Standard bulbs and LED replacements / alternatives

[The Black Adder]

Hi all.

I have a bulb out on my tape machine which are easy to replace.

It's a telephone slide bulb and is rated at 24v 50mA. Pic below.

I'm looking for a suitable LED replacement if possible, if not the olde incandescent are fine but with LED I can hopefully get coloured ones which might be nice :)

Any help would be great as RS have some LED ones but are I can't find any which are rated at 50mA.

Thanks
https://uploads.tapatalk-cdn.com/20180903/fe8097bcb2b0455d11fd62671dcbe644.jpg

[Firebottle]

Hi Josie. 50mA is a lot of current for an LED, particularly as newer LEDs become even more efficient.
50mA for a filament bulb is to be expected as their efficiency is abysmal in comparison.

If there are the slide type LED that is specified for 24V then go with that, the current won't matter.

[Primalsea]

Another option is to use a bog standard 5mm LED and a 1K Ohm, 1 Watt resistor. Connect the resistor in series with the LED. You might be able to mount the LED and resistor inside the old bulb so that it is a plug in replacement.

1K Ohm is not the exact figure, but it should be close enough. The resistor will dissipate approx. 0.6 watts and will get a little hot, so best go with a 1 watt.

[The Black Adder]

Ah... thanks guys.

Very helpful indeed :)

[spendorman]

At work, we used quite a lot of these bulbs, got them from RS Components. Might be useful if you decide against LED.

[Primalsea]

I just based it on the forward voltage and forward current of an LED datasheet that I found on Rapid Electronics. The actual figure was 750 ohm, but I rounded up. Would be much brighter than a filament lamp to be fair.

[Primalsea]

Why is it with LED torches that they don’t seem to produce much illumination but if you accidentally look at them straight on the glare seems almost blinding!

[walpurgis]

Why is it with LED torches that they don’t seem to produce much illumination but if you accidentally look at them straight on the glare seems almost blinding!

Are you kidding? ;) I have two compact LED torches that can light up the whole length of an industrial estate at night. They are wickedly powerful and you would certainly regret looking at one face on.

[Primalsea]

OK, not sure what you’re doing in Industrial estates at night but what torches do you have?

Although the batteries in mine seem to last a long time the light they emit is feeble and barely light up the end of the garden.

[mikmas]

This may be of interest - from a discussion on the DADA forum:

"The 303 is another story. The bulb here is a neon-lamp and hard to find. We usually replace it with a red square LED with a 12K serial resistor, connected to the 80V across the power-supply capacitor.
A 230V Neon-lamp can also cause noise in the input circuits...
See the 303 Upgrade / Revision manual for more information.

Stefaan"

http://www.dadaelectronics.eu/ForumRetrieve.aspx?ForumID=317&TopicID=47318