NEC PC-8801 restoration

[Dunwood84]

Hi all, I am in the process of fixing up this NEC PC-8801 that I found locally.



The first issue that I had to fixed was the keyboard not working correctly. When I press any key at all on it, it showed a different character on the screen. Once i pulled the keyboard apart, I found a Faulty 74LS159. Once I replaced it, the keyboard functioned correctly.

The second issue that I am currently is getting a way to load programs onto the computer. Hence why I purchased this NEC 80S31.



So the current issue I am having is getting a HXC Gotek emulator or a Flash Floppy emulator with this unit. If anybody has a idea how i would set it up it would be good.

 

[Robbbert]

Your first and second photos are blank.

 

[jltursan]

You can install a Gotek just using a 3.5->5.25 connector adapter, the Shugart interface is already supported by the HxC firmware and the PC88 is supported since ages. If you want to use FlashFloppy you'll need some luck, D88 image files are not supported right now; but you can try to export them to HFE format.

Btw, is the barrel battery in good condition?

 

[Dunwood84]

Robbbert I hope its fixed now.

jltursan Amazing the Barrel battery shows no sign of leakage, but it is on the list to be replaced.
Also, I fitted a HXC to the PC-80S31. when I turn on the 8801 with the 80S31 connected it will try to read the emulator for about a second, then it gives up and it constantly tries the second drive constantly. it appears to try to auto load from the 80S31 when its connected, but when it is not connected, the 8801 just loads N-88 Basic

 

[jltursan]

I never tried to use a HxC with a PC-8801; but I've replaced a 5.25" full-height drive with a 3.5" drive in a PC-8031-2 unit without too much fuss; so I guess the HxC could work as is. Btw, is it a classic HxC or a Gotek with HxC firmware?.
Anyway, I would try to connect the device whatever it is as the only one drive, disconnect the second floppy drive. Also double-check the D88->HFE conversion, it must work perfectly with 2D disks.

 

[Dunwood84]

It is a Gotek with HXC Firmware. in regards to the D88 to HXC what do I need to do to make sure that it converts correctly?

jltursan is there anything special about the adapter that l need to keep in mind. Also where can i find a bootable image??

 

[jltursan]

Just use the last HxCFloppyEmulator tool , I think that D88 conversion must work flawlessly given how old it is. Although not NEC but also D88 related, there're pages like this with interesting info about the format.

Related to bootable images, I cannot give you a link; but it's not hard at all, I'm sure that if you look through archive.org you'll find a TOSEC with tons of PC-8801 images ;-)

 

[Dunwood84]

jltursan I must be doing something wrong when l try to convert the image from .D88 to .HFE or something wrong with that tool. as when I view it when i have changed it to .HFE, the first 5 sectors are blank making it un bootable.

also no matter what image i put on it, it will not boot from it

 

[jltursan]

Is that you?. If so, report them the conversion problem, if I'm not horribly wrong, the 5 first sectors must not be blank.

I've tried a quick and dirty test: downloaded the tool and a D88 image and first, "Load" the D88 file and then "Export", no messing with settings at all. The HFE image file is created and it shows data from the first byte, no blank sectors, I can't see anything "zeroed" in it, at least with my untrained eyes...

EDIT: I've just also checked the files you attached in the thread above and I agree with Jeff, the HFE seems good and I can't see zeroed sectors. Why you think the 5 first sectors are blank?

 

[fritzeflink]

Just for information.
For the PC-8801 I have the PC8881 8" dualfloppydrive using on my PC or CP/M system for transfer 8" floppys to images and so on.


http://oldcomputers-ddns.org/public/pub/rechner/other_hardware/nec-disk_unit_pc-8881bd/index.html

 

[Dunwood84]

Is that you?. If so, report them the conversion problem, if I'm not horribly wrong, the 5 first sectors must not be blank.

I've tried a quick and dirty test: downloaded the tool and a D88 image and first, "Load" the D88 file and then "Export", no messing with settings at all. The HFE image file is created and it shows data from the first byte, no blank sectors, I can't see anything "zeroed" in it, at least with my untrained eyes...

EDIT: I've just also checked the files you attached in the thread above and I agree with Jeff, the HFE seems good and I can't see zeroed sectors. Why you think the 5 first sectors are blank?

Yes it is me

The Problem that I am still having is that when the unit tries to run anything on the emulator, when i turn the 8801 on, it tries for two seconds, and then it gives up and goes no further (this is when the emulator is by its self). if there is another drive in the housing, it tries the emulator for two seconds, then it ignores the emulator and constantly tries to access the second drive.

If both of the original drives are in the enclosure, they both access, then the motor that spins the disks stays on constantly. after about 30 seconds, the system goes into N-88 Basic.

 

[Dunwood84]

​For anybody interested, here are some photo's of my NEC PB-80S31








And this is the circuit board.

From what I have found, the blue box is a Z80 Compatible CPU running at 4Mhz, the Yellow box has the ram, The red box is a Double Density Floppy Disk Controller, the orange box is a Programmable Peripheral Interface (Same as what is in the 8801 computer) and the purple box is a eprom which I believe contains the NEC Disk ROM, but the programmer software that I have does not have that chip in the database.

 

[jltursan]

If both of the original drives are in the enclosure, they both access, then the motor that spins the disks stays on constantly. after about 30 seconds, the system goes into N-88 Basic.

So, have you ever loaded succesfully a real floppy with this unit?. They're usually reliable but also have a really complex controller PCB and it's not uncommon to have RAM, buffers or tantalum caps problems. The PC-8031-2 is way bigger and populated and one of my two units needed a deep refurbishment, caps shorted and logic ICs damaged.
I would try first to create a 5.25" real floppy with something bootable, of course you'll need a Win98/XP with a good 5.25" drive to do this.

In your photo is not clear; but the mask rom seems a TMS2516JL, if so, they're totally 2716 compatible; so you'll be able to load them with your programmer for sure.

For the PC-8801 I have the PC8881 8" dualfloppydrive using on my PC or CP/M system for transfer 8" floppys to images and so on.

Nice!, these units are real behemoths!

 

[Dunwood84]

Ok, so i tried to read it with the programmer set to 2716 and it comes up blank??

also what software do I need to use to create a bootable floppy?

 

[jltursan]

But is it really a TMS2516?, if so, you must use the generic 2716 settings to read it. It the read procedure ends successfully and you have a blank read, this is not good and IMO, very strange. What EPROM programmer you have?

To create a bootable floppy, two Windows XP tools come to my mind, the command line tool Samdisk and the GUI assisted Omniflop, both can work with D88 images. With a bit of luck if you have a 5.25" HD (much better having a DD drive) drive and an old PC you'll be able to dump whatever you want.