BenQ W1070 Projector 5v rail

[bermo96]

Hi, I've a BenQ W1070 projector and the lamp isn't working, I replaced it but same problem. Then I checked the voltage inside and the 5v rail is showing 2.3V. The commands for the ballast is powered by this 5v rail. I've the schematics but I can't find any 5v regulator an the 5v isn't coming from the power supply board. Can someone help troubleshoot this ?

Have a nice day

[budwich]

Re: BenQ W1070 Projector 5v rail

page 14 is likely where your answer lies but not sure where that circuit actually sit as the page labelling doesn't reference a board.

[R_J]

Re: BenQ W1070 Projector 5v rail

U42 is located on page 20, top right side of board, L29 is located near U42

[bermo96]

Re: BenQ W1070 Projector 5v rail

Yes I can see the PMD1000 on the board, do you think I must change this IC ? I've checked all the bypass capacitor and they are good

[bermo96]

Re: BenQ W1070 Projector 5v rail

Ok so at L29 I've 2,5v at the pin 23 and 2,25v at the pin 24

[budwich]

Re: BenQ W1070 Projector 5v rail

Yes I can see the PMD1000 on the board, do you think I must change this IC ? I've checked all the bypass capacitor and they are good

how did you check the capacitors?

Its quite possible that one of the circuits is loading down the 5v circuit.

[bermo96]

Re: BenQ W1070 Projector 5v rail

Only for short to ground, but I will check it with my esr meter.

[budwich]

Re: BenQ W1070 Projector 5v rail

I had some "5v supply" circuit caps on an xbox go bad... instead of 3300uf, they were 10kuf... so you might be wise to check them. Mine were also visibly in trouble with slight bulged tops.

[bermo96]

Re: BenQ W1070 Projector 5v rail

The caps are good... I've order a new PMD1000, I hope this will fix it.

[R_J]

Re: BenQ W1070 Projector 5v rail

Do you have a good +12v into the ic? I would also check the other output voltages, that might indicate how the ic is working, Check that D14 is ok.
On page 6 there are a bunch of regulators that are supplied from the P5v, one of there outputs could be shorted loading the regulator and also lowering the input voltage

[bermo96]

Re: BenQ W1070 Projector 5v rail

Ok I'll test all the regulators. I must desolder them to test right ?

[budwich]

Re: BenQ W1070 Projector 5v rail

depending on the track layout, you might think about cutting the track of the 5v leaving pmd1000 (some where on the other side of the caps) and see what happens to the voltage which is then basically in "open circuit" mode. that may help determine if the IC is bad or sometime else is sucking it down. Of course, be wise where you do the cut so that you can repair it readily.

Further... notice that there two 5v being generated / supplied... have you checked both?

[R_J]

Re: BenQ W1070 Projector 5v rail

I would leave the regulator ic's in place and check for a short to ground on there outputs, If you find one that has its output pin shorted, then I would unsolder it.
There are also a couple regulators, (U18 & U20) on page 4, that are feed by the P5V line.
You may want to unplug J14 (ballast ?) to rule that out.

[bermo96]

Re: BenQ W1070 Projector 5v rail

When I remove the two regulators UQ1 and UQ3 I have the 5V back, theirs output are shorted to ground in the circuit but when I remove them they aren't shorted. I've removed all the capacitors but the short is still there.

[R_J]

Re: BenQ W1070 Projector 5v rail

So you have shorts on two different voltage lines? TVDD_3.3V and CVDD_1.8V, page 6, U29 uses both of those supplies.
Does the projector turn on without those two regulators?

[bermo96]

Re: BenQ W1070 Projector 5v rail

Yes TVDD_3.3V and CVDD_1.8V are shorted but only TVDD_3.3V make the 5v disapear. The projector turn on and the lamp is on too. This is fine for me but the power supply make a loud noise (bzzzzz).

[R_J]

Re: BenQ W1070 Projector 5v rail

When you say shorted, what is the actual resistance, Is the noise from the main power supply or from the lamp inverter?

[bermo96]

Re: BenQ W1070 Projector 5v rail

The noise come from the power supply but only when UQ3 is on the board. And the short are close to 0 ohm. I can't find the actual cause of the shorts. It is strange that TVDD_3.3V and CVDD_1.8V are shorted together. The projector turn on fine but the HDMI input are not working.

[R_J]

Re: BenQ W1070 Projector 5v rail

I would guess that U29 is bad, I looked up the number from the schematic but find nothing. That ic does handle the hdmi signals.
I never did like hdmi, I have seen more blown ic's etc on hdmi inputs than any other input.

[budwich]

Re: BenQ W1070 Projector 5v rail

Yes TVDD_3.3V and CVDD_1.8V are shorted but only TVDD_3.3V make the 5v disapear. The projector turn on and the lamp is on too. This is fine for me but the power supply make a loud noise (bzzzzz).

Perhaps it is likely that the draw from the 1.8 isn't great enough to pull down the 5v but puts enough load on some of the power supply points (ie. transformers or such) to make them "noisy".

BUT... it looks like you are making good progress... projector on / lamp on.... what more can you ask for... :-)

Your findings appear to point at the u29 as RJ suggests.... you need a parts listing... :-(