Digital Ballast Bypass Expirimenting

[Andrew Eckhardt]

It's hard to say whether the existing circuit (without seeing it) wouldn't have any problems at such a low duty cycle, even at such reduced power.

*second edit*: Well, depending on what you fed from the original ballast board it wouldn't need to run out of normal range anyway..

Do you intend to use HID or LED, and are you thinking of using the existing board as the only ballast, or having it feed another one with input voltage dependent output?

I think the LED ballast would be much simpler, not even any starting mode.

[Andrew Eckhardt]

With optics and firmware designed for filament illumination, would it be difficult to get the right color balance with an LED source?

[crazifunguy]

Originally Posted by Andrew Eckhardt

With optics and firmware designed for filament illumination, would it be difficult to get the right color balance with an LED source?

From the LED mods I have done this really doesnt seem to have any effect. The optics are happy as long as they get light. The origional lamp was Metal Hallide not filament.

[gmzombie]

just curious as to which projector you used for this mod? im very interested in this to say the least.

[crazifunguy]

Check out some of my other posts or see projectionforums.com where all my future projects will be..

[jeevs]

Originally Posted by crazifunguy

Well I managed to get a copy of the "Holy Grail" for this projector....AKA the service manual. Its funny that you were talking about using a PIC to communicate with the ballast. This projector uses a PIC to control all ballast functions.

After studying the schematics and trouble shooting. I figured that the Lamp_Err signal coming out of the PIC was the place to start. This signal is around 70mV and jumps to 5V when a lamp error is detected. This signal is sent through a buffer IC then to the main processor.

http://www.fairchildsemi.com/ds/74%2F74LCX541.pdf

By cutting the trace from the pic to the buffer and connecting the buffer pin to the buffer ground the projector stays on....

SUCCESS!! So far anyways. I havent tested for more than 2 minutes. I dont know what repeated errors will do to the pic or any other part of the circuit.

Dear crazifunguy, were you able to achieve full success with the digital ballast bypass? I have a ballast that is quite similar to the board you have shown in the pictures. It is in the infocus x10 projector. simple grounding and shorting or resistors havent worked so far. Please help.