RetroPCCupboard wrote on 2026-01-28, 08:50:

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.

All right. You'd need to look at the data sheets if there are differences and how interchangeable they are. They might be the same chip, but with different packaging or there might be something else.

About your second post, bodge wires aren't uncommon and especially in products like this. They are fixes to design flaws in the PCB, but they aren't a sign that the board works somehow unreliably. Especially when they are indeed made as fixes. The most likely thing that would cause chip failures is overvolt, so it doesn't harm to measeure PSUs and regulator outputs. I bet these chips run at 5V, so it may be worth to measure 5V line that it is approximately in the spec. Again, check the data sheet and which one is the voltage pin and measure the 5V input voltage with multimeter.

I personally bet that it is just a chip failure without any particular reason or fault behind it. AFAIK these are vintage chips and have not been in prodction for ages, so the age alone will affect the reliability overall.

CharlieFoxtrot wrote on 2026-01-28, 09:47:

All right. You'd need to look at the data sheets if there are differences and how interchangeable they are. They might be the same chip, but with different packaging or there might be something else.

About your second post, bodge wires aren't uncommon and especially in products like this. They are fixes to design flaws in the PCB, but they aren't a sign that the board works somehow unreliably. Especially when they are indeed made as fixes. The most likely thing that would cause chip failures is overvolt, so it doesn't harm to measeure PSUs and regulator outputs. I bet these chips run at 5V, so it may be worth to measure 5V line that it is approximately in the spec. Again, check the data sheet and which one is the voltage pin and measure the 5V input voltage with multimeter.

I personally bet that it is just a chip failure without any particular reason or fault behind it. AFAIK these are vintage chips and have not been in prodction for ages, so the age alone will affect the reliability overall.

Ok. Well, I guess it will be good to have some spares if that is the case then. I do quite like this little machine. Its a good price compared to getting a genuine XT. Even the NuXT motherboard is double the price of this machine.

I am kinda tempted to get a NuXT though. Mostly because I would be able to use it with a floppy drive. Something this laptop sadly can't do.

RetroPCCupboard wrote on 2026-01-28, 09:54:

CharlieFoxtrot wrote on 2026-01-28, 09:47:

All right. You'd need to look at the data sheets if there are differences and how interchangeable they are. They might be the same chip, but with different packaging or there might be something else.

About your second post, bodge wires aren't uncommon and especially in products like this. They are fixes to design flaws in the PCB, but they aren't a sign that the board works somehow unreliably. Especially when they are indeed made as fixes. The most likely thing that would cause chip failures is overvolt, so it doesn't harm to measeure PSUs and regulator outputs. I bet these chips run at 5V, so it may be worth to measure 5V line that it is approximately in the spec. Again, check the data sheet and which one is the voltage pin and measure the 5V input voltage with multimeter.

I personally bet that it is just a chip failure without any particular reason or fault behind it. AFAIK these are vintage chips and have not been in prodction for ages, so the age alone will affect the reliability overall.

Ok. Well, I guess it will be good to have some spares if that is the case then. I do quite like this little machine. Its a good price compared to getting a genuine XT. Even the NuXT motherboard is double the price of this machine.

I am kinda tempted to get a NuXT though. Mostly because I would be able to use it with a floppy drive. Something this laptop sadly can't do.

If you actually like electronic projects, build a Micro8088 with backplane and IO/controller cards if you need those.

I made mine couple of years ago and it was a fun project. It is nothing really complex, but still something that is fun and it is interesting to bring a whole system alive from a bunch of components and parts. Sure, it is not that cheap, depending on the other cards you want to build the total can be easily over 200€ with all the required chips and passive components (CPU board, backplane, Floppy/serial controller, 8-bit VGA card, XTIDE), but it is definitely worth it. Most of the parts you can buy new from Digikey/Mouser/equivalent, but you also need some vintage chips which you need to source from somewhere else, but I managed to find everything without that much of a hassle or searching. In the end you get a reliable small form factor XT machine.

This is the link for the CPU board, you can find rest of the related stuff including printable case stl files from Sergeys repositories. There are posts/threads about Micro8088 here in Vogons too. I think it was here that I also got the idea to make one myself.
https://github.com/skiselev/micro_8088

CharlieFoxtrot wrote on 2026-01-28, 10:12:

If you actually like electronic projects, build a Micro8088 with backplane and IO/controller cards if you need those. […]
Show full quote

If you actually like electronic projects, build a Micro8088 with backplane and IO/controller cards if you need those.

I made mine couple of years ago and it was a fun project. It is nothing really complex, but still something that is fun and it is interesting to bring a whole system alive from a bunch of components and parts. Sure, it is not that cheap, depending on the other cards you want to build the total can be easily over 200€ with all the required chips and passive components (CPU board, backplane, Floppy/serial controller, 8-bit VGA card, XTIDE), but it is definitely worth it. Most of the parts you can buy new from Digikey/Mouser/equivalent, but you also need some vintage chips which you need to source from somewhere else, but I managed to find everything without that much of a hassle or searching. In the end you get a reliable small form factor XT machine.

This is the link for the CPU board, you can find rest of the related stuff including printable case stl files from Sergeys repositories. There are posts/threads about Micro8088 here in Vogons too. I think it was here that I also got the idea to make one myself.
https://github.com/skiselev/micro_8088

How cool is that project! That sounds very much like something I would like to do at some point. I know that I don't have the time to build such a thing for a while though.

I think for now I just want hardware that works, so I can play with the software side of things.

From looking at it, I think you can make a smaller form factor machine with the NuXT, as long as you don't want to put any add-on cards in. The only card I might want to add would be adlib card. I am not sure if you can get low profile versions of that card? If so, then putting a NuXT in a SFF PC case might be kinda cool.

RetroPCCupboard wrote on 2026-01-28, 10:38:

How cool is that project! That sounds very much like something I would like to do at some point. I know that I don't have the t […]
Show full quote

CharlieFoxtrot wrote on 2026-01-28, 10:12:

If you actually like electronic projects, build a Micro8088 with backplane and IO/controller cards if you need those. […]
Show full quote

If you actually like electronic projects, build a Micro8088 with backplane and IO/controller cards if you need those.

I made mine couple of years ago and it was a fun project. It is nothing really complex, but still something that is fun and it is interesting to bring a whole system alive from a bunch of components and parts. Sure, it is not that cheap, depending on the other cards you want to build the total can be easily over 200€ with all the required chips and passive components (CPU board, backplane, Floppy/serial controller, 8-bit VGA card, XTIDE), but it is definitely worth it. Most of the parts you can buy new from Digikey/Mouser/equivalent, but you also need some vintage chips which you need to source from somewhere else, but I managed to find everything without that much of a hassle or searching. In the end you get a reliable small form factor XT machine.

This is the link for the CPU board, you can find rest of the related stuff including printable case stl files from Sergeys repositories. There are posts/threads about Micro8088 here in Vogons too. I think it was here that I also got the idea to make one myself.
https://github.com/skiselev/micro_8088

How cool is that project! That sounds very much like something I would like to do at some point. I know that I don't have the time to build such a thing for a while though.

I think for now I just want hardware that works, so I can play with the software side of things.

From looking at it, I think you can make a smaller form factor machine with the NuXT, as long as you don't want to put any add-on cards in. The only card I might want to add would be adlib card. I am not sure if you can get low profile versions of that card? If so, then putting a NuXT in a SFF PC case might be kinda cool.

It is cool indeed!

I can't emphasis enough how small footprint this has with sergey's case (not to say NuXT can't be even smaller).

https://github.com/skiselev/micro_8088_case

The 3.5" floppy drive in the pic kind of gives the scale, but 2x3 soda/beer cans is probably quite close. Case is designed for PicoATX PSU so it uses 12V DC and there is naturally external lap top style DC PSU.

CharlieFoxtrot wrote on 2026-01-28, 14:50:

It is cool indeed! […]
Show full quote

It is cool indeed!

I can't emphasis enough how small footprint this has with sergey's case (not to say NuXT can't be even smaller).

https://github.com/skiselev/micro_8088_case

The 3.5" floppy drive in the pic kind of gives the scale, but 2x3 soda/beer cans is probably quite close. Case is designed for PicoATX PSU so it uses 12V DC and there is naturally external lap top style DC PSU.

I saw a video with someone using that case. I researched a bit after you made me aware of this project. I get a sense of scale from about 2mins 40 secs into this video:

https://www.youtube.com/live/u9o0PMgx6vc?si=Pnd7A4Xj9RR9CaaE

It does look cool. Though I was thinking of using a case with 5.25" drive. Since I have a few games in that format to try. Starglider (Rainbird Software), Metropolis (Melbourne House), Sid Meier Railroad Tycoon, Sid Meier Civilization, Battlehawks 1942, F-19 Stealth Fighter....

I have tried running it for a few hours. Nothing getting even slightly warm. Though the VGA card is unplugged in order to have access to the RAM. So not sure if that is stopping the boot process in its tracks. I would have thought the CPU would be doing something though wouldn't it? Even if it's just a loop that does nothing?