Thorn repair help request. - UK Vintage Radio Repair and Restoration Discussion Forum

Nipkowdisc · 22nd Oct 2019, 1:22 pm

Hello fellow enthusiasts!
I have a Thorn Ferguson TX9 Colour T.V. Set which I am trying to mend.
It is almost fully working except that it has no colour.
It is the more recent version with the TDA4600 based Switched-Mode P.S.U.

I wonder if any kind fellow enthusiast could let me have a copy of the Schematic for the main P.C.B. of this which has the P.A.L. Decoder on it.

I would be most grateful.

Welsh Anorak · 22nd Oct 2019, 2:19 pm

Sorry I haven't got the manual, but I seem to remember a lot of tail chasing was due to the delay line or the preset associated with it.
Just a thought.

Restoration73 · 22nd Oct 2019, 4:20 pm

Yes, the preset was RV67. C56 could also go o/c. Check the 4.43 or was it 8.86 crystal.

Nipkowdisc · 23rd Oct 2019, 7:10 am

It's an 8.86Mhz Crystal Restoration73 and my thanks to Welsh Anorak also.

The Oscillator is not running and I really need the Schematic to proceed.

KeithsTV · 23rd Oct 2019, 9:13 am

Here's the circuit and layout.

Keith

Nipkowdisc · 24th Oct 2019, 1:17 am

That's excellent Keith!
Words are insufficient to say how grateful I am.
I have checked that I have 12V on pin 1 of the TDA3560 and next I shall swap out the Reference Oscillator Crystal.

Nipkowdisc · 24th Oct 2019, 12:13 pm

Changing the Reference Oscillator Crystal did not restore oscillation but I noticed that when the Trimmer in series with it was pressed on or prodded at oscillation did occur.
The Trimmer was not dry jointed but had a tarnished look to it.
I had a few spare Trimmers that I had purchased from Bowood Electronics earlier and in went a new 22pF one.
Now of course the Oscillator needed to be set up and one should over-ride the Colour Killer and adjust for minimum run through.
I didn't know how one was supposed to do that though and so I just fiddled with it in the hope that colour would appear (well what's a boy to do?).
Colour did appear-Success!
I couldn't have done it without the help I received here though so thanks again.

22nd Oct 2019, 1:22 pm	#1
Nipkowdisc Triode Join Date: May 2010 Location: Burntwood, Staffordshire, UK. Posts: 33	Thorn repair help request. Hello fellow enthusiasts! I have a Thorn Ferguson TX9 Colour T.V. Set which I am trying to mend. It is almost fully working except that it has no colour. It is the more recent version with the TDA4600 based Switched-Mode P.S.U. I wonder if any kind fellow enthusiast could let me have a copy of the Schematic for the main P.C.B. of this which has the P.A.L. Decoder on it. I would be most grateful.

22nd Oct 2019, 2:19 pm	#2
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 6,925	Re: Thorn repair help request. Sorry I haven't got the manual, but I seem to remember a lot of tail chasing was due to the delay line or the preset associated with it. Just a thought. __________________ Glyn www.gdelectronics.wales

22nd Oct 2019, 4:20 pm	#3
Restoration73 Nonode Join Date: Jun 2013 Location: Surbiton, SW London, UK. Posts: 2,801	Re: Thorn repair help request. Yes, the preset was RV67. C56 could also go o/c. Check the 4.43 or was it 8.86 crystal.

23rd Oct 2019, 7:10 am	#4
Nipkowdisc Triode Join Date: May 2010 Location: Burntwood, Staffordshire, UK. Posts: 33	Re: Thorn repair help request. It's an 8.86Mhz Crystal Restoration73 and my thanks to Welsh Anorak also. The Oscillator is not running and I really need the Schematic to proceed.

24th Oct 2019, 1:17 am	#6
Nipkowdisc Triode Join Date: May 2010 Location: Burntwood, Staffordshire, UK. Posts: 33	Re: Thorn repair help request. That's excellent Keith! Words are insufficient to say how grateful I am. I have checked that I have 12V on pin 1 of the TDA3560 and next I shall swap out the Reference Oscillator Crystal.

24th Oct 2019, 12:13 pm	#7
Nipkowdisc Triode Join Date: May 2010 Location: Burntwood, Staffordshire, UK. Posts: 33	Re: Thorn repair help request. Changing the Reference Oscillator Crystal did not restore oscillation but I noticed that when the Trimmer in series with it was pressed on or prodded at oscillation did occur. The Trimmer was not dry jointed but had a tarnished look to it. I had a few spare Trimmers that I had purchased from Bowood Electronics earlier and in went a new 22pF one. Now of course the Oscillator needed to be set up and one should over-ride the Colour Killer and adjust for minimum run through. I didn't know how one was supposed to do that though and so I just fiddled with it in the hope that colour would appear (well what's a boy to do?). Colour did appear-Success! I couldn't have done it without the help I received here though so thanks again.