement..

Sarma

 

[Hero999]

It isn't carbon, it's tungsten.

You're right, it will be white if the bulb failed due to the vacuum failing because the filament will oxidise forming a white power called tungsten oxide.

Even if the vacuum is still good it doesn't meen the bulb is, if the filament has failed (it has in this case) then it's totally useless.

 

[Bob Scott]

You can replace this bulb with an industry standard #46 bulb. The #46 is a T-3-1/4, screw base 6.3V, 0.25A. They used to be as VERY common for use as pilot lamps in radios as well as the #47 bayonet type. See here:

https://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&pa=209429&productId=209429

This standard bulb uses slightly less current than the Philips bulb. I always found Philips bulb currents to be non standard anyway.

OVer time, these will also develop the silvery coating on the inside of the bulb as they age. It does indeed look like the "getter" coating for trapping ions in a vacuum tube.

 

[xxxxxxxxxxxxxx]

Ok, thanks, I will probably replace them with just the same-spec bulb. Thanks for everyones help, though

 

[mvs sarma]

It isn't carbon, it's tungsten.

You're right, it will be white if the bulb failed due to the vacuum failing because the filament will oxidise forming a white power called tungsten oxide.

Even if the vacuum is still good it doesn't meen the bulb is, if the filament has failed (it has in this case) then it's totally useless.

ofcourse, if filament fails it is gone.
tongston costingon the inner wll due to prolonged use -- OK sir

Sarma