What resistor?

What resistor shout i use for my Iset/RSet on my 8x8 matrix using a MAX7219, I know i should use the table below, BUT i dont have a data sheet for the LEDs (very bright blue)

ISeg 1.5V 2.0V 2.5V 3.0V 3.5V
40mA 12.2k[ch937] 11.8k[ch937] 11.0k[ch937] 10.6k[ch937] 9.69k[ch937]
30mA 17.8k[ch937] 17.1k[ch937] 15.8k[ch937] 15.0k[ch937] 14.0k[ch937]
20mA 29.8k[ch937] 28.0k[ch937] 25.9k[ch937] 24.5k[ch937] 22.6k[ch937]
10mA 66.7k[ch937] 63.7k[ch937] 59.3k[ch937] 55.4k[ch937] 51.2k[ch937]

gave it a go with resister value 22k[ch937], that seemed to work with my 7-segments, but when i upload the sect 90% of the LEDS come on and stay on???

With a multimeter, you can essentially reverse-calculate the important specs for the LED. Make a simple circuit (LED, resistor, 5v DC) then test current and voltage drop across the LED. Test for a couple resistor values until you find something you want in terms of brightness and power, then use the voltage drop and current readings you get from that resistor in your chart. If it’s a typical 5mm LED you might start at 1k ohm and test a few points down towards 200 or 300 ohm.

I’m pretty new to this whole microcontroller scene and have never used a max7219, but can you post your code? I would imagine that getting the wrong resistor values would just alter brightness, not operation.

26K worked well for me with the 8x8 RG “medium” matrix from Sparkfun.

yep switch to a 26 and is working well apart from some dead spots http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1250717714