(I've successfully completed a similar application with the Mac Classic 1's video signals. It was easy to follow into Adrian's Black footsteps, details in my other thread here https://tinkerdifferent.com/threads/macintosh-classic-1-rgb2hdmi-project-complete.832/)
However, documentation is a tad more difficult for the Plus. I'm wondering exactly where I should fork out Hsync, Vsync, video and gnd (gnd being....easiest) from the Plus' analog board. Here's the information pile I have on hand at the moment:
Mac Plus video specs:
Pixel clock is 15.6672MHz (= 2 x 7.8336MHz). f).
Horizontal line frequency is 22.25kHz (44.93us).
Frame rate is 60.15Hz (16.626ms)
which all look pretty much identical to the Classic, and I have slightly more precise values for the first two.
classic2.pdf can instruct on the analog board video subcircuits:
J4 seems to be the place to hook my 4 wires to go external to my RGB2HDMI. Instead of having an exposed external metal piece, I have to add wires either on the backside of the analog board or squish new ones in the plastic connector. Any advice on the best way to proceed?
One difference I have with the Classic schematic is what happens to J4-1, J4-3, J4-5 before they're sent to the CRT - they are inverted with nandgates and tied to pullup resistors like so:
Hsync is discussed here:
Vsync:
In light of all this, do I go righ from the J4 connector or do I intercept stuff right at the exit of the gates? I'd really like the assurance of someone more seasoned in TTL video signals so that I can avoid a potential costly mistake.
The Mac Classic schematic for its analog board was better documented and way simpler; it even tells what form of signal to expect for each of the 4 needed lines (6 W = video, 5 V = hsync, 4 GY = vsync, 12 G/Y = gnd). The RGB2HDMI can deal with inversion variations just fine (you can set it as H+V+, H-V+, H-V- or H+V-).
so in retrospect:
1) where on the Mac plus analog board should I connect my 4 wires?
2) anything special I need to know to add protection?
However, documentation is a tad more difficult for the Plus. I'm wondering exactly where I should fork out Hsync, Vsync, video and gnd (gnd being....easiest) from the Plus' analog board. Here's the information pile I have on hand at the moment:
Mac Plus video specs:
Pixel clock is 15.6672MHz (= 2 x 7.8336MHz). f).
Horizontal line frequency is 22.25kHz (44.93us).
Frame rate is 60.15Hz (16.626ms)
which all look pretty much identical to the Classic, and I have slightly more precise values for the first two.
classic2.pdf can instruct on the analog board video subcircuits:
J4 seems to be the place to hook my 4 wires to go external to my RGB2HDMI. Instead of having an exposed external metal piece, I have to add wires either on the backside of the analog board or squish new ones in the plastic connector. Any advice on the best way to proceed?
One difference I have with the Classic schematic is what happens to J4-1, J4-3, J4-5 before they're sent to the CRT - they are inverted with nandgates and tied to pullup resistors like so:
Hsync is discussed here:
Vsync:
In light of all this, do I go righ from the J4 connector or do I intercept stuff right at the exit of the gates? I'd really like the assurance of someone more seasoned in TTL video signals so that I can avoid a potential costly mistake.
The Mac Classic schematic for its analog board was better documented and way simpler; it even tells what form of signal to expect for each of the 4 needed lines (6 W = video, 5 V = hsync, 4 GY = vsync, 12 G/Y = gnd). The RGB2HDMI can deal with inversion variations just fine (you can set it as H+V+, H-V+, H-V- or H+V-).
so in retrospect:
1) where on the Mac plus analog board should I connect my 4 wires?
2) anything special I need to know to add protection?
