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2016-12-10

Philips 46PFL5507 - Q552.4E - DPS130 - dead stand-by - shorted ceramic C910 - open resistor R915 - dead chips DDA010, ST9M101

This Philips did not do anything once plugged in. Not even the stand-by light was on. That's a pretty clear indication of a broken standby supply. I could not measure any voltages coming out of the power supply and quickly concentrated on debugging the stand by circuit.

That was pretty tough. I found out that the PWM chip did not have its required VCC activation voltage. The reason for that was the open 2.2 Ohm fuse resistor R915, which is connected directly to the main capacitor's V+. The diodes all measured ok. The PWM chip had no short, neither had the line, which the resistor was connected to, so I soldered in a 2.2 Ohm resistor to check.



Booom! It took a fraction of a second to kill the new resistor. How is that possible? There was no measurable short and neither did I find any burn marks anywhere.

After some intensive research, I found a schematic in a Russian forum thread, which fit my power supply model DPS-130 well enough. The only component left, which could cause a short, was the capacitor C910. A 1kV 22pF thingy, which did not look suspicious at all. I unsoldered it and voilà! No reading. It was dead, but not with a measurable short. My DY294 transistor tester confirmed the high voltage instability. Amazing how it did survive without any burn marks.

For a quick and dirty test I replaced the cap with a 4kV 33pF and the open resistor again. Supply not working. At least the short was fixed. Thus, the PWM chip must be broken, too. It still did not charge the starter capacitor (which tested ok, by the way) with Vcc. It is responsible for starting itself up once V+ is present at its drain pin. After the startup phase, it would feed itself through a secondary winding in the transformer.

I ordered 22pF 4kV caps via eBay and DDA010 chips via AliExpress. Three weeks later, the DDA010 arrived. I swapped it and the 22pF cap. Supply still not working. The PWM chip did not build up its Vcc startup voltage. I measured again. There was a constant 100 Ohms against ground on the Vcc rail. Under those circumstances, the starter capacitor cannot charge!

The only suspicious part left was IC902, an ST9M101. The original is impossible to find. The alternative part number is Infinno IM1M101-T6G. The documentation of this chip is ridiculous. It is used to sense the presence of the high input voltage. It can disable the PWM chip.



A jumper wire was conveniently located between the PWM VCC line and IC902. I opened it up and finally, the PWM chip was starting. However, it rebooted in a loop. IC902 was definitely defect, too (or maybe the PWM chip had not been dead in the first place). IC902 is also connected to the FB (feedback) line of the PWM chip and I assumed it was causing some trouble there, too.

Ok, another order from Aliexpress. On eBay there are repair kits available with DDA010 + IM1M101 pairs.

Enough with the blondes already, hallo Frau Green!


13 comments:

  1. Hallo, ich habe eine Fernseher Philips mit genau dieser Problemen... Ich habe alles was Sie gemacht haben, aber da lauft immer noch nicht... haben Sie sonst noch Ideen wie kann ich diese fixieren? Ich danke Ihnen sehr für Ihre Arbeit.
    Herzliche Grüsse,
    Schaller Olivier
    olivier.schaller@bluewin.ch

    ReplyDelete
    Replies
    1. Leider nein, das hier beschriebene Problem war schon kompliziert genug. Ich weiß nicht, was sonst noch alles defekt sein könnte. Praktisch alles ist möglich.

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  2. Hello there

    philips 47pfl6877 / k12 tv have this problem in my cut.
    The red led does not light when I plug in the plug. qfu2.1e power card dps-119cp motherboard 3104 313 65664 what can the problem be? the problem is the main board power card. if i replace these parts

    ReplyDelete
    Replies
    1. QFU series have most likely mainboard problems. See my blobposts about this subject. When the power supply has a proper 3.3V standby voltage available for the mainboard, this is pretty sure the problem.

      Delete
  3. I see 1 and 2 pin 3.3v on the power card. problems are the mainboard. can I find the main board problem.

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  4. When the motherboard socket is disassembled, I see 1 and 2 at the end 3.3v

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  5. Hi, looks like I may have the exact same problem with IC902. What exactly did you connect in 'A jumper wire was conveniently located between the PWM VCC line and IC902.' My board has VCC at 902 and the PWM chip. Thanks

    ReplyDelete
    Replies
    1. I opened the wire, so that IC902 was disconnected from the PWM chip. This isolated IC902 from the business and revealed its fault.

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    2. Hy Alpengeist, can you help me yith a photo or an illustration, how do you resolved this problem? I don't understand this part of descripstion: " opened the wire, so that IC902 was disconnected from the PWM chip. This isolated IC902 from the business and revealed its fault"
      Thank you!
      Have a nice day!

      Delete
    3. The picture above is all I have. The mentioned jumper wire has its one end in the red box in the pic. Once it is disconnected, IC902 has no influence on the PWM chip anymore. Therefore, the PWM chip can start, but only for a short time.

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  6. Hallo, i want to order Im1m101 but cannot find it. Alieexpress also not?

    ReplyDelete
    Replies
    1. That must be a typo. The first character is an uppercase I. I can find it no problem on Ali. I suggest you use copy&paste from my text.

      Delete

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