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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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17th May 2021, 4:33 pm | #1 |
Pentode
Join Date: Jul 2014
Location: Isle of Man, UK.
Posts: 102
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Interlace issue/frame roll on 1983 Decca television.
Hiya all,
I have a nice 1983 Decca with remote control (wow) but it's got an issue where the bottom of the frame is squashed and overlaps. I think it's called either an interlace issue or a frame roll issue. Anyway, I think I've tracked down the culprit. I've tested every component on the board section where the interlace potentiometer is and the only capacitor that does nothing is this odd blue one. Says 220N, K100, 683. It gives absolutely nothing on the multimeter. However I haven't much clue as to what to replace it with. Any idea please? Cheers Nick |
17th May 2021, 7:36 pm | #2 |
Hexode
Join Date: Feb 2018
Location: Durham, County Durham, UK.
Posts: 325
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Re: Interlace issue/frame roll on 1983 decca television
220n is a 0.22uf
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17th May 2021, 7:55 pm | #3 |
Nonode
Join Date: Mar 2010
Location: Sunderland, Tyne and Wear, UK.
Posts: 2,474
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Re: Interlace issue/frame roll on 1983 decca television
First off, what is the model number ?, and/or chassis type ?
Your actual fault is called field fold over, the height pot (pictured) is also set to one end, which is also a bad sign as it will not normally be set that way and is surely masking a proper fault.
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17th May 2021, 8:49 pm | #4 |
Pentode
Join Date: Jul 2014
Location: Isle of Man, UK.
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Re: Interlace issue/frame roll on 1983 decca television
Hi the chassis number is 12/4729 I think.
It isn't clear. It could also be 512826. 12014TN Thanks for the additional information 😏 |
17th May 2021, 8:56 pm | #5 |
Nonode
Join Date: Mar 2010
Location: Sunderland, Tyne and Wear, UK.
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Re: Interlace issue/frame roll on 1983 decca television
The actual model number will be printed on a label on the back of the set, please either quote this, and/or post a picture, please also post a picture of the full chassis as someone here is sure to recognise it.
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17th May 2021, 9:09 pm | #6 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,843
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Re: Interlace issue/frame roll on 1983 decca television
Looks like the 70-series chassis to me, but it's a long time since I've dealt with one, so could well be wrong!
Can you ID it from one of these: https://www.radios-tv.co.uk/decca/ |
17th May 2021, 9:12 pm | #7 |
Pentode
Join Date: Jul 2014
Location: Isle of Man, UK.
Posts: 102
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Re: Interlace issue/frame roll on 1983 decca television
Here you go.
Just noticed some small crackling sounds from the tube area when it's on too.... 😑 |
17th May 2021, 9:17 pm | #8 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,843
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Re: Interlace issue/frame roll on 1983 decca television
Ah, looks like the model number was the label beneath the white serial number one, and has fallen off.
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17th May 2021, 9:35 pm | #9 |
Nonode
Join Date: Mar 2010
Location: Sunderland, Tyne and Wear, UK.
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Re: Interlace issue/frame roll on 1983 decca television
If this is a 1983 model it has a good chance to be a 120 or 130 model, it is definitely not a 140 or later model, what is the screen size ?
What is the chopper control IC ? if it is a TDA4600 type supply it will not be a 70 chassis. It looks like a 120 chassis to me.
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17th May 2021, 9:45 pm | #10 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,843
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Re: Interlace issue/frame roll on 1983 decca television
Yes, the 70-series PCB was vertically-mounted, with the tube neck poking through a hole.
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17th May 2021, 9:51 pm | #11 |
Pentode
Join Date: Jul 2014
Location: Isle of Man, UK.
Posts: 102
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Re: Interlace issue/frame roll on 1983 decca television
14" 120 model apparently
Not sure about the chopper IC? |
17th May 2021, 9:54 pm | #12 |
Pentode
Join Date: Jul 2014
Location: Isle of Man, UK.
Posts: 102
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Re: Interlace issue/frame roll on 1983 decca television
Also, just gave me a nasty jolt when I accidentally touched the chassis with an uninsulated screwdriver... Idiot. Maybe time for bed. Screwdriver flew out of my hand and landed 6ft away.
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17th May 2021, 9:55 pm | #13 |
Nonode
Join Date: Mar 2010
Location: Sunderland, Tyne and Wear, UK.
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Re: Interlace issue/frame roll on 1983 decca television
I have the manuals for both the Decca 120 and 130 manuals C/O of Glyn D (Welsh Anorak of this parish ) which I can supply snippets of if required.
The problem is likely to be tired Electrolytics, or a low value resistor gone high in the feedback circuit, the height control being one ended being a significant clue. I await advice.
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17th May 2021, 9:58 pm | #14 |
Pentode
Join Date: Jul 2014
Location: Isle of Man, UK.
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Re: Interlace issue/frame roll on 1983 decca television
Seems to be the best I can get using my sega master system
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18th May 2021, 12:45 pm | #15 |
Dekatron
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 6,918
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Re: Interlace issue/frame roll on 1983 decca television
When you say you've checked every capacitor, have you tested for value and ESR? If not, then if you don't have a suitable tester I'd change all the electrolytics in the circuit - there aren't many. Then see if the voltage feeding the IC is correct..
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19th May 2021, 9:42 am | #16 | |
Pentode
Join Date: Jul 2014
Location: Isle of Man, UK.
Posts: 102
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Re: Interlace issue/frame roll on 1983 decca television
Quote:
I am going to leave it alone as the picture isnt too bad for what I'm using it for, going to be used mostly for programming on the Beeb or Spectrum, so not bothered about missing the bottom off the screen. After getting that electric shock I am going to back off and let it be Thank you all for your help Nick |
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19th May 2021, 9:48 am | #17 |
Pentode
Join Date: Jul 2014
Location: Isle of Man, UK.
Posts: 102
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Re: Interlace issue/frame roll on 1983 decca television
Also, annoyingly, I had two basic digital multimeters, A sealey and a cheapo non branded one and last night both of them died! No readings on anything and I have changed the batteries, cables, fuses and nowt.
I am now using my Radio Shack analogue one thats 40 years old and still going strong. Like this one - |