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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 15th Nov 2009, 12:01 pm   #1
'LIVEWIRE?'
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Question Type of IR diodes used in BUSH KB200 keyboard?

THere are 3 unmarked IR LEDs in this remote keyboard(used with the Bush Internet TV). What types should be used to replace them, and are they likely to be the cause of low o/p in this device, which is supposed to have a range of up to 10 metres, but will barely operate my IR Tester <1metre away, even with new batteries in both the keyboard and IR Tester? It will not operate the Internet TV at all, although the supplied remote control/keyboard does.
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Old 15th Nov 2009, 1:51 pm   #2
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Default Re: Type of IR diodes used in BUSH KB200 keyboard?

There should be an electrolytic capacitor close to the IR leds. This supplies the current for the leds which can be around an amp. The leds are pulsed so the mean current is small. This cap is charged from the supply via a resistor which cannot supply the required LED current if the cap fails. This is the same method used in IR remote controls.

Another method of checking for the IR output is to point a digital camera or a camcorder at the IR transmitter. These will show if the IR diodes are putting out light.

If the IR diodes are at fault I can let you have some suitable replacements FOC but check the electrolytic first.

Keith
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Old 16th Nov 2009, 1:53 pm   #3
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Default Re: Type of IR diodes used in BUSH KB200 keyboard?

Ther is indeed an electrolytic, Keith, which I was thinking of changing. It's a miniature 100uf 16v type. I have some new caps. of this type & value, so will try this first. but, in the meantime I have ordered some Vishay TSUS5400 950nm IR Emitters ftrom CPC, which should arrive tomorrow, so will use these if changing the caps. brings no joy. I must admit I hadn't thought about poinitng a digicam at the IR Transmitter, mainly because, if it will operate my IR tester, albeit at close range, I felt that meant that the diodes do radiate, but at reduced level.
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Old 16th Nov 2009, 11:12 pm   #4
Norman Raeburn
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Default Re: Type of IR diodes used in BUSH KB200 keyboard?

I am sure I have at least one of these remotes in my "spare remotes box" if it is of any use to you. Please let me know if you would like it. Norman
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Old 17th Nov 2009, 11:06 am   #5
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Default Re: Type of IR diodes used in BUSH KB200 keyboard?

There was little, if any improvement by replacing the 100uf/16v cap. with a 100uf/25v(The nearest I had!), and the IR LEDs haven't arrived yet, so, Norman, you have a PM
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Old 17th Nov 2009, 3:29 pm   #6
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Default Re: Type of IR diodes used in BUSH KB200 keyboard?

Is there a transistor driving the leds?. If there is nothing coming from the leds the driver transistor may be faulty or there may be no drive to the transistor.

Keith
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Old 4th Dec 2009, 7:55 pm   #7
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Default Re: Type of IR diodes used in BUSH KB200 keyboard?

Keith,
I have discovered that a PNP SMD Transistor driving one of the 3 LEDs is S/C between Base & Collector. It is marked either 58p or5Bp, not sure which. Any idea what would replace it?
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Old 4th Dec 2009, 8:17 pm   #8
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Default Re: Type of IR diodes used in BUSH KB200 keyboard?

I'll check on Monday at work when I can access appropriate data sheets but first thoughts are that it will be rated at 500mA to 1A collector current. It will be something like the SMD equivalent of a BC328. You could always try temporarily fitting a through hole transistor to prove the point.

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Old 4th Dec 2009, 8:32 pm   #9
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Default Re: Type of IR diodes used in BUSH KB200 keyboard?

To save your suspense it looks like it's 5Bp which is a BC807-25
http://www.datasheetcatalog.com/data...BC807-25.shtml

(58p references a BSR20 which is a high voltage device)

This site provides a useful guide to device markings
http://www.dl7avf.info/charts/smdcode/c5.html

Jim
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Old 4th Dec 2009, 9:43 pm   #10
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Default Re: Type of IR diodes used in BUSH KB200 keyboard?

Thanks, Keith and Jim. I assumed it was a BC828 or similar, but will check out those data sheets anyway. To be honest I had thought of fitting a through-hole device, (a) because it's easier!, and (b) because I have quite a lot of transistors, including, I'm sure, more than one type which would be suitable.
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