The SPERRY UNIVAC UTS 40 system + 8406 double-sided diskette subsystem : Restoration

Dominique Carlier dce at
Thu Aug 10 13:07:15 CDT 2017

Hi everybody,

After talking about this subject but in a thread following a sale - - 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 
details (hi-res)

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, 
poetry... ;-)

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" 
capacitors ?
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:

Any suggestions?

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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