Investigation into access to magnetic tape transports:-
Of the four Ampex Type 3 decks we have connected to flossie
the attempts to power them up gave us the
following results:
Deck A = Tight / Locked lower servo motor ( investiage later )
Deck B = Loaded tape runs forwrds / reverse and responds to
read, rewind and unload commands. ( Good Deck this one )
Deck C = Loads up tape, responds to rewind, and unload commands.
No response to any other commands and just goes busy.
Deck D = Loads tape, has a servo problem with the upper reel
Drive and needs the forwrds Pinch roller assy adjusted.
tried to resolve the servo problem on the supply reel, but had to postpone
till next visit
So using the best deck from above, we investiagted just
what we could and could not do with the tape control logic
Attempts to read do not transfer any intelligent data into
the machine but the transfers do finish and we tried to run
a simple loop, which included testing the deck ready indictor,
doing a read order, and repeating the loop. This ran perfectly
provided we ran it one instruction at a time, in manual mode.
However any attemts to run this in auto mode, gave us corruption
of the program code. After much head scratching we found that
we had isolated the Control register shift timers whilst
fault finding last year, at 6E3 Pin 13. Restoring this gave
us data input into store, blocks of about 120 words could
be read in but the program corruption problem continued.
This problem has been traced to bay 22, where 22B23 pin 22 there is another
level from the 1900 series standard interface signal comes in,
isolating this gave us a reliable program loop, so we closed
the day with a successful run of the following little loop !
With our one working deck allocated to deck address 3
000 = 834001 004000 ... / wait for Deck 3 Ready
001 = 724002 004000 ... / wait for read unit ready
002 = 390023 000400 ... / read a block into store at address 400
003 = 834001 004003 ... / wait for Deck 3 ready
004 = 724005 004003 ... / wait for read unit ready
005 = 390053 660100 ... / Rewind deck 3 and increment count
006 = 370100 004000 ... / display count in B Reg and loop back.
This loop reads a block, rewinds the tape and displays a
count of how many times it has done the loop. We held our
breath until the count had reached over 50 and then decided
we had actually fixed the problem.
Next visit is with feeler gauges and allan keys to set up the
rest of the Tape Decks. I felt very bouyed up as most of the
tape control unit was working. But we still need to actually read the data from tape
some time ! So we are getting ready for a battle with the DTU !
15th Episode:-12/5/2004
Continued work on store units:-
Barn Door 3 lots of differing errors
Barn Door 4 Acting dead.
Much work on this store including changing
a G1 unit in 10E17 ( decoding unit ) until we finally located
an addressing problem where decode 80/180 and 90/190 were both
comeing up together. This seems to be within the structure of the
door, and much time was spent tracing wiring on the printed circuit
strip panels which run the length of the lower part of the core planes.
Ended this session with a rather blank feeling as the progress had
been zero. We still have Barn Doors 3 and 4 to fix.
Lots of boards are on temorary connectors in this barn door.
However these two bard door's have never worked since the start of the project,
so we have only to fix them once and hopefully they will stay fixed !
14th Episode:-
More work on store units and lots of data bits dropping out:-
Digit 7 Bit 1 + Digit 5 Bit 8 + Digit 7 Bit 2 all failing,
so much sorting of duff A7,s ( store read/write anps ) and we had
reliable access to some store, with a duff -6.3 volt Fuse ( 20 amp )
blown on the way !
We are now down to a single duff word in barn door
2 ( much time spent wiring in the " SPARE " core word on the Store
Plane ) after many tries we re-read the manual and remembered to wire
in the ground connection to the spare address line, we now have a working
second store unit. We can run a small loop of move ( 45 ) orders and
the store does not give parity failures.
The day closed with us trying to run "Ghost" but we
may have a problem with Function 69 ( multiply ) so ghost just produces
a boring single note in the speaker. I bet this is micro orders again,
but only time will tell !
13th Episode:-
Programed indicator tidy up!
We have had problems with two of the
programmed indicators since this project started. Over a coffee before
we started, it was decided that we would indulge ourselves and just
fix these indicators, before we did any more work.
PI 11 turned out to be 7E9 binary u/s = replaced,
and PI 12 was the 7E10 binary , now all ok ! And a big boost to our confidence.
There are still problems with access to the store units, work around
the IAS timing generator resulted in changing the Binary in 10E8 and
Invertor in 10E9 these gave us correct IAS timing and timing signals
W1 and W2 are now correct, Still no access to any store. Checked all
voltages and found 18 volts unit fuse blown.
We can bow run a loop in the first barn door, Much jubilaton
followed! we had access to Bard doors 1, 2 and 5 but word 518 in
Barn door 2 was a solid fault.
12th Episode:-
The First Power up 2004 ( no smoke ! No big bangs ) But the machine is stuck
in micro orders !
30 mins later, during which we checked all fans and
power supplies. The system started to run, but with problems.
Found Binary in 3B17 duff ( not adding one to Control register ) Now OK
but still no access to store at all. Traced to 3E17 Pin 3 duff, also
A1 package in 6F7 and G3 in 6F8, Now able to get some instructions
into the control registers. Well as a start in 2004 it could have
been worse, but we will have to get flossie back to where we left
her last year.
Most of the things we fixed last year do seem to be working, so not a bad 1st day in 2004.