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just picked up an IBM PS/2 model 30 (8086 version), having display issues

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First post, by DaveJustDave

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So I recently picked one up with a monochrome monitor. I am pretty sure the monitor is bad because it only displays garbled text - looks a lot like something is out of alignment.

However, i plug in the 15 pin dsub connector to a VGA monitor and I don't get any display at all. When I power on the machine, it tries to go through the boot sequence, and it even takes the monitor out of power saving mode (monitor LED turns from amber to green), but I get no picture.

I'm assuming these came with MCGA adapters by default? Are they just not compatible with newer VGA monitors?

not sure what to do.

I have no clue what I'm doing! If you want to watch me fumble through all my retro projects, you can watch here: https://www.youtube.com/user/MrDavejustdave

Reply 1 of 4, by Kubik

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It's VGA. My Model 30 / 8086 works fine with regular LCD screen (actually, with rather old one).
I recall seeing one strange thing yesterday when testing one 286 I just purchased. It doesn't work on the other (old) LCD I have, it took the monitor out of sleep, but no picture. My trusty L1710S works fine with the machine again.
Try another VGA monitor.

Reply 2 of 4, by dr.ido

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I vaguely remember these and other other early VGA machines using a couple of pins on the VGA connector to identify the type of monitor connected and set the display mode appropriately. Back in the day this problem could show up as the PC being stuck in B&W mode on a color monitor because the cable didn't have those pins wired correctly. On an LCD (or modern enough CRT) these pins would be used for DDC or I2C data, perhaps these signals are confusing your PS/2.

If your LCD has a detachable VGA cable perhaps taking a spare VGA cable and removing pins 4, 11, 12 and 15 at the monitor end and possibly grounding pin 11 at the PS/2 end would work. This would elimate the DDC signals that may be causing the problem and tell the PS/2 that a color monitor is connected.

Reply 4 of 4, by DaveJustDave

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Tried connecting the cable after turning it on, no dice.

Also by newer VGA monitor, I mean an NEC CRT from 1995.

Time to tear it apart and figure it out.

Also the hard drive makes a crazy loud whining grinding sound, looks like time for XTIDE

I have no clue what I'm doing! If you want to watch me fumble through all my retro projects, you can watch here: https://www.youtube.com/user/MrDavejustdave

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