Emu XL-7 & MP-7 User's Group

Swapping LEDs is probably not going to work. Different LED colours have 
different forward voltage drops and blue LEDs tend to require a larger forward 
voltage drop than most. A typical LED has a forward voltage drop of around 1.2 - 
1.8 volts, whereas blue LEDs often have forward voltage drops of 2.5 to 3.1 
volts. If you merely replace the LEDs you probably won't get enough current to 
get any useful backlighting. Also blue LEDs often require a higher current to 
generate the same luminosity as other LEDs.

Probably [I haven't checked] the backlight input requires 5Volt (or possibly 
3.3Volts) and in that case there will be a current limiting resistor which will 
be too large a value. You would need to find and replace the resistor(s) with 
smaller value ones. Alternatively, some LCDs just provide access to the anode 
and cathode of the LEDs for backlighting and you need to provide some surrent 
limiting of your own. In this case you will need to find that circuit (perhaps 
only a resistor) and modify it appropriately.







________________________________
From: Atom Smasher <atom@...>
To: xl7@yahoogroups.com
Sent: Wed, August 25, 2010 10:00:30 PM
Subject: Re: [xl7] modding LCD ?

  
On Mon, 23 Aug 2010, James Ulibarri wrote:

> I want a BLUE unit to go with my PX-7.  But it's impossible to find a 
> unit that is 14 pin.  I talked to Chrsystal Fontz today and their tech 
> said you probably could use this one, At this point this won't work.
==================

i've done a fair bit of backlight modding, and if it was me, i'd try to 
find a "drop in" replacement of any color, then just swap the LED(s). but 
i'd do it on the spare, or at least have a spare on standby.

personally, i find green LED backlit LCD much easier on the eye's than 
blue LED. the K5000 is a nice blue, but that's EL, not LED.

-- 
...atom