DCC-116 E / DATA GENERAL NOVA 2/10 / Nixdorf 620 - Restoring and restarting

Dominique Carlier dce at skynet.be
Sat Apr 1 14:33:51 CDT 2017

Hi guys !

My name is Dominique, 43 , from Belgium (I apologize in advance for my 
approximate English). I join this forum under the recommendations of 
Curious Marc. It seems there are people here who can help me to get back 
to life the venerable machine that I have just recovered.

Some pictures of the beast :




It is a "Nixdor 600 series" (Apparently a Nixdorf 620/35), upgraded 
several times until 1980, the CPU board is dated from this year. So I do 
not know exactly what machine it is today the equivalent.

Anyway, the Nixdorf 620 is actually built by "Digital Computer Controls" 
and after some researches it seems that it is a "DCC-116 E", the 17 slot 
version of the "DCC-116" which Is a clone of the "Data General Nova 2/10".


The machine has five Key-stations (ENTREX DATA/SCOPE), a Mag-tape Pertec 
8840A - A Disk Cartridge Diablo Model 40 and a big line drum printer 
(Data Products model 2230), strange machine, there is a tape reader 
inside the printer.

Here is the list of the boards I have with the references written on 
them and their position in the machine:

*17    HEX 0 – 15                 ENTREX INC 62 00 01842 002 REV A*

*16    HEX 16 30 31             ENTREX INC 62 00 01842 002 REV A**
15    OPTION 2                  Empty**
14    OPTION 1                  Empty**
13    PRINTER                   ENTREX INC SN598**
12    TAPE 556/800 BPI     2433 LFI 213**
11    TAPE 1600 BPI          Empty**
10    DISK                           2456 00 MP-Kontroller D44an620 
6393500215 2456 7 0 1577**
09    COMMO                     Empty**
08    SCANNER                  Scanner BD 2431 NCAG 54147.1.15 2431 02394**
07    MEM                           1609 0 7 02616**
06    MEM                           Empty**
05    MEM                           1609 0 8 02367**
04    MEM                           1615 01 9 5596**
03    TTY                             Empty**
02    DO NOT USE             Empty**
01    C.P.                              1509 05 4 04436*

Concerning this I also ask a few questions:


    What are the boards in slots 16 and 17 for?


    I do not have a COM card, does that mean that I could not attempt a
    serial transmission (type rs232) with this actual setup ?


    I have no idea how many kilobytes are present, apparently there are
    two core memory cards (8kb each? 16Kb each?), And non-core RAM board.

I first solved a problem with the power supply of the disk pack (bad HF 
filter, short-circuited with the chassis, then it is also dead HF filter 
in the "multi-plug" of the chassis that start to burn, once these 
problems were solved, I cleaned the machine thoroughly, cleaning the 
heads of readings with isopropyl alcohol, I Not yet cleaned the disc 
himself which at first glance looks extremely clean, it has not left the 
machine for 30 years.


I cleaned all the guides and the heads of the nine track tape Pertec 
8840A. There was also a false contact in the ON-LINE button. I did a 
first cleanup. I think there is always a problem with the HI-DEN button 
used to set the magtape to 800BPI. It is currently ineffective, but I 
have a doubt about the contacts of the lamp socket).


I then cleaned all the sockets and contacts at the boards of the 
computer (logic and PSU)


Unfortunately, after a couple of hours, the "POWER FAIL" light has 
started to light up. The problem here is that I have no schematics, it 
is a modular power supply consisting of two elements:


One seems to be dedicated to the 15 VDC regulated, the second module is 
in charge of the regulated 5VDC. Both elements have a "Power fail 
module". When the machine is completely populated I now observe that the 
+ 5VDC collapses at +1,9VDC.

Here what I measured out, you will also see what the boards of these 
power supply look like.



Another thing I noted during my measurements, where I should (I think) 
measure 15V, I have 18V, looking at the documentation on the NOVA 2 (4 
slots), I observed according to the diagrams below That there is 18V but 
before a zener diode and not at the level of connectors where there must 
be 15VDC, should I warn me ? Would the diode be dead ?

I tried to join temporarily a secondary regulated power supply to 
reinforce the + 5VDC so as to be sure that the problem did not come from 
the logical part of the computer which checks these voltages and 
triggers the Power Fail status. By coupling this external regulated 
power supply, the computer restarts again, thus it is definitively the 
power supply (or the comparator component(s) of the power fail module)

If I removes all the boards (printer, core memory, scanner, disk 
controller, etc.), the Power Fail light eventually goes out, I get again 
the 5VDC, so the power has become "too weak" to power the computer when 
it is fully populated.

Despite the temporary (and dangerous) look of my assembly with secondary 
power supply, I could not stop myself and attempt a boot procedure via 
the Cold Start button of the machine from the Disk Pack, and it works! :-)


It seems that I still have problems with the magtape, I had errors 
trying to read a backup, but it may be simply because I still cannot get 
the machine in 800BPI because of the capricious buttons of the front 
panel. I also wrote a tape mark via a "WRITE TAPE MARK AND REWIND" 
function, the mark seems to be written but does not do the Rewind, 
however if I launch a REWIND only function, it executes the action 
appropriately. In short, still things to investigate on this side.

Notes that the Operating system I used to make these tests is a very 
limited OS named DIDOS which was distributed by Nixdorf for his 620 
Serie. As the machine is a clone of DG NOVA 2/10, I wonder if the 
computer is compatible with programs for the NOVA series of Data 
General? So I wonder if the DCC-116 was compatible with the software for 

The other questions I ask myself at this point are the ways to transfer 
softwares or bootable OS on this machine? I have no other disk pack on 
another system but I have a nine track tape TU81 + connected to a VAX 
4000-605A under OpenVMS 6.2, and I can put this computer on my network. 
Do you think there's a way to make a bootable tape for my NOVA 2 clone 
with the Pertec 8840A from a VAX 4000 with a TU81+ ?

Well, to continue, I have to repair this PSU, all information is 
welcome, schematics would be ideal of course.

Finally, note that I am not a professional electronics technician, I 
fixed a lot of machines basic knowledge, intuition, researches, 
comparisons and logic, it is effective but full of limitations too, so 
forgive me in advance If I do not always understand the possible answers 
of electronics in "high engineering" mode ;-)

As a bonus, the V1 of a small video mounted with a few clips captured 
during a session of my nocturnal repairs, during the first boot of the 
machine since 3 decades ! (on my music, yes, I'm also a composer ;-) )


Thanks a lot to all in advance ;-)


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