Interlace issue/frame roll on 1983 Decca television. - UK Vintage Radio Repair and Restoration Discussion Forum

Manx Nick · 17th May 2021, 4:33 pm

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

gallowfields · 17th May 2021, 7:36 pm

220n is a 0.22uf

Red to black · 17th May 2021, 7:55 pm

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.

Manx Nick · 17th May 2021, 8:49 pm

Hi the chassis number is 12/4729 I think.

It isn't clear. It could also be 512826. 12014TN

Thanks for the additional information 😏

Red to black · 17th May 2021, 8:56 pm

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.

Nickthedentist · 17th May 2021, 9:09 pm

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/

Manx Nick · 17th May 2021, 9:12 pm

Here you go.
Just noticed some small crackling sounds from the tube area when it's on too.... 😑

Nickthedentist · 17th May 2021, 9:17 pm

Ah, looks like the model number was the label beneath the white serial number one, and has fallen off.

Red to black · 17th May 2021, 9:35 pm

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.

Nickthedentist · 17th May 2021, 9:45 pm

Yes, the 70-series PCB was vertically-mounted, with the tube neck poking through a hole.

Manx Nick · 17th May 2021, 9:51 pm

14" 120 model apparently

Not sure about the chopper IC?

Manx Nick · 17th May 2021, 9:54 pm

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. ��

Red to black · 17th May 2021, 9:55 pm

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.

Manx Nick · 17th May 2021, 9:58 pm

Seems to be the best I can get using my sega master system

Welsh Anorak · 18th May 2021, 12:45 pm

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..

Manx Nick · 19th May 2021, 9:42 am

Quote:

Originally Posted by Welsh Anorak

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..

Well, considering I had no idea what ESR was until I just googled it, I'd say no.

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

Manx Nick · 19th May 2021, 9:48 am

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 -

17th May 2021, 4:33 pm	#1
Manx Nick Pentode Join Date: Jul 2014 Location: Isle of Man, UK. Posts: 102	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 Attached Thumbnails

17th May 2021, 7:36 pm	#2
gallowfields Hexode Join Date: Feb 2018 Location: Durham, County Durham, UK. Posts: 325	Re: Interlace issue/frame roll on 1983 decca television 220n is a 0.22uf

17th May 2021, 7:55 pm	#3
Red to black Nonode Join Date: Mar 2010 Location: Sunderland, Tyne and Wear, UK. Posts: 2,474	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. __________________ I don't suffer from Insanity. I enjoy every minute of it.

17th May 2021, 8:49 pm	#4
Manx Nick Pentode Join Date: Jul 2014 Location: Isle of Man, UK. Posts: 102	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
Red to black Nonode Join Date: Mar 2010 Location: Sunderland, Tyne and Wear, UK. Posts: 2,474	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. __________________ I don't suffer from Insanity. I enjoy every minute of it.

17th May 2021, 9:09 pm	#6
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,841	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
Manx Nick Pentode Join Date: Jul 2014 Location: Isle of Man, UK. Posts: 102	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.... 😑 Attached Thumbnails

17th May 2021, 9:17 pm	#8
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,841	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.

17th May 2021, 9:35 pm	#9
Red to black Nonode Join Date: Mar 2010 Location: Sunderland, Tyne and Wear, UK. Posts: 2,474	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. __________________ I don't suffer from Insanity. I enjoy every minute of it.

17th May 2021, 9:45 pm	#10
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,841	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.

17th May 2021, 9:51 pm	#11
Manx Nick Pentode Join Date: Jul 2014 Location: Isle of Man, UK. Posts: 102	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
Manx Nick Pentode Join Date: Jul 2014 Location: Isle of Man, UK. Posts: 102	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. ��

17th May 2021, 9:55 pm	#13
Red to black Nonode Join Date: Mar 2010 Location: Sunderland, Tyne and Wear, UK. Posts: 2,474	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. __________________ I don't suffer from Insanity. I enjoy every minute of it.

17th May 2021, 9:58 pm	#14
Manx Nick Pentode Join Date: Jul 2014 Location: Isle of Man, UK. Posts: 102	Re: Interlace issue/frame roll on 1983 decca television Seems to be the best I can get using my sega master system Attached Thumbnails

18th May 2021, 12:45 pm	#15
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 6,916	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.. __________________ Glyn www.gdelectronics.wales

19th May 2021, 9:48 am	#17
Manx Nick Pentode Join Date: Jul 2014 Location: Isle of Man, UK. Posts: 102	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 - Attached Thumbnails