My icr8500 display lights,two are dim,and two are bright,I guess it would be easier if they were out altogether,but why are they dim,and why only two of them,does this tell me that if I replace the two dim bulbs,with new they may still be dim,can’t understand why they are dim and not out altogether,thanks for any help.
Ic-R8500
- Thread starter Frantob2
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That's odd. The service manual shows three of the back lights wired in parallel with each other and the forth has a 10 ohm resistor in series with its negative lead. So they should all be equal brightness unless someone else changed a couple of them or part of the PCB trace that feeds them has failed partially but I'd think that would be really rare.
The positive leads are all tied together. I think the one with the 10 ohm resistor is the one in the meter and the other three are the main LCD display panel.
My bet is someone changed some of the lamps before you got the radio and didn't use the correct part so they are uneven.
The original lamps are typical grain of wheat lamps but I don't know their voltage or wattage or current draw. You would need to open the radio and set the back lighting to its brightest level and then measure the voltage across the three behind the LCD. That will give you the lamp voltage you need if you go back with tiny grain of wheat lamps plus if you measure the voltage on all three, make sure it's the same on all. If not, inspect the copper traces feeding them for a bad solder joint. Possibly at a thru hole on the front panel board.
I've seen where some owners replace them with LED's but I don't remember any part numbers. They usually had to diffuse the LEDs by sanding them a little bit to smooth out the light output so you don't get bright spots.
I don't think it was a hard modification to make switching to LEDs. Or you should be able to still get the tiny grain of wheat lamps by measuring the supply voltage to one of the three wired in parallel. Get four of the same value and replace them all.
My R8500 is shelved and not easily accessed otherwise I'd open it up and try and get the values for you. I don't recall ever needing to replace the back light lamps in mine but it's been quite a while since I'd last used it. Eventually I'll get it hooked up again when I make room for it.
The positive leads are all tied together. I think the one with the 10 ohm resistor is the one in the meter and the other three are the main LCD display panel.
My bet is someone changed some of the lamps before you got the radio and didn't use the correct part so they are uneven.
The original lamps are typical grain of wheat lamps but I don't know their voltage or wattage or current draw. You would need to open the radio and set the back lighting to its brightest level and then measure the voltage across the three behind the LCD. That will give you the lamp voltage you need if you go back with tiny grain of wheat lamps plus if you measure the voltage on all three, make sure it's the same on all. If not, inspect the copper traces feeding them for a bad solder joint. Possibly at a thru hole on the front panel board.
I've seen where some owners replace them with LED's but I don't remember any part numbers. They usually had to diffuse the LEDs by sanding them a little bit to smooth out the light output so you don't get bright spots.
I don't think it was a hard modification to make switching to LEDs. Or you should be able to still get the tiny grain of wheat lamps by measuring the supply voltage to one of the three wired in parallel. Get four of the same value and replace them all.
My R8500 is shelved and not easily accessed otherwise I'd open it up and try and get the values for you. I don't recall ever needing to replace the back light lamps in mine but it's been quite a while since I'd last used it. Eventually I'll get it hooked up again when I make room for it.
I have replaced my R8500 incandescent bulbs with LED's. I bought a big lot of 12v color LED's and wired them in parallel, connecting them to the power connector for one of the lamps. I tried a couple different colors and preferred the green. They work great!
See this thread for a great discussion of this: R8500 Dial Light replacement
See this thread for a great discussion of this: R8500 Dial Light replacement
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