Awhile back, I made a straight through cable for the RGB DIN-8 connector on the back of the system. Image looked great running through the iScan HD out to VGA, however it didn't get picked up by the VGA switch I use when directly connected to the switch. The switch naturally tends to look for a more TTL friendly signal, and it can pick up something like the ~2.5v of the SNES and many other systems.
The Sony PVM that I keep on my bench also does not want to display RGB from the system. Flicking the RGB/Line switch will briefly show an image in a bit of distress, followed by a black screen.
From the A1145, the circuit in the system is
A1145 Pin 11 ->
6.3v 100uf cap ->
75 Ohm resistor ->
DIN8
With the DIN8 cable + BNC adapter hooked up to the PVM, scoping after the 75 ohm resistor mentioned above yields the following:
It would be nice to perform a minor circuit mod to create a more friendly csync for the devices I use with it. Viletim did some experimenting with the Genesis Model 2 (1645 chip, I believe) here: viewtopic.php?f=6&t=36871&p=768708#p768708 that illustrates some examples of Model 2 sync tests with different components here - http://etim.net.au/md2sync/MD2_sync_tests.png. I believe this is grabbing CSync In as there is no CSync out on the 1645.
The specs of my PVM list external sync as: 4.0 Vp-p ±6 dB, sync negative. However, I believe something like the SNES's 2.5 Vp-p is enough to produce an image on the display. Ultimately, Tim recommends using a buffer (74AHCT125).
Assuming the datasheet CXA1145 Csync Out components are the same as this "Sony A1145" chip - It is interesting that Panasonic used a 100uf cap instead of a 470uf. I am also not sure what difference it makes.
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I am interested to hear what you guys would do to produce a compatible image for the switch and PVM. What changes would you make?
