Infocus power supply isssue

[subarub4]

Re: Infocus power supply isssue

Still not working and the MR4010 still heats up as soon as it's plugged in.

[subarub4]

Re: Infocus power supply isssue

I found a diode that's reading both ways.. my microSD card seems to have walked off so I can't get a macro shot right now but it's D103 on the backside of the board, SMD mount the cathode is connected to Q602 & Q603

[budm]

Re: Infocus power supply isssue

That Diode D103 is in parallel with the low value resistor R130 (the value can be from 10~100 Ohms) and connected to the Gate of the MOSFET, the diode is for fast discharging the MOSFET's Gate capacitor when the drive signal goes low to make sure the MOSFET turns off fast.
Looks like there are more things to check.

[subarub4]

Re: Infocus power supply isssue

That Diode D103 is in parallel with the low value resistor R130 (the value can be from 10~100 Ohms) and connected to the Gate of the MOSFET, the diode is for fast discharging the MOSFET's Gate capacitor when the drive signal goes low to make sure the MOSFET turns off fast.
Looks like there are more things to check.

I'm curious why IC203 has no voltage but IC204 has 2.8V on two pins, one thing is how would I know the receiving side is working?

Do you happen to know who makes this? I want to say Fairchild but I lost the info on it..
The chip has this on it:

L1211
817 BW

Wait.. never mind found it here

H11A817BW

http://pdf1.alldatasheet.com/datashe...H11A817BW.html

[budm]

Re: Infocus power supply isssue

That is an Opto-isolator, it is used for feeding the feedback signal to the primary circuit to regulate the output voltage. So right now, you are just running the board with nothing else attached but only the AC input.

[subarub4]

Re: Infocus power supply isssue

I assume where the power ends it's going to end at 160VDC? Or perhaps not because it's going to the MR4010.. which means whatever failed must be on the right side of the board..

Q216 & Q210 I don't get any reading from those, I want to think we went over these before but not sure.. but they read 241 on the chips.

The SMD codebook I have says this

241 PZM24NB Phi C SOT346 24V 300mW Zener

[budm]

Re: Infocus power supply isssue

That section with the Diode question is for PFC voltage booster, which right now will not be running until the main board get the standby voltage from the circuit that you replace the IC. Once the standby power supply works, the main board will send out the signal to turn on the PFC to produce the 380VDC for the ballast ciruits.
The circuit for the standby power supply is real close to the circuit as shown in the spec sheet of the IC. I wonder if there are shorts in the secondary side of the standby power supply circuit, or something in the primary that that cause the new IC to be stuck (not fully on) on instead of switching. I may not be seeing something on the board right now, need to do more thinking.

[subarub4]

Re: Infocus power supply isssue

I assume if it was a short on the primary or secondary side the fuse would blow?

I'm going to have a look at Q103 & Q214A I've had mosfets fail shorted but in that case it blew a fuse each time on start up.

[budm]

Re: Infocus power supply isssue

Short in secondary is not likely to cause enough current in the primary side to blow the main AC fuse unless it causes the IC to short out, the protection circuit can also kick in if it senses over current.

[subarub4]

Re: Infocus power supply isssue

Hmm.. on Q103 which is a Mosfet i'm seeing resistance between Drain and source, and this time to be sure I pulled the drain and source leg out of the circuit.

*edit I must of had left over charge.. I tried again using the standard mosfet test and I'm not getting any reading maybe it needs more voltage to turn on then my meter can do? I've never had issues with any other mosfet testing.

*edit

If I put the (-) probe on Drain and (+) on Source I see a reading of 260 kohm but nothing if it's the other way around (it has a diode)

[subarub4]

Re: Infocus power supply isssue

^ must be be for when the load is shut off so it wont damage the mosfet.. so back to the drawing board.

Where is the primary and secondary sides of the standby power? Would that be the transformer?

it's odd it has 4 legs on one side and 6 on the other side.

[subarub4]

Re: Infocus power supply isssue

Is it possible to test T201? On the secondary side I'm having continuity on all 6 of the secondary pins, it's out out of circuit however.

[subarub4]

Re: Infocus power supply isssue

I want to know this has me curious how much AC should I be seeing near the standby power area?

[subarub4]

Re: Infocus power supply isssue

Blew the fuse.. 250V 6.3A rated

[subarub4]

Re: Infocus power supply isssue

Hmm.. I'm looking at a FET here.. it's part number K20A60U Can anyone confirm that's a Toshiba FET?

I took it out of circuit and I can't get the gate to open, my meter puts out 1.5V in diode test

I followed this which I used in the past to find two Mosfets that were shorted.

http://www.4qdtec.com/mostest.html

[Khron]

Re: Infocus power supply isssue

Apparently, it is indeed:

http://www.alldatasheet.com/datashee.../TK20A60U.html

[subarub4]

Re: Infocus power supply isssue

Is there a reason why I'm not getting a reading with the way shown in the link above?

*edit ok it has a diode but the finger test does not work it pretty much stays at the same reading.

[ben7]

Re: Infocus power supply isssue

Yo, the way you guys are attacking this problem is just going to lead to more problems. The problem clearly lies in the main smps circuit, since there is no standby voltage and the controller ic is getting very hot. I see you guys are jumping back and fourth, from checking things in the main smps, to the pfc circuitry LOL.

Especially the fact that you blew the fuse... what did you do?! It might be likely that you destroyed other things too.

Now, with the psu unplugged, measure the resistance across all the output side electrolytic capacitors (in both directions too). Report back the findings.

Could we get some better pictures of the smps (the area near the connector with the multi-colored wires)?

Thanks,
-Ben

[subarub4]

Re: Infocus power supply isssue

The fuse blew because I did no use a isolation transformer when I was checking with the oscilloscope.

I can try and get some pictures of that area, I wont be able to get macro since my memory card is lost..

I will check the resistance.

http://www.youtube.com/watch?v=ERnUt...ature=youtu.be

[ben7]

Re: Infocus power supply isssue

The fuse blew because I did no use a isolation transformer when I was checking with the oscilloscope.

I can try and get some pictures of that area, I wont be able to get macro since my memory card is lost..

I will check the resistance.

http://www.youtube.com/watch?v=ERnUt...ature=youtu.be

I think you should test the medium sized capacitor on the output side, between the 1000uF capacitors and the transformer.

Basically, the capacitors filter the power rails, and a short across one of them means a rectifier could be dead.