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How to Image DG Nova 3 RDOS Disks?

NF6X

NF6X

Veteran Member
Joined
Sep 9, 2013
Messages
1,534
Location
Riverside, CA, USA
A little while back, I purchased a Data General Nova 3 system and a DEC PDP-11V03-L system, both of which were owned by a fellow named Herman Cohen and used in his electronic alarm company business. He passed on several years ago, but his business is still running and owned by his family.

I've been working on the PDP-11 so far. I'm still working out kinks in the system and playing with upgrades, but I have completed one of my goals: imaging the two floppy disks that were sitting in the drive to archive their contents and to allow me to simulate the system in SIMH in its original configuration. Seeing the boot message ("WELCOME TO ANOTHER DAY IN THE YEAR OF 1987") was like taking a trip back in time, and poking around in the BASIC programs that Herman wrote was a lot of fun.

Now it's time for me to try to bring up the Nova 3, and my first priority is to image its disks. You may have noticed another Nova 3 thread that was just created by another one of us retrocomputing nuts. That's not a mere coincidence… he's lusting after my Nova 3, but I can't consider letting it go until I've had some fun with it and imaged those disks! ;)

I have no prior experience with DG systems or with RDOS. Can any of y'all help me figure out how to get disk images off of the system, assuming that I can boot it up and get the drive working? It has a single drive with one fixed platter and a removable pack. Two packs came with the system.

Can I safely use this kind of drive without a removable pack installed, or does a pack always need to be installed before spinning it up?

Are there any things I should do to the drive before trying to spin it up other than thoroughly vacuuming out as much dust as I can find? I've popped out the air filter once, and it's quite gray on the intake side. I don't have any spare filters.

Come to think of it, I don't even know how to connect a console terminal to it yet. It looks like I may need to wire up to a bank of unmarked wire-wrap posts at the left rear corner of the machine and/or on the backplane. I took some pictures of where cables were connected when I picked up the machine, since I disassembled it to barely-liftable pieces.

This DG noob welcomes any advice on successfully bringing this system up and archiving whatever intact data may still be on it!

IMG_0852.jpg Image 7.jpg IMG_0853.jpg IMG_0856.jpg IMG_0858.jpg
 
Good luck Mark, hope she fires up!
As we say in NY, I don't know from RDOS, so can't be of any help there, but it's always fun to learn new stuff, keeps the brain working. Our 37 yr old daughter lives out in Denver, so will have to pay Mr. Ray a visit when we are out there in September!
Roger A.
 
I never ran RDOS, but the disk drives I used that looked like that always had to have a cartridge loaded to spin up the fixed platter. I did have some exposure to AOS and AOS/VS, but not as the sysadmin.
 
I spent a bunch of time last night and this morning cleaning, vacuuming and recabling the system.

First, the good news: The hard drive spins up, does a brush cycle, and then indicates readiness. I didn't hear any scary sounds. I didn't have the cover off when I spun it up, so I couldn't see if the heads loaded. I think I finally found the shipping lock that I was wondering about when I originally picked up the unit. It looks like it's necessary to take off the drive's top cover, remove a red-painted bracket near the right side of the linear motor, turn it 180 degrees, then reinstall it.

Now, the bad news: Nothing lights up on the CPU cabinet when I turn it on. The fans blow and I didn't find any blown fuses, but I don't measure any voltage on the fuses all over the backplane. So, it seems to have a power supply issue.
 
From top to bottom, the card slots contain:

  1. QUAD MULTIPLEXER
  2. DISK CARTRIDGE CONTROL
  3. empty
  4. empty
  5. empty
  6. empty
  7. empty
  8. empty
  9. CASSETTE I/O
  10. 128K MOSTEK MEMORY
  11. TRIPLE OPTION
  12. NOVA 3 CPU


Hmm, I wonder what that Cassette I/O board is meant to connect to?

IMG_1062.jpg IMG_1063.jpg IMG_1065.jpg IMG_1067.jpg

I took the cover off the hard drive and verified that the heads do load.

I'm still working on the power supply problem. I may need to take the CPU cabinet back out of the rack to get better access to the power stuff at the rear. Ugh, that thing is heavy!
 
Thanks!

I made a short video of the hard drive spinning up and loading the heads. Possibly the most boring video ever?

 
Oh, this looks promising… I thought that all of the fuses were good. I checked again, and found one bad one… the 20A fuse on the backplane between the 32V unregulated power and the power supply board!

I should have replacements by the weekend, and I'm crossing my fingers that the fuse just saw one inrush surge too many or something like that. But I bought ten of them in case the first one immediately blows and I need to dig further into the power supply.
 
I've found that sometimes a little Deoxit D5 and a reinstall goes a long way, at least where old vacuum tube stuff I usually play with is concerned. Hope the PS is OK, Ive done some looking and haven't seen one yet.
 
Good news! With a new 20A fuse in place on the backplane to feed +32V to the power supply card, the power supply came up and the machine sprang to (at least partial) life! The power supply even has an audible "I'm So On!" indicator, if you're still young enough to hear that frequency. :)

I think it has at least a couple of lamps burnt out, but the front panel responds in a sane-looking manner otherwise. I'll do some more poking around with a meter, then I'll try plugging in the hard drive and figuring out the console terminal port once things look right. In particular, the ON lamp isn't coming on, so I need to determine whether the power isn't quite right or the lamp is just burnt out.

Edited to add: Two of the questionable bulbs have obviously broken wires. Does anybody know a bulb number for a suitable replacement?
 
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I've made some more progress, and come up against another stumbling block. I identified the TTY signals, which wasn't at all easy given DG's screwy way of wire-wrapping peripherals to the backplane. I resorted to tracing circuitry on the I/O board to identify the appropriate signals. I also checked the strapping on the I/O board, and found that it's strapped for EIA signaling (not current loop) at 4800 baud.

When I set the front panel switches to the right number from booting from the hard drive (as found in the documentation, and supported by the previous owner marking the ones switches with a sharpie) and then hit the Program Load switch, the RUN lamp comes on and I see some activity on the front panel lamps. However, there's no activity on the TTY output, where I was expecting it to prompt me for a filename to boot. I took off the hard drive's top cover to look for any head motion, and I don't see any.

So, now I'm stuck again. :(
 
Hi All;
NF6X, Congratulations on your next project..
I forgot which type of I/O Board you have.. But, I would trace out the signals to any transistors or 1488/1489 EIA outputs, and of course make sure you don't have the wires backwards.. Ask me how I know..
Also, If you have good working core memory, Output any letter, and check with a scope from your I/O output to the terminal that it is making all the way through it.. Or, an Echo program, I wouldn't be surprised IF I don't have something from Bruce in one of our many emails over that past 15 years or so..
Also, Bruce can tell You how to get the Data off.. I helped Him many years ago get the information off of many Paper Tapes, and transfer them to a PC.. And He has done the same with Disk Drives.. Also, He could advise you on steps to take on carefully bringing up Your Drive.. Bruce, has the largest collection of DG Software of anyone I know of..
I always liked the way DG used the WireWrap pins on the Backplane to access the signals, I could hang a scope probe on what I need to..

THANK YOU Marty
 
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This is my first exposure to DG machines, so I don't know how to talk to a serial port from the CPU end yet. If anybody has any notes handy that might help me figure out how to toggle in something to send a character to the TTY port, I'd appreciate that.

Regarding the console bulbs, I found that one of mine that snapped off at the base still has an intact filament. I was able to probe the wires at the glass seals to light it up and measure current. The bulbs are normally powered from an unregulated 14V rail as I understand things, and I measured the voltage at around 15V on my machine. The broken-off bulb draws 39mA at 14V and the filament color is quite orange. It draws 50mA at 28V and has a normal-looking color temperature. I conclude that the original bulbs were probably designed for 28V operation or so, and are used at lower voltage in the Nova 3 to increase service life (?).

McMaster-Carr and Digi-Key both have some bulbs that look like possible substitutes. I think I'll try some 2185 bulbs from Digi-Key since I'm ordering other stuff from them anyway, unless anybody has a better confirmed cross-ref. Those are 28V 40mA bulbs.

I also received an email from another collector who used KH 4-280-040A-1 bulbs from KH Lamp in his Nova. He reports that he got them from Swedish distributor Elfa as part number 33-657-98. That's a 28V 40mA T1-1/4 bulb.
 
Hi All;
NF6X, I forgot about the Bulbs, so I am glad that You some options..
I will take a look at my old Emails from Bruce, and see what I can send You, But, that may take awhile..
Also, do you have access to to any of the set up books ?? There were three of them, a Red one, a Blue one, and a Green One, I have the Green one, and I can make copies of what it has one the Nova 3.. It is the Set-up Manual for DG products, at that time..

THANK YOU Marty
 
I have several scanned manuals from various sources, but I don't know if any of them are the same as the reg/green/blue books that you have.

I think that my next steps will be 1) replace the bad front panel bulbs and 2) start trying to toggle in diagnostics to exercise parts of the system.
 
Hi All;
NF6X, that was why I suggested the I/O Echo program, once that is working, then You can download from Your PC, Various Diagnostic programs for the Nova 3.. You would need after the I/O is working the Basic Loader, but the rest can be downloaded from a PC with Tera-Term .. And the Basic Loader may in the "3" be already there, in Rom.. I can look, after I find them (my CD's) from Bruce and see what I have for the Nova 3.. Since, I have never had one, I have never looked to see what all I have on it, in the CD collection.. There is a program that tests what all you have on the machine, and then runs the various tests, based on what Hardware it has found in Your machine.. Its very nice and the Paper Tape for it is quite long, so You would not want to type it in.. But, rather download it from Your PC.. I have used a variation of that program for my Nova 1200 in the past, and for my Eclipse S 130.. The thickness of the Paper Tape is how I gauge the length of the program, and what I had was quite thick.. I can check what I have in .bin files or what ever they are, so You could Load them in.. I know there is a Teletype Program, and many others as well, including some to check Your 6045 Disk Drive and associated logic..

THANK YOU marty
 
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Ah, it didn't quite click inside my brain that I might be able to load code in through the TTY port. I was thinking in terms of disk drives and operating systems rather than toggle-in bootloaders and paper tape from the (emulated) console TTY.

I found a bunch of documentation for diagnostic programs, and some of the documentation includes listings:

http://bitsavers.trailing-edge.com/pdf/dg/software/diag/

But, I don't have any paper tape images. Do you know where I can find any, particularly for diagnostic programs?

Is the Basic Loader that you mentioned the one shown in the 093-000002-01_Bootstrap_Loader70.pdf file in this directory?:

http://bitsavers.trailing-edge.com/pdf/dg/software/utility/
 
Hi All;
NF6X, here is your Echo program..
; Read a Character from the Keyboard
starting at address 0000
062677 I/O reset
063610 TTYRD: SKPDN TTI ; Has Character been typed ?
000377 JMP .-1 ; No, then wait
062610 DIAC 0, TTI ; Yes, then Read Character and Clear Done
; Output Character to Terminal
063511 TTYWR: SKPBZ TTO ; Is TTO Ready
000377 JMP .-1 ; No, then wait
061111 DOAS 0,TTO ; Yes, Then echo character
000372 JMP 0,3 ; Return to beginning

THANK YOU Marty
 
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