why won't LED replacement bulbs work?

[ChattingLil]

we have a cabin light with a B15 fitting. It has one of those older style LED bulbs in - pentagon with 4 LEDs in a strip on each side and 4 in a square on the bottom. It's a glass lantern and the bulb is ugly and as some of the LEDs are failing, I though I'd get a nice pretty LED candle bayonet to replace it.

So far I have tried 4 different LED candle bayonet bulbs variying from the cheap as chips from china ones to the £20 from pukka supplier ones and none of them work. The old bulb continues to work.

The fittings look exactly the same and I've tried to examine them carefully to see if I'm missing something obvious, but I can't tell what.

Any idea why?

 

[sailorman]

LEDs wont work if the polarity is reversed

 

[maby]

I don't know much about LEDs, but could it be a polarity problem? The light emitting devices are certainly polarity sensitive - it would be possible for the manufacturers to build in a bridge rectifier style configuration of diodes to make the complete thing not polarity sensitive - not sure if that is the case for all devices.

 

[ChattingLil]

LEDs wont work if the polarity is reversed

I don't know much about LEDs, but could it be a polarity problem? The light emitting devices are certainly polarity sensitive - it would be possible for the manufacturers to build in a bridge rectifier style configuration of diodes to make the complete thing not polarity sensitive - not sure if that is the case for all devices.

but it already has an LED in it that does work..

 

[l'escargot]

Take the bulb that doesn't work out and rotate it through 180 degrees and put it back in again - it is possible to put LED bulbs in "the wrong way round".

 

[LadyInBed]

Check the circuit connections.
Is it pin to pin, pin to case, either pin to case, is the case common to one pin.

 

[ChattingLil]

Take the bulb that doesn't work out and rotate it through 180 degrees and put it back in again - it is possible to put LED bulbs in "the wrong way round".

thanks - I have tried that. Still doesn't work on any of them.

Check the circuit connections.
Is it pin to pin, pin to case, either pin to case, is the case common to one pin.

Sorry, I'm not sure what you mean by that? The fittings look EXACTLY the same.

 

[Steve Clayton]

Go here and use the side link to have an online chat with the experts

http://www.ledhut.co.uk/led-bulbs/b15-small-bayonet-cap.html

 

[lw395]

Hi Lil,
The bayonet fitting is used for both 12V DC car bulbs and mains.
The new fittings you have could well be mains?

The 12V ones sometimes need to be the right way around as others have said.

 

[Steve Clayton]

Hi Lil,
The bayonet fitting is used for both 12V DC car bulbs and mains.
The new fittings you have could well be mains?

+1; just done a looksee at a couple of sites and B15 leds - all are 240v,

eg: http://www.ledconnection.co.uk/led-light-bulbs/b15-fitting/sku-108.html

 

[maby]

but it already has an LED in it that does work..

But as I say, the light emitters are fundamentally polarity sensitive but it would be easy to design in polarity insensitivity - could it be that the original LED is happy with whatever polarity it is seeing, but your new lamp is not?

 

[BERT T]

Most B15 or sbc led candle lamps that I have seen are designed for use on 230v ac so will not work on 12v dc.

 

[ChattingLil]

thanks everyone. This has given me much more to go on.

 

[jwilson]

Take the bulb that doesn't work out and rotate it through 180 degrees and put it back in again - it is possible to put LED bulbs in "the wrong way round".

I think you'll find that turning round a bub in a B15 fitting wont swap the polarity.

 

[BERT T]

The closest lamp I can find is BA15D-15LB from Bedazzled.
http://www.bedazzled.uk.com/12v_LED_Bulb_Replacement.htm#BA15Dtype

 

[l'escargot]

I think you'll find that turning round a bub in a B15 fitting wont swap the polarity.

Are they not twin pin then? If that's the case the polarity on the fitting would have to be changed but then that wouldn't explain the other bulb working unless you can get bulbs with both polarities?

 

[Adrian Jones]

we have a cabin light with a B15 fitting. It has one of those older style LED bulbs in - pentagon with 4 LEDs in a strip on each side and 4 in a square on the bottom. It's a glass lantern and the bulb is ugly and as some of the LEDs are failing, I though I'd get a nice pretty LED candle bayonet to replace it.

So far I have tried 4 different LED candle bayonet bulbs variying from the cheap as chips from china ones to the £20 from pukka supplier ones and none of them work. The old bulb continues to work.

The fittings look exactly the same and I've tried to examine them carefully to see if I'm missing something obvious, but I can't tell what.

Any idea why?

Surprisingly, it is quite difficult, in my experience to find a candle shaped SBC (BA15D) 230V lamp . I think it might be because 230V lamps normally have a large ceramic or aluminium heat sink and the extra weight may be a problem. Most candle lamps are supplied with an E14 screw lamp base. So it's unlikely to be a mains lamp.

A common issue is that customers sometimes purchase lamps with the wrong type of lamp base, so it's always worth checking the contacts on the bottom of the lamp that's not working and the lamp holder. Using a BA15D lamp in a BA15S lamp holder results in no light!

If that's not the issue I would be interested to know where you sourced your lamps from and how the vendor described them.

Regards

 

[nigelmercier]

... Using a BA15D lamp in a BA15S lamp holder results in no light!

And using a BA15S lamp in a BA15D lamp holder results in a lot of light, very briefly, accompanied by a loud bang!

 

[LadyInBed]

Check the circuit connections.
Is it pin to pin, pin to case, either pin to case, is the case common to one pin.

Sorry that isn't as clear as it could be.
By 'circuit connections' I mean the connections on the lamp base.
Which pin is + battery, is the other one - battery. Is the lamp holder case at - battery or not connected.
Then compare that to how the bulb is wired.

 

[William_H]

I would have instinctively checked the new bulb on 12v with wires to a battery. That woulld have proven a point if it was designed for 240v operation.
The whole issue can be confusing. Some 12v LED designed to replace the reflector halogen down lights have a bridge rectifier so they will run off 12v AC which also means they will run on 12v DC either polarity supply. They have the thin pins like a halogen bulb. Similar shaped reflector bulbs with fatter pins with a mushroom end are for 240v operation.
As said the B15 is a designation for small bayonet connection 240v AC mains lamps. This happens to be similar to 2 pin 12v bayonet lamp sockets. So Op needs to check what he has been supplied with by way of voltage rating.
Incidentally (fred drift) I have found the Chinese like to supply 230v AC lamps with many 60 or so small LEDs. These are replacements for old incandescent light bulbs.
They use a very crude rectifier that feeds all the LEDs in series or some times 2 strings in series. Any failure of a single LED will ruin the bulb. The other trap is that they are described as 230v AC they are not suitable for 250VAC the higher voltage giving shorter life. I think 230v AC is quite rare certainly here in Oz it is all 240/250v depending a bit on how far along the line you are from the transformer. So I would only recommend types with just 3 or 4 high power LED tha tuse a switching circuit which gives the correct current to the LEDs. good luck olewill