Sony kdl52v5500 no picture, no T-con VCC

[Dannyx]

Good day folks. I've got a pretty strange and complicated issue with this Sony telly. On top of being this huge behemoth that I can't even lift on my own, there are a couple of uncommon issues with it, as follows: you plug it in, you can hear the relay closing, the green light comes on at the front and that's it - no sound and no picture, though it seems to respond to the remote and buttons on the side (the led blinks), so there may be no sound because it ended up in some random source. When it comes to turning it OFF, the led turns red just fine, but the relay doesn't open back up, so there's still mains present on the board....I'm not entirely sure it's supposed to be like that, because what's the point of the relay if it stays on all the time, so that's one thing which is iffy to me.

Sony seems to like to make things more complex than they should be, so there's a mess of boards inside...there's like two inverter boards (one of them called a "balance board" apparently), which feed ANOTHER set of boards on either side and THESE actually look like what you're likely to call "inverters" so I'm not 100% sure how this setup operates and with so many boards and sub-boards and sh!t, you can see how it's very easy for something to break down and it could be anywhere...getting over the fact, measuring various voltages around the board shows they're all there, including 400v on those fat leads which power those two inverter boards I mentioned. Applying 3.3v standby to the BACKLIGHT pins, DOES turn on the backlight, so those inverters work fine also.

Putting a light up to the screen shows no picture either and for good reason, because there's no VCC going into the T-con either.....it's a mess and it's starting to point more and more towards the main board. Fuse of T-con is fine.

The REAL buzzkill is that the parts are not marked on the bloody thing ! Have you ever encountered a board where the parts are just randomly thrown around with absolutely no indication as to what they are ?! The service manual is thus useless because I can't identify anything ! I was going to measure how power is delivered to the T-con board, but with no markings on the board to indicate what the hell I'm measuring, it's impossible...

So to clarify:
-power supply+inverters seems to be OK (all voltages present and backlight turns on when jumped to 3.3v)
-main board seems to respond
-no power to T-con board
-no BACKLIGHT ON signal from main board

[Andrew F. Ali]

Re: Sony kdl52v5500 no picture, no T-con VCC

I couldn't download the attachment, as my system is really slow today. However, there should be a transistor on the Main Bd. to switch power too the T-CON Bd. I believe the backlights will come on as the bl-on signal with not turn if power is not sent to the T-CON Bd.

[Dannyx]

Re: Sony kdl52v5500 no picture, no T-con VCC

I couldn't download the attachment, as my system is really slow today. However, there should be a transistor on the Main Bd. to switch power too the T-CON Bd. I believe the backlights will come on as the bl-on signal with not turn if power is not sent to the T-CON Bd.

I found said transistor (a TPC8109 )underneath the t-con connector but it doesn't read any shorts and without a scope it's difficult to tell if it's operating or not....after all, it requires an "on" signal from the CPU to the gate, or something close to that, so if that's busted.....no signal either.

[Andrew F. Ali]

Re: Sony kdl52v5500 no picture, no T-con VCC

The transistor may not have failed 'short'. Perhaps it failed 'open'???....Yes that is correct it would have to get a signal at the BASE or GATE to tell it to switch ON. That type of failure is rare but not improbable.

[R_J]

Re: Sony kdl52v5500 no picture, no T-con VCC

Have you checked the F1300 & F1301 fuse on the ba board? (page 27 of manual) Check if you have 12 volts on L1307, Looks like Power3 is the line that turns Q1309 and then Q1312 on to supply voltage to Panel_vcc_sw

[Dannyx]

Re: Sony kdl52v5500 no picture, no T-con VCC

Have you checked the F1300 & F1301 fuse on the ba board? (page 27 of manual) Check if you have 12 volts on L1307, Looks like Power3 is the line that turns Q1309 and then Q1312 on to supply voltage to Panel_vcc_sw

All fuses were ok and despite having returned the TV now, I believe I was not getting any "control" voltage that would switch on the transistor and with no markings on the board whatsoever, the job became a rather fruitless battle....

[CapLeaker]

Re: Sony kdl52v5500 no picture, no T-con VCC

Panel on is sent from the main IC. Usually I don't even bother with things like that. I just replace the main board, because 90% of the time there is something wrong with the main IC. IF the switch had failed, you would have seen it right away.

[Dannyx]

Re: Sony kdl52v5500 no picture, no T-con VCC

Panel on is sent from the main IC. Usually I don't even bother with things like that. I just replace the main board, because 90% of the time there is something wrong with the main IC. IF the switch had failed, you would have seen it right away.

True that, and it's exactly the same method I use: if a control signal is missing from the main board, unless it's something blatantly obvious, I don't bother and just mark the board as bad and proceed to look for a replacement or prompt the owner to scrap the whole thing if none is available.