Casio XJ-A 130 blanking

Perhaps this is buried in one of the other threads, please direct me if I missed it. I am wondering if it would be possible to only harvest the top row of the laser block then picture adjust a wide screen image downward to still have a usable picture. Or if there is some sort of shut down circuit could it be fooled by using just a silicon diode in place of the laser diodes? Since it is a native 4:3 it seems that widescreen would just be blanking (video term) the top and or bottom anyhow. thoughts?

totally random guess: by removing individual diodes you would only lower the total brightness, not get some dark areas on your screen. all diodes' output are focused to a relatively small area on the phosphor, thats what makes me believe this.

I read in one of the many posts that the projector doesnt like it when all diodes are removed. it will probably complain if any of the "rows" of diodes is removed too. good idea to replace it with a similar diode: I would suggest LEDs, for their large voltagedrop and high power-input (you will need to dissipate the original electrical input of the laserdiodes in whatever you replace them with)

curious what will form from this idea!

manuel

The diodes are wired in series. You'd need to replace them with resistors (or better yet, more diodes with similar voltage-drop characteristics) in order to get it to function.

Adam

And if an entire series circuit of six were removed? Does that translate to left, right, top, bottom, or does it even matter? Because I've heard the beams are sent through translucent glass to even it out anyway.

My new projector had a dead laser right out of the box. I don't see any irregularities in the TV picture with either white or blue screens. Would like to remove a few more lasers. What should go in their place?

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Originally Posted by Photonbeam

My new projector had a dead laser right out of the box. I don't see any irregularities in the TV picture with either white or blue screens. Would like to remove a few more lasers. What should go in their place?

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take it back and ask for another projector...that is a $50.00 pointer sale right there!

why would you want to replace them...arent you going to scrap the whole mother?

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Originally Posted by Laserman532

take it back and ask for another projector...that is a $50.00 pointer sale right there!

why would you want to replace them...arent you going to scrap the whole mother?

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Probably voided warranty by opening it. How would a customer know there is a dead laser without opening the device?
I will harvest 4-6 lasers and see if it still projects acceptable video. What should go in place of the missing lasers to fool the electronics? Short? Resistor? Diode? LED?

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Originally Posted by Photonbeam

My new projector had a dead laser right out of the box. I don't see any irregularities in the TV picture with either white or blue screens. Would like to remove a few more lasers. What should go in their place?

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I wonder what the average failure rate is. Hopefully people harvesting can safely power up prior so they know all diode were good prior to shipping.

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Originally Posted by Photonbeam

What should go in place of the missing lasers to fool the electronics? Short? Resistor? Diode? LED?

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Don't short it! Remember, they're in series. If you short one, the voltage that would have been dropped by that diode will be split among the others, causing them to draw *significantly* more current. You'll likely blow the rest.

Not sure if all 24 are in series, or if they're in 4 banks of 6 diodes each, but either way, shorting across one diode is a sure-fire way to kill many diodes.

If you know the voltage drop across one laser diode, you can approximate that with a few standard diodes in series, but be mindful of the current they'll have to pass. An LED would also work, but since the voltage drop will be lower for the LED than for the laser diode, again you'll need more than one.

Alternately, you can measure the current (with an oscilloscope, since it's pulsed), and from that you can calculate how much resistance you'll need to get the same voltage drop. Then you can install the correct-size resistor. But again, be mindful of the current. Make sure the resistor can handle the power. (Probably going to need a 5 watt resistor, and to be safe I'd go with a 10 watt one.)

Adam

actually no, it wouldnt blow the left diodes. diodes and LEDs are current-driven, and all diodes (in series) get the same current. when removing any of them (and shorting the "gap"), you will reduce the voltagedrop of the string. the diodes get the same, constant current and are fine. the "missing" voltagedrop from the removed diode will have to be dropped in the constant current source (transistor, FET). so the energy taken up by the diode (heat and optical output) will be heat and overcurrent in that transistor, and at one point blow it. insert a LED to drop the voltage and the current source wont see a difference.

manuel

I don't want to be nitpicking here but ... :p

Krutz is right, supposing it is a linear current regulator. Seeing that this is such a compact device, the current source will most likely be switchmode.

Meaning nothing will overheat if you short a diode.

I can confirm they are in banks of 6 diodes, in 3x2 arrangements. They are being run constant current in the projector, however the electronics are quite picky about making sure the voltage is in the correct range as well. I haven't had a chance to test it directly, but it will shut down and flash the overheat light of you try to short out a diode. I am working on getting around this however!

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Originally Posted by krazer

I can confirm they are in banks of 6 diodes, in 3x2 arrangements. They are being run constant current in the projector, however the electronics are quite picky about making sure the voltage is in the correct range as well. I haven't had a chance to test it directly, but it will shut down and flash the overheat light of you try to short out a diode. I am working on getting around this however!

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My projector operates normally with a blown laser (now an LED). Perhaps I could substitute good laser diodes with blown ones? There will likely be some available soon as more people experiment.

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Originally Posted by krazer

I can confirm they are in banks of 6 diodes, in 3x2 arrangements.

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...this may 'shed some light' (photo by others...)

http://farm5.static.flickr.com/4012/...d4fbfcc21f.jpg

cheers...
j

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Originally Posted by Krutz

diodes and LEDs are current-driven, and all diodes (in series) get the same current. when removing any of them (and shorting the "gap"), you will reduce the voltagedrop of the string.

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You are correct. I had erroneously assumed that this used a simple linear voltage regulator, rather than a constant current regulator. My bad.

Adam

I know this is an older thread, but just thought I'd chime in. Any news on replacing a row of laser diodes in the projector?

I think you 'll have to use regular 1N400x diodes rather than LEDs to replace them. The pulsed current through these laser diodes (measured by krazer) is nearly 1.5 AMPs. LEDs' typical If (forward current) is 20-30 mA. Maybe 50-100 mA if pulsed. Put 1.5 amps through an LED and you get a great flashbulb.

The Vf (forward voltage drop) of the 445nM laser diodes at that current is close to 5 volts. So, you would need about 7 diodes in series (at .7V drop across each silicon 1N400x) to get 4.9V to be the same as the Vf of the laser diode.

You might be able to use one of the Luxeon or similar very high brightness LEDs. They have a Imax (max forward current) of nearly 1A. The Vf at this current is about 3.7-4.2 Volts.

Standard high brightness (blue, white, green) LEDs have a specified Imax of only 30mA, and the Vf at this current is 3.2-3.9Volts.

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Greg

There really is no reason to use LED's or dead lasers, a simple diode will work fine. A 1A rated diode would probably work due to the pulsing, but it will get toasty so I recommend using a 3A diode. It should also be possible to get away with just a simple resistor, although due to the different IV characteristics the projector may freak out.

krazer, in your post of 6-9, you said:

the electronics are quite picky about making sure the voltage is in the correct range as well.

So, I assumed the electronics would complain about seeing 4.2 volts difference (between the 4.9V laser diode, and a .7V 1N400x silicon diode replacement.

In any case, I think a regular (high intensity) LED running at 1.5amps pulsed wouldn't last very long in there.

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Greg

why not a 5 amperes rated zener diode? it would drop the right voltage and cope with the power

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Originally Posted by shrad

why not a 5 amperes rated zener diode? it would drop the right voltage and cope with the power

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I believe that this is the best solution, heroic also suggested this in IRC chat (y'all miss out on the good stuff :cool:).

-Adam

Sorry for the confusion, of course when using silicon diodes you will need several in series, about 6 per laser removed.

The zener isn't a bad idea, although it will probably take some experimenting to find a zener that exactly matches the laser (with many small diodes you can just add or remove a few from the string to keep the projector happy). A typical low voltage 5w zener diode will have its voltage drop specified at ~250ma, and have 2ohms of series resistance, so to extrapolate for running at 1.5A you will probably want a 4.3V zener, maybe even a few 3.3V ones if you are removing large numbers of diodes.
something like http://www.mouser.com/ProductDetail/...hCX5U1W7aYM%3d should work well.

First off i know this thread is on its way to the dust bin pardon me if resurrecting it irritates anyone, but it has captured my attention and i wish to know more about these zener diodes..

i found this Zener diode calculator
http://www.calculatoredge.com/electronics/zener.htm

i thought it might assist us in finding a suitable diode.seems very easy to use,i personally cannot because of certain variables i do not know,ie the following Maximum input voltage,min input voltage output voltage,load current. so just take wild guess at it and usning some data Krazer told me i got these kinds of numbers.

Maximum input voltage 32v
minimum input voltage 3v
output voltage 4.7v
Load Current 1500ma

=
Resitance 18.08 41.22WATTS
Zener 4.7 7.1WATTS


Krazer had told me in another thread that each channel is ~32 volt @~1.5-17amp so i used that.
Do these numbers look right or wrong to anyone? if so can you explain why?

it looks to me that the best diode to use would be a 4.7-5v 3a 15-20ohm? but in what wattage range? 5w-10w 20w? the Zener Calculator says 41.22 watts but heck i dont know thats why im asking youz guyz lol.


i also found these:http://www.ebay.com/itm/ZENER-DIODE-...item3f07fa7971 but they are only 1 amp. Krazer said that a 1 amp diode would get toasty,so i assume using heat-sinks would be a given,thing is i dont know how to marry a heatsink and a diode,unless i custom make one or perhaps glue them to the heat sink.

when searching for 3amp diodes (as suggested here) I just keep finding only the 30-1000v 3amp rectifier diode, and im thrown off by the rectifier part (AC-DC) and since we are only using 4.5-5 volts...if something like a 40v was used since we are indeed not using 40v but only 4.5-5v @1500ma.would the difference of 35 volts play any a role or have a bearing at all? ie all more voltage than we want through,not allow enough for our needs through..burn something up?,turn our dc voltage back into AC voltage?

i cannot find a 3amp Zener diode in the 4.5-5v range anywhere! and only have the few specs talked about here to go on(i dont know how % or,temp coefficient impacts everything so going to Digkey or Mouser is quite difficult)
.Krazer you told me a 15-20ohm resistor would suffice,does this resistance value apply to the diodes discussed here as well? or should it be higher or lower?
the calculator above said 18.08 ohms which i assume we could easily round off to 20ohms.

http://www.ebay.com/itm/MCC-1N5822-4...item5d2ec952e3
i have no clue if these would suffice or not. if anyone has any suggestions please please post them,id appreciate the guidance.

i also found the following but im not sure they would work cause to me they are rather odball.

http://www.ebay.com/itm/1N1804-6-2-V...item3f0e2a885c
Attachment 28208
i have no idea how to implement this particular kind of diode.



I know i ask alot of questions,and i apologize if that irks anyone,im just trying to learn is all and get my projos going.
.any and all information or advice is greatly appreciated..again sorry if rezing this thread irks anyone.


Keith.

or would something like this:
http://www.ebay.com/itm/MBR7030-Scho...item27bf730107 be more suitable..now i know the specs of the diode i just listed are a total overkill.but i was more alluding to the style and physicality of the diode.it seems this type of diode would be easier to mount to a heating or sandwich in one.

Attachment 28230