Monday, September 9, 2019

Building a Power Supply for a DG Nova / DSS-116 from "scratch"

To keep costs down, I'm going to attempt to start with a modern ATX power supply (and likely 2 or 3 laptop power supplies), and attempt to adapt it/them, simply because I have such a surplus of all of these.

The DG Nova power supply apparently consists of these voltages:

+11v (Front panel lamps only?)
-15v (Optional for customers only?  What does that mean?)
+/-15v Oscilating at 60hz/50hz from the source AC power line input, 30v peak-to-peak
+5V OK   7-8vdc?
PWR FAIL 3-4vdc?
MEM OK   3-4vdc?

Here's some golden information in the 1969 DG Nova Maintence Manual on power signals.
And yet more, somewhat differing information on some/all of the same power supply outputs, in the Technical Manual for the Nova 800 Volume I, page 4-47 (starts at the bottom of 4-46 and goes all the way through 4-50.  Almost all of this seems relevant for creating a power supply from scratch)
The "P2" "lower power supply" connector on this backplane is mapping out as follows:

Well, it ALL depends on how you number the pins on this connector. Are all of the even pins on one side, where all the odd pins are on the other?  Like all of the board backplane connectors? NO.  Turns out that there's inconsistency with the numbering scheme on the backplane.  Some connectors are the all-even side and all-odd side, and others are sequential each side, and then back to the top on the other side where the sequence continues...Talk about confusing!

P2, the main (lower) power connector to the backplane, where the resistor board connects the power supply to the backplane:
01-05 +5v 
06    A9  on Slots 2-12 RINH
07    A11 on Slots 2-12 RINH
08    A15 on Slots 2-12 RINH
09    A13 on Slots 2-12 RINH
10    A19 on Slots 2-12 RINH
11    A24 on Slots 2-12 RINH
12    A28 on Slots 2-12 RINH
13    A25 on Slots 2-12 RINH

14    A27 on Slots 2-12 RINH

15    A29 on Slots 2-12 RINH

16    A23 on Slots 2-12 RINH

17    A21 on Slots 2-12 RINH

18    A17 on Slots 2-12 RINH

19    A18 on Slots 2-12 RINH

20    A7  on Slots 2-12 RINH
21    A5  on Slots 2-12 RINH
22&48 +15v to A10, B46, B84 on Slots 2-12  )
23    POWER FAIL to A5 on Slot 1
24    MEM OK to A9 on Slot 1
25    +/-60Hz AC to B6 on slot 3 
26    Lamp Ground (to P1 pin 40)
27-31 +5v
32-47 Ground
48&22 +15v to A10, B46, B84 on Slots 2-12   
49    -15v "available as a customer option..."
50    +5v OK to A8 on Slot 1 (so is this high or low in an OK state?)
51    -5v unreg. to A6, B81 on Slots 2-9   
52    +15v unreg. LAMP (to P1 pin 33)

There's nothing on the backplane other than a "1" by pin 1, so unless you figure it out through trial and error, you'd never know which way the pins are numbered!  Thus my numbered image above.

From my video below, I mention missing power supply connector "resistor" boards also.

I MAY have found one of those here on bitsavers...
And then, for schematics for these power supplies, first, from my own site right here, I've posted 2 books full of schematics, and here's 12 schematic excerpts that may be relevant  (warning, 11Mb file)

And more continued below.....
So HERE'S one of the power supply connector board schematics!  I think it's the "upper" one, but I"m not sure...  Download the highest resolution here
And here's the the whole set of power supply specifics (schematics 
You might want to right-click and download instead of just clicking, because it's 
Now, from Dominique's power supply repair (that he chronicles on the CCTalk email group)

Below is the
Backplane to Front Panel connector 
(NOT to be confused with any P1 designation to the power supply)

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