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No power to Sony KDL55W905A - Running out of solutions!

I’ve had this TV for some time now and it’s been flawless up until 2 weeks ago. The problem first occured when the TV wouldn’t turn on immediately. Then it would freeze while being on, the picture would show artifacts (almost like a mesh of green snow) that got worse for about 10 seconds then it would power off. I was able to get it to restart and stay up for hours until eventually the set wouldn’t power on. During this it only flashed the red light dianostic system once and it was either 2 or 3 flashes. Also the standby light would operate almost at random, some times on, other times off.

What I have done:

  • Tried all factory reset options
  • Check the fuse in the plug and the socket
  • Open the TV up to look for bulges or burn marks on the boards (nothing)
  • Bought a new power supply which didn’t help so returned it (could have been faulty though unlikely)
  • Took a multimeter to the previous power board and I just can’t get any readings from the board except for some remaining charge in the capacitors

I looked at the triage page in the service manual to try and diagnose the problem and it seems to point towards the mainboard. Problem is there are none for sale anywhere. Some things I am unsure about after testing the power supply is why there is NO voltage anywhere and also the strange artifacting exhibited by the screen before it powered off.

Hoping someone can advise me further before I begrudgingly have to buy a new television. I love this set. Thank you.

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Hi @ytsol ,

Did you try following the No Power troubleshooting flowcharts as described in the service manual, you didn’t say?

Here’s a compilated image showing the 3 flowcharts taken from the manual. There are more images in the manual showing the locations of the test points.

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I ran the checks through to SL9103. When I got there, the contact with SL9103 tripped the power supply and now everything is powered off. The power board clicks as soon as it's turned on.

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@ytsol ,

Just confirming that when you placed the DMM Voltmeter test probe on the SL9103 test point it tripped the power?

Very unusual for a Voltmeter to trip the power unless the probe accidentally bridged two points

Did you check if fuse F9102 is now OK?

I assume that this is on the power board which was replaced and the replacement board didn't solve the problem either.

I'm wondering if all the test points are actually all the voltage supplies required by parts of the TV. It appears to be check that the voltage is there, is it the correct value and if not there, check the fuse.

Unfortunately there are no schematics for the boards so what the 3.3V supplied at SL9103 is required for i.e. where it goes to next I don't know

由完成的

I was able to test SL9111, SL9109 and C7348 and C7349 (all registered the correct voltage). I initially skipped SL9103 because I was worried about removing the cover as it's attatched to the X-Reality chip pretty firmly. I went back and carefully removed the cover from the A side to test SL9103 and at that point it tripped the power and will not come back on at all now. No readings on any part of the main board. So I don't think I can test F1902 because it recieves no power.

Hope I'm making sense, this is new to me.

由完成的

@ytsol ,

So no readings at all back at Step.1 on in the flowchart then?

When I said "Did you check the fuse.....?" I meant, with the power disconnected from the TV, test F9102 for continuity using an Ohmmeter, although there maybe should have been power on one side of the fuse. If there isn't and the fuse tests OK with an Ohmmeter, then it is further back in the power supply. Something else may have blown when you removed the cover and reapplied power to the TV. (Hopefully you disconnected the power first before removing the cover?).

If it is blown you can try replacing it with an equivalent smd housing package fuse and then recheck if it now holds.

I don't know its' current rating as there is no parts list in the service manual so this will be difficult to know, unless there are some markings on it that will help to identify it, as the incorrect fuse can cause more damage i.e. more current allowed to flow to the components it feeds than designed for before it blows due to a fault condition.

Then check that there is now power and start again with the flowchart

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