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A strange fault....
Topic Rating: +2 Topic Rating: +2 (2 votes) 
February 14, 2017
9:24 am
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nuvistor
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As far as I remember the 405 system did not use equalising pulses. It was argued that with a correctly designed frame sync circuit they are not required. From that I understand a more expensive frame sync circuit would not require them. The set makers wanting to keep costs down wanted the pulses in the system but they were overruled.

Again corrections gratefuly accepted if my memory is wrong.

Edit. I have found a Wikipeadia page which more or less states similar, hopefully Wikipedia has it correct, but treat with caution.

https://en.m.wikipedia.org/wiki/405-line_television_system

Frank

February 14, 2017
10:08 pm
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PYE625
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I think it’s high time to put the back on and forget all about it.

Has been an interesting wild goose chase though.

Andrew.                                                                                   

                         

February 14, 2017
11:44 pm
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Brian Cuff
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Equalising pulses were never used in the 405 line system as transmitted but afaik, the 525 and 625 had them from the outset. They are basically to ensure that the sync pulse transition is in the same direction at the trigger point for both fields which eases the design of the field TB. 

Cheers

Brian

February 15, 2017
1:44 pm
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PYE625
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The interesting thing will be to try the Stella on a different standards converter sometime.

I keep threatening to buy myself an Aurora, but I never seem have the spare cash when they are in stock.waa_gif

Anyway,  I may re-visit this pain in the  erm, sorry, “interesting fault”  in the course of time.

Andrew.                                                                                   

                         

February 15, 2017
3:48 pm
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nuvistor
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Does the Aurora allow the switching on/off of the pulses?

Frank

February 15, 2017
3:54 pm
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Chris
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yes

August 12, 2017
11:50 pm
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PYE625
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PYE625 said
The interesting thing will be to try the Stella on a different standards converter sometime.

I keep threatening to buy myself an Aurora, but I never seem have the spare cash when they are in stock.waa_gif

I still don’t have the spare cash but have bought one all the same, so the condition described in this thread will be re-visited soon.

Andrew.                                                                                   

                         

August 12, 2017
11:58 pm
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nuvistor
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Bread and jam then for the next few weeks.eek_gif

Frank

August 13, 2017
8:46 am
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sideband
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nuvistor said
Does the Aurora allow the switching on/off of the pulses?  

I turned the equalisation pulses off on mine (I can’t remember if they are off by default) but I know I was playing about with it when I first got it and one set (Ferguson 45) didn’t like them. So I turned them off and that’s how it’s been ever since.

Is it supposed to do that?

August 13, 2017
11:25 am
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PYE625
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nuvistor said
Bread and jam then for the next few weeks.eek_gif  

Not even that luxury Frank…  Just rainwater from puddles and a few wild berries.  grin_gif

Andrew.                                                                                   

                         

August 17, 2017
1:45 pm
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Terry
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+1

Brian Cuff said
Equalising pulses were never used in the 405 line system as transmitted 

Not initially, perhaps, but I’m sure I remember seeing them in the early 60s.

Only before  the broad pulses, though, not after.

I thought I check up in Alan Pember’s marvellous collection of data – no longer available on-line alas but I have an archived copy and there is also a copy on this site.

I’ve extracted the relevant drawing and here it is:

System-A-VBI.pngImage Enlarger

… complete with (pre)equalising pulses just as I remember them!

Terry

When all else fails, read the instructions ...

August 19, 2017
9:16 am
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PYE625
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Hooked up the Aurora to the Philips (Ahem, Stella) and it seems to be operating without any of the problems highlighted earlier. May leave it running for a while and keep an eye on it.

rsz_12img_3152.jpgImage Enlarger

Andrew.                                                                                   

                         

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