I don't have this machine and I don't know what that error code means but the most likely explanation is, indeed, faulty RAM.

EduBat wrote on 2026-01-25, 01:03:

I don't have this machine and I don't know what that error code means but the most likely explanation is, indeed, faulty RAM.

Oh. I guess that's not going to be repairable then. Should I take it apart and see if I can find the ram chip? If it is a BGA chip then I think I am out of luck. I can only solder at an amateur level.

According to schematic, there are two 628512 RAM chips marked as U9 and U10. For sure not BGA. I would start with reseating of CPU and any other chip placed in a socket....

For what it is worth, I have seen desktop pcs suddenly failing to detect the proper amount of ram and the like due to a worn out power supply.

rasva wrote on 2026-01-26, 11:27:

According to schematic, there are two 628512 RAM chips marked as U9 and U10. For sure not BGA. I would start with reseating of CPU and any other chip placed in a socket....

Ok. Thanks. I shall try that first! I could try swapping the CPU, as I have spares. But CPUs don't usually just die.

Peter Swinkels wrote on 2026-01-26, 11:58:

For what it is worth, I have seen desktop pcs suddenly failing to detect the proper amount of ram and the like due to a worn out power supply.

It's a 12v plug. I could measure it to see if voltage is wrong, but I get same behavior with RAM when running the laptop on batteries.

Ok. So I took it apart. To my untrained eye it looks like a beautifully designed machine.

Anyhow, I replaced the 8088 with an NEC V30 and I get an error even sooner in the RAM check (obviously this is 16 bit bus rather than 8 bit):

Here are some photos of the motherboard. I can't see any bad solder joints. Most looks very neat:

Here's some more photos

The only bit that looks a bit suspect to me, is this chip that's covered in what I assume is flux:

I couldn't find my bios chip remover to take out the two square chips. The small chip that's socketted near the CPU is really tightly in. I couldn't get my pry tool between it and the socket to remove it

maybe there is something under VGA board (daughter board in blue)?

roytam1 wrote on 2026-01-27, 08:54:

maybe there is something under VGA board (daughter board in blue)?

This is what's under the VGA module. Looks ok I think?

RetroPCCupboard wrote on 2026-01-27, 22:17:

roytam1 wrote on 2026-01-27, 08:54:

maybe there is something under VGA board (daughter board in blue)?

This is what's under the VGA module. Looks ok I think?

The attachment 20260127_221206.jpg is no longer available

these are the main memory, either one is failing?

RetroPCCupboard wrote on 2026-01-27, 22:17:

roytam1 wrote on 2026-01-27, 08:54:

maybe there is something under VGA board (daughter board in blue)?

This is what's under the VGA module. Looks ok I think?

The attachment 20260127_221206.jpg is no longer available

That's the RAM as previous poster said. What I would do to diagnose the chips is to test if either of them gets unusually or at least warmer than the other, which indicates a short in the chip. Power it on and touch them with your finger and feel if one of the chips is getting hot. Thermal imager is even better if you have access to one.

Of course chips can fail without them getting hot, but to diagnose such fault you need a probe at minimum or preferably oscilloscope to see how the data and address lines behave. If you don't have such tools, it may be easier to just change both chips as the fault is most likely in the memory chips.

CharlieFoxtrot wrote on 2026-01-28, 06:42:

That's the RAM as previous poster said. What I would do to diagnose the chips is to test if either of them gets unusually or at least warmer than the other, which indicates a short in the chip. Power it on and touch them with your finger and feel if one of the chips is getting hot. Thermal imager is even better if you have access to one.

Of course chips can fail without them getting hot, but to diagnose such fault you need a probe at minimum or preferably oscilloscope to see how the data and address lines behave. If you don't have such tools, it may be easier to just change both chips as the fault is most likely in the memory chips.

Ok. Thanks. I will try to see if either is hotter than the other. I had, had the laptop on for quite a few hours when it died. I was learning assembly on it.

Is this what I need to order? I can't tell from the picture if it is surface mount:

https://ebay.us/m/ifLWcB

I do have an oscilloscope but its one of those cheap pocket-size MiniDSO ones and I think max frequency it can see I think is 1mhz.

RetroPCCupboard wrote on 2026-01-28, 07:59:

Ok. Thanks. I will try to see if either is hotter than the other. I had, had the laptop on for quite a few hours when it died. […]
Show full quote

CharlieFoxtrot wrote on 2026-01-28, 06:42:

That's the RAM as previous poster said. What I would do to diagnose the chips is to test if either of them gets unusually or at least warmer than the other, which indicates a short in the chip. Power it on and touch them with your finger and feel if one of the chips is getting hot. Thermal imager is even better if you have access to one.

Of course chips can fail without them getting hot, but to diagnose such fault you need a probe at minimum or preferably oscilloscope to see how the data and address lines behave. If you don't have such tools, it may be easier to just change both chips as the fault is most likely in the memory chips.

Ok. Thanks. I will try to see if either is hotter than the other. I had, had the laptop on for quite a few hours when it died. I was learning assembly on it.

Is this what I need to order? I can't tell from the picture if it is surface mount:

https://ebay.us/m/ifLWcB

Looks about correct and you can definitely see SMD legs and I believe the chips on your pic is also HM628512ALFP-7, which means they are identical. That is for 10 chips, so if you don't need more than two, it may be worth looking at few other sales for individual or 5 x chips to save some money,. Of course spares and parts for future projects do you no harm, but just a thought.

RetroPCCupboard wrote on 2026-01-28, 08:02:

I do have an oscilloscope but its one of those cheap pocket-size MiniDSO ones and I think max frequency it can see I think is 1mhz.

Not the best tool for sure, but might be enough to probe the pins and see if there is life or not and to compare the two chips, so I'd get the data sheet for the chip and do some probing if not for anything else than to learn and find out what I can actually do with that scope. There is not that much you can lose, except your time.

CharlieFoxtrot wrote on 2026-01-28, 08:10:

Looks about correct and you can definitely see SMD legs and I believe the chips on your pic is also HM628512ALFP-7, which means they are identical. That is for 10 chips, so if you don't need more than two, it may be worth looking at few other sales for individual or 5 x chips to save some money,. Of course spares and parts for future projects do you no harm, but just a thought.

That's the cheapest I can see with that exact part number. There are cheaper ones that begin HM628512 but the letters afterwards are different. I am not sure if the final letters matter. Anyhow, this 10 pack is barely more expensive than the prices of those other chips in lower quantities. It gives me some spares if I screw up the soldering, or if one dies again.

I will see if I see anything different between the chips with the oscilloscope.

Is it possible that something in the design of the motherboard could have killed the RAM I wonder? Perhaps it's being run out of spec somehow. I did notice one wire on the VGA module that's been hand soldered after assembly. Which makes me think that perhaps there could be some errors in the design.