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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions. |
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6th Sep 2022, 7:54 am | #21 |
Octode
Join Date: Jan 2009
Location: Falmouth, Cornwall, UK.
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Re: Standards Converter recommissioned.
Hi David,
Would like to see your circuit please to compare chip choice for the interpolator / line store compared to the MK2 dinosaur, think the MK2 was redesigned to use the mach210-20 CPLD which cut down on the chip count to a mere 18!
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Stephen _________"It`s only an old telly" ___ |
8th Sep 2022, 8:40 am | #22 |
Dekatron
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
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Re: Standards Converter recommissioned.
stevehertz, was your modulator made by David Grant I wonder back in the 80's? If so a top class piece of kit, as was the standards converter.
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G8JET BVWS Archivist and Member V.M.A.R.S |
8th Sep 2022, 11:39 am | #23 |
Dekatron
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Location: Gateshead, Tyne and Wear, UK.
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Re: Standards Converter recommissioned.
Interpolation, done at analogue levels from the DACs. Been thinking about doing a digital solution but to be honest I just haven't got the time to get around to doing something about it.
History of the converter. The project started in the autumn of 1984; the plan was to have a workable converter ready for the close-down of 405 of transmissions in January 1985. But wasn't to be so because I developed a serious health issue and it wasn't until the autumn '85 the project was restarted. The period between 1980 to the early 1990s was the busiest time I've ever experienced in the TV trade. DFWB. |
8th Sep 2022, 4:13 pm | #24 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
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Re: Standards Converter recommissioned.
How I remember those incredible years! I was placing bulk orders to Toshiba for colour TV and VCRs. Looking through my old stock books I once ordered 24 X 12" mono portables and sold them all in 14 days. Great times never to return.
I built the David Looser modulator David. It still works fine. Your standards converter stood alone in 1984. Absolutely amazing! John. |
8th Sep 2022, 5:32 pm | #25 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
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Re: Standards Converter recommissioned.
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8th Sep 2022, 10:48 pm | #26 |
Pentode
Join Date: Oct 2003
Location: Henley on Thames, Oxfordshire, UK.
Posts: 244
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Re: Standards Converter recommissioned.
Hi David, thank you for sharing your converter with us, a great achievement.
Can you be credited as the first person to produce a home built 405 line standards converter? I too would like to see the circuit diagrams if ok with you. Mark. |
9th Sep 2022, 7:52 am | #27 |
Nonode
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 2,300
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Re: Standards Converter recommissioned.
I too would love to see the circuit diagrams.
PM sent Peter |
9th Sep 2022, 1:23 pm | #28 | |
Heptode
Join Date: Feb 2006
Location: Roscommon, Ireland
Posts: 732
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Re: Standards Converter recommissioned.
Quote:
It was an incredible achievement to build something as complex as a standard converter from TTL. Getting it to work at the speeds required for the converter couldn't be easy especially not having a PCB and using vero board. It had to have taken a huge amount of work and great commitment especially when no one had done it before. David showed it could be done. Thereby making it easier for anyone after that. Frank
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9th Sep 2022, 11:28 pm | #29 |
Dekatron
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Re: Standards Converter recommissioned.
I will be pleased to show to all those interested the circuit diagrams of the two standards converters I constructed in the mid nineteen-eighties.
But I'll need time to redraw the diagrams and descriptions of the workings of the circuits. DFWB. |
13th Sep 2022, 10:00 pm | #30 |
Dekatron
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Re: Standards Converter recommissioned.
Peter Scott wrote: "I think the set is not doing justice to your converter"
Hi Peter, A regular client brought his Decca DM45 in for repair. The set has a frame timebase fault. Using a 625 line Test Card C generator as the signal source for the converter, the 2.5Mc/s definition bars can clearly be seen and the 3meg bars also. The Marconi VT161 was struggling to resolve the 2.5meg bars. Also, the stability of vertical details is bad. Let's see what the picture looks like when the Decca is repaired. DFWB. |
13th Sep 2022, 11:28 pm | #31 | |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
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Re: Standards Converter recommissioned.
Quote:
Go for it David. Peter |
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17th Sep 2022, 11:23 am | #32 |
Dekatron
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Re: Standards Converter recommissioned.
Attached picture was taken from the screen of the Decca DM45. Showing the 2.5Mc/s definition bars. Camera captures only one picture field.
DFWB. |
17th Sep 2022, 1:09 pm | #33 |
Dekatron
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Re: Standards Converter recommissioned.
Got to get rid of the overshoot on the step response though.
Peter |
17th Sep 2022, 2:09 pm | #34 |
Dekatron
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Re: Standards Converter recommissioned.
Hi Peter,
the video waveforms at the control grid of the video amplifier valve and the grid of the sync separator. Clearly, the video amplifier needs some attention. DFWB. |
17th Sep 2022, 5:15 pm | #35 |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
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Re: Standards Converter recommissioned.
Strangely the first photo (video amp??) looks quite well controlled. Can you probe the video amp anode?
I just looked at the circuit. I see the sync separator grid probably looks much the same as the video amp anode. What happens when you adjust VR10? Peter Last edited by peter_scott; 17th Sep 2022 at 5:31 pm. |
17th Sep 2022, 9:06 pm | #36 |
Dekatron
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
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Re: Standards Converter recommissioned.
After replacing C48 in the video amplifier the over-shoot effect has gone.
However, there is a slight loss of definition. The 8.2K anode load resistor has risen to 11K. That component will be replaced. VR10, the white spot clipper is inactive. DFWB. |
17th Sep 2022, 10:20 pm | #37 |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
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Re: Standards Converter recommissioned.
Excellent! That test card image must be looking much healthier now.
Peter |
17th Sep 2022, 10:21 pm | #38 |
Dekatron
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Location: Kilmarnock, Ayrshire, UK.
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Re: Standards Converter recommissioned.
Hi
Check C49 for correct value it may have drifted low reducing HF correction.
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20th Sep 2022, 10:53 am | #39 |
Dekatron
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Re: Standards Converter recommissioned.
The first attachment shows the converted picture on a Bush TV62. That set needs some attention having not been switched on for ages.
The second attachment shows the divider network employed to produce the 405 and 625 timing pulses. DFWB. |