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Interest in a DIY/cheap ADC to HDMI(DVI) adapter? (DVI screen on ADC card)


Interest in ADC2HDMI?  

6 members have voted

  1. 1. I would…

    • Buy one for 20€
      1
    • Buy one for 15€
      2
    • Buy one for 10€
      0
    • Buy a kit for 10€ or less
      0
    • Make one myself
      0
    • Naaahhh I have a working Cinema Display…
      3


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This week-end during a retrocomputing chat someone mentioned the video card in his mac was DVI+ADC and he didn't have the adapter to connect a second DVI monitor to it, and the few available were horrendously expensive.

 

Thinking about it, after discarding the idea of soldering stuff on the card because of space, I believe it should be possible to recreate a good enough connector with a PCB and pins soldered directly, and have an HDMI (and possibly USB) connector on it to plug an HDMI-DVI cable. It would avoid having to source a dual DVI card and throwing those with an ADC connector just because of that.

 

The schematics and pinout is available and it's just wiring anyway. Since Apple screwed up on the connector by not using screws, I think it should be possible to solder staples to the PCB to serve as lock. Using two or three PCBs stacked with spacers would bring mechanical strength… HDMI plug is smaller, lighter and signal compatible with DVI (rather the other way around but), so the whole thing would probably fit under a G4 Cube. (Anyone knows the available height under a Cube?)

 

I believe it could be made as low as 15 or even 10€. But since I already have so many projects going on I figured I'd probe the interest before actually designing the PCBs :-)

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Btw, anyone knows the pinout for the 6pin connector for those cards? Is it only 28V or does it pass USB over? Some cards seem to show a small trace going from it, but others have all 3 pins on each side joined. Maybe there are several versions of it?

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An ADC to DVI/HDMI would be a neat little gadget. 

 

IIRC the "6" pins on the supplemental power connector are all for the 28V supply and USB is done through unused AGP pins. It's been a while though so that might not be accurate... I'll see if I can find my notes and then report back. 

 

As for the prices of such adapters on the current market: supply and demand is just a b*tch sometimes. eBayers will take advantage if they can. Just look at how expensive Griffin iFires are getting. Hundreds of dollars for a 15W amplifier. I figure they're one of those things that people don't look twice at and just throw out, leading to even greater scarcity of what was a niche product to begin with.

Edited by PowerMac_G4
Correcting a typo
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I already have several ADC-using displays (and I also managed to find both an ADC-to-DVI adapter for connecting a DVI display to the ADC port and a DVI-to-ADC adapter to connect a Cinema display to a normal DVI port, evidently before both became prohibitively expensive), but I fully support this project, as it would make life easier by allowing one to obtain adapters more affordably, not to mention the increase in flexibility.

 

c

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  • 68kMLA Supporter

I’m personally set with an ADC display and an ADC-to-DVI adapter already, so although it would be nice to have the option I probably wouldn’t get one.

 

If you could manage HDMI+audio out, I’d spring for that. Before I got the ADC display for my Cube I mainly used a VGA-to-HDMI+audio adapter (not ADC-to-DVI-to-HDMI). That one adds audio via USB, which is convenient for the Cube.

 

In theory it should be possible in a single adapter, but you’d need a lot more circuitry: a USB DAC (cheap enough?), 28V-to-5V to power it (no +5V in ADC?), and an HDMI audio inserter (uncommon? $65 on Monoprice). Probably too complicated and expensive.

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Ugh no I wouldn't try to stuff a USB soundcard inside or any other active HDMI thingy, it's just plain wiring.

But it should expose the internal ADC USB so it doesn't preclude you to use an existing USB sound card… Oh, wait… Geee… I just noticed the connector doesn't have a 5V pin… how crude from Apple!

 

So that means without a step-down or some other 5V source it's not possible to use the USB from it directly. Crap.

Not like it couldn't be done but it would make it more complex than it should be and should probably be optional.

Either with a step-down converter, there are cheap and small ones now that could even fit. But so close to video signals it could cause interference.

Another option would be to use those Y charging cables and solder the charging part, or, yeah use some USB-to-jack cable and a small barrel jack on the PCB so it would be less ugly.

Looking at it again, anyone knows what those LED and Soft Power pins are? I suppose the later is equivalent to the power button on the ADB keyboards.

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Yeah, a button on the screen turns the computer on, probably by grounding Power. That button lights up when the computer's on and pulses in sleep mode, which might be the function of LED.

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Right so it's probably PWMed and not straight +5V, sad.

Still most users will only case about the HDMI output, so it's probably ok to leave a small barrel jack as 5V in for those who want.

Possibly some USB devices with external power wouldn't care about the missing 5V. Oh well.

 

Anyway I might have a look at it but first I want to make an AAUI to AUI cable.

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This is true.  Still useful because the adapters are rare and expensive now.

 

Trying to make new ADC male connectors using PCB and pins may encounter the same sort of issues that BMOW did with his DB19 adventure.  Doesn't fit quite right, etc.  I hope it can be figured out though.

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Posted (edited)
On 3/8/2021 at 5:35 AM, androda said:

Trying to make new ADC male connectors using PCB and pins may encounter the same sort of issues that BMOW did with his DB19 adventure.  Doesn't fit quite right, etc.  I hope it can be figured out though.

Which is why I don't want to. The plan is to fake one with pins soldered onto a PCB, and have it good enough to hold there, not being unplugged 10k times.

Edited by mmu_man
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  • 1 month later...
Posted (edited)

The card I bought to test things arrived and… of course it was for a G4 and doesn't fit in the G5 because the extra connector for the 25V was moved for the G5, thanks Apple…

I can make measurements at least.

And I found the LED pin (3) of the ADC is wired to the A11 pin on the AGP connector (normally reserved). The Soft Power pin (13) I just noticed is A3 on the AGP bus. Seems I missed it firsthand but wikipedia says both pins on AGP were used for power on G4. Still not sure what they are supposed to be though.

Edited by mmu_man
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I'm creating the ADC connector part for KiCAD and I'm wondering, is the second DVI link implemented in any card at all? Like DVI they provisioned 6 pairs + clock which I guess is dual link, but I see only 4 pairs going to the chip on the card I have.

I want to use an HDMI A connector as output for space reasons, but it only has a single link so we'd loose the second one. It could be possible to add a second connector I suppose but I don't think it'd be of much use. Anyone has a card which supports dual link over ADC?

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5 hours ago, mmu_man said:

and I'm wondering, is the second DVI link implemented in any card at all?

 

Not that I know of. ADC and dual-link DVI turned out to be mutually exclusive. The only cards that support dual link are post-ADC and the only monitors that need it are also post-ADC.

 

 

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