CurtPalme.com Home Theater Forum

bitsquad · Joined: 13 Jan 2020 Posts: 26

Hello!

Are there easy instructions somewhere for pulling the YA board, looking at the chips and determining if a G90 is good to purchase?

Anything else that I should check before considering a unit?

I'm looking at one now and I'm hoping there are already clear instructions written out that I could forward to the current owner.

Thank you!

**Curt Palme** · Posted: Tue Jan 21, 2020 10:28 pm Post subject:

G90s have two weak points.

1) Imploding green tubes (no one is quite sure why, some sets never do it, others have done it more than once.)
2) The YA board.

The Dallas chip is near the back right corner of the board, and will have a 4 digit date code on it. 1198 means it was made in the 11th week of 1998, and 3617 means it was made in the 36th week of 2017, etc. The Dallas chip should be less than 5 years old. Any one with a date prior to 2015 should be replaced at this point.

Bottom line on a G90 is to get the owner to pull the lenses and send you a flash and non flash image of all 3 tubes. The green will wear first, but good used tubes are now becoming hard to find. The Dallas chip is around $50 to change, I wouldn't bother asking the current owner to check that. There's a big long post here somewhere that I put up a bunch of years ago that talks about IC421 that had one run of those chips go bad after some time. I'd say now though if the set is working, that IC 421 is OK. If IC421 fails, then the picture will shake, very few adjustments will work, and eventually the set shuts down. There is no replacement for IC 421, but both myself and Craig Rounds have spare YA boards if you ever have a bad IC421.

OVerall though, you should be spending well under $1000 USD for a G90 at this point with even lightly worn tubes. Most G90 owners have a spare set for parts in case of failure of their main set.

HaydnG90 · Joined: 22 May 2006 Posts: 1335

Everything that Curt says plus I would add that the YA has more than 2 Achilles heels (IC421 and Dallas). The 'good IC421' serial number is 040A02E.
Another weak point is a short that can occur on older YA's. Its intermittent and can have a variety of symptoms however the worse one is if the G90 is on and you get error 88. This will nuke the tubes with spot burn.
I would recommend at a bare minimum, have Craig do some preventive maintenance on the YA. The tubes need to be protected at all costs if you want years of trouble free G90 viewing. He can also copy over the existing memory on the current Dallas chip (assuming it still works) so you retain SN and operating hours.

CIR Engineering · Posted: Wed Jan 22, 2020 6:55 am Post subject:

**Curt Palme** · Posted: Wed Jan 22, 2020 3:28 pm Post subject:

^ thanks gents! Smile

bitsquad · Joined: 13 Jan 2020 Posts: 26

I'll be honest, this has all got me reconsidering if it's worth taking the plunge, if I should just enjoy the direct view CRTs I have instead, or if I should just look for a free or almost free lower-end model that I could play with and not feel bad when it goes out, like a D50 or something.

I'll forward this to the seller but I'm unsure what I'm going to do. I think this one is likely a little bit too pricey, especially if it will need service immediately before use. I mentioned at first that I would like to be in the $500 range, and I think the seller would rather keep it than let it go for that price. From the impression that I get, I think they may come down to $1k or so but unlikely much lower than that.

Thank you for the replies! I truly appreciate it, even if I end up changing my mind about getting one. Better to know beforehand if it's going to be too much trouble.

**Curt Palme** · Posted: Wed Jan 22, 2020 6:29 pm Post subject:

Hey, there's still people that think their CRT is worth big $$$. Sadly, that time has long passed. Keep an eye out on CL and Facebook, etc. Lots of bargains to be had out there.