Replacement Keyboard LEDs

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jonwarby
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Replacement Keyboard LEDs

Post by jonwarby » Mon May 20, 2019 9:43 pm

Can anyone please recommend some replacement LEDs for the keyboard for the Model B. I have just picked up a model B and it's missing an LED and has a broken key. I have managed to find a replacement keyboard switch on ebay and gone through the LEDs that I have but they aren't a good match, the red is quite different from the others when lit. I could replace all three but I would prefer to try and keep it as close to the original as possible and was wondering if anyone else had found a good match out there.

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AndyF
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Re: Replacement Keyboard LEDs

Post by AndyF » Mon May 20, 2019 11:17 pm

Welcome! :)

I can't personally say I'd noted much difference in them when on the very odd occasion I'd change one or two. Perhaps the 'new' one is correct and 'age' has effected the others ?

I don't think they age as such but I am thinking the 'yellowing effect' on the plastic casing of them, similar to how the case can 'age' , which would result in a slightly darker or tarnished output luminance perhaps.

Is the problem just that the new one is a bit brighter than the other two ? :)
Last edited by AndyF on Mon May 20, 2019 11:18 pm, edited 1 time in total.
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tom_seddon
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Re: Replacement Keyboard LEDs

Post by tom_seddon » Mon May 20, 2019 11:26 pm

The shift lock and tape LEDs stopped working on my model B about 20 years ago, and I only got round to finally fixing them this year. Just needed some dry joints resoldering - looked like all 3 LEDs are the originals. Of course, the caps lock LED has had a lot of use over the years. Shift lock and tape, perhaps not so much. And, indeed, caps lock is noticeably dimmer :(

My post at the time: viewtopic.php?f=3&t=16393&p=225879#p225879

At some point I'll probably swap caps lock and tape so that caps lock is nice and bright again. Can't see myself using tapes again.

--Tom

jonwarby
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Re: Replacement Keyboard LEDs

Post by jonwarby » Tue May 21, 2019 7:29 am

Thank you both for the replies. The top of the led has been picked off leaving just the two stalks. It could well be that the leds looked like this originally and have changed over time. Physically they are a good match just the colour of the red glow is noticeably different. I may swap the good cassette one for the broken caps lock led and fit the new led to the cassette if they look the same when off otherwise will replace all three.

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1024MAK
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Re: Replacement Keyboard LEDs

Post by 1024MAK » Tue May 21, 2019 7:53 am

LEDs do age, but only when used. That is, the more often they operate, the faster they age. As they age, the light output decreases.

In practical applications, red LEDs appear to age the most, but this is not a fair comparison, as red LEDs were more common.

Red LEDs are available with different wavelengths, hence there are different colour red LEDs. And modern red LEDs are more efficient than red LEDs from the 1980s. This means, for the same current, a modern LED will look far brighter compared to an old red LED.

If you want the best match, just renew all three.

Mark

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Elminster
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Re: Replacement Keyboard LEDs

Post by Elminster » Tue May 21, 2019 9:08 am

If you got new LEDs and ran them slightly over voltage 24x7 for a while could you 'age' them?

(Edit) i.e. artificially aged them and then solder into Beeb.

@Mark. Your signature is getting longer and longer .....
Last edited by Elminster on Tue May 21, 2019 9:10 am, edited 2 times in total.

beeboldie
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Re: Replacement Keyboard LEDs

Post by beeboldie » Tue May 21, 2019 10:55 am

LEDs are cheap enough - just replace all three. Not only brightness will be different but also the actual colour (as mentioned previously in this thread). I could never get old and new looking the same in a panel that I had to fix - in the end I replaced the lot (OCD cutting in!)

Don't get the high brighness ones though - they are really bright :-)
Make sure you get the standard brightness 5mm diffused.

Regards

Grant
Last edited by beeboldie on Tue May 21, 2019 10:56 am, edited 1 time in total.

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1024MAK
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Re: Replacement Keyboard LEDs

Post by 1024MAK » Tue May 21, 2019 3:05 pm

Elminster wrote:
Tue May 21, 2019 9:08 am
If you got new LEDs and ran them slightly over voltage 24x7 for a while could you 'age' them?

(Edit) i.e. artificially aged them and then solder into Beeb.

@Mark. Your signature is getting longer and longer .....
Yes, you can artificially age them, but in doing so, you are damaging them... Who knows how long they will last then...

Ahh, you mean it’s not long enough yet :mrgreen:

Mark
Last edited by 1024MAK on Tue May 21, 2019 3:06 pm, edited 1 time in total.

jonwarby
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Re: Replacement Keyboard LEDs

Post by jonwarby » Fri May 24, 2019 12:11 pm

Thanks all for the replies. Worked on it last night. Got some new LEDs that were a bit closer to the originals and went with moving the cassette LED to the CAPS LED and fitting a new one on the cassette LED. Pleased with the result, it looks a lot happier now.

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