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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions. |
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4th May 2016, 6:19 pm | #1 |
Octode
Join Date: Jul 2006
Location: Solihull, West Midlands and Beaford, Devon
Posts: 1,626
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Aurora - Strange "wobble" on verticals
Hi all.
I was wondering whether anyone else had come across a strange effect on the Aurora whereby the verticals of many direct-sync sets are very slightly corrugated. It doesn't happen on all sets but it does happen on both my Auroras (one old one and one later model) using different signal sources and different power supplies (One down in Devon and one up here in Solihull.) I mentioned this to a pal of mine in Stourbridge and has says that he gets the same effect. The effect is like slight sound on vision but occurs whether or not there is audio present at the input. (I have the "Tone" switch turned off inside and I haven't tried it with Tone set to on.) The signal level to the set seems to have no effect (even an enormous amount of attenuation doesn't help) and connecting the Aurora up to a reasonably posh Farnell power supply using a screened lead doesn't help either. The problem occurs using the built-in TCC test pattern although I have to admit that I haven't tried it using an incoming 625 line test card. The only way I can stop the wobble (using the Farnell PSU anyway) is to reduce the voltage down and down until the sound disappears. There is a tiny voltage range where the picture is still present but the sound is gone. However, I don't know what the consequences of running the Aurora like this are so I don't want to risk running it like that for any length of time. It's not really a huge problem but now I've noticed it, it annoys me (not that much) whenever I see it. Thanks all. Kind regards. From Mike.
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G7TRF |
4th May 2016, 7:44 pm | #2 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,147
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Re: Aurora - Strange "wobble" on verticals
Hello Mike,
I get exactly the same problem on a VERY limited range of models. The Pye D16T comes to mind. I have three and they all do it so some extent on four different Auroras. The effect is similar to a very slight leak on the sync coupling capacitor causing 'cogging'. It is certainly not a problem and I can thoroughly recommend the splendid Aurora. [It costs about the equivalent of 20 packets of fags and it won't put you in hospital] Regards, John. |
4th May 2016, 7:48 pm | #3 |
Heptode
Join Date: Jun 2006
Location: Eindhoven, Netherlands.
Posts: 642
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Re: Aurora - Strange "wobble" on verticals
Hi Mike,
I experience this wobble also. Currently I am restoring a Pye B16T and there it is visible quite pronounced. When the set is on my workbench again, I will try a different standards converter and a different testcard-C source to see if that changes things. I haven't tried different supply voltages for the Aurora SC. Is it most pronounced on TCC (because of the black blocks on the beginning of some lines that can influence the precise horizontal sync timing), or on normal program material as well? Is the effect identical on other receivers? Including or omitting the equalization pulses in the Aurora makes no visual difference on the Pye w.r.t. the horizontal timing problem. Jac |
4th May 2016, 10:00 pm | #4 |
Octode
Join Date: Jan 2009
Location: Falmouth, Cornwall, UK.
Posts: 1,990
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Re: Aurora - Strange "wobble" on verticals
I have this also on my two Aurora`s, the MK2 dinosaur is fine though.
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Stephen _________"It`s only an old telly" ___ |
5th May 2016, 7:20 am | #5 |
Heptode
Join Date: Jun 2006
Location: Eindhoven, Netherlands.
Posts: 642
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Re: Aurora - Strange "wobble" on verticals
Mike, as a second thought, did you observe with an oscilloscope if the video to sync ratio changes when you apply the very low supply voltage?
Jac |
28th May 2016, 9:18 am | #6 |
Octode
Join Date: Jul 2006
Location: Solihull, West Midlands and Beaford, Devon
Posts: 1,626
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Re: Aurora - Strange "wobble" on verticals
Hi all.
Thank you for the replies - and apologies for the delay in my replying. Jac - I've not looked at the output on a 'scope to be honest, but it may well be worth a look to see what happens at that point when the voltage reduces to the level where the problem goes away. John - Please don't think I was moaning about the Aurora in general - It is a brilliant piece of kit and I'd be really lost without mine. I do see the problem, however, on quite a few different sets including the Philips 1100U (shown in the picture below) as well as the Ekco TS88 and TS46 models among other sets. As you say though, it really isn't a big deal - just the tiniest of annoyances really - once noticed, never not-noticed. Thanks all. Kind regards. From Mike.
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G7TRF |
28th May 2016, 3:24 pm | #7 |
Heptode
Join Date: Jun 2006
Location: Eindhoven, Netherlands.
Posts: 642
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Re: Aurora - Strange "wobble" on verticals
Thanks for that screen photo Mike.
This is a different phenomenon than I thought you meant and that I have with some sets. See attached picture what I see on my B16T (work in progress...). It is largely dependent on the black blocks on the left (beginning of the lines). I have seen it on other sets, but can't recall at this moment which ones. (My Pye 817 has it in the extreme-extreme.) I'll have to investigate this much further... What you see on your set(s) looks somehow like a wobble / HF-ripple in the horizontal time base. Is it independent of the picture contents? Is it the same if you use the Aurora as TCC-generator or SC only, and use it's video output to feed a different modulator? Best regards, Jac |
29th May 2016, 12:45 am | #8 |
Nonode
Join Date: Jun 2008
Location: Coningsby, Lincolnshire, UK.
Posts: 2,820
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Re: Aurora - Strange "wobble" on verticals
I've noticed the same wobble effect too, I thought it was just me not being very good at restoring telly's! I'm sure it affects my Ekco TMB272, and a Perdio Portarama. I've sat for ages trying to tweak the tuning to get rid of it!
Regards, Lloyd |
29th May 2016, 1:24 pm | #9 |
Octode
Join Date: May 2009
Location: Stevenage, Herts. UK.
Posts: 1,518
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Re: Aurora - Strange "wobble" on verticals
Is this a beat between harmonics of the 50Hz of the Aurora and the 50Hz of the mains? In the old days the transmission was locked to the mains, but this is no longer true when using the Aurora.
It must've been an issue sometimes back in the day as Bush produced a non-sync version of the TV22, the TV22U, for unsynchronised mains. Basically the smoothing caps were beefed up. Mike do you have an AC/DC set showing the problem that you could try running on DC? |
30th May 2016, 4:52 am | #10 |
Rest in Peace
Join Date: Jul 2011
Location: Bridgnorth, Shropshire, UK.
Posts: 787
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Re: Aurora - Strange "wobble" on verticals
It might be slight FM on a PLL oscillator. I had the same effect when I was making my own 625 to 405 converter. If that's what it is then sets with good flywheel action will show it up while those that can follow the tiny phase changes won't.
All speculative, of course |