Hi all,
I continued my investigations about the power supply if the 8406 subsystem.
Here is what I observe:
With the PSU in charge, I mean with a disk drive connected but without
the +24V :
+5V -5V +12V -12V: OK
If I connect the +24V to the drive this is at this moment than the power
supply goes mad and sends erratic alternating voltages to the + & - 5V
and + & - 12v.
The question remains complete, which is the guilty component? :
http://www.zeltrax.com/classiccmp_forum/uts40/subsystem05.jpg
Is it possible that rectifier diodes become mad only when they have a
significant load? Or is it finally a faulty capacitor that a ESR-meter
can not detect as broken when is it not in charge?
Dominique
On 10/08/2017 20:07, Dominique Carlier via cctalk wrote:
Hi everybody,
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).
http://www.zeltrax.com/classiccmp_forum/1.jpg
http://www.zeltrax.com/classiccmp_forum/2.jpg
http://www.zeltrax.com/classiccmp_forum/3.jpg
I take the opportunity to show you the 4 motherboards of that beast in
details (hi-res)
http://www.zeltrax.com/classiccmp_forum/uts40/4boards_presentation.jpg
The CPU board
http://www.zeltrax.com/classiccmp_forum/uts40/cpu_board.jpg
The communication board
http://www.zeltrax.com/classiccmp_forum/uts40/communication_board.jpg
A memory extension board
http://www.zeltrax.com/classiccmp_forum/uts40/memory_extension_board.jpg
And a - I don't know exactly - board
http://www.zeltrax.com/classiccmp_forum/uts40/unknown_board.jpg
(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" ;-)
http://www.zeltrax.com/classiccmp_forum/uts40/dce1980.jpg
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 ^_^
http://www.zeltrax.com/classiccmp_forum/1989.jpg
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
board).
http://www.zeltrax.com/classiccmp_forum/uts40/psu01.jpg
http://www.zeltrax.com/classiccmp_forum/uts40/psu02.jpg
http://www.zeltrax.com/classiccmp_forum/uts40/psu03.jpg
- 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.
http://www.zeltrax.com/classiccmp_forum/uts40/broken_connector.jpg
- Missing battery on the CPU board and some traces of corrosion.
http://www.zeltrax.com/classiccmp_forum/uts40/cpu_accu_position.jpg
- 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.
http://www.zeltrax.com/classiccmp_forum/uts40/new_connection_and_capa01.jpg
http://www.zeltrax.com/classiccmp_forum/uts40/new_connection_and_capa02.jpg
http://www.zeltrax.com/classiccmp_forum/uts40/new_connection_and_capa03.jpg
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)
http://www.zeltrax.com/classiccmp_forum/uts40/cleaned_cpu.jpg
http://www.zeltrax.com/classiccmp_forum/uts40/cleaned_cpu_w_accu_connector.jpg
- 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.
http://www.zeltrax.com/classiccmp_forum/uts40/new_accus01.jpg
http://www.zeltrax.com/classiccmp_forum/uts40/new_accus02.jpg
- 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.
http://www.zeltrax.com/classiccmp_forum/uts40/uts40_wont_boot.jpg
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
http://www.zeltrax.com/classiccmp_forum/uts40/subsystem01.jpg
http://www.zeltrax.com/classiccmp_forum/uts40/subsystem02.jpg
http://www.zeltrax.com/classiccmp_forum/uts40/subsystem03.jpg
http://www.zeltrax.com/classiccmp_forum/uts40/subsystem04.jpg
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
knowledge.
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:
http://www.zeltrax.com/classiccmp_forum/uts40/subsystem05.jpg
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 !;-)
Dominique
