Background Picture Noise With Panasonic TV? - UK Vintage Radio Repair and Restoration Discussion Forum

OldTechFan96 · 5th Oct 2021, 8:25 pm

Every now and again I use a Panasonic TX-21V2 which was given to me by a neighbour in 2019. It was made in 1994.

I've noticed that there is a fair bit of noise/fuzziness in the picture no matter what input is used. I also see the same thing with no input. It gives the picture a 'jittery' quality.

I tried to take some photos but I don't think the camera captures the issue.

Is this normal for CRT televisions? The last time our main TV was a CRT was 2010 so I can't remember how things were.

Thank you!

Graham G3ZVT · 6th Oct 2021, 12:03 am

A bit of noise is possible using the aerial input but I wouldn't expect any at all using "AV", I think this set is capable of using composite, RGB, and Y/C (S-Video).

It's difficult to advice without seeing the fault, could you take a short off-screen video and upload it to Google Photos, Youtube, or similar?

Tester. · 6th Oct 2021, 6:33 pm

IME, quite a few models from that era seemed to leak/leave the last tuned channel "in the background", as a byproduct of the bidirectional nature of the SCART connector.

On lesser/cheaper units, this was unavoidable and quite noticeable... but better, fully insolated SCART cables helped to a degree. And normally, the RCA inputs (if present) were less affected or not at all.

Anyway, the easy solution was always having an aerial (or modulator) connected and a channel tuned in. (Ideally, with a black background to avoid the 'leakage' of high-contrast images.)

OldTechFan96 · 7th Oct 2021, 1:35 pm

I'll try taking some videos if these pictures don't illustrate the problem.

The first photos show a PS2 connected via RGB SCART. The PS2 itself is set to output RGB. The game shown is using a 60Hz video mode.

I agree with both both Rambo and Tester that noise from the tuner could be leaking into other inputs. I think this is what I see when there is no input. I'd expect the screen to be solid black, but it isn't.

Tester. · 7th Oct 2021, 2:09 pm

Yep, it seems your TV 'leaks'. That 'black screen w/ noise' is the telltale sign you would see on those models.

Do you have a VCR or anything with a modulator that you can connect to the 'aerial in'? Try tuning to their channel and then select the SCART input; the noise pattern should disappear.

Graham G3ZVT · 7th Oct 2021, 11:32 pm

Quote:

Originally Posted by Tester.

IME, quite a few models from that era seemed to leak/leave the last tuned channel "in the background", as a byproduct of the bidirectional nature of the SCART connector.

On lesser/cheaper units, this was unavoidable and quite noticeable... but better, fully insolated SCART cables helped to a degree. And normally, the RCA inputs (if present) were less affected or not at all.

Yes I agree.
To the OP, try a different SCART cable, the thick ones are the ones that are likely to have individually screened signal wires (good) and the thin ones are likley to be prone to crosstalk. (bad).

If you can't find a better cable, try cutting the wire on pin 19 on the TV end of the SCART cable.

Sideband · 8th Oct 2021, 9:53 am

Surely you can just prove it's the cable by pulling it out and running the TV 'blank' as it were with no inputs. Should give a clean raster then.

I found that the flat Scart leads were better than the round ones, easier to manipulate and each connection was screened. As mentioned, the thicker Scart leads are better than the thin ones but are rather cumbersome.

Welsh Anorak · 8th Oct 2021, 12:29 pm

If that doesn't help you could do as Sideband suggests and see if the SCART cable is your problem. If there's still hash, then easiest to disable the input to the AV switching chip provided you don't want the RF input, of course.

OldTechFan96 · 10th Oct 2021, 10:45 pm

I connected up a VCR via RF to see if signal is bleeding into the SCART input. The Matsui VCR has a switchable test pattern which was used in place of a video tape. Once the test pattern was on I switched to the SCART input.

With the pattern on the fuzz clears up. There is some rolling bars in the background. Presumably from the VCR.

The fuzz comes back once the test pattern is switched off.

I'll disable the RF modulator and see if anything changes.

I think the picture could be sharper. I've had a look at the service manual and it does not give any setup details.

5th Oct 2021, 8:25 pm	#1
OldTechFan96 Octode Join Date: Jul 2017 Location: Newcastle Upon Tyne, Tyne & Wear, UK. Posts: 1,186	Background Picture Noise With Panasonic TV? Every now and again I use a Panasonic TX-21V2 which was given to me by a neighbour in 2019. It was made in 1994. I've noticed that there is a fair bit of noise/fuzziness in the picture no matter what input is used. I also see the same thing with no input. It gives the picture a 'jittery' quality. I tried to take some photos but I don't think the camera captures the issue. Is this normal for CRT televisions? The last time our main TV was a CRT was 2010 so I can't remember how things were. Thank you!

6th Oct 2021, 12:03 am	#2
Graham G3ZVT Dekatron Join Date: May 2010 Location: Greater Manchester, UK. Posts: 18,725	Re: Background Picture Noise With Panasonic TV? A bit of noise is possible using the aerial input but I wouldn't expect any at all using "AV", I think this set is capable of using composite, RGB, and Y/C (S-Video). It's difficult to advice without seeing the fault, could you take a short off-screen video and upload it to Google Photos, Youtube, or similar? __________________ -- Graham. G3ZVT

6th Oct 2021, 6:33 pm	#3
Tester. Triode Join Date: Oct 2016 Location: Madrid, Spain. Posts: 28	Re: Background Picture Noise With Panasonic TV? IME, quite a few models from that era seemed to leak/leave the last tuned channel "in the background", as a byproduct of the bidirectional nature of the SCART connector. On lesser/cheaper units, this was unavoidable and quite noticeable... but better, fully insolated SCART cables helped to a degree. And normally, the RCA inputs (if present) were less affected or not at all. Anyway, the easy solution was always having an aerial (or modulator) connected and a channel tuned in. (Ideally, with a black background to avoid the 'leakage' of high-contrast images.)

7th Oct 2021, 1:35 pm	#4
OldTechFan96 Octode Join Date: Jul 2017 Location: Newcastle Upon Tyne, Tyne & Wear, UK. Posts: 1,186	Re: Background Picture Noise With Panasonic TV? I'll try taking some videos if these pictures don't illustrate the problem. The first photos show a PS2 connected via RGB SCART. The PS2 itself is set to output RGB. The game shown is using a 60Hz video mode. I agree with both both Rambo and Tester that noise from the tuner could be leaking into other inputs. I think this is what I see when there is no input. I'd expect the screen to be solid black, but it isn't. Attached Thumbnails

7th Oct 2021, 2:09 pm	#5
Tester. Triode Join Date: Oct 2016 Location: Madrid, Spain. Posts: 28	Re: Background Picture Noise With Panasonic TV? Yep, it seems your TV 'leaks'. That 'black screen w/ noise' is the telltale sign you would see on those models. Do you have a VCR or anything with a modulator that you can connect to the 'aerial in'? Try tuning to their channel and then select the SCART input; the noise pattern should disappear.

8th Oct 2021, 9:53 am	#7
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,580	Re: Background Picture Noise With Panasonic TV? Surely you can just prove it's the cable by pulling it out and running the TV 'blank' as it were with no inputs. Should give a clean raster then. I found that the flat Scart leads were better than the round ones, easier to manipulate and each connection was screened. As mentioned, the thicker Scart leads are better than the thin ones but are rather cumbersome. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

8th Oct 2021, 12:29 pm	#8
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 6,928	Re: Background Picture Noise With Panasonic TV? If that doesn't help you could do as Sideband suggests and see if the SCART cable is your problem. If there's still hash, then easiest to disable the input to the AV switching chip provided you don't want the RF input, of course. __________________ Glyn www.gdelectronics.wales

10th Oct 2021, 10:45 pm	#9
OldTechFan96 Octode Join Date: Jul 2017 Location: Newcastle Upon Tyne, Tyne & Wear, UK. Posts: 1,186	Re: Background Picture Noise With Panasonic TV? I connected up a VCR via RF to see if signal is bleeding into the SCART input. The Matsui VCR has a switchable test pattern which was used in place of a video tape. Once the test pattern was on I switched to the SCART input. With the pattern on the fuzz clears up. There is some rolling bars in the background. Presumably from the VCR. The fuzz comes back once the test pattern is switched off. I'll disable the RF modulator and see if anything changes. I think the picture could be sharper. I've had a look at the service manual and it does not give any setup details. Attached Thumbnails