dead power supply board in Computer Projector

I have a Astrobeam X211 LED computer projector. 800x600 resolution, ~ 4 years old. Made by A-K electronics in Germany I think. I do not think they were very popular. I suspect they were allot more expensive that projectors such as those from InFOCUS.


The projector was totally dead when the power was applied. No fan or anything. I thought maybe a fuse...

I then opened up the case and pulled out the power supply board. There was a fuse buried that I replaced and voila.....

the projector worked!!! Nice bright picture!!!

I then turned off the projector and when I turned it back on it was dead again. It also tripped the breaker in the wall outlet.

Hindsight at this point would have been to stop and determine what is causing the fuse to blow.

Nice systematic study with the circuit diagram in hand where you apply power to one segment of the circuit at a time. 2 day job.

Did I do that?

Of course not. I pulled the board out of the computer, replaced the fuse and then applied full AC power to the board. . . . . . . . . . . . . . . . . . . . Poof!!! Vapo-resistors!!! Surprise-surprise!!

I vaporized a line of small resistors that were all in parallel.


I will now try to salvage the board. I will replace the vaporized transistors and try to scrape off the darkened parts of the board. I will also probably remove components and try to set if I can figure out the front end of the board. I will try to do this in stages so that I do not do anymore damage to the board.

Any suggestions at this point for how to proceed would be welcome. Of course, I have very little chance of getting the schematics given that the projector is no longer made. I also do not have a scope. I have a voltmeter and a PhD but I suspect the later is more a hindrence than anything else in the case!

I was wondering though...

What I might wind up doing is scrapping the power supply board completely. Though this board provides multiple DC levels it does not power the lamp directly. Rather, it provides 650VAC to another board that then drives the lamp.

What I am thinking I might have to do is to generate the DC levels and the 650VAC in a separate box and feed this via a wire harness into the projector. Probably attach the power supply box to the first box with duct tape to enhance the "Red Green" effect!!!

The DC levels to be generated are 3.3, 6.15 and 16.V. What would be the best/cheapest way to do this?

How about generating the 650VAC? This I think is the most challenging. Any suggestions here would be appreciated.


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Well you obviously have some shorted semiconductors, that shouldn't be too hard to track down. Just start at the rectifier on the input and work your way towards the output. Then the more tricky part is to figure out *why* the problem came about in the first place. Did you put too large of a fuse in there? I'm wondering this because the fuse *should* blow to prevent other damage, but it's all too common for people to stick a bigger fuse in and cause many times more damage than they started with. Make sure you check carefully for cracked solder joints as that may have been the original cause of the problem.

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James Sweet

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