Saturday, September 27, 2014

Activity, progress, minor complications but nothing completed today


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.


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.


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 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

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