PCjr motherboard won't POST - Blank screen, 2 beeps

[booboo]

I'm testing a spare PCjr motherboard and have symptoms just like an older thread here: motherboard won't post, blank screen, and 2 beeps. Only motherboard and PS on the bench, tried multiple known good PS. Not even keyboard or IR module installed.

What I have observed though is that the middle 73LS374 (next to the 2nd column of RAM) is cooking, can't touch it after a few seconds. Rest of the board is room temp. Those 3 LS374 are flip-flops connected directly to RAM... So the question here is:

• Should I suspect a bad LS374? I can order 74LS374N, should I replace and re-test?
• Would a bad RAM chip be causing the LS374 to heat up?
• Should I instead try to find a short perhaps towards the LS374?

The other 2 LS374 (immediate above / below) are room temp...

Thanks!

 

[wowbobwow]

Sorry to revive a long-dead thread, but I've got a PCjr with similar behavior (no display, two beeps at power-on) and I'm wondering if you ever solved the issue?

Thanks for any info you can share,

Huxley

 

[modem7]

Related information at [here] and [here].