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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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22nd Oct 2019, 1:22 pm | #1 |
Triode
Join Date: May 2010
Location: Burntwood, Staffordshire, UK.
Posts: 33
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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 |
Dekatron
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 6,916
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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. |
22nd Oct 2019, 4:20 pm | #3 |
Nonode
Join Date: Jun 2013
Location: Surbiton, SW London, UK.
Posts: 2,801
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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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23rd Oct 2019, 7:10 am | #4 |
Triode
Join Date: May 2010
Location: Burntwood, Staffordshire, UK.
Posts: 33
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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. |
23rd Oct 2019, 9:13 am | #5 |
Nonode
Join Date: Aug 2007
Location: South Bradford, West Yorkshire, UK.
Posts: 2,573
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Re: Thorn repair help request.
Here's the circuit and layout.
Keith |
24th Oct 2019, 1:17 am | #6 |
Triode
Join Date: May 2010
Location: Burntwood, Staffordshire, UK.
Posts: 33
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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 |
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. |