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Tube❄️Time

looks like it might be the power switch. I'm expecting less resistance than this.

43 comments
Tube❄️Time

power switch tests good. sigh, I hate working on big AC power supplies

Tube❄️Time

i'm having a lot of trouble getting the screws out (holding the board in place) so i think i'll take a break.

Tube❄️Time

got the board out. the hex screw heads are a loose fit for 3/16 and 5mm but a very tight fit for 4.5mm.

Tube❄️Time

twitch.tv/tubetimeus think I'll do a little reverse engineering stream. this should be fairly straightforward.

Tube❄️Time

made a good amount of progress, but the control circuit is quite involved and has lots of discrete parts, so it's slow going at this point.

Evgeniy Latuhin

@tubetime Thank you for sharing the plate picture. For some reason looking at them brings a feeling of comfort in me.

On slightly related note since Factorio become mainstream I need to doublecheck plate photos. Some of them are really looks like a Factorio maps and other way around.

Tube❄️Time

and the reverse engineering is basically done. it is missing a couple of capacitor values but you get a pretty good idea of how this thing works.

github.com/schlae/ps2-80-power

Tube❄️Time

so the bias voltage rail isn't high enough. it hits about 9V and that is it. the supply checks it and won't power up until it hits 11.8V.

Tube❄️Time

which means i probably have to dig into this tricky little circuit. this is a preregulator that chops the incoming AC voltage if it detects 220V. then it goes through a 120V->12V linear power supply circuit that is pretty normal.

Tube❄️Time replied to Tube❄️Time

burn mark on this capacitor is very sus. turns out it failed in a dead short!

Tube❄️Time replied to Tube❄️Time

well that was the problem, it's powering up now.

Tube❄️Time replied to Tube❄️Time

this is the cap that failed. it basically shorted the bootstrap supply for the bootstrap supply (heheh)

Evan replied to Tube❄️Time

@tubetime Odd question but is it still possible to get replacements for those big red switches on the 5150 power supply?

Tube❄️Time replied to Tube❄️Time

all buttoned up and ready to be reinstalled.

Tube❄️Time replied to Tube❄️Time

also the computer works fine now. *phew* now what was i trying to do with it anyway? 🤔

Eli the Bearded replied to Tube❄️Time

@tubetime

Isn't the answer always Commander Keen?

Tube❄️Time replied to Tube❄️Time

oh yeah i was swapping out the Type 1 planar (16 MHz 386) for a Type 2 planar (20MHz 386).

A type 2 PS/2 model 80 planar.
Tube❄️Time replied to Tube❄️Time

well that works! this is the planar that had the cracked chip on it that I fixed (see the yellow labels in the previous photo).

Tube❄️Time replied to Tube❄️Time

the type 1 planar is on the left and the type 2 is on the right. i've got a Kingston 486 upgrade card in the one on the left.

Tube❄️Time replied to Tube❄️Time

after putting the Type 1 planar/motherboard back in, the computer failed AGAIN. this time with a black screen and no beeps. 😦

Tube❄️Time replied to Tube❄️Time

OK, i put my MC Mechanic POST card in it. this is a Micro Channel machine so you can't use an ordinary ISA POST card, which is why i designed this one. looks like it is running code!?

Tube❄️Time replied to Tube❄️Time

weirdly enough, it booted to the setup disk just fine, but during automatic configuration, the screen goes blank and the whole thing locks up. from then on, any cold power cycle results in the error code 0F! i've pulled the battery again to clear whatever was loaded in there.

Tube❄️Time replied to Tube❄️Time

OK i let it sit and then rewrote a new reference disk. perhaps it detected the type 2 planar and screwed something up in the type 1 planar's CMOS?

Tube❄️Time replied to Tube❄️Time

it runs now. i get a 201 error and a 164 error on boot. hmm, memory error and memory size error.

Tube❄️Time replied to Tube❄️Time

looks like I need to get my system unit serviced. error 10400 is pretty generic.

Tube❄️Time replied to Tube❄️Time

my guess is that it is the system board memory that has gone bad. funny coincidence, i'm designing a memory tester right now! however, i hadn't thought about putting in sockets for these little guys. can you even *get* sockets?

IBM memory board with weird little SLT metal can modules instead of regular chips.
Michael Cook replied to Tube❄️Time

@tubetime What kind of packaging is that? I’ve never seen anything like it.

Tube❄️Time replied to Michael

@foobarsoft IBM's crazy odd MST modules (later versions of their SLT modules that they invented in the 1960s)

Garrett Wollman replied to Tube❄️Time

@tubetime Because of my unique personal history, my first thought was "I wonder if those were made in Burlington" (which was actually Essex Junction).

Tube❄️Time replied to Garrett

@wollman see where it says "IBM 14" in the middle? the number there indicates the factory it was made in. apparently the code 29 indicated Essex, so this was a different factory. (see righto.com/2021/01/)

Tube❄️Time replied to Tube❄️Time

twitch.tv/tubetimeus let's do some more board layout -- this time, i'm cloning an IBM PS/2 model 80 memory card (gee i wonder why)

Tube❄️Time replied to Tube❄️Time

some folks are wondering what those metal cans are in the other post. here's a handy reference chart from IBM that shows modules with the lids removed.

SLT: ceramic slab with discrete diodes/transistors
ASLT: two stacked ceramic slabs
SLD: solid logic dense; just more parts crammed on a single slab
MST: ceramic slab with one or more IC die flipped over and soldered down with solder bumps.
Eric Carroll replied to Tube❄️Time

@tubetime
What the heck is that metal can style package?

Yet Another Weird IBM Package I guess. All part of its early days vertical integration and vendor lock in strategy?

Tube❄️Time replied to Eric

@EricCarroll IBM MST. based on an earlier tech they called SLT (solid logic technology) that they developed in the '60s.

Eric Carroll replied to Tube❄️Time

@tubetime I thought it looked like the SLT package from the IBM 1130 & 370 I had my hands on at one time. Never seen MST before.

Thanks!

Chuck replied to Tube❄️Time

@tubetime Quick, call IBM Field Service! Oh wait ...

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