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

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Old 10th Jun 2006, 4:58 pm   #21
Kat Manton
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Default Re: FOTH RGB combiner problems

Hi Sean,
Quote:
Originally Posted by m1ecy
I have some problems with the ICL7660 - although a great device, it does get intolerably hot when asked to do any work
It's only really needed to provide a -ve rail for op-amp(s) so I can have my black-level at 0V and negative-going sync, (or for sync at 0V, so the op-amp output can swing to 0V) - the +5V rail will be doing the bulk of the work, so I suspect a 7660 will suffice.

Quote:
Long live discretes and high component counts
I think it's my commercial background showing (Klark Teknik, AMEK, Pace [1]) - holes in PCBs cost money, extra components cost money just to place and solder... if I can do the lot with one square surface-mount thing with lots of legs and some software inside I probably would...

Cheers, Kat

[1] Note, none bar Pace have anything to do with video (and I was merely a software engineer there), which is why I'm rubbish at video
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Old 10th Jun 2006, 5:27 pm   #22
oldeurope
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Default Re: FOTH RGB combiner problems

Äh sorry, I don't want to replace an opamp by several transistors.
It is vise versa, I replace several opamp stages by a few transistors.

Darius
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Old 10th Jun 2006, 6:17 pm   #23
Paul Stenning
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Default Re: FOTH RGB combiner problems

The only problem with a microprocessor is that it needs to be programmed. This involves people having to buy or build a programmer, or order the chip from somewhere programmed, which goes away from the self-build approach of the project.

An exception may be a PIC or something with a USB interface that can be programmed with a bit of software on the PC (and maybe even controlled that way to tell it what video standard it is sorting out the sync for).

Another problem with more complex ICs is that they have a tendancy to go obsolete as soon as you have done the design, which can result in an unbuildable design. With descrete components and op-amps etc, it is usually not a big problem to find a suitable alternative.
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Old 10th Jun 2006, 8:00 pm   #24
Kat Manton
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Default Re: FOTH RGB combiner problems

Hi,

Point taken, Paul - this is partly why I have no problem with other designs being produced; as long as the originator has no problem with the design being released under a Creative Commons licence it can be submitted and published on the website; more details will appear in the relevant section of the website.... (taking shape somewhat slowly here...)

With a bit of luck we can end up with plenty to choose from. This could range from something involving little more than resistors and a transistor or two (I have an idea for something rather minimalist... ideal for "trying it out" without having to build much) via something with a PLL and a bunch of digital logic but still no programming needed (better syncs, better interlace on "picky" sets); up to something with a microcontroller in it just because I like an excuse to play with them sometimes...

Choice is good, I like choice

Anyone feel like designing something entirely with valves? Lock an oscillator at about 20.250kHz to incoming line-sync from the computer then generate perfect sync "to standard" using similar circuitry to how it was done originally...? Could be fun... could be big, though...

Regards, Kat
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