Fooling the Projector





Introduction: Fooling the Projector

I will try to give you a general idea how to fool the projector that was designed to squeeze some extra $$ out of your pocket. I will illustrate it with the pictures taken while I was fixing a certain projector but this model is rare and the idea I want to share with you is general. Sorry, it's not a real 'instructable'. I can't name the exact steps for your particular projector but the ideology will remain the same for any case.

Disclaimer - you are going to work with the device that has several dangerous components:
circuit board with live terminals, high-voltage power supply unit, pressurized lamp that can blow up if not handled properly. Think twice and take corresponding precautionary measures to avoid injuries and death :)

P.S. As you can see from the comments in some cases the old lamp may blow up.
I never faced with that myself and the bulb in my friend's projection TV is more
than 10,000 hours old but this "statistics" is not enough so  "forewarned is forearmed".
The safest (and most expensive) way to avoid this problem is ... to buy a new lamp but this
defies the purpose of this very instructable. The compromise is to study the construction
around the lamp and if it looks weak then one can install a metal mesh screen.
The design is up to you - it should have fine openings and at the same time it should
not hinder the cooling.

Step 1: General Ideas

Let's assume that you own a projector that says that its lamp is to be replaced.
There can be two reasons for lamp replacement:
1) The lamp really doesn't work because the electrodes are damaged or there was a leak and
the gas inside the lamp has mixed with air or the lamp has blown. These are the real reasons
and of course one has to put some light source instead of the one that got damaged. is full of various recipes for that. Surely, one can buy the original lamp for
$250-300 but it seems to be a bit overpriced comparing with a projector's cost :)
If you decide to follow one of the instructions from this site briefly read what is written
on the page "Bypassing the control module - 1" below. This will help you to use any light source
while the projector will keep thinking that a new lamp was installed.

2) The lamp is NOT damaged. It's the projector that thinks it needs to be replaced.
Moreover, it tries to convince you. If you remove the lamp and re-install it, it won't start. "How does it know that the lamp is old? May be it's really worn out?", you think and go to the store. Read the following pages to find out the truth :)

Step 2: Bypassing the Control Module - 1

In both cases described above the projector won't start since it somehow knows that
we try to fool it either by inserting a "wrong" lamp or by re-installing the old one.
How it can be? I can imagine two scenarios.

a) The hi-voltage module tries to ignite the
lamp, measures the current, compares with a certain value and produces logical "1" or logical "0"
on one of its outputs. The main board recognizes the signal and doesn't start. In this case one has to identify the signal wire that leaves the hi-voltage module and goes to the main circuit board. ATTENTION: the high-voltage wires are dangerous. You can easily tell them from the signal ones by the insulation type - it's thick and "different" (see the pictures: the white hi-voltage wires are definitely thicker than black and red power wires). This very projector doesn't have a signal wire that goes from the lamp power supply unit but some others do.
If you can identify this wire, try to figure out the logical voltages in your projector. Use a
voltmeter to test the voltages at some logical IC (find the one on the main board not on the hi-voltage board), search the Web for IC by its type and read about the voltages. Usually it is 0/+5V but double check that. Once the wire is identified one has to put the corresponding voltage to this wire to make the projector think that everything works as designed. Check the voltage on this wire with the voltmeter. If it is grounded, cut the wire and put +5V (assuming this is the logical "1" in your system).
If it is at "+5V", cut it and ground it.

Step 3: Bypassing the Control Module - 2

b) Imagine that the high-voltage power supply unit is not that sophisticated and it can't tell a working lamp from a non-working one. It always produces high voltage and goes through the same ignition
cycle once the Power ON button is depressed. Imagine also that the lamp is still operable but you can't
use the projector since 2000hrs have passed. You want to re-set the lamp counter but one has to
see something on the screen in order to do that (there's a corresponding menu item). It looks like a vicious circle.
The trick is that some manufacturers add a small (0.1A in the current case) fuse on the lamp housing (marked by red arrows on the pictures).
When the 2000hrs period has passed the projector sends a short pulse to this fuse and fries it.
Now your lamp is "dead" though it's still operable.
You can easily tell if it is your case by measuring the resistance of this fuse. In the case shown on the picture it sits near the lamp on the lamp's housing. One can hide it anywhere but it must be mounted
on the part that is replaced along with the lamp.
If it's blown then the recovery is easy. Find a similar fuse and solder it in the blown fuse's place.
I didn't have anything handy at the moment I discovered it so I used a piece of thin wire. It's not a real fuse in a sense that it doesn't protect any circuit. It only protects you from saving your money :)

Step 4: Final Touches

Mount everything back, double check the wiring, and try your refurbished projector.

Good luck!



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    111 Discussions

    sir,my projector is infocus IN102; bulb fused; there are 3 optocouplers with two facing one side and one facing opp side, i tried shorting the two terminals of that opp-side-optocoupler near the mbd end. but thats not working pl help . thanks in advance

    Hello artemff,

    I have a projector BENQ MX805st, I opened it for service and when I assembled it again it is not coming up instead it is showing to red light temp and lamp. Can you please help me in this.

    Hi artemff! First of all, congrats for the article, it is great!

    I recently got an Epson Powerlite 5500C for a bargain (as it is not working but in overall great shape). Once I turn it on, it goes to a "startup trial": lamp warm up cycle (30 seconds), then the lamp turns on for 2-3 seconds, and then it goes off. This cycle repeats for 3 times until the projector "give up" and the lamp indicator led goes to a flashing red.

    I then took the lamp out and was happy to find the fuse you described above. With an ohmmeter I confirmed the fuse was indeed open. I got very excited! I fixed it (as you did) with a thin wire and was very excited to see the projector fixed... but... it didn't work! :(( Now, with the fuse fixed, the projector simply skips the "trial cycle" and instantly goes to the lamp led indicator flashing red mode.

    I almost bought a new bulb, but luckily I didn't ? as the bulb seems to be ok (the lamp turns indeed on once the fuse is removed).

    What is probably happening? Anything else I should check?

    Thanks for the knowledge shared!

    1 reply

    Hello and sorry for late reply, I was overloaded with a number of things :)
    Regarding your case - I have two possible explanations:

    1) just to be on a safe side - are you sure that everything is assembled with all contacts/connectors/switches doing their job properly?

    2) may be this projector is smarter than mine and uses some fuse of a known resistance. It's difficult to guess the value, but I would say that it should be on the order of ohms or tens of ohms. In the old Chevys one used this trick as an additional security feature in the ignition key.

    If nothing helps, I would search for the circuit diagram, attach the scope to the (open) fuse contacts and check the request coming from the projector - is it some pulse at the beginning or a constant voltage or something else.

    My church's BenQ PB8263 light comes on for 5 minutes and then turns off. The red lamp light flashes. I replaced the bulb with the same result. BenQ support says it is most likely the ballast but that parts are no longer available. I this a case to try a different light source or is there an easier way to fix it?

    1 reply


    I would say that this is a case for fooling the projector if everything works OK during these first five minutes.

    However, it's difficult to say with the information I have whether it is a real problem or just a false alarm. If it is the former, one has to check what are possible consequences of using the projector with failing lamp PSU.

    If the power supply unit sends a false alarm flag to the main board then one can try to bypass this - it's highly recommended to find a curcuit diagram and check a corresponding part. If it's a simple logical "1" or "0" then the fooling is straightforward.

    Switching to an alternative light source is an option, but one has to find the way to tell the main board that PSU is up and running.

    This is a good post. It proves that these manufacturers are so wicked that they do not want to give us best product or best solution, they just want to rob us in daylight.

    Good day, can you help me fool my projector thinking it have a bulb. its a canon lv x6 with a ballast of ushio. what wire and where to attach pls detailed it. i just starting doing this electronics thing and still learning. i will put different light source with different power source.

    5 replies

    hi, is it a lamp power supply board or something else? The image is quite fuzzy, I don't see what is written. In any case, start with searching for the schematics - you will see clearly what leaves the main board and what kind of return signal it receives from the PSU. If you still don't manage to find it, then make hi-res photos of this module from both sides and put here.

    i made it work, not bypassing through the cable of ballast but through the motherboard itself. the projector is running, still figuring out what light to use. i sampled it using a flashlight and image is coming out. thank you fo replying i apprecite it. i would love to send pics but its already assembled.

    If I understand correctly, you have identified the control wire on the motherboard's side and put the right signal there to make it think that the PSU works correctly, right? As for the DIY light sources - it's clear that today these should be LED-based, but I never built them myself, so I can't give the specs.
    There are several good instructables on this topic here, though.

    yes your right, just 1 wire it takes to make it work. I've seen some diy light, i'm working with dsu reflector, and car headlight bulb. assembly is hard but fun and time consuming. good or bad i'll update you. i hope it work's

    the two on the right side are the same, one at the left is upside down.


    2 years ago

    Help me brother... please.

    I have lg bs275 model dlp projector.
    I dont have much money for buy new and original lamp.
    So i think use high beam diy led and drivers.
    I want to bypass bulb check circuit.
    I tried many times....but failed...
    I shorted that two wires from reverse opto couplers....didn't work.
    I grounded each wires...again failed...
    It have keeps red indicator after blinking green. It displays lg logo for 3 seconds when i put external light source. After it shows blank screen.
    I dont know what to do.
    Really i want to make it work.
    Pls pls pls help me...
    Sorry for my bad english.

    I hope you can help me

    1 reply

    did you play with wires coming to the lamp itself? If yes then it shouldn't have helped - the power supply won't send the "OK" signal to the main board since it runs all the "ignition" tests.

    How many wires connect the lamp's power supply with the main board?

    I don't know this particular model, but I would say that there should be ground, +VCC, one signal wire to the PSU and one signal wire from the PSU = at least four. I hope it doesn't use some sort of serial bus since emulating the protocol is out of the question in our case.
    Can you take a picture of the lamp's PSU from both sides of the board and send it?
    (I would also search for the circuit diagram for this very model)


    2 years ago

    Hai....i have lg bs275 model dlp projector.
    Lamp got damaged. I want to do bypass it's bulb check circuit.
    It have 5 wires from octoplers
    I am confused that which wire should i connect...
    Pls help me

    1 reply

    start with searching for the circuit diagram - then it'll be clearer which wires come to the lamp and how the protection is organized.
    At the first glance I would say that one has still track the wires from the lamp's power supply unit to the mainboard. In any case, you'll remove the PSU since you don't want to have high voltages without load in your projector.

    sir i have a sony projector vpl-cx76 which i need to convert i have got the led lamp but i am not able to figure out how to fool the projector .i have got the service manual for this projector but i am confused .please help .service manual

    Hi! I have just the same problem with my Benq PE8700. Although I found the service manual in no time (, unfortunately I was not able to obtain how to bypass the lamp. Could you give me a hand in this?

    1 reply

    first of all, I don't see the comment you are referring to as to "the same". Can you give more information? Do you want to install another light source or you want to use the old one once again?
    In any case, see p.43 of the manual - J1 pin 1 and J1 pin 3 of DMD board - the bypassing starts there.
    Lamp hours reset is done through RS232 serial interface - see the commands list on p.60 - lamp reset is a "public function" accoding to p.59.