Schedule December 2008

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Wed Dec 3 - General, Thurs Dec 4 - tape team
Wed Dec 10 - General, 1401RFI-Music, Thurs Dec 11 - tape team, Sat Dec 13 - 4th Sat
Wed Dec 17 - General, Thurs Dec 18 - tape team
Merry Christmas :-)) , Sat Dec 27 - 4th Sat

Wed December 03 - general

Thursday December 04 - Tape Team

from Bob Feretich
TAU Debug Status - 12/4/08  (Jeff S., Sam S., and me)

We last worked on the CT system 3 weeks ago. The "Skew Error" problem that we saw then was back today. We traced the error to the Emulator. It was dropping "Ready" too early. I don't know why we didn't see this problem on the German system. We delayed the drop by 400 uSec and the error disappeared.

CT System Status:
  • Hand entered magnetic tape read and write loops work.
  • We successfully booted a program from an Emulated Tape Drive. Note that we had to preload the instruction address register with 0001 for it to work. It appears that the "Load Tape" button does not force the instruction address register to 0001. (A bug.)
  • We wrote an Autocoder Tape-to-Tape copy program and tried to run it with the Emulator emulating three tape drives, boot drive, source drive, and destination drive. When we ran the program everything crashed. A bug in the program resulted in trying to write very long records to tape (>2k). The Emulator can only handle records less than 2048 bytes long (there is only 4096 total bytes of RAM on the PIC module). Given the limited memory size of the 1401, we didn't think that this would be a problem, but we don't know the physical record lengths of the moon dust tapes. (Typical physical record lengths through the 1980s were 800 to 1600 bytes.)
  • The Emulator truncated the records to 2K characters, but the Windows USB drivers use 1024 byte buffers. The driver code that was to handle records spanning multiple buffers didn't work. (The code was never tested.)

[ an internal comment ]

Bob Feretich

Wednesday December 10 - General

  • Present were: Ron Williams, Bob Erickson, Bill Flora, Frank King, Allen Palmer, Glenn Lea, Joe Preston, Stan Paddock, Ron Crane, Ed Thelen and Robert Garner.
    Kirsten Tashev and Dag Spicer of the museum staff smiled as they came to visit us. The timing was fortunate - everyone was looking busy!!
    I told them that we are just like puppy dogs, we like to have our heads patted.

  • Frank King was able to get the CT 1403 printer to print a little. He took pictures of 1403 chain and print slugs to help discuss the strange dots on the printouts last Wednesday -

  • Allen Palmer and Glenn Lea worked on the second 729 mod 5 tape drive. Allen found why it wouldn't do a high speed rewind. The thermal cutout on the coils of rewind motor did not reset properly - from a previous heating due to a logic failure (or forgotten power supply regulator card?) A tap of a screw driver released some hang up in it, the circuit was restored, and all better now :-))

  • Radio Music - 'IBM 1401 memory music' finally came to our 1401 - Robert Garner found a 1401 card deck/program on e-bay that made musical radio noise - Hold an AM radio (tuned away from a station) near/on a 1401 running this (or many other programs we may/maynot have) and listen to the radio or click here to see and hear compressed file. .wmv file, YouTube version. (The compression hurt the video, but not the sound. The sound is NOT concert hall quality!!)
    (Added Dec 22) - Jóhann Gunnarsson, of Icelandic "IBM 1401: A User's Manual" music fame, has identified the tune as "Wheels". He e-mails " It can be found in various versions on Youtube, for instance performed by Chet Atkins:"..
    (Added Dec 23)
    I appealed for help
     "Unfortunately I don't know how to give it a good category
        One can say "1403 Chain Printer Music"
        But the best I can come up with for music generated by 
            Radio Frequency Interference
                from a 1401 is
           "1401 RFI Music"
        which is an even a less lovely name than "Chain Printer Music"
    The whole field of "computer music" seems to beg for more descriptive names:
          - computer composed tunes
          - audible music caused by actions of a computer by
                 - printers of various kinds
                 - a loud speaker connected to various parts of a computer circuit
                 - Radio Frequency Interference
         - and probably many categories I have forgotten"
    Jóhann Gunnarsson responded with:
    "Regarding descriptive names for this kind of music, I have always connected it with the magnetic core memory. The music pattern, pitch and length of notes is after all controlled by what is going on in the memory.
    "If I remember correctly, in order to get best results we used to put the AM radio right on top of the memory module. I vaguely remember that we could hear RFI noise from the IBM 1620 as well, although we never really tried to find out how to play it.
    "In my opinion, 'IBM 1401 memory music' is quite a descriptive name for this phenomenon."

    Jóhann's comments, above, seem good to me:

    1. A major source of the Radio Interference is likely the core memory. To make our "coincident current" core memory work, two sizeable currents ( X and Y currents, about 1/2 amp each) need to be started and stopped suddenly. These take large paths in the core memory area (useful to radiate magnetic pulses efficiently).

    2. The IBM 1620 at Computer History Museum had its memory in a temperature controlled metal box (a long story). The metal box likely shielded much/most of the RFI that would otherwise escaped to be received elsewhere, like by radio near the memory.

  • A theme for this section could be "1401 Control Panel Lamps", hosted by Ron Crane -
    Ron Crane reminds me of C.T. Winter at General Electric Computer. Charlie never hurried, was never slow, (like a bull dozer driven by a pro.) He analyzed carefully and thoroughly, any changes documented carefully and completely, and when he fixed something, you had confidence it was better than new and could never be troublesome again!

    The panel lamps of "our" 1401s have never worked visually well. Some adequately bright, some faint, and some you cocked your head, squinted at, and more or less said it looked ON (or OFF). And some of the control buttons were not back lit at all - giving a ragged appearance.
    Ron Crane apparently decided to "Make Them Right".
    Some of the problems he found included:
    1. About 50 percent of the installed indicator bulbs were wildly wrong, rated at 6 volt 150 ma. instead of the specified 10 volt 40 ma. lamps. (This could have been due to fit problems in replacements discussed below.)
    2. Some of the indicator lamps could not be pushed in all the way.
    3. The sockets behind some of the control buttons were distorted/mashed so that no lamp could be installed.
    Ron made this document clarifying the correct lamp to use for the indicator bulbs. And a picture of the correct lamp. (The reamer at the bottom will be discussed below.
    Unfortunately, the current production of this lamp, especially from "off-shore" is a few thousandths over size - sometimes making a too snug fit in the plastic two part holders, especially if mis-aligned or incompletely de-burred.
    The incorrect replacement bulbs were slightly undersized, and fit well into the German (DE) 1401 lamp holders.
    This is back of the German (DE) indicator panel. Note the misalignment between the front and back sections, and the strangely unfinished plastic in the holes. This made compete insertion of off-shore lamps impossible with out a little reaming. The reamer Ron used to clean and enlarge(re-align) the holes. The (later production?) CT 1401 has no such problems
    Ron showed me tables resembling the following:

    Tungsten resistivity is 52.8 Ωm at 20 °C, however as temperature increases, also does resistivity.


    R/R 300 Temperature
    R/R300 Temperature
    R/R300 Temperature
    1.00 300 7.14 1500 14.34 2700
    1.43 400 7.71 1600 14.99 2800
    1.87 500 8.28 1700 15.63 2900
    2.34 600 8.86 1800 16.29 3000
    2.85 700 9.44 1900 16.95 3000
    3.36 800 10.03 2000 17.62 3000
    3.88 900 10.63 2100 18.28 3000
    4.41 1000 11.24 2200 18.97 3000
    4.95 1100 11.84 2300 19.66 3000
    5.48 1200 12.46 2400 20.35 3000
    6.03 1300 13.08 2500 - -
    6.58 1400 13.72 2600 - -

    R300 -Resistance of tungsten filament at room temperature
    R -Resistance of tungsten filament when hot.
    Temperature -average temperature of filament. There are hot spots near the middle and cool spots near the support leads.

    Using the resistivity ratio above gives the temperature of the filament, which gives spectoral info. from
    Using percent rated voltage,
    Output vs. life

    output vs. watts
    Ron has a catalog giving the illumination out of a 1/4 inch hole in front of the lamp. There are three common filament configurations - the best for illumination as indicators being the "v" configuration a plane parallel to the front panel

    Ron wanted to know if the excess current through the lower resistance lamps "cooked" the series resistors on the lamp driver cards. This is of a dedicated driver card circuit resistor which had driven one of the low resistance lamps (photo using overhead illumination). Hard to tell if card had been overheated - This is a STorage Address Register (STAR) card circuit resistor which had driven one of the low resistance lamps (photo a flashlight for illumination). Easier to see that both the resistor and card have been overheated a little. (The resistance was within specification.)
    Here is Ron at work - reaming the DE 1401 Examining and prying the lamp contacts in the Check Reset switch of the CT 1401. They were mashed and maybe not repairable? This is the correct lamp (no problem) for the button switches on the panel of a 1401

  • Bob Erickson, Joe Preston, Glenn Lea continued to work on the 1402 Card Reader - Regular work day almost done - Who was it said -
    The job's not done until the paper work is complete?
    Ron Crane and Ed Thelen continued on to 7:00.

    Wednesday from Allen Palmer
    worked on German #1 … problem was failing to go into hi-speed rewind. Found that there is a thermo-interlock in the circuit. Took awhile where it was, it is on the outside of the hi-speed motor against the windings. Removed the motor but there is no way to replace the switch. Tapped the switch capsule ‘gently’ with a hammer and the bi-metal strips released. Reinstalled motor and hi-speed rewind function now working again. Ed has a picture to add to the report.

Thursday December 11 - Tape Team

TAU Debug Status - 12/11/08  (Jeff .S, Sam S., Ron C., and me)

We fixed a bug in our Autocoder tape copy program that was writing accidentally very very long records.

We troubleshot the I-STAR load bug. (The "Load Tape" button was not loading it.)
It turned out that just bit 4 in the hundreds digit  was not getting reset. We replaced that STAR card and the problem went away.

We were then able to reliably run the below scenario:
  1. Define tape drive 1 to map to the PC object file that we wanted to boot and run. The program was a tape-to-tape copy program that copied records from drive 4 to drive 5.
  2. Define tape drive 4 to map to the PC text file to be copied. An ASCII text file that contained only legal BCD characters.
  3. Define tape drive 5 to map to a scratch file on the PC.
  4. Press the "Tape Load" button to successfully load and execute the program.
The CT 1401's tape subsystem is now "mostly working". There are several things that we haven't  checked out yet (odd parity, backspace, etc.), but there are diagnostic decks to test these functions and it would be inefficient to try to check these functions out without a working card reader and printer. So, we are going to turn our attention to improving the stability features of the emulator.

Emulator bugs and enhancements:
  •  It has problems with records of more than 1000 characters. We need to make some changes to make it operate with its maximum 2048 character records (PIC RAM limitation).
  • The "Load Rewind" button on the virtual operators console does not rewind a virtual tape that has been previously read or written.
  • Under some circumstances closing a virtual tape drive causes the web application to crash.
The other operator controls need further testing (tape density controls and tape indicator status).

We also want the Emulator to work via wireless intranet from a student's notebook computer. We were able to run the Emulator today wirelessly from my notebook computer, but it would be easier if certain changes were made. Jeff will publish a request for CHM IT actions to simplify this connection.

Bob Feretich

from Sam Sjogren, Dec 12
Bob forgot to mention the successful testing of the new optical interface between the tape emulator and the 1401. Photos attached.

Saturday December 13 - 2nd Saturday

Wednesday December 17 - General

Tuesday - These are some of Ron Williams' pictures - scanned by Stan Paddock -
Ron Williams is spraying? some of this secret sauce on a 1403 printer ribbon. Rumor has the recipe of this jungle juice is 2/3 "mineral spirits" an 1/3 regular motor oil. Ron says his lawyer has looked into all Ron's contacts and firmly denies any wrong doing, in spite of rumors of carbonized bat wings and toads. The theory being that the ribbons already have enough black die (carbon??) in them, but need more liquid.
The following pictures were taken several weeks ago - see
here for the start of the action.
This is the card path, minus the read and check read brushes, in the CT 1402 card reader. This is the "before" picture of the 14 thousandths concavity of a roller. Ron took the roller home, heated it to 200 F. for three hours. It swelled up 20 thousandths of an inch. (Conavity 26 thousandths) Here is the roller in the lathe -
to have the expanded material removed, leaving a cylindrical roller of original dimensions. And here is the "after" picture. Apparently the cards moved more smoothly and remained better in line after this roller treatment. But - now there are apparently electrical or logical problems preventing proper card reading using the CT machine.

Thursday December 18 - Tape Team

from Bob Feretich
TAU and 729 Debug Status - 12/18/08 (Jeff S., Sam S., Allen P., Ron C., & me)
First, using the CT System, we verified  bug fixes that were developed over the last week.
  • We were able to successfully write and read 2000 character records between the 1401 and the Emulator.
  • We verified that he "Load Rewind" button on the virtual operator's panel really performed a rewind.
  • We were able to close() virtual tape drives from the emulator without crashing the Emulator.
  • However, once all the tape drives have been closed, we can not reopen a drive without reloading the driver. More work needed here.
  • The "Load Tape", "Tape Read", and "Tape Write" operations on this machine are stable. The Tape-2-Tape copy program works first time/every the time.
Allen noticed tape errors being reported by the German System:
  • We found and fixed a bad card in the TAU R/W Reg parity tree. We can now successfully run "Move Tape" and "Load Tape" diagnostic programs again.
  • However there still seems to be a problem with multiple consecutive Backspace operations. When a program performs four, only two seem to be performed. ???
While we were working on the German System, the smell of burning electronics started to fill the computer room. The odor was coming from the CT 1406 Storage Unit. We found that the the Fan Circuit fuse (F7 in the 1402) had blown and all the fans on the CT system had stopped. The whole system was overheating, but the 1406 seemed to bear the worst of it. While we were searching for the root cause, we dissembled and examined the 1406 fan assemblies. In one of the  assemblies, between the fan and the top row of cards, we found a roasted peanut shell (photo below). We are not sure if the peanut was pre-cooked or slow roasted over the years by the 1406.
We removed the shell and replaced the fuse. The 1401 powered up and ran OK. However, we did not have any programs that would test the 1406.
We will resume testing on January 8th. Merry Christmas & Happy New Year to all.
When we resume, we will move the Emulator back to the German System. We are ahead of the 1402 and 1403 bring-up. More advanved bring-up of the CT Tape Subsystem is inefficient without a functioning printer.

Bob Feretich

Thursday from Allen Palmer
Worked on the German #2 drive.

  1. The ‘supply-side’ capstan motor was making some bad noise.. pulled and replaced. Problem solved.

  2. When pulling out the capstan motor noticed that there was fine coat of gray powder. It was from the rear clutch unit. Not sure if it is problem (a steady leak of magnetic powder) or just a ‘break-in’ temporary problem. Will watch and if necessary will have to pull the whole clutch shaft & replace it. Hope not to.

  3. There is good news.

  4. The drive is now fully mechanically operational.

  5. Connected drive to TAU through Drive #1 ….( TAU à Drive #1 à Drive #2 à terminator shoe on Drive #2.)

  6. Full mechanical and program control from TAU panel and Main Frame programs to both drives.

  7. Other than the problem Bob reported both drives now on line and functionally ‘up’

  8. Next thing is to write to Drive #1 move the tape to drive #2 and see if we can read it. (R/W compatibility)

Please note. I will not be coming to ’’work’ ’on Wednesday since all mechanical work is finished and now ‘read/write’ debug which is best done on Thursday with emulator team.

I do ask that from now on nobody try to fix any problems that come up either drive. Just either call me/send an email or leave a note on the machine and I will fit it when I come in. Reason is that I want to have one-person maintain the drives from here on until we have them running perfectly.


Saturday December 27 - 4th Saturday

[ from Stan Paddock ]
Ron Williams, Bob Erickson and his son Dean, Bill Worthington and Mike Cephonis all came in today.

Bob brought in a Teletype ASR 33 like mine. It belonged to his neighbor. I spent some time on it and got most of it working. He also brought in several, never been used, ribbons for the TTY. They are dry.

We have at least a dozen rolls of paper tape and 5 boxes of fan fold paper tape which I gave to Mike. His PDP1 uses that stuff.

The CT machine is really acting funny. Put the machine in Alter and store a byte and the printer prints a line of that byte. (byte = BCD character) That byte is not in the print buffer.

I am not sure, but I think the machine had a stroke coming from the East coast to California.

There is a possibility that the problems with the printer and the card reader may be related.

Of course, there is a possibility that Elvis is still alive.

Bill Worthington and I ran my simple tape test of 729 #1 of the DE 1401.

As in the last try, the error count was appraching 50%.

Bill said "Have you tried a new tape?"
The answer was no.

We took a tape from the back rack and put it on.
Out of 8000 records, 14 recorded an error. .175 %
It appears that the DE #1 79 is ok.

I am headed for Carson City in the morning. I will be back in the shop on Wed the 7th, the good lord willing.

Have a happy new-year.


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