LG 55" OLED Repair 55eg910t

[jaksun]

I posted this previously on a non-repair forum, but I thought I'd have better luck here.

I have the above LG 55eg910t OLED TV, it's 55" FHD/1080p. It's completely dead, no LED. After popping the cover off and everything looking pretty new, I've check the main fuse on the smaller power board and it was faulty. After replacing the fuse and turning on the power point, it seems that on the secondary power board a *fast/ultrafast diode BYV10X600BQ fried. After replacing that, testing again, the same thing happened, specifically that as soon as I plug in and switch the power on at the power point, that diode smokes (I don't get to the point of turning on the actual TV)

I'm not a tech, I'm just a curious person, so I'm wondering if anyone has any advice. Some links to show the parts:

Small primary power board where AC plugs in: (this is the one that I replaced the fuse in the middle) https://www.aliexpress.com/item/4001099175161.html
Secondary power board where the diode keeps frying: https://www.aliexpress.com/item/32950706646.html
(for reference the diode that fries in the picture is under the heat spreader at the top of the picture, and is the one on the far left, you can see a bit of black on the heat spreader from where it burned.

Pictures of my actual board: https://imgur.com/a/MStFqnA

Apart from general advice, as you can see the 2 boards are about 30 and 70 bucks respectively. What I'm wondering though is:

If I replace the larger board first, is there a risk that either the primary board or a board downstream is causing this component to blow and not a fault on it's own board? I figure for the downstream ones I could just disconnect the ribbon cables before I plug in, but I can't unplug the primary board because that's where it's getting it's power from
the diode didn't look blown when I initially checked the TV, it only blew once I replaced the fuse and then plugged it in. Hopefully that info might be useful.
Otherwise I could try just fixing the secondary board again, and getting a new primary board which is the cheaper one, but then I might be out of pocket for both boards, which I'm trying to avoid
Anyway, I figures there's some handy techs here that might be able to provide some insight, or maybe worked on this TV before and know it's ins and outs.

[ESTechnical]

Hi,

If you can check for short circuits after the power supply you will probably find the reason the fuse blew and the diode failed. It sounds like there's a short somewhere after the PSU, where it draws a lot of current via the diode and burns it.

Good luck!
Ed

[jaksun]

Thanks, yes I will check to see if there are any shorts. Do I need to check past that board, to the rest of the TV's boards? I'm considering replacing the board but I wanted to eliminate the downstream boards from being an issue before I did so.

[ESTechnical]

To start with, yes, connect the boards to the rest of the TV and check for v+ to ground shorts. If there is a short, you can then disconnect the pcbs from each other and work out which board the short is located on. Then go down to component-level looking for the short(s).