My G68J started showing what I thought were some worrying signs - occasional minor thuds through the subwoofer while on standby, volume control sluggish and very occasionally the centre channel would stop working until it was rebooted.
I had bought it secondhand through the restaurant around 6 years ago and when I opened it up I discovered it still had the original UMEC power supply which allegedly could fail high and take out some boards with it.
Around the same time I noticed a G68XXV on eBay being sold by a dealer I had done business with before and decided to go for it and asked them to upgrade it to the Meridian Linear PSU at the same time.
I have to say I'm really pleased with the sound of the new (to me) G68. It really seems like a very decent step up - but I do realise that I've changed multiple things at once. As well as the PSU change I'm now able to use balanced connections to my Bryston power amp and I suspect that the balanced output boards on the G68 may have a slightly different sonic balance as well as better noise immunity.
I liked the sound so much I ended up buying a Raspberry PI and a lifetime Roon subscription

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The only "downside" is that I still get the occasional minor thuds through the subwoofer (probably something electrically noisy in the neighbourhood) and I've also had the center channel dropout on the new G68 (it only seems to happen with the optical out from my Sony Android TV so it's probably the TV).
I've fitted a new XP power supply to the G68J and it seems to be running fine but given the prices they seem to be going for just now I'll probably hold on to it as a spare.
-Ronnie