VGA connections

[Dave Plowman (News)]

I fairly recently got an LCD TV for the workshop which has a VGA input. It's situated conveniently for the electronics workbench. The idea being I could use it for testing any video signal.

It occurred it would be nice to have it parallel fed off the RPC which is on the other side of the room to save having to print out circuits etc I might be following.

So I bought a 5 mtr VGA lead from Ebay. And a secondhand Rextron VSA18 splitter which has 8 outputs.

I made up the input lead for that as it requires a male to female type. I Googled for SVGA pinouts and got different stories - so simply made it pin for pin compatible with the existing monitor lead using co-ax for the video signals. The pins with no connection are 4,5,8,12. If I piggy back it to the RPC monitor lead that works as normal. The same with the long cable to the TV.

But plug in the splitter - nothing. The 'active' light on the DA does come on, though, presumably indicating it's getting an input.

I've no paperwork with the Rextron but their site says it works with VGA, SVGA etc etc.

The obvious conclusion is the DA is faulty - but given the variety of SVGA connections could I be missing something?

[meow2222]

If it doesnt work at all with vga, how can it be anything but faulty or not compatible?

NT

[Andrew Gabriel]

What will it be doing with the serial connection for the EDID data (to read back screen size, refresh rates, etc)? If this isn't connected, some systems will assume there's no monitor connected, and it might not be passed through the splitter (and if it does, which socket is it connected to?)

It might not feed through your VGA lead either -- that could be why it's on eBay ;-)

(I've no idea if acorn systems use the monitor's EDID data.)

CPC do loads of video cables of different lengths with different gender connectors.

[BigWallop]

Have you tried using the SVGA pinout scheme to the splitter

units are better supplied with SVGA signalling, than a VGA signalling method. The splitter will do the rest of the conversion for you. You'll notice that the pins connections are different from what you have now, but if you've ever tried connecting a VGA to SVGA you'll know what happens. Try the other way round and you get a signal.

I think it's worth a try.

[BigWallop]

Should also have said that a cheap SCART lead will give you the best ready made cable for the fly lead to the splitter.

[Dave Plowman (News)]

Well the maker's site seems to reckon it's compatible with all the various standards.

Don't think so.

Indeed - but I was curious to know what it should be. Each site I look at gives different connections for SVGA.

But it's sorted. The DA came without its wallwart PS - which could be why I got it cheap. Normal 2.1mm? socket marked 9 v AC. And not having an AC one I used DC. Which is usually ok. But not when the internal PS gives +/-

5 volts...

[Dave Plowman (News)]

That would need two 15 pin D plugs fitted. Altering a VGA lead only one. ;-)

I did look in the local Maplin. 17 quid for a VGA male to female. Asked the assistant if they had a cheaper range and he said to go to Currys.

[BigWallop]

But Dave, you want the thing to work, don't you? Two 15 pin plugs are cheap enough for a project like yours. And, with the quality of your assembly techniques, it will last for years and years.

quids for twenty metres with male to female connectors. Ready made.

[geoff]

In message , BigWallop writes

There's a company here in Watford who will make up quality leads to spec.. I have a 15m VGA lead which gives an excellent picture cost me £15 + VAT

Or contact RL Supplies

[Dave Plowman (News)]

The 5 mtr one I got from Ebay cost 5.90 inc postage as a BIN. And it works just fine. Of course the TV I'm feeding it with hasn't got the resolution of a decent monitor. I'd guess. But It looks fine for my purpose.

[BigWallop]

I was wondering how many leads I'd get from the one X twenty metre lead and a few plugs. How much do 2 metre leads sell for?

[Dave Plowman (News)]

Couple of quid on Ebay - you'd have to by a lot of cable and plugs to get the material costs down to that sort of level. And I'd say it takes about

1/2 hour to fit one plug properly.

[BigWallop]

That's that idea out the window then. :-) Oh bugger.

[druck]

BigCobblers more like.

Pull the SVGA one, it has bells on it.

There is no such thing as a SVGA cable, signal levels or pin outs, VGA is the electrical standard. SVGA is denotation of resolution and colour depth.

---druck

[BigWallop]

WOW !!! I thought there was a difference. According to this link

the VGA connections are not similar to the connections in the linked page above.

Or is this just because it's a different manufacturer? I didn't think they could that with these types of leads.

[Rob Kendrick]

They look the same to me, except the first one doesn't include the extra data pins for examining the monitor.

As druck says, VGA is the electrical connection. The only difference between VGA ans SVGA is signal timing.

B.

[BigWallop]

What a load of pedantic buggers there are in here. :-)

OK then. Dave, your splitter may need the extra ID connection to obtain the correct resolution for your monitor. A simple lower resolution VGA connection scheme may not be enough to allow the splitter to convert to your monitor timing signal.

Does that satisfy everyone?

:-)

[Dave Plowman (News)]

Well, that's the Acorn groups for you. But the true story is always forthcoming from someone on them. ;-)

I'm just curious why when you Google SVGA you get so many different 'definitive' pinouts.

But as it happens the problem was finger trouble on my part as so often.

[Rob Kendrick]

Hardly pedantic. Those data pins are an extension, and you can still use SVGA monitors without them, it's just you'll have to tell your computer what modes it can do, rather than have it automatically detect it.

I certainly wouldn't want to use a passive cable at all to split higher-resolution modes (say, 1600x1200@85Hz) - for that I'd recommend an active box.

B.

[Dave Plowman (News)]

Passive splitters never work *properly* with any baseband video signal as they expect correct termination. I'm using the correct active DA.