Matsui 14T1, G1000 chassis

[Lloyd 1985]

I’ve been digging in the lock up and found this little telly that I rescued from the side of the road back in 2008, probably should have left it there, but it was either that or have to sweep up it’s remains after the local yobs decide to launch it into the middle of the road!

It had been rained on, and had a bit of rust in it on the heatsinks, but after a bit of a dry out with the hairdryer I plugged it in and was met with a picture that came and went as it pleased, I guessed there was still some water hidden in it, so cooked it some more. After that it would then come on to a bright raster which would then collapse to a narrow out of focus mess, at which point I gave up on it.

Now I’m having round 2 with it! First thing it did on power up was display the narrow raster, but in green with flyback lines, if you poked the tube base panel it would change to white, so I disassembled the base connector, and reassembled it, as it looked a bit damaged, the spark gap was touching some of the pins, now that’s sorted, I can get a sensible raster, well, a 6” wide one with all 3 colours doing what they should!

Now for the crazy bit, I can get a full screen raster with a very good picture when switched to AV, but as soon as one of the normal RF channels is selected, it collapses again! But to add to the crazyness, if I then press the Teletext button whilst on one of the RF channels, it comes back full screen! And the Teletext works too!

I’ve checked voltages on the power supplies, which all seem good, I pulled most of the caps out and tested them on my Chinese ESR component tester, they all passed, all the diodes around the LOPT check fine, I haven’t checked all the resistors, but the ones I have checked were bang on too. I’ve read several things on this chassis which say ‘narrow defocussed picture, LOP TR running hot- IC500 micro faulty’ they mention to check the I2C bus pins for low resistance to ground, which I have done, and both are OK, I even stuck the scope on them and could see the activity when buttons are pressed. I also tried resoldering around all the big IC’s just in case, and gave the board a good scrub with IPA, but the set still refuses to work normally!

So is there anything else to check that can cause this before I condemn the micro? If it really is that causing it then I’ll have to admit defeat (again!!). I also saw mention of a mod kit for this problem, but no details as to what exactly it was.

Regards
Lloyd

[ben]

Have you checked the scan coils?

edit: just realized this is in modern tech section, mods please consider moving it to 'vintage TV' - this set came out in the early 1990s!

[Lloyd 1985]

Hi Ben,

I’ve taken them off and had a look for any corrosion, couldn’t see any. I’m guessing they are ok as the picture is perfect when on AV, and it stays rock solid for over an hour, same when Teletext is selected. I’ll get some photos in a bit.

I was in two minds as to whether this thread should be in the vintage TV section, I was surprised to find out how early this set was! It’s got less in it than my later Daewoo 14” set from 1997!

Regards
Lloyd

[Paul Stenning]

Originally Posted by ben

... just realized this is in modern tech section, mods please consider moving it to 'vintage TV' - this set came out in the early 1990s!

Moved. All CRT TVs are regarded as vintage here now.

[ben]

I wonder if the tuner is pulling one of the supplies down? Very odd one, this!

[Lloyd 1985]

Cheers Paul

I think you might be onto something, Ben, I went to get some photos of it tonight to be met with a new fault, or should I say almost the original fault that I thought was caused by water, the tuning seems to be drifting about, the picture comes and goes as it pleases and is noisy.

Anyway, here’s the pictures! Picture 1= the set on power up, showing the RF input. Picture 2= RF input with full screen raster after switching the teletext on. Picture 3= AV input showing a nice clear picture, without the Teletext on.

I have been putting a video together of it for YouTube, but it needs a bit of trimming down, it’s already got to 15 minutes long!! That’s enough to bore the pants off anybody.. I’ll put a link to it when it’s done.

Regards
Lloyd

[Welsh Anorak]

This has some very odd circuitry and was not a very welcome visitor to the workshop back in the day.

It uses a Gooding chassis which had a tendency to run at double line frequency when IC500 failed. It used a sort of half analogue half digital circuit with dividers internally in the IC. If you have a manual you'll find it's very little help as there are lots of unlabelled black boxes!

Besides the speaker and the main smoother, the main problem was, you've guessed it, the jungle chip.

I think you might just want to watch in AV!

[Lloyd 1985]

Cheers Glyn, I do have 2 manuals for this chassis, the Grundig one which is the full bells and whistles stereo version, and one that covers the cut down portable versions. The Grundig one does go into some detail as to how it all works, which is nice. I really hope it’s not the IC, as it looks a pig to try and get one now! The manual also mentions that certain things were programmed at the factory, so I’m guessing that a generic ST6365 without the G1000 label won’t work. I have an old jam jar full of large IC’s which may yield such an IC, when I can find where I stashed it!

Regards
Lloyd

[marceljack]

Is this TV using a kind of "one chip TV" IC which combines vision and sound IF, H and V sync, vertical output and video processing (like for example the TDA8362 from Philips) ?
Or is the reception part (IF) separate from the "baseband" part (sync and video processing) ?

[Welsh Anorak]

This chassis is quite different to anything else! The main IC is an ST6365 which AFAIK wasn't used in anything else. The subsequent Grundig/Gooding chassis reverted to a more familiar design.

[Lloyd 1985]

this is the service manual I’m using, which shows what chip is doing what. It looks to me like IC500 does all the tuning, AFC, IF (with help from IC400). IC800 does all the horizontal and vertical drives, and also the colour drives, but it needs telling what to do by IC500, otherwise it just defaults to running the line speed too fast.

I managed to sort out the drifting tuning simply by putting the set in service mode, it settled down after that! Very weird, I did stick a meter on one of the I2C lines whilst it was going nuts, and the voltage on there was jumping up and down, in time to the tuning drift.

Regards
Lloyd

[Maarten]

Originally Posted by Welsh Anorak

This chassis is quite different to anything else! The main IC is an ST6365 which AFAIK wasn't used in anything else. The subsequent Grundig/Gooding chassis reverted to a more familiar design.

ST6365 is the microcontroller. The jungle IC is a Motorola MC44002.

P.S. @Lloyd1985: It's not an early 1990's design, I think, but mid 1990's so comparable in age to your Daewoo. It's likely the Daewoo was a bit behind in technology.

[steve1010uk]

I repaired quite a few of these in my younger days, forgotton most of what i knew about them but i do remember having many weird problems with the small surface mount transistors under the chassis.