Few minutes ago i replace the rom chips for new ones, so it can last at least 25+ years.
Only have to test the board and see if it works again.. But i keep my older roms as backup for now.

Did some progress this day.

- My new 5.25 gray sony 1.44MB floppy drive arrived today (very happy)
- Tried to align the drives both 5.25 360KB and 5.25 1.44MB with the front of the case (it looks better but it wasnt still good) Need to fiddle to get this right but this can when everthing is done.
- After some boring feelings, i wanted to do something.. So i decided to disamble the front panel from the case hood.. When everything was loose i have cleaned both..
So they are look more cleaner now..

What i have to do now

* Iam still waiting on some memory chips to arrive.. (there will be two more shipments i need to wait for)
* Iam still waiting on the 8087-1 ceramic co-processor i will install in this laser unit.
* Also the new harddisk has arrived.. Thinking of upgrading the old one NEC 5124 20MB to a 40MB seagate ST-251 MFM harddisk (maybe i follow another route, going for IDE-XT or maybe SCSI)
Iam also thinking of install two harddisk drives for about 60 - 80MB of storage space..

* When the motherboard is done, it can refitting the case.

How did you go with this?
I just found I had one of these in the shed. It has a TSENG LABS ET3000 in it with VGA!
I got it to post but need to find a 360k drive for it 🙁 - turns out it just wont recognise a 1.2mb drive boo.

kevmif wrote on 2021-06-16, 10:31:

I got it to post but need to find a 360k drive for it 🙁 - turns out it just wont recognise a 1.2mb drive boo.

A standard PC 1.2MB drive rotates at 360RPM. A standard PC 360K drive rotates at 300RPM. The result is that the data is read 20% faster than the PC/XT floppy controller expects. Maybe your 1.2MB drive has a jumper to select the rotational speed. This would make it PC compatible to read DD disks, but incapable of handling HD disks in any PC-like computer.

OTOH: The standard BIOS should be able to read and write the first 40 tracks of a 720KB 3.5" DD drive without any problem, and most likely even all 80 tracks. Most 3.5" HD drives should work, too, at least if you pull the density select pin low. Of course, the floppy controller will not handle the 1.44MB format, even with a HD drive.

Few days ago, i started again with this machine. Its already some years ago that the motherboard wont recognize all my floppy controller cards any more. After starting up the system seems to be hanging.
And i had also some problems with the memory chips i added to the motherboard, to make any use of the extra EMS memory it could resides on the motherboard.

1 year ago i also found an upgrade for my current 20MB MFM harddrive. Its an Seagate- ST277R rll 66 MB harddisk.. And a few days ago i also bought a nice RLL controller which almost match the green color of the motherboard.
I tested the RLL controller also a few days ago, and the controller as the harddrive seems to be in operatable condition.

An half hour ago i replaced the IC socket for the DMA controller. The old one became bad. The old DMA controller was stuck in the socket and by pulling it out the socket got damaged. (this happed a while ago)

Also a year ago i bought a new dma controller IC.. But because its a pile of parts in my hobby space i seem to lost this DMA controller IC. ( i dont know where it went) but if everything got shorted out i will find it later.

The things i have to do now are:

- Waiting on a new DMA controller IC
- I need a power strip USA type 110volt one) to add two sockets at my current power converter ( 230volt to 110 volt) So i can use my simcheck device and testing all of my memory ICs. So i can see if there is one bad or not)
(when installing all the extra chips i got a parity error some where) Iam guessing maybe there is a bad chip some where. ( but now i have to check all the chips if something isnt right)
- Have to see if the floppy controllers get working again on the motherboard.
- If it will, then starting building up the system. And getting it done.

The parts in the system will be:

Cirrus Logic CL-GD510/520 8Bit graphics card (do VGA / CGA/ EGA)
Original Laser XT/3 motherboard with pimped up with more memory and an Intel co-processor.
HD Floppy disk controller card with RTC / Parallel/ serial
Sound blaster 1.5 with CMS / adlib.
Adaptec RLL controller
Seagate- ST277R 66MB harddrive on 1 partition.
Original Chinon 360KB floppy drive
Upgraded Gray teac 1.44MB floppy drive and caddy.
OS will be MS-DOS 4.01 Dutch version (like it was back in the day)

I still got the original floppy controller card (keep it for troubleshooting)
And the original graphics card with 9 pin CGA / MDA port. (could always use it with an CGA to VGA convertor box (on serda shop)

They are very nice XT machines ! Hope you get it all working good !

kevmif wrote on 2021-06-16, 10:31:

How did you go with this?
I just found I had one of these in the shed. It has a TSENG LABS ET3000 in it with VGA!
I got it to post but need to find a 360k drive for it 🙁 - turns out it just wont recognise a 1.2mb drive boo.

They came with either two 360k or one 360k and one 720k floppy drive. If you can find a 720k drive you should be able to get it to work.

Horun wrote on 2021-08-01, 02:01:

They are very nice XT machines ! Hope you get it all working good !

Yes iam trying and see what i could do.

Horun wrote on 2021-08-01, 02:04:

kevmif wrote on 2021-06-16, 10:31:

How did you go with this?
I just found I had one of these in the shed. It has a TSENG LABS ET3000 in it with VGA!
I got it to post but need to find a 360k drive for it 🙁 - turns out it just wont recognise a 1.2mb drive boo.

They came with either two 360k or one 360k and one 720k floppy drive. If you can find a 720k drive you should be able to get it to work.

Mine have the 360KB Chinon drive with the 720KB drive as secondary. But i swapped it out with in Sony 5.25 grey colored 1.44 MB drive.
Because 720KB floppys are already very hard to find.

And moving games on 720KB doesnt make any sense for me.. Now days its better to have more games on a HD 1.44MB diskette otherwise i had to format those disks to 720KB instead. But thats a waste on space.

The system is like running again.. But now i have some problems with it again.

It boots up normally..

1. It says that the memory size is only 64KB, which i think is strange. I had installed new memory chips on the board. And it should let me see 512KB as total memory. (that is just to see if the system is behaving normal / how it should.
If have only installed the memory in the first two back on the inside of the board. (knowing the 2 outside banks is only for expended memory (ems)

2. It also complains (because i have the ram parity enabled, just because) on a Memory addr error 00000, 04. Do somebody knows which DIP ram IC this is?

Good news: you did not get a "base 64K ram error". The 64k memory thing is because somewhere between that and your max installed ram there is a bad chip (from what I experienced with a different board that had same issue) and only way I found the bad chip was through swapping each chip out with known good one. I never could figure out which exact chip as the error code would change as I swapped good one in ram until the bad one was found, then no error.

Those Chinon drives are like rocks ! Mine are both Chinon originals and they just work ! Side note: got mine about 2002 and had to store it about 2010, good friend was moving and brought it back after sitting in his shed for a decade. Changed the old dead MFM out for a Data Cannon SCSI card and IBM 200MB SCSI HD and thing works good except needs a PSU re-cap (currently have a modded newer AT PSU to fit the case).

No i dont get the base 64K ram error. It only says the total system memory is just 64K

I have got memory testers here. But they are also not going to help me out. (because they dont show me an error.) I had already problems with the older memory, so thats why i thought, then replace everything.
Its good to here that only the bad chip is blocking the rest of the memory showing up.

I dont know how the understand that memory error. I think its address 00000 on row o4 ??

Is the address 00000, 04 actually in the memory chips it self.. Or has something to do with the bios rom?

If it detects only 64KB in total memory chips.. How much chips do i need to getting 64K (the chips that are installed are all 256Kx1.)

How can i see where the first chip is starting on the motherboard.

If I understand you correctly, it says "memory addr error 00000 04", the word "addr" at that position seems to point to an addressing problem, so take the address given with a grain of salt.
If your chips are 256K x 1, you need eight (or nine with parity) of them to provide 256KB, and less than eight or nine won't work at all. You could try swapping the eight or nine 256K x 1 chips from bank 0 (which should provide 0..256K) with the chips from bank 1 (which should provide 256K..512K). I hope the banks are marked on the board or you can find which bank consists of which chips from a manual. If not, you can also try it: If you pull a chip from bank 0, you get a "low 64K error". If you pull a chip from bank 1, nothing should change. Banks 2 and 3 (used to upgrade from 512K to 640K) usually don't have 256K x 1 chips, but 64K x 4 or 64K x 1 chips, so they are easily distinguishable from banks 0 and 1.

If I understand you correctly, it says "memory addr error 00000 04"

Yes that correct.

Its a good idea to first put in the 9 chips. But iam not sure if the board would also use 256KB also.. It came stock from the factory with 512KB installed.

The conventionel memory banks are not marked. But the EMS banks and Optional 128KB is listed in the manual.
For the chips its using U-25, U-26 ect as indentification.

I freed up one memory bank, but the screen doesnt go on.

I think the minium memory requirements are just 512KB as base memory . rest is for upgrade.

I can switch the memory from bank 0 over to 1 and from one the zero. But i think the memory problem would still be there. And i dont know if the memory is the culprit.

I have fixed it.

There was two 64 x 1 chips installed between the other 256k x 1 chips. How this happend? I looked at the date code and not at the size of the chips. 512KB seems working now. Parity is on.

Only have to wait for the upgrade to 640KB.. Had them ordered few days ago.