DB15 to DB15 Apple VGA cable pin-out

[V.Yakob]

I need to get a few DB15 cables of different lengths to connect the Mac to the KVM Switch. Unfortunately, I can't find ready-made and suitable options for me.
I have an idea:
buy PC VGA cables of the required length, cut off the connectors, and install DB15 Apple VGA in their place.

But I can't find a pin-out for the DB15 cable (m) <-> DB15 (m) anywhere.

Will my idea work and can someone share the pin-out of this cable?

Thanks

 

[joevt]

I don't understand the problem. You have 15 pins on one side and 15 pins on the other. Connect one pin on one side to the corresponding pin on the other.

Basically, the signals on the female connector of the KVM that connects to the Apple display need to match the signals on the female connector of the Mac.

Do you have a link for the KVM Switch?

 

[V.Yakob]

Usually the cables do not have a direct pin 1 - 1, 2 - 2, etc, there are always some intricacies.
I should get this KVM from eBay in a while. I have no other information about this device, at least not yet.

I don't have a single DB15 cable, so I can't call the contacts myself. And all the schemes that I find on the Internet are mostly about adapters.

 

[joevt]

Usually the cables do not have a direct pin 1 - 1, 2 - 2, etc, there are always some intricacies.

I believe the intricacies are usually at the computer end and the display end. The KVM cable is just an extension cable.

I should get this KVM from eBay in a while. I have no other information about this device, at least not yet.

I don't have a single DB15 cable, so I can't call the contacts myself. And all the schemes that I find on the Internet are mostly about adapters.

The KVM is probably not an adapter. You should be able to test continuity of all the pins between the computer side and the display side of the KVM switch with no computer and no display connected. That should be sufficient to determine if the missing KVM extension cables are just straight through cables.

What kind of electronics does the KVM have? I know some switch boxes are just mechanical switches. This KVM might be more complicated than that. A simple mechanical switch for ADB is unlikely because ADB is not supposed to be hot pluggable. Does that mean it has some kind of ADB controller to keep alive the ADB devices of one computer while switched to the other computer?

I suppose there should be some kind of keep alive circuitry for the display connection as well so that a computer doesn't think the display disappears when the KVM is switched to the other computer.

 

[phunguss]

Here is one version of an adapter pinout. I see that your KVM can output to Apple DB15 or VGA DB15, so it must have internal intricacies/adapter. I would agree with @joevt that the cables required are likely straight through from the 3 computers to the KVM.

 

[V.Yakob]

@phunguss I need a pin-out of the standard Mac DB15 to DB15 video cable.
I don't think anything else will be needed.

I saw this scheme, it's an adapter, Apple VGA to PC VGA, when I searched myself. But unfortunately it doesn't fit. If everything was so simple, I wouldn't have written here.

 

[phunguss]

What about this one? And this thread says it is a straight through cable but ALL pins must be present for it to work.

 

[V.Yakob]

@phunguss, It's interesting and worth trying.
Thanks!

When I have a cable and this KVM, I'll come back with the result.

 

[joevt]

Here is one version of an adapter pinout. I see that your KVM can output to Apple DB15 or VGA DB15, so it must have internal intricacies/adapter.

I'm not sure how this would work. The VGA connector of the KVM might have a diode to select VGA mode from a Mac? But such diodes shouldn't exist on the Mac display connector of the KVM because they would interfere with those in the display and different displays have different diode arrangements (Apple Sense Codes https://tinkerdifferent.com/threads/documentation-for-db15-to-vga-adapters.318/post-21288 ). So maybe the VGA connector doesn't support Apple monitor sense codes unless an adapter is connected to it?

I suppose some complicated circuitry could test both the VGA and Mac output connectors of the KVM and copy that info to the input connectors of the KVM? It would have to be able to copy both Apple Sense Code info and EDID info and be able to do DDC etc.