The SPERRY UNIVAC UTS 40 system + 8406 double-sided diskette subsystem : Restoration
dce at skynet.be
Thu Aug 10 13:07:15 CDT 2017
After talking about this subject but in a thread following a sale -
http://www.classiccmp.org/pipermail/cctalk/2017-July/036578.html - I
decided to start here a thread but this time fully dedicated to the
restoration of this rare computer, I named the SPERRY UNIVAC UTS 40 and
its Subsystem 8406 (2 X 8 "DSDD).
I take the opportunity to show you the 4 motherboards of that beast in
The CPU board
The communication board
A memory extension board
And a - I don't know exactly - board
(Any information ?)
In the other thread some topics were discussed, I will copy some part
here in the idea of grouping these information.
This machine has an historical importance for me. I have an
unforgettable memory of the data center in which my father worked. He
sometimes took me with him in the early evening to start some procedures
to be done during the night (process, tape backup, printing), my father
worked on a UNIVAC 9200 II and then on a SPERRY UNIVAC 90/30. I remember
the look of this big room in the dark, it was beautiful like a Christmas
tree ;-) (that's what I was saying when I was five).
Me in 1980 at 6 ... yes, I had hair like the kid in the movie "Shining" ;-)
I even remember the exact configuration of the 90/30 : 3 X disk pack
drive of 30 MB each, 3 X nine track tape drive Uniservo 10/14, a punch
card reader/writer, a frightening and noisy drum printer, an indefinable
number of UTS20D terminals, a beautiful Uniscope 100 that was standing
next to the control panel on the central console, and a little bit later
(1983) ... a UTS 40 and its subsystem. All these beautiful machines
shone in the darkness of this data center during the night, it was
beautiful, there was also the characteristic smell of hot machines in
these places, well ventilated but smokers allowed. It is indeed of this
time that I come to me an attraction for the technology and mainly for
computers, preferably big, imposing and spectacular.
In 1987, my father acquired a VAX 8350 (3 X CPU - 6 X RA82H - 2 X TU81
plus - a lot of VT220s and one VT340), progressively they started the
migration from the 90/30 to the 8350, some part of the 90/30 are been
progressively decommissioned and I received sometimes some gears. Notes
that at the age of 14 I had only an Amiga 500 and a Commodore 64, when I
received the UTS 40 and its subsystem 8406 (with a UTS 20D bonus) in
1987 from my father's hands, I considered this computer as my first
"serious" machine. Besides the sentimental value through the paternal
donation, this machine evoked me the loved mainframes and computer
terminals from my childhood.
I used this machine from 1988 to 1999 (the date of the breakdown). I
wanted to give it a major utility in my own "data center" and under CP/M
I coded in BASIC a program to manage a database, a kind of big
help-memory-reminder, in which I noted all that passed by my mind, a lot
of funny stuff, dreams, projects, technical stuff, music annotations,
Here I was 16 and so happy to have fun with my dear UTS 40 ^_^
My UTS 40 was ON every day and I used it constantly, the machine seemed
indestructible however after 20 years of good and loyal services it
began to show signs of fatigue. I had sometimes an error message during
the POC TEST at initialization (RAM or ROM error, I can not remember).
At this time I incriminated my brave cat who was watching me tapping on
the keyboard and sleeped regularly on the top of the screen that served
her as heater, thus blocking the normal ventilation of the machine.
Important thing : after a POC test error asimple reset was enough to
restart the machine.This can be a useful data regarding components that
were tired at that time. In the case of an eprom that breaks down, the
change from the operating state to the non-operating state is direct, is
it not? (i mean, without return possible to an operating state).
Anyway, one day I turned my UTS ON and instead of the POC TEST and the
short BIP, just a long "BEEEP" and nothing on the screen. As I
remembered the RAM / ROM issues displayed via the POC TEST, I suspected
the ROMs on the "program cartridge". In fact I knew a lot less
electronics compared to today. Fortunately I had printed all of my
writings with the Manesmann-Tally dot matrix printer that was connected
to the machine shortly before the failure.
I finally decided to try (again) to resurrect this machine.
Two weeks ago, the situation was:
- The blank screen + long tone (the situation in 1999) permanently
replaced by a blank screen without sound alert.
- Swollen capacitors in the power supply board (which is also the CRT
- A broken/burned Molex type 14-pin connector, the connection of the PSU
to a junction board on which is inserted the 4 motherboards of the computer.
- Missing battery on the CPU board and some traces of corrosion.
- Power supply problem in the 8406 disk drive subsystem which does not
start anymore, "fibrillation" of the LEDs.
- The belts of the two 8-inches disk drives model M2894-64D are melted.
Since then, here is what I did:
- Cleaning of all connectors.
- Replacement of the suspicious capacitors of the PSU board.
- New links between the PSU and the junction board to eliminate the
broken/burned connector from this path.
After these various repairs I returned to the situation of 1999, again a
long tone with blank screen, it's a good thing in fact but because I
still had some doubts about the state of the PSU and also about the
electronics associated with the screen display, I connected the
motherboard of the UTS20D, this one displays a perfect image and a POC
test successfull. Thus the PSU and the display is working, YES :-) ...
but well .. there is only one motherboard in a UTS20D, thus i don't know
if this test is a complete confirmation of a good PSU.
- Cleaning of the corrosion due to this battery which had leaked.
- Cleaning of the CPU board (IC sockets)
- Creating of a a clone of the missing battery stack. I discover on
internet a battery to sell for an UTS20, the voltage mentioned : 2,4V.
- Checking the capacitors of the CPU board (except a little bit out of
value, all were good)
Unfortunately I'm still at the same stage.
because I always suspect the cartridge program from the beginning,
that's why I decided to buy the UTS 40 which was on Ebay, this one Is
finally on the way and I should soon receive it. In the meantime I
concentrated on subsystem 8406.
- Cleaning of rubber residues
- Replacement of the belts melted, waiting to find better I used big
elastics, wide, thick and flat. Je trouverai mieux plus tard.
- 8406 PSU Inspection
Here I am blocked. I am not an electronics engineer, so I repair by
deduction and I have always encountered a big problems with switching
power supplies in general. Without diagrams, in case of discreet or
vicious breakdown I am very quickly limited by my lack of academic
Maybe you could also guide me here. Without the drives connected I have
the right voltages: + 24V, + 5V, -5V, except the + 12V and -12V which
are at + -3V. In this case the controller seems to be started, the LED
power lights up and briefly a "CHECK" LED (normal). With the drives
connected all led blinks quickly and very weakly, like a fibrillation.
Primary or/and secondary stage of that PSU, I do not know. Pseudo "good"
I checked with my ESR meter, all the capacitors, numerous diodes, I
checked the two Darlington transistors, I found no breakdowns. Visually
I do not see anything abnormal. But yeah .... without schematics ...
Finally, I get to the point of doubting my ESR-meter. I read a lot of
documentation that roughly said, yes the ESR meter is a good tool but
when the capacitors are not in real charge they do not behave in the
same way. What do you think of that?
Here is in green everything I tested and in sepia the untested components:
When I receive the other UTS 40 I will be able to make comparative
tests, to make sure that the battery is of good voltage, if the program
cartridge is incriminated or not, hoping that the design of this UTS is
not too different from mine, I can test everything independently. Hoping
also that this UTS did not have exactly the same breakdown as mine.
All information are welcome !;-)
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