C̶r̶a̶z̶y̶ b̶a̶l̶l̶s̶ Rally Race (ttl only).

[Mc-Q]

to generate a composite signal with colourburst overlay is complex - nobody did it.
Bally almost did it with the cardrack, but thats because they used a home computer chipset - they had to use a small board to split the colours afterwards that a lot of people lose!
if you look at what you need to generate NTSC or PAL it's a lot of circuitry.
to generate RGB they just need to run the signals through some buffers and resistors.composite monochrome is actually more work
you take the colours, feed each into different resistors to create the shades of gray.
then combine them and add the sync.

i put a monochrome monitor on a Defender once - just because i was bored

 

[Lurch666]

With home consoles being able to produce composite colour I guessed arcade game could do the same but apparently not.
Will go back and check the outputs to see if I can see anything that could be RGB signals since this game was in colour according to the picture.
Unless there were two versions-B/W and colour.

 

[Mc-Q]

maybe it was an extra board - i know some private company in italy did something similar for Atari sprint series

 

[Lurch666]

Had another poke with this since it's been sitting around for a while hoping I might find something new out and.....

We are now in colour.
I noticed a few edge connections by themselves on the edge of the main PCB so decided to see if there where any signals on them. Found nothing but since I was scoping stuff out I checked the edge connector on the daughterboard that provided power,sync and composite sync and found three new signals that turned out to be R,G and B.
I had checked before but some of the repairs and chip replacements must have restored those signals since they weren't present before.

If I put the PSU on a very specific voltage I can see it trying to put cars and other stuff on the screen again but this time I can use my video probe to help.

I have found a multitude of signals that only appear at that certain voltage but have yet been unable to find the source.

 

[Lurch666]

So can anyone explain why on a 7416 hex inverter I have a signal going into pin 1 but nothing coming out of pin 2?
At first I thought something on the output was holding it low but if I have pin 2 out of the socket so it's not connected to anything I still get no signal.
I replaced the chip thinking it's faulty but two replacements behave the same way.
Are all the chips faulty or is this some property of the none LS chips I don't know about?

 

[philmurr]

So can anyone explain why on a 7416 hex inverter I have a signal going into pin 1 but nothing coming out of pin 2?
At first I thought something on the output was holding it low but if I have pin 2 out of the socket so it's not connected to anything I still get no signal.
I replaced the chip thinking it's faulty but two replacements behave the same way.
Are all the chips faulty or is this some property of the none LS chips I don't know about?

7416 have open collector outputs https://www.ti.com/lit/ds/symlink/sn7416.pdf