Ferguson Colourstar 3792 TX9 Chassis

[beltinge bore]

Hello All

I have just had this left on my doorstep to save it from the tip!

Not really my era (9" EKCO's are more my thing) but it is in exceptional condition and comes with a some nice family history so I want to give it a chance.

Can anyone advise me as to what are must change components on this. I have had a quick look at the chassis nice layer of thick dust and no sign of any visible traumas. The PCB is marked 1001A. Before I fire it up is there anything I should check or change?

Can provide pictures if it helps.

Many thanks Seasons Greetings

Steve

[toshiba tony]

There were two main versions, one was a switch mode PSU and the other was a thyristor one. Which is yours, either shouldn't be an issue. Very predictable.

[dazzlevision]

Your set is the earlier PC1001 main board, with a thyristor power supply and the large choke. The colour decoder IC was also changed in later versions of the TX9 design.

I would suggest you have a close look at the solder side for any joints that are suspect, particularly on the big choke. Reflow with fresh solder any that look suspect. Soldered joints on the parts that get hot or vibrate (such as the big choke and line output transformer) should be carefully examined.

[jayceebee]

Originally Posted by beltinge bore

Hello All

The PCB is marked 1001A. Before I fire it up is there anything I should check or change?

Steve

PC1001 is the very first production version of the TX9, thyristor PSU and an NEC uPC1365 chroma IC. Might be worthwhile reforming the large can C147/8. Also give the line hold pot a squirt of cleaner and rotate it end to end a couple of times, it can develope a dead spot. Other than that it will probably work just fine.

John.

[emeritus]

I have a copy of the Thorn TX9 service data that I got from Mauritron that I now have no use for, my last TX9 -chassis'd set having been disposed of a decade ago. If you would like it, pm me your address and I can stick it in the post FOC, postage to your favourite charity. It covers the variations in power supply types.
Trying to declutter!

[beltinge bore]

Thank you emeritus PM sent

[beltinge bore]

Good Morning

Thank you for your replies and advice which I will follow.

I will post an update as things - hopefully - progress.

Thanks once again

Steve

[Welsh Anorak]

Not much to add, but I would mark the position of the set HT preset, douse with switch cleaner then reset it. Bear in mind on this early chassis ISTR the pot works backwards. Then set the HT a little low and the TV should work fine.

If you've a blown mains fuse there's a bit of a procedure to follow.

[Nickthedentist]

Assuming the tube is OK, this should give an exceptionally good picture. Amazing reliability for a late 1970's British set as well.

[hans]

Originally Posted by Welsh Anorak

If you've a blown mains fuse there's a bit of a procedure to follow.

Where I live these sets were rare. I've only encountered one. It had a blown mains fuse. I had no knowledge of a procedure, so I checked what I suspected could be the cause, but didn't find anything. I replaced the fuse and it worked. I still couldn't find anything wrong with it, and it kept going for years. It was a nice set.

Maybe it was a glitch in the crowbar circuit?

[Philips210]

Yes, the TX9 was generally a very reliable chassis which was introduced in late 1979. There were three versions of the chassis. The first was type PC1001 which was updated to version PC1040. Both of these had a thyristor regulated power supply. The final version was PC1044 which was of the switched mode type.

Random fuse failure on the thyristor versions could be quite a problem to pin down and Thorn issued a number of likely possibilities. The version PC1040 largely overcame these problems. In one of the Television magazine servicing articles, quite a lot of detail was provided to help puzzled service engineers find the underlying problem. The Switched mode version was extremely reliable.

Just before the TX9 became available, Television magazine gave a run down on the chassis and mention was made about Thorn engineers visiting Japan to learn techniques from TV manufacturing there so that reliability could be greatly improved. The diode split LOPT was very reliable, I don't ever remember any of the sets that I handled having one fail. I think it was a Hitachi type LOPT.
There weren't many other problems. The occasional tuner fault giving low gain, field output troubles but not too common. The line output stage is reliable as is the decoder. I've had a few cases of a dark picture due to low G2 (A1) voltage caused by a resistor in the line output stage increasing in value.

Regards,
Symon

[FERNSEH]

In the early production TX9 chassis the crowbar thyristor had a 0.1uF capacitor between the gate and cathode. To prevent intermittent fuse failure that capacitor was replaced with a 220uF electrolytic capacitor.
Apart from that minor problem solved by the capacitor replacement these sets were very reliable, as good as anything from Japan.
Excellent picture quality. Had a good number of these sets on rental.

DFWB.

[Philips210]

I think I read somewhere that the TX9 chassis was the first in the world to have a single chip decoder. I believe Thorn had some input to the design of the UPC1365 with the manufacturer NEC.
The Mullard TDA3560 followed soon after in the summer of 1980 but wasn't used in the TX9 until some time later, perhaps around 1982 or thereabouts.

Regards,
Symon

[Philips210]

There was a good fault finding guide on the thyristor power supply in the TX9 in Television magazine, July 1987 by Gordon Haigh. This can be found on the WRH website.

Regards,
Symon

[FERNSEH]

From the Ferguson Feedback bulletins.
Information about servicing the TX9 chassis.

DFWB.

[Welsh Anorak]

Like the G11, a good mains plug was essential.

We always carried a box of 'TX9 only' fuses - proper antisurge types with the spring inside. Anything else would blow randomly, and the HT voltage had to be set slightly lower than recommended for reliability.

The dual input choke used to get warm and short out which could blow the fuse. On early versions it was on the live side of the mains switch.

[beltinge bore]

Thank you all for your help and advice and particular thanks goes to emeritus (Ron) who took the time and trouble to post me the factory manual - very comprehensive.

Have now had the chance to examine it in more detail. The loudspeaker had broken away from all 4 mounts (it had been dropped on the righthand side at some point by the looks of it) and the front colour control was in bits. I have rebuilt the mounts with Milliput and slightly longer screws and re fixed the speaker. Luckily the POT was repairable. I gave it a long slow start up on the Variac and have good sound and a more than a passable testcard F so looking good so far fingers crossed.

Will update and add pictures later.

Happy New Year and once again Thanks

Steve

[Welsh Anorak]

Good to hear. As others have said, a good reliable chassis and one that Thorn built their Eighties reputation on. TX9, TX10, TX100 and TX90 and derivatives were all good chassis.

Then it all went a bit wrong...

[FERNSEH]

A rare TX9 variant, the model 3760. Described as a transportable. Solid wood cabinet, 18" CRT.

DFWB.

[Red to black]

Looks a similar style to a Philips KT3

The MK3 TX9 was the best of the TX9, the lightweight TDA 4600 chopper design was far better and paved the the way for the TX100, 99 and 98 PSU arrangements.

The MK3 TX10 (plastic chassis) was on the other hand a sort of cross between the TX10 and the forthcoming TX100 chassis rather than a major step change away from the TX9 'old fashioned' earlier Thyristor PSU was IMO.

The TDA 4600 PSU was a much more moderner spin on The TX9 chassis.

Edit: nothing wrong with the good old TX10 chassis btw

Edit 2: I suspect the TX10 MK3 was a lot cheaper to produce than the earlier MK1 and 2 versions, I can only really remember that chassis fitted to the 22B5 professional set?