Rather than modifying the internals of the PSU to support analog modulation directly, what would prevent you from mounting a power mosfet right at the output of the existing PSU and using that to give you analog modulation? (You could build a voltage divider to knock down the zero-to-five volts of the analog blanking signal to somthing more reasonable - say, zero to 1 volts - and then apply that to the gate of your mosfet.) [/qoute]
Good question., Might be where we will end-up at ..
At first look , it looks easy depending on the original setup of the board.
Some are not so easy or have no room inside.
Right now I have built a driver using a video op-amp and an mosfet for a TTL green laser and trying to avoid hacking up the original supply..(this is for Astroguys unit).
works well..needs to be mounted to a beefier heatsink..but I think I will prolly also have to use an external 5v supply as the one included in his old supply is iffy.
Dunno yet.. still tuning ..to me it seems like it would be all to easy to blow up the diode by overcurrent
if the setting are not just right. seeing that I dont know what the original current draw is for the head unit which I dont have ..I will have to make a guess what that diode needs..
This board I made is capable of doing a few amps easy.
I did this so that later on..we all could maybe convert more of these units to analog without too much
inside intervention and have plenty left over.
Also, I the circuit I have is very linear ...smooth transitioning and fast.
[qoute]Heck, you could even bias the gate of the mosfet so that zero volts on the analog blanking line would drop the current down to just below lasing threshold, but would not completely kill it. That way you'd be in a better position to come back on at full power quickly. (Limit the blanking-induced power loss!) To complete kill the diode just hook the shutter control to the TTL blanking line on the PSU itself.