Projector SMPS Faulty - Blows IC

[kolbep]

Hi All.
I do repair work for my church (just to help out)
They have 4 Faulty projectors
1) Optoma #1, Was working fine, then Just went POP. MOV, Onboard Fuse, and other parts of the powersupply had died
2) Optoma #2, Used to work, then just started switching off like the bulb was failing. Replaced Bulb with a new one, problem persisted. Left projector in storage for about 3 months, tried it again without bulb - it was trying to start fine. Put in a new bulb, and POP, powersupply onboard fuse popped, charred SMD resistors, etc - Powersupply had it.
3) Optoma #3, Don't know the history, except that the Onboard Fuse blew, and that the Common mode choke on the input was shorted. Bridged out the common mode choke, and replaced the onboard fuse - Powersupply still messed.

The latest one is a Benq MP611C projector. Some time ago it's bulb died (exploded).
I replaced it with one of the bulbs out of the Optoma (Same Wattage, Same type) 250w Discharge MV.
It powered on, I could use the menu's and everything. But then it switched off with Thermal Fault.
Tried Several times after that to get the projector to start. Some times it Cut out while playing the jingle, Other times it would not switch on the bulb, then if it does fire up the bulb, it either showed a white or orange screen, etc

I then took the projector to my workbench. Plugged it in, It's Light turned on then off. A few Seconds later POP, the powersupply blew the top of it's TOP247YN offline switcher chip (http://dalincom.ru/datasheet/TOP247YN.pdf).

I have given up all hope on the Optomas, but the Perhaps somebody can help me out with figuring what went wrong with the powersupply on the Benq MP611C. (Hopefully we can fix it, 'cos they are renting one every weekend for their childrens services.)

The Powersupply code is 4H.J2C40.A00.

Anybody have any experience at what could cause the chip to pop?

Thanks
Peter

[Psi]

Pics?

Ok, id do something like this..

*) Look long and hard for a service manual with circuit diagrams.

*) Remove the psu board from the projector so you can work on both the board and projector separately.

Even when working correctly the psu will likely only produce a standby voltage while sitting on the bench. You will need to pull a pin high or low to signify a "start up" or "run" condition before the other voltages appear.
Figure out which pins are what, startup, 5v 12v 20V etc..
(quite often that's written on the pcb silkscreen)

*) If you have enough lab powersupplies with current limit, you can power up the entire projector without using the projectors own powersupply board.
If you're able to do this it's a really good idea, it can quickly prove/disprove a fault in the projector itself.
That way you don't wast time fixing the psu only to have the projector blow it up again.
(Note:, Doing that isn't always possible, if for example the PSU board has complex communication with the main cpu board,  however most of the time its just various voltages and one pin for standby/on)

*)  Move on to fixing the psu by replace the IC and any other components that are dead. Power it up and check all the voltages under load.

*) Once the psu is working again reinstall into the projector and try it out.

[SeanB]

Most likely the caps in the power supply are dead or dying, and as well the lamps are way past the rated service life as well, and the stress of trying to start them has blown the lamp inverter.

As you are detonating power input boards like popcorn I would also suggest looking at the power feed, from where Eishkom brings it into the church, all the cabling and all the extension leads and plugs, sockets and breakers. Check if you have poor neutrals, or are dropping the neutral in the supply and running at a high voltage. Check mains voltage for a while, and pull a load similar to when people are in, turn on AC with doors open to simulate a high people load, lighting on full and PA system running. That should help to narrow down if you have any power issues. If it is running off a multiplug replace it, or build one with a couple of industrial SSO's chained together on a board and use proper NO0 cable glands for the cord, as well as 1.5mm or 2.5mm cable to wire them, they are a lot more reliable, and are small if you buy the 4x2 double ones.

[kolbep]

Re : PICS : Will do that tomorrow
Re: Service Manuals : Made in China. I tried. and Tried and Tried
No such labelling on the silkscreen. I have managed to identify certain groupings, such as a few pins being ground, and then 3 Other sets of pins being +ve to the board (I think 3 different Voltages). Then there are some control lines (probably Soft Power, Inverter on, etc)

*) If you have enough lab powersupplies with current limit, you can power up the entire projector without using the projectors own powersupply board.
My only lab PSU's are 7AH 12v Alarm Batteries, and a LM317 Regulator

*)  Move on to fixing the psu by replace the IC
Done That, Still not powering up. I am getting 1.5v on the secondary side, but I cannot get anything to turn on. I am trying to figure out the circuit. It has another section with seperate controller IC, but I do not see any other faulty components. All Diodes and Resistors I have tested are fine...

I need to sleep on it. If it is salvageable, it definately will not be this weekend....

[kolbep]

Most likely the caps in the power supply are dead or dying, and as well the lamps are way past the rated service life as well, and the stress of trying to start them has blown the lamp inverter.
Inverter on all of the projectors seems fine. It (the Inverter board) gets it's supply from the rectified and smoothed DC on the Primary side of the SMPS. There is a transistor on the PSU board that gets switched from the Control Board. So I do not think that could be the problem.

Re : Floating Neutrals.
Doh! I am a trade tested electrician, and I do know of the damage a floating Netural can do (had it just the other day at a butchery in Margate). But as I did the wiring for the Church buildings, I could only think that there cannot be a problem with the Neutrals, because I did it all myself. It totally slipped my mind that Eskom could have an intermittent problem. I am busy kicking myself at the moment.
Of course I have not checked that yet, but now I will be hooking a voltage logger up to check it out over a full week.

Thanks for all the Posters suggestions.
Bedtime, and then when I get time I will post pics of the PSU board

[SeanB]

Might help if this is the right info........

http://www.eserviceinfo.com/index.php?what=search2&searchstring=benq+mp611

I have the file if you want.......

[kolbep]

Thanks Sean.
I Not the same model, but I will download all those files, maybe one of them has a similar psu board

[kolbep]

Pictures 1

[kolbep]

Pictures 2

[kolbep]

Pictures 3

[Psi]

My only lab PSU's are 7AH 12v Alarm Batteries, and a LM317 Regulator

If you make a mistake using 12V SLA's it will blow up stuff and melt wiring/tracks.
And even if you don't make any wiring mistakes the existing fault could be a short which may damage the board more if you dump unlimited energy into it.

A proper current limited lab power supply really is needed for electronic repair.


On the plus side, that power supply board looks pretty simple which makes fixing it easier.

You could try searching for service manuals for similar models.
Sometimes the power supply section is the same or very similar.

[salman]

Hi all

My computer power supply suddenly dead.when i open it i found blown Mov and fuse,then i replace both of them then again power up the supply it again blown the same components plz suggest me what is the problem in it thanks.

[MikeCL]

I hope you can figure this out since I have the same issue just not a blown IC.

[SeanB]

Salman, normally you will find the bridge rectifier is short as well, along with the standby power supply transistor. That will be on the big heatsink next to the 2 big capacitors. You will fing that the small transistors there are dead as well, and the low value resistor there is open circuit. Most likely there was a mains spike or high voltage and they died from this. Repairable but often cheaper to replace the power supply.