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

Dominique Carlier dce at skynet.be
Tue Apr 4 09:09:23 CDT 2017

Many thanks for these detailed answers ! :)

Indeed, I finally do not know exactly what Nova my DCC is the clone. 
Another specialist suggested that it was rather a clone of NOVA 1200?

Note that in Nixdorf contracts for the 600 series, these machines were 
sometimes updated with a new CPU over the years of service.
In the doubt here are pictures of the board in slot 01 dedicated to the CPU:




Do you have any idea what that is?

Concerning the PSU I will analyze your suggestions.

Concerning the memory, I analyzed more in detail, I think finally that 
all the memory is core type, 1 X 16KW (it is marked on it) and 2 X 8KW 
(according to the size of the core package in comparison with the 16KW 
board). Thus a total of 32KW.

For transmission via serial port, unfortunately I do not have this 
"basic board" in slot 3 (TTY), it's empty. Can we still find board like 


> Er.  My DCC-116 is more a clone of the mapped Nova 840 than the Nova 2,
> with the DCC/Keronix "64Kword" hack that gives up more than one level of
> indirect memory reference in exchange for having 16, rather than 15,
> bits of logical memory reference.
> IIRC the functionality of the basic I/O board normally found in slot
> three is subsumed into the CPU card of the DCC116, so you should be fine
> as long as you can find the signals on the back of the machine.
> It's a word oriented machine, so memory is sized in KW, not KB. You can
> probably tell how big the boards are by looking at the physical address
> jumpers; core boards were typically 8KW, MOS boards were typically 16 or
> 32KW, depending on vintage. Hint:  The more jumpers, the smaller the board.
> I have no idea how this machine packages things, but in jumbo-chassis
> Novas the lower PS generates five and 15 volt supplies, the top PS
> generates only five.  The reason for this is that the 15 volt supply is
> only used by core memory boards and the memory bus is only available in
> the lower chassis.
> Sounds like one of the +5V switchers is having issues.
> +/-5V and +15V but not -15V should be regulated.  In the original DG
> power supply both five and 15 volt supplies were derived from a common
> +30V unregulated supply, but it's not clear that DCC followed that
> model.  It may be helpful to know that the +15V supply is not regulated
> to 15V but temperature compensated downward with increasing temperature,
> such that at 55C it's closer to 14.4V; this is done to maintain margins
> on the core planes. The consequence is that you're probably looking at
> something having drifted in the voltage divider that feeds the voltage
> comparator or something having drifted in the temperature compensation
> stuff (if it's actually there) rather than a simple zener gone bad.
> /POWER FAIL is asserted by the power supply itself, as is MEM OK.
> It's a switcher; look at the caps in the LC filter (downstream of the
> series pass transistor) that, together with the inductor, form the
> energy storage mechanism of the power supply; check the source supply as
> well.  The fact that it eventually comes back suggests that the
> reference, comparator and pass device are probably functioning.
> Should be, as long as the machine isn't running in extended logical
> address mode (my DCC has a front panel switch to enable/disable this
> feature).
> Nice job on getting the machine to boot!
> Cheers,
> Chris

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