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Monday, September 1, 2014

Beomaster 8000: Replacing Indicator Light Bulbs With LEDs

I moved on to rebuild the display board of the Beomaster 8000. One of the four indicator light bulbs was broken. It is difficult to find appropriate bulbs these days, so we decided to replace all four indicators with LEDs to get this Beomaster ready for its big journey to Australia. LEDs are much more resistant to vibration and shock that can occur during transit.

Since LEDs have a much more directed emissions profile than light bulbs, it takes two LEDs to replace the light bulbs. I used generic 15 mCD, 2 V, 20 mA red LEDs made my Multicomp (Newark  14N9416). Two of them just generate about the same light output as one of the 80mA 6V bulbs that are originally used. Since the bulbs run at 5V, the two 2V LEDs needed a current limiting resistor to get them to run at 20mA. I used 47 Ohm 1/2 W resistors, which is what I had in stock. Smaller 1/4W ones would be o.k., too. Note that one needs to remove resistors R34, 36, 38, and 40 on board 8 to ensure that the LEDs turn off properly. Another interesting question was whether the Clipping indicator would still work properly after this procedure.

I made a short video about the entire project where all aspects are discussed. Enjoy:

On to the LED displays!

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