UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Television Standards Converters, Modulators etc

Notices

Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

Closed Thread
 
Thread Tools
Old 4th May 2016, 6:19 pm   #1
Mikey405
Octode
 
Mikey405's Avatar
 
Join Date: Jul 2006
Location: Solihull, West Midlands and Beaford, Devon
Posts: 1,626
Default 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.
__________________
G7TRF
Mikey405 is offline  
Old 4th May 2016, 7:44 pm   #2
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
Default 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.
Heatercathodeshort is offline  
Old 4th May 2016, 7:48 pm   #3
Jac
Heptode
 
Jac's Avatar
 
Join Date: Jun 2006
Location: Eindhoven, Netherlands.
Posts: 640
Default 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
Jac is online now  
Old 4th May 2016, 10:00 pm   #4
Freya
Octode
 
Freya's Avatar
 
Join Date: Jan 2009
Location: Falmouth, Cornwall, UK.
Posts: 1,987
Default Re: Aurora - Strange "wobble" on verticals

I have this also on my two Aurora`s, the MK2 dinosaur is fine though.
__________________
Stephen
_________"It`s only an old telly" ___
Freya is offline  
Old 5th May 2016, 7:20 am   #5
Jac
Heptode
 
Jac's Avatar
 
Join Date: Jun 2006
Location: Eindhoven, Netherlands.
Posts: 640
Default 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
Jac is online now  
Old 28th May 2016, 9:18 am   #6
Mikey405
Octode
 
Mikey405's Avatar
 
Join Date: Jul 2006
Location: Solihull, West Midlands and Beaford, Devon
Posts: 1,626
Default 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.
Attached Thumbnails
Click image for larger version

Name:	WP_20160511_20_04_03_Rich.jpg
Views:	283
Size:	57.7 KB
ID:	125103  
__________________
G7TRF
Mikey405 is offline  
Old 28th May 2016, 3:24 pm   #7
Jac
Heptode
 
Jac's Avatar
 
Join Date: Jun 2006
Location: Eindhoven, Netherlands.
Posts: 640
Default 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
Attached Thumbnails
Click image for larger version

Name:	2016-05-02 B16T 89 TCC.jpg
Views:	240
Size:	39.5 KB
ID:	125108  
Jac is online now  
Old 29th May 2016, 12:45 am   #8
Lloyd 1985
Nonode
 
Lloyd 1985's Avatar
 
Join Date: Jun 2008
Location: Coningsby, Lincolnshire, UK.
Posts: 2,814
Default 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
Lloyd 1985 is offline  
Old 29th May 2016, 1:24 pm   #9
wd40addict
Octode
 
wd40addict's Avatar
 
Join Date: May 2009
Location: Stevenage, Herts. UK.
Posts: 1,515
Default 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?
wd40addict is online now  
Old 30th May 2016, 4:52 am   #10
Karen O
Rest in Peace
 
Join Date: Jul 2011
Location: Bridgnorth, Shropshire, UK.
Posts: 787
Default 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
Karen O is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 10:09 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.