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Hi,
With power connected to the TV there should be 3.3V DC on pin 5 of the connector, lower right side of the power board as shown in your image.
Everything looks OK on the board i.e. no obvious damage and since you said that the main fuse is OK, without a schematic it will difficult as you would have to start checking if there are any voltages appearing on the "secondary" side of the board to know if the problem is on that side of the board or the high voltage primary side.
There is a "Power On" pin mentioned on the board (same connector as the Stand by pin) but this is only to turn the power board fully on once the mainboard gets the signal to turn it on from the remote or power button. So there should be no other voltages on the connector on the secondary side except the 3.3V which is supplied to the mainboard.
这个答案有帮助吗？
So you just answered my question posted minutes ago; so there is no need to short the power on pin(#9) ?
Thanks,
Bai
@Bai Gu
What are you going to "short" pin 9 to?
It may be that there is either a voltage value returned on pin 9 from the mainboard or an earth and I don't know which it is.
In either case if there is no 3.3V Standby voltage, more than likely there won't be any other voltages either as it is derived from what is supplied by the input voltage.
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Bai Gu your Klein tool will not work for this. You do need to get a simple multimeter (analog or digital will work) You need to measure the voltages on CN6401 of your power board and see which ones are present. Those are DC voltages. You need to have the STBY voltage. If you do not have that, it is your power board that is having problems. There is also a reason why this power board seems to be very difficult to come by. It is common that boards that are widely unavailable are those that are having a high failure rate. The xbr-75x850G can use the xbr-75x850F power supply.
这个答案有帮助吗？
Thank you all for your answers; another question: shopjimmy.com has a video seems to suggest that in measuring PSB pin voltages (stub, 12v etc), the power pin must be shorted or you won’t measure voltages at other pins. I reviewed other posts on YouTube, this seems the only one suggest that. Is it necessary?
Thanks,
Bai
Bai Gu without having seen the video etc. this is usually "shortened" to either pull up- or pull down the power supply to turn it on to measure the voltages. Before going that route, measure the points that you have to have power on, which is your STBY voltage. Do you have that?
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5条评论
Is the display showing any signs of life at all?
由 Repair Skeleton 完成的
Hi, Have you checked if the fuse on the power board is OK, you never said?
由 jayeff 完成的
1. No sign of life, but my Klein voltage tool beeped on high V area as well as low V area; multimeter detected no voltage at every point I checked, including pins should show stay, and 12v
2. Fuse is ok
由 Bai Gu 完成的
@Bai Gu
Post a close up image of the power board back here. Here's how to do this on ifixit 在已经存在的问题里加入图片
What model is the Klein voltage tester? Looking online it seems that some will detect AC but this may mean that they can't detect DC.
To do board level repairs you really need a DMM (digital multimeter) with a display that shows what the voltage is be it AC or DC and not one that just indicates that voltage is there with a beep or a LED, be it high volts or low volts
For example- if low volts it may not be enough - it could be 5V when it should be 12V and you would still get a beep but it is not enough to make things work, if you get what I mean
由 jayeff 完成的
The Klein tool is ncv t-2; it does not specify whether it can be used for DC; if it cannot, then it clears my puzzle and the tool seems to suggest there are low voltage but my digital multimeter shows 0 or 0.2-0.3 at almost all low V side points.
Thanks for your suggestions
Bai
由 Bai Gu 完成的