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

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 : http://www.actingmachines.com/classiccmp_forum/overview01.jpg <http://www.zeltrax.com/classiccmp_forum/overview01.jpg> http://www.actingmachines.com/classiccmp_forum/terminal.jpg <http://www.zeltrax.com/classiccmp_forum/terminal.jpg> http://www.actingmachines.com/classiccmp_forum/comrack_closeup.jpg <http://www.zeltrax.com/classiccmp_forum/comrack_closeup.jpg> 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". http://www.actingmachines.com/classiccmp_forum/DCC.jpg <http://www.zeltrax.com/classiccmp_forum/DCC.jpg> 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. http://www.actingmachines.com/classiccmp_forum/disckpack01.jpg <http://www.zeltrax.com/classiccmp_forum/disckpack01.jpg> 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). http://www.actingmachines.com/classiccmp_forum/ninetrack.jpg <http://www.zeltrax.com/classiccmp_forum/ninetrack.jpg> I then cleaned all the sockets and contacts at the boards of the computer (logic and PSU) http://www.actingmachines.com/classiccmp_forum/clean_contact.jpg <http://www.zeltrax.com/classiccmp_forum/clean_contact.jpg> 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: http://www.actingmachines.com/classiccmp_forum/psus.jpg <http://www.zeltrax.com/classiccmp_forum/psus.jpg> 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. http://www.actingmachines.com/classiccmp_forum/psu_module_1.jpg <http://www.zeltrax.com/classiccmp_forum/psu_module_1.jpg> http://www.actingmachines.com/classiccmp_forum/psu_module_2.jpg <http://www.zeltrax.com/classiccmp_forum/psu_module_2.jpg> 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! :-) http://www.zeltrax.com/classiccmp_forum/first_boot.jpg 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 NOVAs? 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 ;-) ) https://youtu.be/5jWOUtLKRIU Thanks a lot to all in advance ;-) Dominique