Falcon cap C6 incorrect polarity?

[Steve]

Hi all,

Someone on Discord shared this recently, I haven't been able to confirm it or anything, just sharing for future reference

Falcon_C6-cap.jpg (423.56 KiB) Viewed 3854 times

Just another reversed polarity cap to add to what we already know: https://exxosforum.co.uk/forum/viewtopi ... 98&p=19310

[Rustynutt]

Nice find. Wonder if some of the VSYNC issues dml brought up years ago are related to the cap in your link to the Exxos post?

Recently found on the KB ACIA, polarity on that IC to be reversed according to the data sheet. Was pulling power for an oscillator off the pins, and noticed this on the meter.

Could you take a peek there and see if I was drunk at the time?

[Rustynutt]

Never mind, looked up terminology and data sheet again. Seems the ACIA Vdd is normally 5V, pin 12. Had it backwards for some reason.

[exxos]

Atari really struggled with cap polarity didn't they

[T'PAU]

And here's what my multimeter has to say about that:

Falcon_C6-cap_voltage.jpg (429.8 KiB) Viewed 3756 times

Although the picture in first post is from me, someone else from german atari-home.de forum stumbled over this issue a year ago.
I just confirmed (and fixed ^^) it.
https://forum.atari-home.de/index.php/t ... 690.0.html

[mikro]

Does it have some effect, though?

For example, isn't possible that it's one of those places where polarity isn't important?

[Badwolf]

Does it have some effect, though?

The side cutters would answer that!

BW

[Steve]

@exxos I just cracked my Falcon open to check the polarity on the legs of this capacitor, I put my multimeter on continuity test and connected one probe to ground and then tested each leg of the capacitor. The bottom leg (the leg pointing to the inside of the motherboard) *is* connected directly to ground, where as the top leg (closest to the outside of the case) is not connected to ground (and is marked '+' on the silkscreen)

So I am starting to believe that the capacitor is correctly orientated? So the positive side must be carrying -12v, as shown on @T'PAU's multimeter?

Is it correct to connect the positive side of a capacitor to a negative voltage rail, and the negative side to ground?

[Steve]

I see TPAU had the same misgivings and asked the same question, joejoe answered with:

Screenshot_20221204_131420.png (56.66 KiB) Viewed 3691 times

Would you agree with joejoe?

[HigashiJun]

An answer from a pro would be nice (before I start to unsolder the cap).