1 Feb
2025
1 Feb
'25
3:14 p.m.
On 2025-02-01 6:37 a.m., Frank Leonhardt via cctalk wrote:
IME +/- 12V was a de-facto standard on microcomputers
because they
already had a +12V and -12V rail, along with +5V. The ubiquitous 4116
DRAM needed +5V, -5V and +12V so +/- 5V was a popular option too.
Apple was smart with their switching power supply.
I picked up a S100 bus kit, and all I could build was the +8? supply
that later exploded taking out every thing. The real pain was that
most memory was static ram with like 8K per card.
These days you can, of course, get RS-232 driver chips
that take TTL in
on one side, +5V, and derive the correct voltages internally. For only a
few pence. Problem gone (except they tend to be SMD and a PITA to mount
on strip-board. Grrr).
That was ok when you had one brand of max232, now you have several,
and not all connections are the same. I pulled a schematic off the web
and got burned when I used the wrong brand. Worked like 10 minutes
before it died.
Regards, Frank.