Locutus wrote on 2023-07-27, 19:08:

Does anyone know the purpose of the LED near keyboard adapter ?

AFAIK it's an "On" LED, I've seen those on some XT and early 286 mobos. I suppose these can be useful in systems where the PSU is quiet and/or the 5V rail can remain energized a few seconds after the mains switch is flipped (to prevent removal of cards or touching anything in general). But why they used those in PCs... maybe it was the equivalent of blue RGB LEDs we have now?

Locutus wrote on 2023-07-27, 19:08:

Time to play with "dead" ST-157A...

I think I've seen you post about that in other thread? No spin or something more complicated?

Yay! This was exact same thing with dud 206 which was CHIPS on a american megatrends designed series 19 with cache 386DX 25 motherboard. Swap and is fine, and was not CHIPS brand 206.

Cheers,

Deunan wrote on 2023-07-27, 20:09:

Locutus wrote on 2023-07-27, 19:08:

Time to play with "dead" ST-157A...

I think I've seen you post about that in other thread? No spin or something more complicated?

Hi.
I've created new thread here:
Dead SEAGATE ST-157A...

Deunan wrote on 2023-07-27, 20:09:

Locutus wrote on 2023-07-27, 19:08:

Does anyone know the purpose of the LED near keyboard adapter ?

AFAIK it's an "On" LED, I've seen those on some XT and early 286 mobos. I suppose these can be useful in systems where the PSU is quiet and/or the 5V rail can remain energized a few seconds after the mains switch is flipped (to prevent removal of cards or touching anything in general). But why they used those in PCs... maybe it was the equivalent of blue RGB LEDs we have now?

I've replaced burnt LED, new one stays off all the time.
I've asked the guy who send me pictures of the same MB, and he confirmed, that in his MB, this LED is off all the time also ...
¯\_(ツ)_/¯

In a free time, I'll draw a wiring diagram to see how it is connected.

Well, that PCB is in a case now, in a different location as well. I'll see if I can take another look at it next week - but I'm not removing the mobo from that case. It requires taking the MFM HDD out, as well as both floppy drives, along with the entire mounting assembly. And then mounting that all back. I simply do not have free time to do that now.

UPDATE: I had a quick look - that LED lights up when power is applied and neither turbo nor reset button, nor any keyboard keys or keylock status, have any effect on it. But it is super dim, I thought I saw it shine much better but perhaps I'm mistaking this mobo with some other one.