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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 21st May 2017, 5:47 pm   #21
dazzlevision
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Join Date: Sep 2003
Location: Near Swindon, North Wiltshire, UK.
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Default Re: The 3.5V 150mA unobtainable bulbs

Unfortunately, that RS link states "discontinued product".
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Old 21st May 2017, 6:28 pm   #22
Boater Sam
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Location: Middlewich, Cheshire, UK. & Winter in the Philippines.
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Default Re: The 3.5V 150mA unobtainable bulbs

Had a couple of hours to play with this VHF80 and solved the scale light problem.
I have a reel of white SMD LED lamps, they are arranged in threes with their own regulator, for 12volt DC fed from the end. They can be cut into 3s, 12v applied, self adhesive with 3Ms tape.
I used 2 X 3 sections glued behind the light diffuser, shunted the existing 680 ohm resistor and Brimister with 180 ohm half watt resistor, 1N4007 diode in series, connected across the shunts.
That gave 11.6 volts AC across the shunts, 12.7 volts DC on the LEDs.
Plenty of light evenly spread, and the near correct 39.2 volts across the rectifier heater. Better than with the bulbs.
I'm happy with that, there is barely noticeable flicker, I tried a capacitor across but it made no difference except a slight voltage rise.
Job done.
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