Philips 42PFL9603D won't turn on. Need specs for Lelon capacitors.

[Globulus]

Re: Philips 42PFL9603D won't turn on. Need specs for Lelon capacitors.

If you get some chipquick you can remove the small components pretty easily. I would try out the freeze spray. I bet those little fets are less than 3 bucks each, and most of the pins are connected together so soldering doesn't have to be super accurate.

Here are some in-circuit source-to-drain measurements of the FDS8884 MOSFETs (cheap multimeter set to 2KOhm):





7U08: 850 Ohm
7U02: 709 Ohm

7U05: 10 Ohm
7U06: 34 Ohm

With the inaccuracies of my measurements in mind, I suppose 7U05 + 7U06 (or the surrounding circuitry) could explain the 42 Ohm resistance between +12V and GND.

Yes, those FETs are cheap, but I have to pay $12 for shipping unless the total order amount is around $120, so I try to at least find some more things I really need before I order anything (I am located in Denmark and would have to order FDS8884 chips from the Danish branch of RS Components).

As for the freeze spray, I have not tried that yet. I am a little concerned that I might cause even more damage to the board (or the power supply) if I apply power from a source that does not shut off when faced with a short. I saw someone on YouTube using a scooter battery with a 10 Ohm resistor in order to limit the amount of current going to the board. That might be an idea, though I am still concerned about damaging the board.

[Caleb]

Re: Philips 42PFL9603D won't turn on. Need specs for Lelon capacitors.

Well I would start with 7U05 after you get it desoldered check the board and the parts again- but it is probably both of them. The scooter battery could certainly source enough amps to fry the traces off the board, I would be very careful if you try that. Most of the techs use freeze spray on a regular basis to isolate problems, just let the liquid evaporate a little before applying power. If your concerned about the rest of the board just freeze the section around those fets, electricity will always take the path of least resistance.

[Globulus]

Re: Philips 42PFL9603D won't turn on. Need specs for Lelon capacitors.

Well I would start with 7U05 after you get it desoldered check the board and the parts again- but it is probably both of them. The scooter battery could certainly source enough amps to fry the traces off the board, I would be very careful if you try that. Most of the techs use freeze spray on a regular basis to isolate problems, just let the liquid evaporate a little before applying power. If your concerned about the rest of the board just freeze the section around those fets, electricity will always take the path of least resistance.

Hence the resistor. This is the video I was talking about:
http://www.youtube.com/watch?v=XhqwC3BFBug

The battery and resistor (12 Ohm, sorry) is seen at around 3m35s.

But good point about electricity taking the path of least resistance, thereby limiting the potential for further damage.

I was mainly concerned about the following warning in the service manual:

"Defective (in short-circuit) power MOS-FET's lead usually
to their controller IC broken; if one or more high-side MOS-
FET's (7U05, 7U08, 7U0D-1 or 7U0H-1) is broken then the
platform can be heavily damaged if started in SDM-mode
(SUPPLY-FAULT signal is then ignored, while higher than
normal supplies will be generated)."

Time to order more tools and supplies ...

[Globulus]

Re: Philips 42PFL9603D won't turn on. Need specs for Lelon capacitors.

42 ohm is really low, you need to start looking at the ssb. If it was me I would hook up a 12v 500 milliamp power supply (wall wart) tied to 12v and ground and freeze spray the board, then see what melts the fastest. Generally it will be your short. However most of that board is fine pitch stuff, if you can prove the fault into the ssb you might be better off getting a replacement. I would bet its probably one of those tiny fets 7u05, 7u08, possibly driver chip 7uoa, or maybe 7u02 or 7u06. I suppose it could also be a short on 2u14 or 2u0y capacitors but pretty unlikely -schematic is on page 96 of the manual.

To test the power supply I usually just solder the bulb in wherever its convenient, but you can unclip the wires from the ssb side of the connector and hook to them with alligator clamps.

Well, I've got a dust spray now and I have a drawer full of "wall warts" so I should be ready to do the freeze spray test.

You are suggesting a 12V 500 milliamp power supply?

I've got a couple of those, but they are not stabilized, so without a load my multimeter is telling me that they are outputting 17V-19V.

My stabilized, multi-voltage PSUs are in the 1A-2A range, but I really do not wish to connect those to a circuit which might have a short.

The only (fixed-voltage) stabilized 12V PSUs I have are the ones that came with my external WD Elements Desktop USB 2.0 drives. I've got a lot of these drives and hence a lot of these PSUs I never use but they are all 1.5A. Would that be OK for this test or would it be too much current?

[Caleb]

Re: Philips 42PFL9603D won't turn on. Need specs for Lelon capacitors.

You can use the 1.5 amp, but you cant leave it connected for more than about a second and a half or you run the risk of melting traces, you could use the 1.5a with a resistor to limit current- by my calculations 100 ohm resistor will give you about 200 mw, a 47 ohm 425 mw. However the resistor will be dissipating a lot of heat so if you have a 1 watt that would be good. Alternately you could wire in a 12v regulator to keep the voltages down on the 500ma supplies.

[Globulus]

Re: Philips 42PFL9603D won't turn on. Need specs for Lelon capacitors.

It has been a while since last time I looked at this.

I (finally) did the freeze spray test with an non-regulated 0.5 amp power supply. At 7.5V it would measure 12V without a load, so that was what I tried first. Not much to see. Upped it to 9V. Still not much to see, though the 7U05 (the one measuring 10 Ohm in-circuit) seemed to thaw a little quicker than the rest. At 12V (19V without a load), however, the 7U05 would thaw instantly whereas the three surrounding FETs would stay frozen.

Given that this single FET acted this way, I presume the problem is within that package rather than the surrounding circuitry. I have not measured it out of the circuit yet because I need to order a few things before I can take it out.

[Globulus]

Re: Philips 42PFL9603D won't turn on. Need specs for Lelon capacitors.

The latest (the last?) on this is that I replaced the 7U05 and 7U06 MOSFETs. This got rid of the shortcircuit and the light guide (small strip of light at the bottom of the cabinet) started pulsing when I connected the power. I got my hopes up for a few seconds, but the light guide just kept pulsing and the set never got any further than that.

Another freeze spray test did not reveal any (other) shorted components.

I'm afraid that the shorted FETs might have taken more critical chips with them but I can't say for sure.

Time to buy a new TV. With extra warranty so I know that it will last me for at least 5 years - and if not, someone else will have to fix it.