I'm trying to get an LP120 DLP projector working with an LCD bulb (not worried about the loss of brightness as will be using it for controll purposes , not watching movies)

I managed to trick the projector using a 100 ohm resistor insead of a bulb but , it heats up super hot and eventually melts after about 15 mins so would like to trick the projector using some other method.

Anybody had any luck at doing this?


Thanks.

Can you take some photos of the ballast ? There have to be some wires connected to the controller board.
sometimes it's just a matter of connecting the detection wire to ground sometimes you have to bridge a photocoupler.

Heres some photos for you. Hope this helps.

http://www.flickr.com/photos/51328142@N00/

cheers

Gav

On the power supply next to the connecter you will see 3 white IC packages with 4 legs. These are the opto-isolators that protect the smarts from excess voltage. They’re basically a light sensitive transistor and an LED all in the same package. The function of each opto is: on/off, high/low and lamp lit. Two of the optos will receive a signal from the main board (on/off, high/low) and the other will send a signal (lamp lit). Lamp lit is the one you will be interested in.


Looking at this, I’d say that pin1 (first line) is lamp on but this is the best guess I can do without actually tracing the circuit myself. With the connector unplugged, fire the projector up and see if there is a voltage (3.3v) on pin 1 of the main board, not the power supply. If it is close to 0v then It would be reasonably safe to short this pin to gnd or maybe try it first with a 100 ohm resister just in case.
Do this at your own risk!

DJ

Without warranty

http://www.flickr.com/photos/51328142@N00/2328876632/

the ICs on the left side are the optocouplers you are looking for. Usally there are 2 facing in one direction and one in the other. Only the one in different direction can send signals to your mainboard. Usally there is a mark, like a circle or something on them. (from the picture i would say it's the highest)
So find that IC and trace the circuit to the connector. When you find the wires just short those two.
Possibly there are some other saftey features, like a light sensor or a switch that ensures the case is closed, in your projector. You may have to bypass those too.

And be aware that there can be high voltages even if the projector is switched off, when working on the PSU or something.

I tried this an unfortunately it didnt work. I identified the correct OC as it was the other way around and both the leads from the non-diode end conencted to pins 1&2.

Could there be something telling the projector to wait for a signal at a precise time or something? If I fire it up with a bulb, its lights after exactly 14 seconds, the same as with a 100 ohm resistor. If I fire it up with nothing , then after about 10 seconds it says, failed to light bulb. retry in 10 secs.

Hmmm.. This is doing my head in!

Cheers

gav

hmm...strange. But i never heard of a specific timing. Have you reconnected all fans ? Without them the projector won't start eighter.

Maybe you should post your problem in the german community (www.diy-community.de). There are very experienced ppl when it comes to modding commercial projectors.
Most of them understand english too. Maybe with a better close up picture of the ICs.

Thanks for the link, I tried to subscribe, but its in German and I've given up trying to understand the google translated error messages I keep getting.

I posted some new pics of the optos on my PJ here, if you wanna have a look.

http://www.flickr.com/gp/51328142@N00/8720f2

cheers

Click to view attachment

i would bridge those contacts. The projector should start without the lamp.
If it doesn't start there might be another sensor, like a light sensor in the light path, which have to be bridged too.
again without warranty

I'm having the same struggle with my LP530. After bridging the opto-coupler that leads to the "lamp lit" pin (pin 3), it still won't produce an image. The color wheel will continue to spin once bridged, but it will not pass an image. I still have the (semi) functioning lamp. Ironically, the entire projector works normally with the lamp plugged in despite the bridged coupler. I have to agree, there seems to be an additional light sensor checking the lumenocity of the lamp. I can find no other communication path between the ballast and the main board. I think I will start playing with stronger, independant light sources...

The only other alternative is that some pin changes voltage briefly to signal the controller board in addition to the lamp lit pin going high to 3 volts... If it does, my simple DMM hasn't shown it. HELP?!

This thread has been dead for over a year, so I'm closing it.