The Classic, as all the other compact Macs (the 128k, the 512k, the
Plus, the SE and SE/30, both Classics and both Color Classics) use a
non-standard horizontal refresh frequency (about 22 KHz, where CGA/NTSC
use 15.75 KHz and VGA uses 31.5 KHz). Most monitors out there won't be
able to display it, as they expect either an NTSC signal (15.75 KHz), or
a (Super)VGA one (31.5 KHz or more). Maybe an active converter would do
the trick, but it isn't trivial. A monitor able to support the
Macintosh's 512x384 mode (for example, the Apple-branded 12" monochrome
one provided with the Mac LC) would work. PC MDA/EGA/Hercules monitors
would work, too. But we are talking here about vintage displays made
over 30 years ago (more than 40 in the case of MDA and Hercules), which
are rare and would end showing the same problems as your Classic's
analog board.
Also, IIRC, the video output on the Classic (and all other monochrome
compact Macs) is 5 V TTL, where most video connectors out there
(including Apple's ones) are 1 V analog. That one would be easy to
solve, though: a simple tension divider, using two resistors in an 4:1
relationship (say, 1 KOhm and 270 Ohm) would do the trick.
Sincerely,
Antonio Rodríguez
El 10/04/2024 a las 20:47, Pizzaboy192 escribió:
I remember seeing some youtube video where the person casually showed
an adapter to use a Macintosh Classic logic board outside the factory
chassis. I cannot remember which video and cannot find it in my watch
history.
I have a Macintosh Classic that has a perfectly happy logic board but
the board supplying power and doing the display control is slowly
dying. I am wondering if in the 30 years since it was built there has
been an attempt to replace the CRT and power supply with VGA or
similar and a regular PSU.
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