I recently found a bad fan motor, just below the lamp in a LCD projector. So, I ordered and replace a suspected Power Block assembly thinking it was a bad ballast.

In the types of fans commonly used with CPU's.

What process would you use to diagnose it ?

Ohm ? Amp ? Feedback ?

Thank you in advance. ..............kv

 

Replace the fan in a (panasonic model#pt-l711u)

Everything is working fine. ( The fan part # is UDQFSDH05F) dc5v 0.17a) $39 us

Previous problem shutting down just after power up !

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So, it has three wires and I'm not sure how to other than seeing it stopping might I know it's bad ?

dc5v 0.17a) fan shaded pole.

Edit: I have taken the motor and began to just spin it with my finger and I noticed that it vibrated a little as it spun. My guess is mechanically it was creating a physical resistance that translated as a increase in amperage. The cpu on the projector detected it instead of being open circuit. Once this occurred the cpu reset and went into shutdown ? (JUST A GUESS)

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Who are you talking to here?

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Just simply adding it for anyone seeking a search ............. no need for anyone else unless they can come up with a better fault finding method ?

That was my original questions : I have no idea how the circuit in this case knows why to shut down. Let alone how the motor runs in it. Why the third wire on the motor what is it used for (sensing ?)

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Just the same as on a PC, to ensure it's spinning, and shut down if it's not.

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You couldn't see it because the projector's board is on top of it and all I could see was the wires.

Those wires could have been anything it was very hard to spot. Plus it also ran.

But based on the wobbling I observed while spinning it by hand seemed that it would spin but slowly ? Until I power it up and figure it out I guess I'll never know.

Besides who care's right ? it's just a fan right ? what the big deal anyway Right ?

Well in this case.

The guy who originally diagnosed it as a (Power Block Assembly) we paid him $50.00 for nothing in the end he would have ripped us off.

He would have wanted $450.00 for the repair.

In addition I have about 100 said projectors here. And they are just sitting around. All over campus.

(Seems to me $39.00 x 100 = $3.900 Working Projectors.)

(or $450.00 x 100 = $45,000 not working collecting dust because not in the budget.)

That's why there just sitting around gathering dust or being robbed of there bulbs for part's.

And instead of replacing the projectors they will now go back into service. Parts x my hourly rate paid for by the University.

How many other campuses are there and how many projectors like this one are there ?

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You're rather assuming that all have the same fault?, and if they do it's obviously a poorly specified fan. You just need to hang a scope on the hord wire to the fan, and see how it's running (check a good one first).

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yes, the third cable is for sensing purposes. I don´t know, maybe it sends pulses for each spin, and thats how the system reads the speed of the blades. Maybe there is any expert on the forum who can tell you how to make a circuit for reading the pulses and the RPM's, without removing anything just putting testing probes on the PCB.

I have seen fans spinning slower by dirt and poor oil, or overvoltage. If the firstone is your case, do the following:

1. Remove the sticky label
2. Use a flat screwdriver to remove the rubber cap
3. Put some oil on the (now exposed) shaft
4. Install the rubber cap again
5. Turn on the fan to ensure the oil covering.

Sounds silly, but It fixed lot of my everyday problems, and if you have a massive ammount of projectors as you said, It can save you a lot of money instead of changing the fans.

 

Thanks Nigal,Menticol. I have been able to get inside the fan it is well put together the housing is a combo aluminum case.
It has a tiny air duct directing the hot air from the bulb an forced to mix with air channeled by power supply fan. Then pickedup by the big fan in the rear and out.

I don't think oil will work because the bushing is bad. I don't trust oil to cover a $350.00 bulb I won't risk it. For anything else I would.
Nigal, I will check the good one first and I'll only guess the ones that seemed to shutdown will be suspected.

Edit: Yes to the design(failure.) could have done a better job and used a better fan.

I pull the top off the motor has 4 poles it's like a VCR head. So it must uses a hall effect to control it and I would need a schematic to see where to pick it up.

Thanks Guy's for the input.

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Cheap fans use crude bushes, better quality ones use roller or needle bearings, oiling worn out bushes is only a very short term 'fix'.

They are DC brushless motors, just stick your scope on the third wire, you should see logic pulses, their frequency based on the speed of the fan.

One thing, assuming the projector is shutting down because of fan failure, I would expect it to display an error 'code', usually by flashing the standby LED a certain number of times. Do you get any such codes?.

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Yes, I did. But I didn't watch (how many.) I didn't know how to read it so I ignored it. I know where your going easy way to detect the fan as the culprit.

Your right. Thanks.

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Truthiness Monkeys : Obedience, Ignorance, Fear.

 

Unplug the fan, then count the error code flashes, this will then allow you to tell if the same fan is duff on other units - if there's more than one fan, different fan failures may give a different code.

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