The most important thing is to get that barrel battery out of there asap and if it has leaked to clean the area where electrolyte went with light vinegar first and lots of water afterwards! I think it has already leaked and either corrosion or the electrolyte may be causing the issues.
If you power up the machine the battery gets charged. It then heats up and more electrolyte will leak.

Oh, and welcome to the forum!😃

Thanks for the suggestion, and the welcome. 😀

I will remove the battery first chance I get, hopefully it only affects the clock like in later computers and I won't need to replace it for the machine to work. It may be a bit tricky since it seems to be glued to the motherboard, but I think I can remove it safely with some care and patience. I don't want to take the computer apart just yet though, so I'll see if I can just cut the contacts without desoldering.

Although it seems a bit corroded on the sides, it doesn't seem to have leaked yet thankfully, though I do see the green contacts in the nearby components, as well as that little capacitor that has gone weird.

I'm attaching some photos of that area to get a better look.

I'm pretty confident that there's been some leaking, you can see the green corrosion on some of the items near the battery. Definitely want to get that cleaned up.

Yeah there's definitely corrosion around the battery. I wouldn't try to power it on again until that is cleaned and fixed.

The ceramic cap that's hiding the C120 designation kinda looks like it is broken.

and yeah, battery leakage corrosion.

Got it, looks like I will have to take it apart after all to clean the other side of the board as well. I thought it would be more visible like a stain but apparently I was wrong. 😅 Removing the battery and cleaning the corrosion is priority one now, I'll probably do it in the weekend and post the results here. I still don't know what to do about that little busted-looking capacitor there, but I'll start with the battery and see how things go. Thanks everyone. 🙂

You should be able to just use some wire snips to cut the battery out, then take a few well lit photos of the area. Depending on how much damage there is then PCB might already be broken and cleaning the area can remove signs of where the traces went. If you've got good photos of the area (can be tricky getting good contrast between the green PCB and green traces) before you start cleaning then if any traces are removed you have a chance of being able to work out where they went.

UPDATE: I successfully snipped off the battery and cleaned all the nearby corrosion with a isopropyl alcohol, a cotton swab and a toothbrush. It was easier than I thought.

Attached are photos of the battery (the mass on the bottom is glue) and the area it used to be after a bit of cleaning.

I have noticed a bit of corrosion on some other unrelated places though like the isa slots, though not in the one the graphics card is. I think air humidity may have caused that in storage. It doesn't seem like it did a lot of damage though, at least on this side of the board.

I cleaned everything I could, but didn't help at all. The result when I turn on the computer is the same as before.

Unfortunately I don't have the equipment to take off the motherboard right now to check the other side, since it appears to be secured to the case with bolts instead of screws. I'll see to it, but I may put this project on ice and focus on my other project, restoring my childhood's 586 computer.

Shame though, it's such a beautiful machine and I would love to see it working again. Maybe in the future I'll figure something out.

By the way, if anyone knows what this computer is called so I can look it up, I would appreciate this information.

Probably won't help much, but there's this: https://www.ultimateretro.net/en/motherboards/6839

Not quite the same model, that one's the MXM/10 rather than the MXM/10-II. Only big difference I can see is the battery. There doesn't seem to be any information on it, just the photo. The BIOS file given there looks to have a date of 04/20/88 at the end, so seems like a fairly late 8088 board. Looks like it has on board serial, parallel and gameport (guessing based on the headers near the keyboard port, maybe they are configured with SW1), plus FDC.

It looks like the battery powers the HM68167 RTC chip when the machine is off. I can't see any external battery header, so it might be worthwhile getting some AA batteries and a diode and hooking that up to where the battery was. It looks like there was a bit of damage from the battery (slightly bubbly looking trace), but I can't see anything actually broken.

Graphics card looks to be here: http://www.vgamuseum.info/index.php/component … 504-ram-mcg2502 , also seen something similar listed as a Reaktron 2502. Output can apparently be either MDA or CGA. Maybe it needs a jumper on P2 for mono/LPT disable or colour? I haven't been able to find anything on the monitor.

For me it seems the battery caused quite some damage which you can see on your photo taken after the removal. This also explains why the PC still worked ten years ago.

You need to check the continuity on every trace that is potentially affected. You should also fix that ceramic cap as described above.

For further diagnostics it makes most sense to program a supersoft ROM. You already have a suitable video card, but it will also work with the speaker only.
http://www.minuszerodegrees.net/supersoft_lan … dmark%20ROM.htm

Thank you for all the info everyone, these links are extremely useful! It's gonna take some research, because I gotta find more info on jumpers and switch configurations, and all this info will make it much easier. I really appreciate the help. 😀

I didn't even notice the damaged trace, I'm gonna have to test it, but that will take time since I don't even have a multimeter right now, and I'm also focusing on some other retro hardware restorations.

Also, about the screen: It's monochrome, screen size 13 inches (20x22 centimeters), and I remember it being a beautiful green colour, but really hard on the eyes. Times were rough back then.

And, unrelated but I gotta say it, this computers keyboard is the best, clickiest, most satisfying keyboard I have ever had the joy to use in my life! Until I fix this machine I will definitely be using it on the 586 I'm also trying to restore.

I will post any future updates here.

Keyboard is probably XT, so may not work on AT or PS/2. There may be a switch on it to change modes, or you can get converters to change them. Good luck with it.

It does have an A-X switch on the back, I didn't even know about that! You just saved me from a lot of confusion later on, thanks. 😀

I already connected it to the 586 as it is, and though I don't have image on the screen just yet (waiting for a few parts by mail to fix it), the caps/num/scroll lights respond correctly, in contrast to when I connect it to this topic's computer.

XT keyboard don't get the luxury of things like lights, so they won't work on the Star, even when it's working properly. The protocol is only one way, keyboard to computer, so there's no way for the computer to signal the keyboard to turn a light on (like there is in AT mode), or for the keyboard to confirm that the computer received a press of (e.g.) caps-lock. So it'd be easy for the light and the computer to get out of sync with each other.

Nice that you've got a switchable keyboard.

your isa slots look full of corrosion, but maybe its a colour reflection I dont know.
I'd bet some of that 74 logic is also dead.

your going to have to be systematic I think, and rule out if its motherboard, ega card or monitor.

Hi @piggy i do have this motherboard fully functional, this is a left over from my FIRST PC, and i can tell i had exactly this PC setup (case - monitor - keyboard)
i have struggle to find all switches but i can help if you are not able to boot up.

Fro the photos, this board will need extensive work to come back to life and stay living. There's battery corrosion everywhere, including the ISA slots.

You absolutely need to do a vinegar bath to the board, not just use toothbrush and alcohol to go over things. The electrolyte travels and gets inside the materials and without it getting neutralized (which is what the vinegar is for) it will be able to continue its job of corroding everything it gets to.

I'm excited to see this!

In 2019 I got a similar motherboard from a logic analyzer, which included a nice amber screen, Tseng ET1000 display card, two 360k floppy drives and one of those PLUS 20MB Hardcard drives (which is likely totally dead). Unfortunately, it has only 256kB RAM. At the time I could not find any information on the motherboard. How times have changed!

Mine is not marked with the VIP logo, just "USA ENT MXM-10" on a silver sticker. The one Predator99 posted is similar, though mine is like yours (with the barrel battery), Predator99's has a coin cell in a slightly different place. Fortunately my barrel battery hadn't done much damage before I removed it.

I extracted the 8k BIOS (Phoenix 2.52) and found that it was byte-for-byte identical to "Phoenix XT Turbo BIOS v 2.52" archived here. If I trim the BIOS Predator99 posted down to 8k (I think it duplicates the same bios 8 times, but I'm not sure?) it matches that byte-for-byte also.

My original Switch block settings were:

_____12345678
SW1: 10000011
SW2: 11110111

SW1.8 appears to be a turbo switch. Turning it off turns off LED1, and the memory test takes significantly longer.
SW1.3 and SW1.4 cause the machine to sit with a flashing cursor when switched ON.
I have not had much luck deciphering the other switch settings.

My original Jumpers were:
JP3: Jumper across pins 2-3
JP4: no jumper

I identified some of the headers and their functions:
JP5 "HRS" - Hardware reset (one pin has a diode pullup to +5V, the other is GND. Small polarized cap across pins, pulled up to +5V with a resistor to form an RC power-on reset function)
JP6 "POLD" - Power on LED (one pin has a 330 ohm pullup resistor to 5V and the other pin is GND)
JP? "SP" - speaker (One pin has a 22 ohm pullup to +5V, the other is connected to a transistor collector through 22 ohm resistor R32)
LED1 - possibly a TURBO indicator LED. (one pin is pulled up to 5V with a 330 ohm resistor, the other is connected to a transistor collector)
JP? "HWHL" - not sure. (one pin is GND, the other has a low impedance to ground. I didn't do any circuit tracing)
"KYLO" - keyboard lock? (one pin is GND, the other is connected to the keyboard CLK signal through a 24 ohm resistor. I suspect shorting these two pins would disable the keyboard)

I recently acquired an 8-bit ISA VGA card, and it seems to work and display the POST message, memory test and keyboard error.

My XT keyboard died with a bad trace on the keyboard membrane, so I am stuck until I have another solution. Do the alternate XT bioses allow the use of AT keyboards?