Benedikt wrote on 2021-05-09, 13:54:
Could that have been an XOR chip, i.e. the proper way to join the sync signals? The 7486 and 4070 come to mind.
Joining the sync signals without resistors sounds dangerous.
maxtherabbit wrote on 2021-05-09, 14:59:
I believe the 1084 supports separate syncs. The sync combiner "circuits" discussed here would not be necessary.
There is no way to properly combine sync with basic combinational logic, but XNOR is the best of the worst.
That's slightly off-topic perhaps, but personally speaking, I came to the conclusion,
that quick&dirty/temporary solutions are sometimes longer lasting than the real thing. 😁
('nothing is more definitive than the temporary'.)
Also, the simple, hacky solutions not seldomly do cause less trouble on the long run.
For example, passive ciruits usually do not introduce so much noise (hi transistors, ICs, switching PSUs).
I'm speaking under correction, but I believe in case of an SCART RGB plug,
for example, using a little 1. xV battery (coin cell?) for the Composite/RGB switch signal might be unconventional,
but less dangerous/noisy than doing it “properly“ with a 5v or 12v signal that goes through a DC step down converter (1 to 3v out?).
Same goes for all these Composite mods for old consoles:
Yes, RF is noisy by comparison, but sometimes there's a much easier fix to the issue.
Like, for example, using a clean power source, like a 9v battery/rechargeable, instead of a cheap power brick (modern switching PSUs or old unstabilized bricks with just a trafo) .
Speaking of rechargeables, there's something so incredible simple, yet elegant.
Instead of a modern, over-engineered charging regulator
with a microcontroller, a simple lamp of the same voltage will also do. 🙂
If installed in series with a power source, it will protect both the rechargeable battery and the power source (acts as a fuse, even).
But that's not all, it will also work as a visible indicator. If the lamp stops glowing, the rechargeable battery is fully charged.
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