11AK45, strange CUT-OFF issue

[Welsh Anorak]

Yes, that's exactly what I mean. Either the frame chip will overheat or the line stage will. As mentioned above, the CRT can be destroyed if left running with no picture.

[3CX15000A7]

Hmm, seems the EEPROM noted in the schematics (24c08) seems not the one on the chassis. Seems in real life it is a 24lc16b . . .

Also the board says indeed 11ak45b5, where on the cover stays 11ak45A. Consistancy isn't the best with those sets . .

Ordered again . .

[Red to black]

You can use a 24C16 (16k eeprom) in place of a 24C08 (8k part) higher capacity is usually ok within reason, lower obviously isn't, ie. you cannot replace the 24C08 with a 24C04 (4k part), the micro just ignores any addresses above what it needs.
Things start getting a bit tricky above 32k due to paging issues.
In fact when I was ordering the blank chips I always mostly ordered the 24C16, usually in bulk to get a discount, as these would also fit sets that used the lower capacity types up to 16k and lower. I did order some 32k parts for some Philips sets too when needed as these cost more than the 16k type (plus these were usually SM parts), the 16k parts were about the same price as their lower capacity counterparts, just down to economics on my account.

[3CX15000A7]

I had ordered the 24c08 but they used a 16 in this set

But meanwhile I managed to program a correct 24lc16b chip and tested it. There where some small vertical geometry settings that needed a tweak but nothing blew up

Sadly, it did not solved the original fault. The auto greyscale still doesnt function in 16:9 mode and in 4:3 it still seems to dynamically adjust it's greyscale depending on the content with gives a bad color balance sometimes and poor shadow detail. Going to 16:9 mode will stop the dynamical adjusting, so I am pretty sure its a regulation loop or something.

Could it after all be the tube that is just too much out of spec? There arent coils in the heater circuit as with many old philips sets but theres a 1OHM resistor(R618). Would it safe to short it to test the set with more emission?

[Red to black]

We didn't have problems with flat tubes back then, as they were going faulty with many other problems just out of the guarantee period, you really have nothing to lose at this point so a quick try is in order, Thomson tubes are a bit more resilient than Philips ones of this era, they just produced poorer pictures in my opinion.

[3CX15000A7]

shorting the resistor makes the picture sharper (no surprise) but the problem stays.

I think its just a dumb feature of the vd3130 video chip or their configuration . . . . Or my expectations are just too high. Although otherwise it's picture wise pretty decent. Even the beam regulation is not bad at all.

I know the Thomson A66EHJ13X tube pretty well from a Panasonic Z8 set. I like their picture, sharp, lots of contrast and good color volume. Only real downside of this tube is the mask, that one just too weak and gives discoloration with bright images. Dont know the Thomson widescreens maybe they are not that good . .

[Welsh Anorak]

It was the same with all the Vestel and Profili widescreen TVs. A great picture meant a Philips tube until its inevitable failure. The Thomson widescreens were poor picture-wise, but did last forever (except, for some odd reason, in a Thomson!).
The occasional LG and Samsung CRTs fitted to AK45s could lose their necks for no obvious reason - I've had them also fail on 'real' Toshibas and Hitachis, possibly due to overheating scan coils. The latter two manufacturers used to replace them free of charge out of warranty until stocks were exhausted. The last one I had that failed was in a six-year old Toshiba who, true to form, simply gave the amazed customer a brand new TV!

[3CX15000A7]

The LG CRT's were also philips I think? (LG philips displays?)

How's your expierienxce with the non widescreen Thomson CRT's?

I never had a widescreen CRT, they are also less common here (although regurarly offeree). Widescreen take off here when all CRT were replaced by flatscreens. Dutch broadcasters were very conservative. For years, all the live 16:9 events were cropped to 4:3. Digital tv around 2005 was just a digitzed PAL signal, occasional widescreen was in letterbox. Even the BBC was in 4:3 only, cable provider chopped everything until around 2010 . .

[Welsh Anorak]

The non-widescreen Thomson CRTs were pretty good as far as I remember. In fact most of the 4:3 tubes by that point were all very good with the exception of the Philips ESF series that used the widescreen gun assembly.
The LG widescreen CRTs weren't Philips as far as I know, though I'm sure Maarten would know for sure. They had pinkish labels and were fitted to Hitachi 28" and 32" widescreens which used either, though there were electrical differences. Also their mode of failure was different - Philips shorted intermittently and LGs went down to air.
Don't recall seeing LG CRTs of this type on any other TVs, though I expect LG themselves used them.

[Maarten]

That must have been Korean imports from before the joint venture. I've never encountered one.

[Welsh Anorak]

They were in the first generation of Hitachi widescreens, so that's perfectly possible. They did give good pictures, but as I mentioned several went down to air for no reason we could find and they were replaced without question.