Very OT - Anyone have experience using LEDs for meter backlighting?

[Tom Hammond-2]

PLEASE REPLY OFF-REFLECTOR...!!

I'm undertaking a project to replace the much too costly tiny plug-in meter
lamps in my Alpha 76 amp with a PC board 'light bar' using LEDs.

So far, I think I've determined that LEDs with diffused lenses will probably
be too dim, not illuminating the meter scale adequately, and I've certainly
determined that hi-output clear lens LEDs create a 1/2" 'spot' on the meter
scale unless a semi-opaque filter (even a sheet of typing paper) is inserted
between the LED and the back of the meter.

The LEDs will be about 3/4" behind the meter scales, so I don't have a lot
of spacing to work with.

Anyone who has had success (or failure) with trying to do something similar,
I would appreciate hearing from you OFF-REFLECTOR.

I'm about to place an LED order with Mouser Electronics, but if you can give
me some "BUY" or "DON'T BUY" suggestions, I'll certainly take them to heart
BEFORE I place the order.

Thanks,

Tom   N0SS

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[Nelson Moyer]

Order replacement panel lamps from Mouser at $0.58 each (a couple of years
ago), part number 606-CM85 (if your Alpha 76 uses the same bulbs as my Alpha
78 and I'm pretty sure it does). I replaced all four lamps in my Alpha78 for
less than the price of just one lamp from Alpha, including shipping! You're
right - they're ridiculously overpriced at Alpha. Be careful if you have to
remove the green and amber rubber boots from the old bulbs. They get brittle
with heat and split easily. I lucked out and was able to reuse all four of
mine, and my amp is 26 years old.

Nelson, KU0A

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Tom Hammond
Sent: Wednesday, August 27, 2008 1:55 PM
To: [hidden email]
Subject: [Elecraft] Very OT - Anyone have experience using LEDs for meter
backlighting?

PLEASE REPLY OFF-REFLECTOR...!!

I'm undertaking a project to replace the much too costly tiny plug-in meter
lamps in my Alpha 76 amp with a PC board 'light bar' using LEDs.

So far, I think I've determined that LEDs with diffused lenses will probably
be too dim, not illuminating the meter scale adequately, and I've certainly
determined that hi-output clear lens LEDs create a 1/2" 'spot' on the meter
scale unless a semi-opaque filter (even a sheet of typing paper) is inserted
between the LED and the back of the meter.

The LEDs will be about 3/4" behind the meter scales, so I don't have a lot
of spacing to work with.

Anyone who has had success (or failure) with trying to do something similar,
I would appreciate hearing from you OFF-REFLECTOR.

I'm about to place an LED order with Mouser Electronics, but if you can give
me some "BUY" or "DON'T BUY" suggestions, I'll certainly take them to heart
BEFORE I place the order.

Thanks,

Tom   N0SS

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