Adding C4S boards to a FPIII

[arveedub]

I have some old C4S anticipation upgrade boards from a FPII that I'd like to use to load the CF stage in my FPIII. I was hoping that somebody could check my math on the values for R1 and R2.

The FPIII's B+ is 150V. In order to bias the LED's to 1mA R2 would need to be 150K. I should use at least a 1/2W resistor.

As near as I can tell, the FPIII's CF passes 3.4mA. This should give a value around 300R for R1.

Am I correct on any of this? Thanks!

 

[Paul Joppa]

Yes, we use 150K for R2. We use 237 for R1, which is about 3.8mA with the current HLMP-6000 LEDs. The older LEDs would take a bit more resistance, so 300 is a good starting point. It's not too sensitive for the CF load.