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Amiga 1080 Monitor Cables

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First post, by pewpewpew

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I've kept two of these, and they handle Grounds differently. Does anyone remember why?

To refresh, this cable is for RGB & SYNC, and there are two Ground pins.

At the A1000 end, one of those Grounds goes to three pins, and the other goes to two pins.

Obvously ground-pin 1 is the shields for the RGB, and pin 2 is the shield for the SYNC and... um, actually why was there two for that one?

BUT ANYWAY - the newer old cable ties all of the grounds together. The older one keeps them separate in the two groups I've described. There's an illustration here, http://bboah.claunia.com/1080.html

Memory does tell me that the older cable was "better" somehow, but it's been decades since I've had a computer that used them. Possibly the older cable worked with the A1000, and the newer only with my A500's? (I might have had an A1200 as well, and one or more other Commodore monitors.)

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Reply 1 of 2, by Jo22

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pewpewpew wrote on 2020-03-10, 19:05:

Obvously ground-pin 1 is the shields for the RGB, and pin 2 is the shield for the SYNC and... um, actually why was there two for that one?

Hello! It's just a wild guess, but maybe they used two different ground to keep things more separated.
One ground for RGB signals, the other one for the Sync (+CVBS ?) signal. Anyway, I don't know the schematics good enough.
Maybe the Sync pin / Sync ground has something attached to it, a resistor, a cap, a coil etc. which would interfere when mixed directly with RGB ground.
(In a perfect world, each of the R/G/B lines would have gotten his own ground, even, for best shielding)

Edit: Hey! That multimeter is mine! Just kidding, I own a similar model though! 😁

Last edited by Stiletto on 2020-03-11, 06:16. Edited 1 time in total.

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Reply 2 of 2, by pewpewpew

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Jo22 wrote on 2020-03-10, 23:15:

Hey! That multimeter is mine! Just kidding, I own a similar model though! 😁

Those things are the Casio F-91W of meters.

About the cable - yes I understand the reason for separation. The point here is the other cable doesn't have that, and I can't remember why.

I vaugely remember these cables were not completely interchangeable. Which seems odd, given the slight difference. But we have some true Amifreaks here, so there's a good chance one of them will know.

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