Northstar Advantage - Need some guidance

[riddleywalker]

I have a Northstart Advantage i'd like to restore. Currently, when i press a key on the keyboard i get a beeping sound coming out of the computer and on the screen the letter appears for a second then gets erased. Not sure if this is normal or not but it seems unusual. I don't know much about these computers but i would love it if i could get this thing back to a working state.

Here's a link to a video of the issue. Or is this normal behavior? ignore the parrot in the background mimicking the beeps

Make sure to unmute video if muted.

https://imgur.com/b4bKt8e

https://imgur.com/b4bKt8e

 

[shirsch]

I have a Northstart Advantage i'd like to restore. Currently, when i press a key on the keyboard i get a beeping sound coming out of the computer and on the screen the letter appears for a second then gets erased. Not sure if this is normal or not but it seems unusual. I don't know much about these computers but i would love it if i could get this thing back to a working state.

Here's a link to a video of the issue. Or is this normal behavior? ignore the parrot in the background mimicking the beeps

Make sure to unmute video if muted.

https://imgur.com/b4bKt8e

https://imgur.com/b4bKt8e

Looks like you are laying your finger directly across the pads of a capacitive keyboard (not pushing a key). I would not bet on that working reliably under the best of circumstances. Based on experience with my Advantage machines I'm going to guess the foam pads on the keytronics keyboard are completely shot. You can pickup a set of replacement pads from TexElec:

https://texelec.com/product/foam-capacitive-pads-keytronic/

It's considerably simpler than making them yourself. Ask me how I know . Anyway, that's where I'd start before assuming there's anything wrong.

 

[riddleywalker]

Looks like you are laying your finger directly across the pads of a capacitive keyboard (not pushing a key). I would not bet on that working reliably under the best of circumstances. Based on experience with my Advantage machines I'm going to guess the foam pads on the keytronics keyboard are completely shot. You can pickup a set of replacement pads from TexElec:

https://texelec.com/product/foam-capacitive-pads-keytronic/

It's considerably simpler than making them yourself. Ask me how I know . Anyway, that's where I'd start before assuming there's anything wrong.

Haha, well yes - i'm not pressing a key and yes my finger is what is closing that part of the keyboard circuit, but that's really beside the point. The point is that when a key is pressed using my finger or the keyboard key with its foam and mylar bottoms or whatever they are, the computer would make a loud beeping sound. I was told this is actually normal behavior which puts that issue to rest.

I do thank you however for pointing me in the right direction for replacing the pads. That is extremely helpful. Thank you.

I have another issue perhaps you can help me with. The right side of the CRT shows these vertical lines. I swapped around the video RAM to see if the lines would move or indicate somehow that one of the chips was bad, but the lines stayed in the same position regardless. See image below.



Any pointers would be greatly appreciated.

 

[daver2]

As this is your first post, welcome to VCFED.

I would suggest adding your State (or whatever) to your profile so we know roughly where you are in the universe. Someone locally may be able to help out.

Your first 10 or so posts will be moderated, so hang in there... There may be a bit of a delay between you posting and us seeing them. It keeps spam down very nicely!

What is the message on the screen? It looks like “LOAD ERROR” (or something similar). The system should try and boot the operating system (CP/M) from a boot floppy on startup. I suspect that is not happening and you will probably be getting a boot error. Either no key presses are required after that, or a specific keypress is required to attempt a reboot. The beep is possibly telling you that you have either pressed the wrong key, or to go away!

Have you got copies of the correct documentation that goes with the system?

If not, start at bitsavers.org (our favourite website for all things vintage documentation)!

Dave

 

[daver2]

Just had a look at the User manual.

You should get the message "LOAD SYSTEM" on first powering up.

Hit the <RETURN> key to boot from drive #1 (the top drive).

Enter the keys:

D2<RETURN>

to boot from drive #2 (the bottom drive).

Other keys (with the exception of 'S') are invalid - and could result in the system beeping at you - plus annoying the parrot !

See what happens if you just press the <RETURN> key. You should get the drive light illuminating on the top disk drive - indicating that the system is trying to boot from there.

Do you have a set of boot CP/M floppy disks for the machine?

Incidentally, the manuals are here http://www.bitsavers.org/pdf/northstar/advantage/.

Start here for disk images https://www.itelsoft.com.au/advantage_disk_archive/advantage_disk_archive.html and https://www.itelsoft.com.au/advantage_disk_archive/holger_disk_archive.html.

EDIT: Ah, I see your next post (#3) has been been moderated and I can clearly see the "LOAD SYSTEM" message now... I'll have a look at the schematics regarding the screen issues. Do you have any test equipment (e.g. multimeter, logic probe and/or oscilloscope)?

EDIT: Just reading the Technical Manual. The key sequence D1<RETURN> can also be used to boot from drive #1 (top drive) - but <RETURN> is somewhat quicker!

EDIT: The key sequence S<RETURN> can be used to boot from the serial port. But, of course, you will need something at the other end of the serial port to respond!

Dave

 

[daver2]

I am looking at the schematic.

Which chips did you move around?

I assume that the RAM chips are in sockets then?

There could be a number of 'culprits' in the video line:

1K (SN74S86).
Link W2 (bad contact).
8D? (SN74LS166). Can't quite read the schematic reference.
8D? (SN74LS373). Ditto...
4116 video DRAM.

It looks to be a specific data bit (the errant bits are all in line with each other) - but it is not 100% consistent.

Rather than be on the READ side of the RAM, it could also be on the WRITE side of the RAM of course. This is why we need some test equipment...

However, before we tackle this problem, you need to try and get the machine to boot. The N* has a set of diagnostic programs that should make short work of detecting faulty video RAM (if that is what it is)!

Dave

 

[daver2]

Just had a thought and checked the specifications.

The N* Advantage uses hard sectored disks. Do you have any of these? If not, they are now unobtainium (unless you can find some nice person willing to sell you some).

You can purchase and fit a soft to hard sector converter PCB so that you can use standard soft-sector floppy disks.

Just a thought in passing.

A few people on VCFED have already gone down this route if you want some further information.

Dave

 

[daver2]

Sorry for making so many posts in the thread - but I had a 'hunch' regarding the video problem and it seems to work out.

The RAM containing the 'strange' bits extends from 4800 to 4FFF (i.e. the last block of VIDEO RAM). What I had assumed is that the memory was aligned horizontally from top to bottom (in ascending address order). This appears not to be the case - and the memory is arranged from top left to bottom left and then working horizontally to the right in ascending address order.

I can't quite work out which data bit appears to be illuminated in error within the bytes. It may be any bit from the photograph in post #3.

Not absolutely useful in identifying exactly where the fault is - but it may point us in the correct direction presently.

I will give you a chance to absorb what I have written - and let the mods approve your posts before writing any more!

Also worth a read here http://www.vcfed.org/forum/showthre...riting-floppy-disks-with-NST-by-Dave-Dunfield

Dave

 

[whartung]

Other keys (with the exception of 'S') are invalid - and could result in the system beeping at you - plus annoying the parrot !

This suggests that what he's seeing is ok. He may be hitting an invalid letter, the system is echoing it, beeping "bad key", and then erasing it ready for the next prompt.

That's just a guess, though, for sure.

 

[daver2]

Isn't that what I posted?

Dave

 

[riddleywalker]

Thank you Daver2! Yes, I've downloaded the manuals and figured out the booting "LOAD SYSTEM" question.

Greatly appreciate the link for the disk images!

 

[riddleywalker]

Sorry for making so many posts in the thread - but I had a 'hunch' regarding the video problem and it seems to work out.

The RAM containing the 'strange' bits extends from 4800 to 4FFF (i.e. the last block of VIDEO RAM). What I had assumed is that the memory was aligned horizontally from top to bottom (in ascending address order). This appears not to be the case - and the memory is arranged from top left to bottom left and then working horizontally to the right in ascending address order.

I can't quite work out which data bit appears to be illuminated in error within the bytes. It may be any bit from the photograph in post #3.

Not absolutely useful in identifying exactly where the fault is - but it may point us in the correct direction presently.

I will give you a chance to absorb what I have written - and let the mods approve your posts before writing any more!

Also worth a read here http://www.vcfed.org/forum/showthre...riting-floppy-disks-with-NST-by-Dave-Dunfield

Dave

Thank you Daver2 for all the helpful information. I will try a few things this weekend. Will keep you posted.

 

[shirsch]

Thank you Daver2! Yes, I've downloaded the manuals and figured out the booting "LOAD SYSTEM" question.

Greatly appreciate the link for the disk images!

To save you some time / frustration, keep in mind that the Gotek floppy emulators do not work with Northstar machines. I worked a bit with Jeff (Mr. HxC) towards getting N* support, but there were some fundamental limitations in the hardware that made this unreliable. The DREM emulator does work, however, and supports multiple virtual drives. It even supports the N* hard disk, which is a completely proprietary format.

 

[redjr]

Just had a thought and checked the specifications.

The N* Advantage uses hard sectored disks. Do you have any of these? If not, they are now unobtainium (unless you can find some nice person willing to sell you some).

You can purchase and fit a soft to hard sector converter PCB so that you can use standard soft-sector floppy disks.

Just a thought in passing.

A few people on VCFED have already gone down this route if you want some further information.

Dave

I'm still doing a lot of reading on this hard-sector disk factor. Does the floppy drive itself have to be physically compatible with a HS, or SS disk? This stuff has long passed from my memory cells. If so, how can you tell if a drive will support the sector format? I have a drive that was supported by an early 80186 machine(Slicer). I'm assuming it used soft-sectored disks?

 

[daver2]

No, the hard sector / soft sector is a function of the floppy disk itself and not the drive.

The soft sector disks have a single index hole for each disk rotation - signifying the start of a track. The sector information is encoded in the magnetic media. A hard sector disk has one index pulse per sector, with a double index pulse signifying the start of a track.

Because not a lot of machines used hard sectoring, the disk media for this type of floppy disk went obsolete first.

As previously mentioned, there is a small add-on electronic board to convert a soft sectored disk to make it look like a hard sectored disk to the controller.

There was also a punch available I seem to remember to manually convert a soft sector disk into a hard sector disk (with a hammer)!

Dave