Insignia NS-PDP42 Powersupply not turning on after Zsus chip change

[2dbit]

Anyone who's made the attempt to replace the IPM chip on either X or Z boards knows it is a PITA.

Well, I managed to do something horribly wrong while operating on mine, and after replacement the tv turned on for a few seconds (didn't see the screen, it was still face down for smoke check) and clicked right off.

Since then, the power supply will just click on for a few seconds, then click right off.

I knew I did something horrible, and didn't want to risk futher damage, so I ordered a replacement board. Hopefully the problem stayed on that board, but unfortunately with the new board installed, it still presents the same click on for a few seconds, then click off issue.

The power supply has a solid 5v standby, and when checked, 3.4, 12, and 19, all check good.

Even the VS_ON presents a momentary 5v signal.

However, the actual VS remains dead.

VA climbs slowly, but doesn't actually go anywhere.

I don't see any fuses on the actual power supply, aside from the 115 input fuse. The Xsus board has 4 fuses on it, all check good, and I'm reading right off the power supply.

I suspect the easiest answer would be that the powersupply got shot in the incident and would require replacement.

Thoughts?

[2dbit]

Re: Insignia NS-PDP42 Powersupply not turning on after Zsus chip change

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[2dbit]

Re: Insignia NS-PDP42 Powersupply not turning on after Zsus chip change

http://lcd-television-repair.com/new...eshooting.html

I removed the power supply and followed the guide that is linked at the top of this post.

I found that each step of bringing the SMPS to full operation passed(progressive check of each lower voltage) up until the last, being the step where a 100ohm resistor is jumpered 5v-STB over to VS-ON.

When I complete that step, the SMPS begins to cycle. Each time it clicks on, the two 40watt bulbs that I have in series on the VS line begin to glow, but then the power supply trips off and resets.

[tom66]

Re: Insignia NS-PDP42 Powersupply not turning on after Zsus chip change

You should use an ohmmeter and check the Z-sus is not shorted.
Note these sets will blow up Z-sus if the Y-sus ER link is removed.

[2dbit]

Re: Insignia NS-PDP42 Powersupply not turning on after Zsus chip change

The z-sus was bad and has been replaced. Not sure if the new one is good, or if the old one caused harm to the x board, but the SMPS is now on the fritz. The power cycling is occurring with the SMPS removed from the set and being triggered on with 100ohm resistors. The load on the VS bus is two 40watt incandescent bulbs in series

[tom66]

Re: Insignia NS-PDP42 Powersupply not turning on after Zsus chip change

Does Vs go to more than about 220V then shut down? you might need more load to keep it in regulation.

[2dbit]

Re: Insignia NS-PDP42 Powersupply not turning on after Zsus chip change

The two lights connected to the VS barely glow before it shuts down

[2dbit]

Re: Insignia NS-PDP42 Powersupply not turning on after Zsus chip change

Well, since something is clearly wrong with the power supply, I started ripping things off the board.

I pulled the blue stripped fuse and found it to be open, so I pulled the heat sink containing Q852(W20NK50Z), Q851(same as 852), Q151(P6NK90ZFP), and Q801(same as 151).

Q151 and Q801 both check good.

The two FETs, Q852 and Q851 are both dead shorts across all pins.

Suppose the question is, knowing the two FETs blew, how far is the carnage going to go? Should I be looking at replacing the IC U851(L6598)as well?

[tom66]

Re: Insignia NS-PDP42 Powersupply not turning on after Zsus chip change

Is there a transformer-coupled gate drive to L6598? If NOT, I would always replace the IC because it can be damaged.

[2dbit]

Re: Insignia NS-PDP42 Powersupply not turning on after Zsus chip change

Nope, there's a Resistor and Diode between gate and IC and on the Source there's a resistor between the FET and IC.

[2dbit]

Re: Insignia NS-PDP42 Powersupply not turning on after Zsus chip change

Perhaps for good measure, a new diode... Going to have to unmount the diode so I know what to order

[2dbit]

Re: Insignia NS-PDP42 Powersupply not turning on after Zsus chip change

Looks like the diodes survived. Removed and checked good. They're SB140A diodes. Gonna order new ones regardless.

[2dbit]

Re: Insignia NS-PDP42 Powersupply not turning on after Zsus chip change

Well, changed all the bits and pieces, powered it on, and for a moment it was nice, two 40watt bulbs glowing, but, that was only for about 5 seconds before there were explosions and a small fire that went out after I finally got it unplugged.