VOGONS


First post, by synacktic

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I have a dead Paradise EGA card. One capacitor needs replacing for sure, but only two of the capacitors on the board have any markings that I can see.

Main question: How can I determine the size/specs for the other unmarked capacitors?

Wishful thinking question: While I know the RCA ports won't output composite, does the PEGA 1A chip have that ability at all? Could a pin be tapped somewhere to get composite out?

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The one that is dead is in the lower right of this pic (upper right of the card), but I'll just replace them all, if I can work out the values.

Thanks!

Reply 1 of 11, by Grem Five

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I'm not sure if you have it but here: Help configuring this EGA card is a thread where Shagittarius was kind enough to put the manual up for your card.

This video https://youtu.be/GTai7o5E0Qk?t=1115 has a card similar to yours with the same bad cap although his is a PEGA 2A where yours is a PEGA 1A. He doesnt seem to know the specs of the cap as well but the card appears to work.

Reply 2 of 11, by vstrakh

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Those are bulk caps, their exact capacitance is not that critical for the application, just make sure you have the voltage rating above the rails they're sitting on.
Most likely you won't even be able to find lower voltage caps (assuming you'll be replacing it with tantalums to maintain the original look), and you can just put there something like 10uF 25v or 35v.

Reply 3 of 11, by synacktic

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The bottom ones by the bus are 10uF 16V, the upper ones are physically smaller. So, would keeping the voltage and lowering the capacitance a little for those make sense?

vstrakh wrote on 2023-07-20, 08:02:

Those are bulk caps, their exact capacitance is not that critical for the application, just make sure you have the voltage rating above the rails they're sitting on.
Most likely you won't even be able to find lower voltage caps (assuming you'll be replacing it with tantalums to maintain the original look), and you can just put there something like 10uF 25v or 35v.

Reply 4 of 11, by vstrakh

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16v are ok for 5v rails.
For 12v rail having 16v capacitor is not that great, there are recommendations on derating the caps, many debatable though, as current quality of tantalums is way higher than before.
But it's safer to put higher voltage rated caps on 12v rails. The size of current 25v/35v caps is not that different from the old 16v caps.

Reply 6 of 11, by vstrakh

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Yes. I'd say that was the "rule of thumb" back then.
I've just looked through a bunch of old videocards, Trident, CHIPS, etc. Every single one had a single nominal of 10uF 16v tantalums used all over the board.
Only the ancient Jovian Logic RUBY 451 used smaller 4.7uF 16v for the same purpose, and those were not yellow but deep ruby colored 😀

Reply 7 of 11, by synacktic

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So, feeling a little silly. I actually broke out a digital microscope my dad got me recently and found that there are markings on all the capacitors. I just could not see the orange on orange at all on some. (Stupid old eyes) Every single one is 10μ 16V. Even the shorted one sitting on the 12V rail leading to the feature connector. The rest seem to be on the 5V. So, I'll replace all but one with the same spec and get a higher voltage one on that 12V.

Reply 8 of 11, by root42

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synacktic wrote on 2023-07-19, 21:20:

Wishful thinking question: While I know the RCA ports won't output composite, does the PEGA 1A chip have that ability at all? Could a pin be tapped somewhere to get composite out?

I think nobody talked about your composite wish. Composite would ever only make sense in the CGA resolutions of this card, as everything else would be out of spec for a TV signal I think. You would need at least the Luma signal and the H/V sync and combine that via some transistor or such to a composite B/W signal. For color you would need even more, I think. As there is no datasheet to my knowledge of the PEGA chip, you would need to start probing the pins with a scope.

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Reply 9 of 11, by synacktic

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Yeah, from what I have been reading, there is probably no such signal premade. I would need to create composite maybe by tapping the feature connector and then do the ntsc encoding of I wanted color. Could be a cool project though to basically enable (cga) composite our on people's ega cards. Maybe even make those RCA jacks do something useful! 😀

root42 wrote on 2023-07-20, 16:46:

I think nobody talked about your composite wish. Composite would ever only make sense in the CGA resolutions of this card, as everything else would be out of spec for a TV signal I think. You would need at least the Luma signal and the H/V sync and combine that via some transistor or such to a composite B/W signal. For color you would need even more, I think. As there is no datasheet to my knowledge of the PEGA chip, you would need to start probing the pins with a scope.

Reply 10 of 11, by zyga64

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synacktic wrote on 2023-07-20, 17:22:

Yeah, from what I have been reading, there is probably no such signal premade. I would need to create composite maybe by tapping the feature connector and then do the ntsc encoding of I wanted color. Could be a cool project though to basically enable (cga) composite our on people's ega cards. Maybe even make those RCA jacks do something useful! 😀

To get started, you can take a look here (B/W only): https://github.com/monotech/EGA-Mono-Composite-Coverter

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Reply 11 of 11, by synacktic

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Thanks! I read Hugo Holden's article that is based on yesterday. Very helpful. Also, I recapped the card last nigt. I don't have an EGA or CGA monitor, but I was able to use the CGA2RGB from GGLabs to connect it to my PVM. After some fiddling to work out the right config, and dealing with an angry motherboard, I'm happy to report it works in all it's EGA glory!