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Vercus
September 27th, 2009, 10:54 PM
Hello,
I just recently acquired two Northstar Horizons with a Heathkit H19 terminal. They came with several disks, and I've been trying to figure out what I need to do to get one of them to work. When I power the system up, the floppy drive spins, but it doesn't boot, even after trying several different disks. I even swapped out the floppy drives and systems, and both do the same thing.

I can only use one system at a time right now, as I am short a memory board- it caught fire:confused:

I have a whole box of old hard sector floppies, but I'm assuming I can't write those with a modern DOS PC and a 360K drive, correct? What would be the best way at getting a known good CP/M or N* DOS boot disk? I've found some software on the internet, but have no idea how to write it.

On the upside, I have TONS of manuals for this thing! Just about everything I could imagine is discussed in there. I'll definitely pour into them and see what I can dig up. Still, it seems to me if the drive is spinning and a disk is in it, something should happen, right?

Thanks in advance,
Jon

bugman2112
September 28th, 2009, 08:09 AM
Unless your system was configured with a boot PROM (which was rare), you are correct in that you need someone to send you a boot disk (I'm assuming your system is configured correctly, is not damaged, and that you do not have an actual working boot disk). I went through this same process when I purchased by Northstar a few years ago (I just sold it). Once you get a working boot disk (N*DOS), you will be able to use a serial cable and a small program to transfer disk images back and forth from a modern PC. This webpage contains links to that software and you should be able to figure it out (http://www.classiccmp.org/dunfield/). But you won't be able to do anyhting until you get a working N*DOS disk. Note: the program used for tansfers is under N*DOS not CP/M. So focus on getting the booting N*DOS disk, then you will able to make real disks to your heart's content, including CP/M. Full instructions can be found with those files at the link above. The good news is that Northstar systems had a fairly common configuration so these bootdisks are not impossible to find. A generous member of these forums helped me out.

Chuckster_in_Jax
September 28th, 2009, 08:12 AM
I have both a Northstar Horizon and an Advantage with the same problem. Won't boot from what should be a good boot diskette. Your problem may be more than just a bad diskette or misaligned drive. If you do a search on this forum you should find other threads discussing this same problem. I have shelved my project until I have more time to work with them.
I did purchased a new boot diskette from Dynacomp Software. They are regular sellers on eBay.

Their recent listing is eBay # 380158017691

CP/M Boot Disk/Utilities - North Star Format Diskette
This disk will boot to the CP/M A> prompt on a North Star Horizon with a terminal connected to the serial port. You will need at least 24K RAM as it loads a 24K version of CP/M.

and eBay # 380158018280

NORTHSTAR DOS/BASIC Disk for ALTAIR/IMSAI/S-100
The Altair and Imsai computers really got going when North Star introduced the 5-1/4" 10-sectored disk drive; these computers then became truly useful. This disk contains two different types of BASIC (one for a floating point board), having various digit precisions. This disk also contains North Start DOS.

RichCini
September 28th, 2009, 12:41 PM
I have a working N* and the last time I used it earlier in the year, it exhibited similar booting problems. Last time I worked with it, it booted just fine for part of the operating session and then stopped booting later in the same working session, giving me only a blinking drive light. Even after a cool-down period it still didn't work, so I don't think it's a heat-induced temporary failure.

I have read that it relates to flakiness with the disk controller (not that the design is flaky, rather that it goes out of tolerance somehow over time) but I haven't bothered to troubleshoot it yet (too many other projects). I did buy a spare MDS-2AD controller but I haven't swapped it in yet.

Vercus
September 28th, 2009, 06:22 PM
Wow, I must admit, this doesn't make me too optimistic about my chances of getting these things going! I wonder what could be causing the controllers to go? I question whether it is the controller on mine or not, as the drive does turn, it just doesn't seem to read the disk. I do get a clicking noise as the stepper motor moves a little bit, but it doesn't really seem to advance.

I have read about the need to lube drive rails. What would be a good lubricant to use? I have lithium grease, 3-in-1 electric motor oil, and WD-40 available. I'm guessing of those 3, lithium grease would probably be the best?

Any thoughts would be appreciated.
Thanks,
Jon

MikeS
September 28th, 2009, 06:31 PM
Check out Dave's NST utility; you might be able to make a boot disk over the serial port.
He might also have some tips for you; there's also a Northstar Google group AFAIK.

http://www.classiccmp.org/dunfield/img/index.htm

Good luck, and have FUN!

RichCini
September 29th, 2009, 05:14 AM
Wow, I must admit, this doesn't make me too optimistic about my chances of getting these things going! I wonder what could be causing the controllers to go? I question whether it is the controller on mine or not, as the drive does turn, it just doesn't seem to read the disk. I do get a clicking noise as the stepper motor moves a little bit, but it doesn't really seem to advance.

I have read about the need to lube drive rails. What would be a good lubricant to use? I have lithium grease, 3-in-1 electric motor oil, and WD-40 available. I'm guessing of those 3, lithium grease would probably be the best?

Any thoughts would be appreciated.
Thanks,
Jon


I don't think I've ever lubed the head carriage rails on my drives. I always thought they are zero-maintenance except for picking fuzz off of them. I have Teac and Tandon drives from the 80's that have had no maintenance of this type and work just fine.

If I had to lube them, probably white lithium grease would be the best. The other two are pretty thin lubricants and might spatter on the diskettes or otherwise collect more dust and grime. If you plan on doing this, I would put the grease on a Q-tip and then lightly run it over the rail and work it in by accessing the drive.

I personally don't think this relates to the problem, but having said that, maybe it's possible that if the head carriage is binding, the controller is timing out on a sector seek. I didn't think the tolerances were that tight, but I'm curious as to how you progress.

My N* uses standard PC floppy drives -- the Tandon TM-100A. I had to replace the original MPI drives because of blown motor controllers in both when I adopted the system.

bugman2112
September 29th, 2009, 05:28 AM
If your not 100% sure you have a working boot disk, I would try that first. Its the easiest and problay most likely problem. Dave's NST utility works great, but there is no way to bootstrap the northstar like other systems because it has no ROM. There is no way to enter code (front panel, monitor program, etc.) without dos. I agonized over this for quite a while until someone sent me a boot disk. But if you are sure you have a working boot disk, then you are of course on the right track troubleshooting the hardware.

MikeS
September 29th, 2009, 10:08 AM
If your not 100% sure you have a working boot disk, I would try that first. Its the easiest and problay most likely problem. Dave's NST utility works great, but there is no way to bootstrap the northstar like other systems because it has no ROM. There is no way to enter code (front panel, monitor program, etc.) without dos. I agonized over this for quite a while until someone sent me a boot disk. But if you are sure you have a working boot disk, then you are of course on the right track troubleshooting the hardware.
---
Ah, I thought it was a similar situation as his CRT program which lets you create a boot disk over the serial port. I had a Northstar once but scrapped it long ago, so I don't remember much.

But this seems to be talking about a monitor ROM being available, or at least a place for it:

http://newsgroups.derkeiler.com/pdf/Archive/Comp/comp.sys.northstar/2007-05/msg00021.pdf

Maybe Andrew will see this thread and have some insights to offer.

mike

bugman2112
September 29th, 2009, 10:35 AM
Yes, one of the boards had an option for a boot ROM to be installed. I can't remember which board (memory, CPU, etc...). But to my understanding this was rare to find one configured that way. Mine wasn't for sure.

MikeS
September 29th, 2009, 01:11 PM
Yes, one of the boards had an option for a boot ROM to be installed. I can't remember which board (memory, CPU, etc...). But to my understanding this was rare to find one configured that way. Mine wasn't for sure.
--
Well, there'd have to be a *boot* ROM, wouldn't there, or else how would you read the boot disk? But apparently they didn't all have a monitor that'd let you talk to it via RS-232...

bugman2112
September 29th, 2009, 04:11 PM
I guess "boot" wasn't the best terminology to use. I meant what you said, it lacked any kind of monitor program for basic I/O that would initialize seperate from the drive controller. The CPU board did have a small component area where you could add a ROM (2708 ) as an autostart option. I 've not heard of many of them being populated, though.

Vercus
September 29th, 2009, 04:22 PM
I've got 5 or 6 disks that I'm told should boot- Northstar DOS and CP/M. I would think with that many disks, at least one should still be good, right? As far as boot PROM, mine doesn't have it. I'm travelling with work til Thursdaym but I'll have to check out that NST program when I got home. I hope I can get one of 'em going, as they're cool looking computers, and there seems to be a lot of boards made for S-100.

billdeg
September 29th, 2009, 04:38 PM
check the voltage regulators in the back left of thr moboard, the middle one especially. Your symptoms indicate that this may be bad. To confirm check volatage to the drive.
bill

Dwight Elvey
September 29th, 2009, 05:06 PM
I guess "boot" wasn't the best terminology to use. I meant what you said, it lacked any kind of monitor program for basic I/O that would initialize seperate from the drive controller. The CPU board did have a small component area where you could add a ROM (2708 ) as an autostart option. I 've not heard of many of them being populated, though.

Hi
How does the N* start if there is no boot ROM?
I don't think the disk controller is DMA based with an auto
boot ( I do have a ROM-less S100 but the disk does DMA ).
There is a monitor program for the N* but you need the
disk working before it will work( chicken&egg problem ).
Dwight

Dwight Elvey
September 29th, 2009, 05:22 PM
Hi
How does the N* start if there is no boot ROM?
I don't think the disk controller is DMA based with an auto
boot ( I do have a ROM-less S100 but the disk does DMA ).
There is a monitor program for the N* but you need the
disk working before it will work( chicken&egg problem ).
Dwight

Hi
A little research answered my question. The controller
has a small bootstrap loader ROM located at E800H.
This is how it boots, this is the boot ROM.
Dwight

RichCini
September 29th, 2009, 06:20 PM
check the voltage regulators in the back left of the moboard, the middle one especially. Your symptoms indicate that this may be bad. To confirm check volatage to the drive.
bill

I don't have the dox handy -- is this the 5v or 12v regulator?

Update: never mind -- I pulled out my N* last night. There's a trio of 7805 regulators in the upper-left corner, right above the 7812 TO-3 regulators. I tested the voltage at the drive connectors -- there is a slight difference between the voltages at either connector -- 5.02v and 5.12v. The boot drive is on the connector with the lower voltage. I guess there could be a transient voltage sag which causes the voltage to drop below 5v, but I'd have to put a scope on it to see.

The schematic notes that there are several bypass capacitors on the outputs of the voltage regulators supplying the disk drives that are not used (C5, C6, C8 and C9). The docs I have already reflect this ECO, so the parts list doesn't have the values. I don't know if it's worth populating those with, say, 4.7uF tantalum caps or something like that.


I will probably swap the power connectors and see if that makes a difference.

Vercus
September 30th, 2009, 04:33 AM
Hello,
I have just about every manual made for the thing at home. I can take a look inside at the regulators, and between looking the part numbers up online, and looking in the manual, I should be able to find out which is which. They seem to be a common failure point. I have a DEC RL02 with a bad one as well. Hopefully I have the service manual for the N*, as that would be more helpful.

-Jon

joesulldux
October 1st, 2009, 06:50 AM
Hi Jon,

As the former owner of the N* Horizons you are asking about, maybe I can help a little bit here -- with a little history, at least.

I tend to agree that it's not likely to be the boot disks that are the problem. Of course disks that old can go bad, but it's highly unlikely that all of them did. Of the box full that I gave you, there are many others besides the half-dozen or so that I pointed out that should boot if the hardware is good. The disks were stored in metal cabinets, in reasonable indoor conditions, so I believe that most if not all should work fine. One obvious way to check would be to send some off to someone with a working Horizon to try.

Unfortunately, the computers were stored in less favorable conditions. Although they were kept covered under plastic, they spent some years in a garage (the same one where you picked them up), where the temperatures can sometimes get below freezing during the winter even though it's part of the house.

Although I'm mostly a software guy myself, I sometimes found the extensive schematics that came with that old documentation useful. They really told you everything in those days! (The oldest of those two machines was purchased by March 1978.) Somewhere in there, I believe, with the right testing equipment and hardware skills, the answer will be found.

Although the disk controller boards are obvious suspects, I wouldn't overlook the memory boards as possibilities. One of those boards, the one with the post-it note, is definitely blown. For a (fun?) picture of the actual event, see

http://www.dropshots.com/joesulldux#date/2006-09-29/22:24:41

(The memory board is the frontmost, and you can just see a wisp of smoke still curling up from its left side. I had decided to put out the fire before taking the picture ...)

I hope this has been of some help, and wish you luck (and fun) getting these systems going.

All the best,
Joe

RichCini
October 1st, 2009, 08:03 PM
check the voltage regulators in the back left of thr moboard, the middle one especially. Your symptoms indicate that this may be bad. To confirm check volatage to the drive.
bill

Bill --

I started up the N* tonight and I got the boot monitor prompt for a few minutes and then all of a sudden it appeared that the system wouldn't reset (or at least I lost the console connection). So, on a lark, I put a probe on a random 74xx chip on the motherboard and I got 4.88v. That seems a bit low to me.

I'm thinking that not only is the 7805 regulator for the drive flaky, but maybe the regulator for the motherboard is as well. I took off tomorrow so I added this to my list of things to tackle. I have a few 7805s laying around so I'm going to replace both and see what happens.

UPDATE: I replaced all three 7805 regulators. The reported voltages on all three are 4.97v. Interestingly, it did restart once and give me the "NORTHSTAR..." monitor banner, but refused to accept input. Shortly after, it wouldn't give me the startup banner and the drives won't spin up.

I have to go out for a while, but I'm going to try it without the floppy card and see if I can just get the CPU working.

Vercus
October 2nd, 2009, 07:18 AM
Well, I've definitely got multiple issues going on. At least one of the floppy drives seizes immediately and will not spin whenever it's closed. Most other disks won't spin properly even in a good drive. I'm not able to tell if the terminal is communicating right with the computer because the baud rate setting has been modified with a rotating knob. You turn it to select different baud rates. I guess it's too early to be trying to communicate with the terminal when I can't even get the system to boot up. The drive turns on for 10 seconds or so, makes a few clicks, and that's it.

I'll have to try using the terminal with my Win98/DOS machine, and see if I can communicate via CTTY. Vice versa, I'll try my known good DEC VT-102 terminal with the Northstar, as it is easier to reconfigure baud rates.

This is confusing!

Vercus
October 2nd, 2009, 03:58 PM
I just checked the voltages at the floppy drive power connector, and they were 12.04 and 4.96, which seems within spec to me. So, where to look next?

Does anyone have the ability to make a CP/M boot disk for this? I have plenty of spare hard-sector disks I could send for someone to write to.

-Jon

Vercus
October 2nd, 2009, 04:52 PM
I took a closer look at both my memory cards, and I found that BOTH have blown up capacitors in the upper left corner. As mentioned earlier in this thread, one of the memory boards had caught fire. It was C8 (6.8 uf) that blew, and it scorched the pins on the voltage regulator next to it. The other board wasn't quite as violent, but it does have a disentegrated C1 (2.2 uf), and the others look pretty dark.

So, it looks like both memory boards should be recapped. I'm thinking I should probably change out the voltage regulators as well, to be on the safe side.

Looks like a total of 6 caps, and two voltage regulators (7805C and 7812C).
Is this stuff I could get from Mouser? Anyone know the voltage ratings on the caps?

Thanks,
Jon

Chuckster_in_Jax
October 2nd, 2009, 05:13 PM
Looks like a total of 6 caps, and two voltage regulators (7805C and 7812C).
Is this stuff I could get from Mouser? Anyone know the voltage ratings on the caps?

Thanks,
Jon

Yes, Mouser or Digikey should have the parts. For the Tantalum capacitors, I have been ordering ones rated at 50 volts. You'll be surprised at how much smaller the new ones are than the ones you are replacing.

Vercus
October 2nd, 2009, 07:28 PM
I just placed an order with mouser for the caps and VR's. Should work out well I hope. I'll let you know how I make out.
-Jon

Vercus
October 3rd, 2009, 07:58 AM
Does the Horizon have any onboard ram, or will I have to wait til I recap the memory boards to be able to run it?

RichCini
October 3rd, 2009, 02:08 PM
Bill --

I started up the N* tonight and I got the boot monitor prompt for a few minutes and then all of a sudden it appeared that the system wouldn't reset (or at least I lost the console connection). So, on a lark, I put a probe on a random 74xx chip on the motherboard and I got 4.88v. That seems a bit low to me.

I'm thinking that not only is the 7805 regulator for the drive flaky, but maybe the regulator for the motherboard is as well. I took off tomorrow so I added this to my list of things to tackle. I have a few 7805s laying around so I'm going to replace both and see what happens.

UPDATE: I replaced all three 7805 regulators. The reported voltages on all three are 4.97v. Interestingly, it did restart once and give me the "NORTHSTAR..." monitor banner, but refused to accept input. Shortly after, it wouldn't give me the startup banner and the drives won't spin up.

I have to go out for a while, but I'm going to try it without the floppy card and see if I can just get the CPU working.

After some troubleshooting today, I'm no further along. I can't get the N* to reset and the drives don't spin up. I tried starting up with nothing other than the CPU card and one RAM board, but I still get nothing.

UPDATE: I was playing around with it again a few minutes ago and I noticed that one of the backplane connectors had something in it. So, I blew it out with air, reseated everything and now, it seems to work.

I have two boot diskettes -- one works and one doesn't. I have to make a copy before something *bad* happens.

I guess the moral of the story is -- don't overlook the simple. I probably didn't need to replace the regulators but at least they are new :-)

Off to figure out how to make a copy of the disk.

joesulldux
October 8th, 2009, 05:46 AM
Hi Jon,

As I recall, there was no onboard memory (other than the eprom at e800, for booting). So you'll need to get those memory boards up -- let's hope those caps are the only things blown.

Regards,
Joe


Does the Horizon have any onboard ram, or will I have to wait til I recap the memory boards to be able to run it?

Vercus
October 9th, 2009, 03:38 PM
I just got the caps and voltage regulators in from Mouser today. I'll try to repair the boards this weekend and report my findings.

-Jon

Vercus
October 11th, 2009, 12:06 PM
I recapped one of the memory boards, and swapped out what looked like a defective DB-25 cable, and it lives!

I booted up to CP/M with it connected to the DEC VT-102 at 9600 baud. So far, I've only attempted to load Wordstar from the second drive. It gave an error saying "NOT ENUF MEMORY". I only have one board installed, so perhaps that's not enough? I find that surprising, as that's how he was using the systems in the past. Perhaps it isn't enough though. The drive also sounded funky while trying to load it, so it could be a bad disk. I'll have to try some others.

In the meantime, I'm stoked to have it going again! I'll have to try conencting the Heathkit terminal, and see if that works with it.

I'd eventually like to re-do the other memory board, but it definitely needs more work (singed voltage regulators as well), so it'll take me a little longer to get that one done.

-Jon

joesulldux
October 11th, 2009, 06:29 PM
Hi Jon,

Super! I'm really glad to hear that the cap got it going. I'm pretty sure that those memory boards gave you the maximum memory that the system could handle, which as I recall was 64K. I also vaguely recall that the EPROM at E800 was inconvenient for some software. I suggest trying to boot one of the N* DOS disks, which is the simplest (and original) system. You may also find one labeled "IDOS" -- that's just DOS with a small patch that I introduced so that the serial I/O was interrupt-driven rather than relying on polling. (I type fast, and the polled I/O was missing some characters. No such problem when you use interrupts, which are supported in the Z80 chip but not used in the original N* DOS code. Likewise CP/M and "ICP/M," as I called it.)

Cheers,
Joe

Vercus
October 12th, 2009, 10:13 AM
Hello,
I got N*DOS to boot. After learning the commands from the manual, I ran a ram test on one of the disks, and it got part way through and locked up the system. I have had several memory related problems with this board. It's looking like there's some kind of problem that's preventing it from accessing the higher levels or banks of memory. Every program I try to load either reports a load error or insufficient memory.

Hopefully it's nothing I did. I didn't notice the bad cap for a few days, and was running the system with it in, so I don't know if that damaged the board or not.

There are some dip switches on the board- I don't know what they do. Both boards appear to be set the same though, which suggests they are fine.

I did try swapping floppy drives around, and seem to have found a pair that work fine, as far as I can tell.

Any thoughts would be appreciated!
Thanks,
Jon