Monday, September 29, 2014

Repaired the delay board and prepared to use it to replace the original time delay relay in the disk drive

1131 INTERNAL DISK DRIVE RESTORATION

I ran out to a local supply shop to pick up the surface mount timer chip then installed it into the delayed on relay board that was broken when I received it. The bad behavior continued. I then traced the circuit to figure out what they were attempting and from that to determine what was wrong.

It appears that the through holes near the potentiometer don't have enough clearance around the internal ground plane, so that some boards are shorting one of those pins, causing the circuit to be reconfigured into the astable (cycling) mode.

I planned a way to wire around it - removing some components and connecting them differently to set up the right circuit wiring. When I wired in the planned component values - 1000uf capacitor and 100K resistor - the timing came in close enough to target that I don't need to tweak the part selection.

Resistor and capacitor wired around the flawed circuit board traces
The target is 90 seconds before the relay turns on, and the board as it sits activates after 100 seconds. That is close and on the safe side (longer means more time for disk platter to adjust to the air temperature inside the drive).

This replaces the original, malfunctioning relay in tight quarters in the AC power box of the disk drive. I attached the relay board to the mounting bracket removed from the relay. It fits in the intended space.

Relay mounting bracket used to hold delay board in place
Before I install this, I need to put together a resistor voltage divider to drop the 48VDC input down to the 12V that the relay board uses, cut the spade lugs off the existing wires and attach them to the terminal blocks on the board. Once that is done, it can be put into place and the drive closed up.

I had to spend most of today preparing for my business trip tomorrow morning, but am pleased that I was able to revive the delay board and establish the behavior required to support the disk drive disk loading sequence. When a cartridge is in place and the switch thrown, the motor begins spinning the cartridge  and energizes our delay circuit. We hold a signal line low until the 100 seconds has expired, then disconnect the line from ground. That signal is normally grounded through the relay and only allowed to pull up high after the delay.

The disk drive electronics won't pick the disk head loading solenoid until this signal goes high, along with other required conditions such as adequate rotational speed. Now that I have a good time delay to raise that signal, it will be fully operable. More importantly, the covers can be put in place and the annoying door closed up.

1132 PRINTER RESTORATION PREP WORK

I spent a good hour with the FE maintenance and theory of operations manuals, plus the illustrated parts catalog, to discover the mechanisms I need to lubricate and check in order to get the print wheels striking the paper with enough force to leave a clean character image. No time to begin the cleaning, but that will be first up when I return from my trip.

Sunday, September 28, 2014

Finishing new keypunch interface unit, progress testing the 1132 and a bit of work on card reader and disk drive

NEW KEYPUNCH INTERFACE CONSTRUCTION

I spent many hours carefully wiring together the interface, using the connectors, checking wiring and soldering, double checking which wire I was holding before putting it on a connector. At this point, the unit is closed up but one task remains before I begin code development and testing. I have to install a power brick inside and a suitable molex power connector, then wire up the corresponding connection inside the keypunch to bring power to everything.

Wiring complete other than power brick
A lot of connections, finally complete
Wires soldered to header pins, inserted in the Arduino
Molex connectors hooked to relay board, barely visible mid-upper right

Unit closed up until I add the power brick and start testing.
I am will be unable to work on the machine from Tuesday through the following Friday due to intensive business commitments, thus will wait to do the exploratory testing and hardware checkout until I am back in the workshop.

1442 CARD READER/PUNCH WORK

My next step to get the cards moving from the cornering station to the stackers is to increase the pressure on the rollers pulling the card into the stacker area. I began to adjust the indicated screws but I need to spend more time to be sure I get this pulling more firmly. I don't want to introduce skew into the card movement, which is possible if the pressure on the two rollers is not the same.

1132 PRINTER WORK

I put in some fresh paper and reloaded the test program. I have an instruction which is supposed to decrement a counter each time I find and print one of my target letters, but the value in that counter, index register two, is not going down. After a look at the program, I realized I was using hollerith code (card reader and keyboard), not 1132 printer codes.

Instead of stopping when I get four matches, I am going to take 48 read emitter interrupts, which is one complete cycle of the print wheels. That should ensure I issue the scan codes to print in all eight of the last columns.

Running with the full 48 character interrupts gave me a satisfying sound of printing, but the page was blank. I probably have a ribbon that is so dried out there is essentially no ink to transfer. I pulled out a spare ribbon, which is about 25 years past its 'use by' date but might just have a bit of ink left. I had to read the manuals to learn how to change the ribbon, but I did get it changed.

It was definitely full of ink - got on the printer cover where I rested the ribbon spool as well as on my fingers! Running the print program again produced very slightly darker letters but only in a few spots. It appears the print hammers are likely partly glued with old lubricants and can't snap crisply into the print wheel.

Ink stains on printer top from the replacement ribbon resting there temporarily
Only some of the hammers can leave an impression, others don't strike with enough force. I also see one case where the letter D printed in the column where I was requesting to print a C. Since that is the next sequential character after the one I requested, it is consistent with a gummed up mechanism latching up too late to match the C.

The next step for this unit is to clean the old lubrication from the hammer and print related moving parts, putting on new oil and making sure it is all moving freely. Once that is done, I can try the print test again and see where I am in the restoration of this device.

1131 INTERNAL DISK DRIVE WORK

I toyed around with the broken delay board from yesterday, finding a way to get it triggering but not correctly. With the original capacitor, it worked on a 10 second delay which is too short for my purposes, thus my second set of tests were with a much larger capacitor to produce a longer time interval.

The first tests, with the 10 second time interval, were supposed to show a turn on delay, meaning the circuit should start with the relay off, wait ten seconds, flip the relay on, and stay in that monostable state while power remains on. Instead, it began latched, then each ten seconds it turned the relay off or on, alternating forever in a bistable mode. It should not be oscillating.

The second tests, with the longer interval, showed even stranger behavior. It would start out active, blip the relay off and on for less than a second, wait the long interval, then repeat the blip. Each interval had a momentary blip and a long wait. Again, not useful for my purposes.

My working assumption is that the LM555 chip (timer) that is the heart of the circuit is malfunctioning, since all the components seem to have proper values and be wired correctly. I desoldered the chip from the board, using my hot air rework gun, and will pick up a surface mount 555 chip to replace it. I am feeling hopeful that with a bit of work I can get this board doing what I want, replacing the original time delay relay in the disk drive startup circuitry.

Saturday, September 27, 2014

Activity, progress, minor complications but nothing completed today

1132 PRINTER RESTORATION

Although I hadn't achieved the printed output I wanted in the first test this morning, I was able to verify that the printer interface works well. I can start and stop print operations, get the interrupts, see correct/rational sense bits, read emitter returns valid characters, and I know it is reading the scan field because of print scan checks if the last bit of the last word is not set.

However, the tests I performed this afternoon didn't come out right either. The scan field is being fetched and there is a definite difference when bits are on - I can hear hammers firing - but I am not seeing all the columns I should and sometimes the characters are not the same. Since I am setting a nonzero pattern into the scan field for just the first read emitter interrupt and then using zeros for the rest, I should have some random character repeated in the pattern I chose.

I used a pattern of AAAA first, in the first 48 columns of the printer, but saw only five or six columns of text printed and these were not all the same character. Another test with a pattern of 5555 to exercise the alternate hammers of the first 48 positions gave similarly incorrect results.

More testing will be required to figure out what is going awry before I can resolve it. Another issue is that I have been reusing the same few pages of paper for multiple tests and see that I do have a line with most of the first sixteen columns displaying the same character ($). Therefore, I might not have the problem I thought, but it will be better if I put fresh paper into the printer and annotate each test to ensure I am not chasing phantom problems. Out of test time for today due to other obligations.

NEW KEYPUNCH INTERFACE CONSTRUCTION

I spent many hours today wiring up the relay boards, read cable connections, building the screw terminal boards to connect to the Arduino and to the relay boards, and ultimately was not happy with the add-on boards that provide screw terminal connections.

Add on boards for Arduino for screw terminal wiring - too cumbersome when installed
I yanked them off and began wiring Molex connectors to hook to the relay boards. I don't yet have a good choice for the wiring on the Arduino, but will be making that decision soon.
Molex connector being created to hook to relay boards
I did most of the mounting work for the Arduino and the DB9 serial input connector, leaving only the 'power brick' to insert and fix down inside the enclosure. Wiring of the connectors to the relay boards for the punch cable is done, but the control signals from the relay board to Arduino are dependent on that connector decision I must make.

Relay boards and connectors installed

Arduino sitting in approximate mounting location

Punch cable connector from keypunch

Reader cable connector from keypunch

Serial link connector to link to PC or other system using the interface
The common power for the punches and space mechanism are partly wired - I have a few more relay poles to add to the chain, but all the activation wiring is just about ready.

1131 DISK DRIVE STARTUP TIMER REPLACEMENT

The part I ordered to restore the disk drive 90 second timer, which is used to delay loading the heads while the drive stabilizes, arrived but was nonfunctional. About a third of the reviews on Amazon.com mention DOA units, so not a huge surprise I guess. The first problem is an open potentiometer. I scrounged up a pot from my supplies and a larger capacitor, but still get the instant firing. Likely either the NE555 IC is bad or the transistor that drives the relay based on the chip output, but this thing is useless as it sits.

Defective delay timer after replacement of first few bad components
This is strike two on what should be a simple component purchase to replace the time delay relay. The first was a unit that provides a 90 second delay for air condition and other units, but while the promotional material and store entry implied it worked for both DC and AC sources, this thing needs AC to work. It has to go into a 48V DC environment, so scratch solution 1. The broken part I received today is solution 2.

This is annoying to stretch out because I have the door hanging open in front of the disk drive, two switches dangling, and would really like this closed up and completed so I don't keep walking around or bumping into the door whenever I move around the system.

Door I can't close, waiting for time delay relay replacement, always in the way

Friday, September 26, 2014

New keypunch interface construction work and 1132 printer testing

NEW KEYPUNCH INTERFACE CONSTRUCTION

I picked up the enclosure and connectors then launched into soldering up the wiring inside the box, from the DB-25 connectors to the two banks of relays. The punch cable is done - 23 wires involved. I mounted one of the relay modules in preparation for hooking it up.

Punch cable connector wired up and one relay module installed
Tomorrow I will wire the connector for the read cable, mount the second relay bank and then wire all the relays to their appropriate connector pins. The remaining steps of wiring the read wires and a few sensing wires from the other cable to the Arduino will have it prepared for initial testing.

1132 PRINTER RESTORATION

I placed the long program in memory and cabled up the printer to do some quick testing. My first run had some flaw - I could see the printer sending the emitter interrupts telling us a new character was rotating into position on the print wheels, but I wasn't properly checking the value or setting the print scan buffer at x0020-x0027 with the proper end bit.

Printing involves the following. An XIO to the printer starts it printing. In that mode, as the print wheels are spinning, each character that comes in position to print causes an interrupt. My interrupt handler has to sense the device status, verify that it is a emitter interrupt, meaning a new character is ready to print, then set up bits for each column where that particular character should be printed. These bits are set in a fixed area of memory, locations x0020 to x0027, called the scan area. Along with the string of bits matching the 120 columns of the printer, the last bit of the scan area (word x0027) has to be set on.

The printer begins fetching the scan area words and firing print hammers in any column where a 1 bit is found. It checks the last bit of the scan area since that is proof that the software has set up the proper columns. If the bit is off, meaning a new character interrupt came to us but we didn't respond fast enough to set up the scan area, then the printer recognizes a print scan check error.

When our program is sure that there are no more unprinted characters, having already received an emitter interrupt for each character that exists in the print line, then we command the printer to stop print. That simply means it should no longer send emitter interrupts or fetch scan words. At this point we can ask it to space down one line or skip to a channel with a new command for that purpose.

My code verifies it has an emitter interrupt, then checks the character against the specific set we plan to print. If no match, we set the scan area to all zeroes except for the last bit. This says that the character doesn't exist in our print line so don't fire any hammers. If we match, it sets the scan area to a specific pattern for which column will have that character printed, plus the final 1 bit. As well, with a match we decrement the count of characters to print. Once the count goes to zero, we command the printer to stop print.

I looked over my code and found a few mistakes - hand assembling code, keeping track of addresses, calculating relative addresses and watching for proper alignment of long format instructions is a lot of work using paper and pen, thus easy to slip up in longish sequences that must be entered in with the console data switches one word at a time.

It is late and it will take a while to toggle in the code again, since enough of it has shifted or changed to warrant a reload. This will be done tomorrow.


SOMETIMES WHAT SEEMS LIKE A CONVENIENT SHORTCUT IS NOT A GOOD IDEA

Fortunately, this entry has nothing to do with the 1130 restoration. Yesterday, my wife and I visited the pharmacy to get flu vaccinations. While there, the pharmacist talked us into adding the pneumonia vaccine, getting both injections in the same arm.

By late evening yesterday, my arm was extremely sore, very painful to move or touch. It is common to have some soreness, particularly if the muscle is abused with two separate injections on the same day. In this case, the arm was essentially unusable until the evening today and the pain was enough to keep me from getting any sleep until it began to abate around 6AM, but with work commitments I snatched only a couple of hours sleep.

The amount of work I did on the 1130 before 4PM was zero, but once the arm began to be usable without much pain, I did accomplish a few things as you read above. Moral of the story is that, where feasible, injections should be separated by a week.

Thursday, September 25, 2014

Finished keyboard, wired interface cables to keypunch, and prepared software for 1132 printer restoration work

1131 PROCESSOR KEYBOARD RESTORATION FINISHED

I had to partially disassemble the bail contacts to rebend the bail and contacts, but eventually I had it working properly. I took the time to burnish the oxide from the 40+ latch contacts on the bottom of the keyboard, to ensure that all contacts will be made properly for any keypress.
Removing black plate to get to keyboard underneath

Bail contacts detached to get to bails thenselves

Bails with removed contacts at right

Closeup of bails which pivots for certain keystems, touching bail contact plate
Reasembled bail portion of permutation assembly on keyboard
After reassembling the keyboard, I installed it into the 1131 but only hand placed the black plate over it - didn't want to tempt fate if I had to go back in yet another time to tweak the contacts. Turns out that was a good idea. The keyboard is correctly encoding all the characters but also spuriously firing up and entering keystrokes. When it fired, I saw only bit 2 turned on.

A bit of deductive reasoning with the schematic of the permutation unit connections told me that it had to be a specific bail whose gap was too narrow and intermittently made connection. Only a few contact pairs emit bit 2, but only one does so only when the keyboard is in alpha mode but not numeric. That is bail 13, which is right next to the one I was bending in the repair. It makes sense that one might have been disturbed a bit.

I was able to check and adjust the bail contacts without removing the keyboard, since they are on the sides. However, the problems continue. It may be that I adjusted the bails with the keyboard on its side, due to cable length restrictions for the wiring coming out of the 1131, but with the sag of gravity I might need to adjust them better.

I spent some time but it was hard to determine where my extraneous triggering is occurring. It does not seem to be the bails, which makes me suspect I might have a more devious connection through latches that are producing the behavior. To resolve that, I do indeed have to unscrew the keyboard from the 1131 and tilt it up once again.
Latches on bottom of permutation unit, under bails
I cleared up the issues with the latches, put it back onto the 1131 and checked that operation was now normal. No spurious clicks and I walked through every key and character to ensure it was encoding the right characters.
Working keyboard back in 1131, ready to be closed up
With the problems all fixed, I declared the keyboard fully restored and complete. I mounted the black plate and closed up the machine.

NEW KEYPUNCH INTERFACE CONSTRUCTION WORK

I decided to try to adjust the connectors I have in hand, using some wire lead cutters to gently bend them to a slightly tighter fit. I get this mostly right, but some become too tight to slide onto the SMS pins. After a half hour of careful work, I had nine of the twelve punch magnet connections affixed properly. For each problem connector, once I rule out issue on the pin itself, I will cut off the old and install a new connector, gently pinching it, and installing on the pin. This took two hours overall to complete.

Having fixed the connectors, I was able to complete the wiring of the punch cable, joining the read cable I previously wired in. The last step was to install a reed switch on the side of the card lever relay, allowing us to sense when the relay is energized. The wiring was tied down neatly and the keypunch tested to verify that its functionality was not impaired through any wiring foulup or incidental damage.

It is now time to begin wiring the relays and Arduino to the corresponding DB25 connectors. I will put this in a hobby box of some type - time to pick up some connectors and miscellaneous supplies.

1132 PRINTER RESTORATION PREPARATION

I retrieved my hand code to test out the 1132 printer, generalized it a bit, and carefully laid it out so it can be entered into memory. When that is done, I will be able to test the printer.



Wednesday, September 24, 2014

Very little time for 1130 today, but got into the shop for a bit

I had a heavy workload from my day job, plus I spent my lunchtime at the Computer History Museum working with others to get the twin 1401 systems back in operation. My team solved a problem with the power supplies but the impact of that failure may have damaged some other circuits - more work to do next week. The other teams worked on the other machine and some other equipment, but by the afternoon when I left, the score was equipment 3, restorers 0.

NEW KEYPUNCH INTERFACE WORK

My connectors arrived to hook wires to the pins on the back of the SMS socket panel and I started to hook the 22 wires into the keypunch tonight after soldering connectors to the cable half. Some of the connectors don't seat sufficiently firmly, something I will have to correct. First I will try to adjust the connectors I have, otherwise I need new connectors to replace the ones I just soldered onto the cable.

1131 KEYBOARD CONTACT WORK

I opened up the keyboard area once again and took some extra time burnishing and sanding contacts until I had very reliable connections for all the bails. Right at the end of this process, on bail 15, the screwdriver holding the point against the contact plate slipped while I was burnishing, bending the contact arm. I spent 15 minutes trying to get it back where it would connect reliably when keys were pressed but not otherwise.

It appears I might have done something to stop the bail itself from rotating, perhaps a tab jumped out of a slot, so this could end up as a much more painful repair than just rebending a contact arm. I will wait until I am rested and have good daylight before I tilt at this windmill again.

.

Tuesday, September 23, 2014

CE Disk Cartridge inspected: not usable - surfaces too damaged

CE DISK CARTRIDGE INSPECTION

I realized that with the markings that were visible through the cartridge door, it was essential that I open up the cartridge, inspect it and clean it if it can be used in the drive. I unscrewed the bottom plate and opened up the container. Immediately, I could see scoring, scratches that glinted because they were deep enough to expose the aluminum substrate of the platter. Oh dear.

Cartridge open, platter visible for inspection and cleaning
Top cover of the cartridge, with platter removed
Circular scratches fill an area somewhere near where the CE information was recorded, rendering it unusable because any heads flying on this pack would be damaged. I took several pictures looking at the scratches, plus the dark circular area on the other surface which may be rubbing wear but does not show the aluminum at the base. 

Scratched through to the aluminum underneath

Another view of the scatches

Evidence of one scratch beginning, where a particle jammed between head and disk temporarily

other surface, dark rub marks
 In addition to the scratches, there are quite a few spots were some contaminant settled on the platter and affected the material. These may be water spots or other materials, but if they altered the surface it might be uneven enough to cause head-disk interference and a crash. One set seemed to have removed quite a bit of the binder, showing some of the bare metal underneath.

Melting away the binder and magnetic material

Contaminant spot

Spray of drops across left to right, affecting surface

More streaks of contaminant across surface, top to bottom