JP21 proper levels

[kamiboy]

Let us say that you have a correctly wired JP21 cable connected to a system in addition to a multimeter.

Using this multimeter, if you want to test whether the signal pins have the correct "levels" what would you measure, voltage?, ohm?, amperage?, and which ranges would you expect each of the signal pins (R, G, B and Sync) to be at?

If anyone could document the important signal properties and their standard levels for a JP21 scart I would appreciate it a lot.

[Fudoh]

0.7V on the RGB lines with a fully WHITE picture (peak voltage level). Sync is fine with the same, but can theoretically be higher without doing anything negative to the picture.

[kamiboy]

So voltage levels are the only thing to look out for?

Unfortunately I do not have the ability to control what appears on the screen, but 0.7v still gives me a reference point at least.

I assume a black screen would result in near 0 volt on the R,G and B lines, but not change the sync.

Once I get home I'll take some measurements.

[kamiboy]

By the way, anyway to tell by just measuring the signal levels whether the 220uF capacitors on the SCART RGB line are not doing their job right?

I only have a very rudimentary understanding of electronics and for the life of me cannot wrap my head around how a capacitor changes the properties of electric current in a measurable way.

I know their job is to store and release electrons but deuce if I can work that to a change in voltage or amperage. I am guessing their effect is of a another nature though.

[Fudoh]

capacitors filter out voltage peaks and the can remove a DC offset (if there is one). If you would measure a NTSC SNES RGB Signal and there are no capacitors you end up with elevated BLACK levels (maybe 0.1V instead of 0V).

[kamiboy]

That sounds pretty ambiguous. I'll report back once I've completed some measurings.

[kamiboy]

Turns out the 220uf caps had leaked making a mess of things. I suspected as much.

What is it with these subpar early 90's capacitors anyway? Someone dropped the ball back then creating millions of ticking time bombs.

[nZero]

What is it with these subpar early 90's capacitors anyway? Someone dropped the ball back then creating millions of ticking time bombs.

http://en.wikipedia.org/wiki/Capacitor_ ... implicated

[kamiboy]

I know qbout that incident, alas that documented scandal is for capacitors made in thr early 2000's. Nothing is ever mentioned of all those early 90's capacitors that have been failing way before their time.

I am talking about all those SMD's failing in PC Engin Duos and radials in X68000's etc. I suppose th failiures began to occur too late for it to grow into a scandal.