Water damaged projector fixable?

[akorcovelos]

Hi, haven't been on for a while, but last time I got great help here so I'm back!

I got an INFOCUS N1100 DLP projector from my work because the roof leaked and it was water damaged. I opened it up and found the bottom of the power supply board has crud from the water pooling up in the bottom of the case, and the ceramic surface mount fuse was blown.

I cleaned up the power supply circuit board, and it looks pretty good, and I soldered in a new fuse (glass but same specs). When I got it back together it popped the fuse as soon as I plugged the power cord in, even before hitting the power button.

What could cause this to happen? Is it something I can trouble shoot to see what needs to be replaced? I'd like to get this thing working again if possible, its a nice little unit and the bulb is still good.

Here is the online manual for it: http://www.projectorcentral.com/pdf/projector_manual_4260.pdf

Thanks in advance!

 

[(*steve*)]

You need to (at the very least) take the board out, clean it, dry it, and then check for faults before you try to power it up again.

The fuse fails before you turn it on because either:

a) it's a soft-on switch (the power supply is always running)
b) there's a short somewhere (maybe even in the switch)

edit: Post photos of both sides of the board. Don't use a flash, and ensure the images are clear enough that we can read all the writing on the board.

 

[akorcovelos]

No problem, here you go. I cleaned the board with CRC Electronics cleaner and a soft toothbrush, which seemed to work pretty well.










Let me know if you want to see something in more detail. I assume it is a soft I/O since the projector will run the cooling fans for a time after power down to cool the bulb off.

 

[(*steve*)]

For instant fuse failure, there are two common faults:

1) rectifier is short circuit
2) main switching transistor/mosfet is short circuit.

First read the resistance across the mains plug, second the resistance across the high voltage capacitor (make sure it's discharged first).

Naturally both of these measurements should be taken long after the power has been disconnected and with a good fuse installed.

 

[cjdelphi]

Chances are there's still water/moisture in hard to reach places, get the washing up liquid out, scrub it all down rinse... and leave out to dry for a few days, or maybe use a hotplate on very low and leave it to dry out...

Another way might be to use liquid isopropyl and soak it before drying out...

Basically the water trapped is shorting it out

 

[akorcovelos]

For instant fuse failure, there are two common faults:

1) rectifier is short circuit
2) main switching transistor/mosfet is short circuit.

First read the resistance across the mains plug, second the resistance across the high voltage capacitor (make sure it's discharged first).

Naturally both of these measurements should be taken long after the power has been disconnected and with a good fuse installed.

So check resistance across the two main pins on the power plug? Is the high voltage capacitor the one with the copper winding visible?

Chances are there's still water/moisture in hard to reach places, get the washing up liquid out, scrub it all down rinse... and leave out to dry for a few days, or maybe use a hotplate on very low and leave it to dry out...

Another way might be to use liquid isopropyl and soak it before drying out...

Basically the water trapped is shorting it out

The water damage happened about three weeks ago, and its been disassembled for about ten days, plus I doused the whole thing with the electronics cleaner so I 'think' its probably dry as its going to get, no?

 

[cjdelphi]

So check resistance across the two main pins on the power plug? Is the high voltage capacitor the one with the copper winding visible?



The water damage happened about three weeks ago, and its been disassembled for about ten days, plus I doused the whole thing with the electronics cleaner so I 'think' its probably dry as its going to get, no?

maybe, some of the components can trap water underneath where it's hard for the water to evaporate totally...

 

[(*steve*)]

So check resistance across the two main pins on the power plug?

Yep

Is the high voltage capacitor the one with the copper winding visible?

No it will be a large cylindrical (probably black) component near that thing with the copper winding (that's an inductor of some sort). It may have a silver or black top, and on the sides it will be marked as having xxx uF where XXX is probably between 50 and 400, and a voltage rating in the order of 200 or 400 volts. It will have 2 pins and is quite capable of holding a charge that can make you wish you had never put your fingers near it.

The water damage happened about three weeks ago, and its been disassembled for about ten days, plus I doused the whole thing with the electronics cleaner so I 'think' its probably dry as its going to get, no?

No problems likely with still charged capacitors then

I would try warming your oven (under 100C) then turning it off and placing the board in there until the oven cools (a couple of hours). This will help get rid of any moisture in there.

Don't turn the oven on to cook anything during this time or you will be very unhappy.

 

[akorcovelos]

ok, got it in the oven now, I'll test it tomorrow and post up results. Found the capacitor, and its marked 420v.

 

[akorcovelos]

New fuse installed and both the primary pins on the plug and the capacitor read .000 for resistance. From my understanding that's good, right? What would I test next??

 

[(*steve*)]

That is suggestive of the switching mosfet having failed.

Can you show us what is on the heatsink closest to the mains power socket.

It's a long heatsink. I'd normally be expecting a single device here, but it looks like there's more here...

 

[akorcovelos]

Is this what your looking for?

 

[davenn]

so what are the part numbers on the deviceds on the heatsink ?

Dave

 

[akorcovelos]

The bigger one in the fist pic is GBU605, the smaller ones have the following on them;

BYV29X
500
PJA1032 B7
4988

 

[akorcovelos]

bump.

Any insight into my next move on this? Throw it in the trash bin? lol.

 

[(*steve*)]

OK, all of those things are rectifiers.

There must be another device attached to a heatsink somewhere.

 

[akorcovelos]

Sorry for the delay, got side tracked with another project. I have attached some pics below of the other heat sink and its surroundings, As usual just let me know if you need a better more clear view.
Thanks for all the help!

 

[KrisBlueNZ]

OK, it looks like that power supply has a power factor correction (PFC) stage, so it's really in three parts. Mains comes in through the bridge rectifier (marked GBU605) and is smoothed by a capacitor of a few µF, probably the rectangular blue component beneath the centre of the heatsink. Then there is the first stage, the PFC circuit, which uses the inductor next to that capacitor to boost the voltage, and feeds the large electrolytic that you identified earlier. The voltage across the large electrolytic then feeds the main switching circuit, which drives another transformer that provides the input-output isolation. There's a filter inductor with multiple windings, and it looks like four diodes - possibly connected as a bridge - and final smoothing, then the DC output comes out on a connector.

Can you please upload high-resolution, properly illuminated photos of both sides of the board, viewed from directly above the centre of the board, showing the whole board. See https://www.electronicspoint.com/threads/how-to-take-photos-of-circuit-boards.267883/

You said you measure a short circuit between the two pins of the mains plug. Most likely this means the bridge rectifier and/or the MOSFET in the PFC stage has lost the magic smoke. I suggest you remove the bridge rectifier (GBU605) by drilling out the rivet and desoldering the pins using a solder sucker. Once it's out of the board, measure resistance between the two middle pins, either way round. If it measures short, you'll need to replace it, but you may also need to replace other parts too. My guess is that the PFC MOSFET will be dead too.

We need to know more about the board. Steve asked you for the markings on all the components on the heatsink. You said the first one is GBU605; that's the bridge rectifier, and the others are BYV29X500. But I don't think that's right. There are four more devices on the big heatsink, along from the bridge rectifier. They can't all be BYV29X500s. We need to know what they are.

That information, plus some good photos, should give us more to work from.

 

[akorcovelos]

Excellent! I'll get some good pics posted and take another look at the heat sink and see if I can find any other markings. Thanks!