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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 22nd Oct 2019, 1:22 pm   #1
Nipkowdisc
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Join Date: May 2010
Location: Burntwood, Staffordshire, UK.
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Default 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.
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Old 22nd Oct 2019, 2:19 pm   #2
Welsh Anorak
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Default 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.
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Old 22nd Oct 2019, 4:20 pm   #3
Restoration73
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Default 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.
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Old 23rd Oct 2019, 7:10 am   #4
Nipkowdisc
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Default 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.
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Old 23rd Oct 2019, 9:13 am   #5
KeithsTV
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Default Re: Thorn repair help request.

Here's the circuit and layout.

Keith
Attached Files
File Type: pdf tx9cct.PDF (1.47 MB, 45 views)
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Old 24th Oct 2019, 1:17 am   #6
Nipkowdisc
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Default 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.
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Old 24th Oct 2019, 12:13 pm   #7
Nipkowdisc
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Default 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.
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