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president madison green display

bioman

Active Member
Nov 13, 2005
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reading,pa
my madison has a dead segment in the display LED so i plan to replace it with a green one to match the clock

will i need to change the resistors on the board to be combatible with a green display since it currently has a red one in it/?

i know the regular green 5MM LED lights want 2.2V but am not sure aboiut the displays and id hate to ruin the new one

thanx
scott
 

i see what you mean

i had thought that maybe green LEDs would want a different voltage than the red ones .....

changing the resistors to a different value would give a different voltage correct?
 
Yes. A larger resistor would drop more voltage across it there for affecting the final voltage of the circuit. Not enough to be noticable unless a large change was made to the resistor.

For example I was experimenting with my 13.8V power supply and a diode trying to dim it. when i put a 50 ohm resistor in series with the diode it only dropped the voltage going to the diode to 13.7V. A tenth of a volt wasn't noticed in my experiment, but it gave me a base line to work with. I now know that i need a 500 ohm or greater resistor to drop my voltage by 1 volt.
 
ok so it shouldnt make a difference in spots where a LED already was such as on the channel display and and the lights for AM/LLSB etc.....

i know i will need resistors where i replace the 12V bulbs behind the meters to make them light up green as well but i DO have a calculator for that so i'm good there

i have the LEDs and the display just need to stop at rat shack on the way home to get the resistors i'll need to run 2 LEDs in series where there WAS 12V bulbs

i'll put up pics after is done

thanx for the help

scott
 
formulamojo,

the reason that resistor in series with the power supply only dropped the voltage by .1 volts is because you did not have a load on the supply.
that series resistor will act very differently when a load is applied.
(resistor placed across positive and negative)
LC
 
formulamojo,

the reason that resistor in series with the power supply only dropped the voltage by .1 volts is because you did not have a load on the supply.
that series resistor will act very differently when a load is applied.
(resistor placed across positive and negative)
LC

I know, I was trying to explain voltage drop to him. To answer his question.

They did teach me a thing or two in college where I earned a degree in electronics, :LOL: But a newbie doesn't want to be bored with theory.
 
the "kit" comes with the display and one LED

i needed the display and 4 LEDs for AM/LSB/USB/CHAN9 on the madison PLUS i wanted to put green lights on the meters

the channel display is in and looking nice i just need to wire the LEDs for the meters and it is done but alas i leave for work momentarily
 
thanx 74 ......

i already have a calc for the resistors and plan to pic them up at radio shack on the way home.....

now if i could just find a clock motor for that radio.....
 
ok after playing around with a bunch of resistors i had got from radio shack and some more out of my "parts" bin i just couldnt find the level of "brightness" i was looking for so i ended up tying the ground and the 15.2V sources from the original 2 lights together in parallel and ran 6LEDs in series .....PERFECT!!

i set them up in a triangle behind each meter so ive goot a nice green glow coming off of each one

after it gets dark ill take some pics and throw them up

scott
 
zzz018.jpg



zzz021.jpg


as promised pics of the green

pics came out kind of crappy.... with the flash it was too bright and without was too dark and i havent really figured out how to operate this camera yet

everything came out nice and bright with the exception of the lights behind the clock....

IF i keep the clock in it i may end up going to white LEDs behind it since the light has to filter behind green numbers

the clock in it does not work <needs a motor> and if i cant find a motor for it i think i'm going to tear down a freq counter and install that in the window..... a green LED one of course

scott
 

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