Saturday, December 13, 2014

SAC interface final wiring, power on test and adjustments of the 1053 console

Major jet lag so not making as much progress as I had hoped, but at least I am visiting the machine for a few hours at a time.


I began the adjustment sequence for the IO Selectric mechanism for everything that was disturbed in order to partially remove the cycle clutch shaft during the installation of the new drive belt. The first adjustments are for the backlash of the gear train that couples the cycle clutch shaft to the filter shaft and print shaft. The bottom adjustment was easy, but the top adjustment is difficult to figure out.

Gear train, top two are too far apart
The print shaft gear is so loose on the idler gear that it doesn't get turned. I loosened all the screws that appeared to affect its position but nothing is changing the relative position of the idler and print shaft gears. I looked at the diagrams from the parts catalog but that didn't shed any illumination on the matter, nor does the maintenance manual.

I will go watch some online selectric repair training course videos on YouTube to see how this is done on a regular machine, then infer the changes for the IO Selectric model I am working with.
Once I get an idea of what is needed, I can go back to the typewriter mechanism and give it a go.


I hooked up the power connector on the box to hook up the power cable from the 1131 bringing the 24VAC control voltage that will power up this interface. In addition, I wired up the rear fan and tested the operation of fans and power supplies. The fpga board powered up, the fans came on, and the signal interface boards are receiving clean 3.3V and 3.0V power.

Final power wiring, remote control relay at top
Connector for power cable from 1131

Connector installed in enclosure

Connector with power cable attached for power-on test

Completed SAC Interface box ready to have signals cable from 1131 connected
The hardware is now ready for testing although there is one more connection I can wire up - hooking up the USB based serial port to the enclosure front panel USB connector, avoiding the need to snake a cable inside the box if a serial connection is used with any peripheral interface that may be implemented in the unit.

Front panel of enclosure with two USB connectors
I don't have initial plans for any device connections that would make use of this but the work to add the outside connector is minimal and the box becomes more generally usable as a result.

My first test had the fpga set up to assert no control signals to the 1130 (e.g. don't request cycle stealing or interrupts), and to monitor the CPU run and interrupt level 4 states on the two LEDs. That should show success with some minimal communication, particularly the ability to properly receive and interpret signals from the 1131. In addition, I set up a switch on the fpga board to request an interrupt on level 4.

As I attempted to hook up the microUSB cable into the connector, which was not sliding in, I had to attempt it several times and wiggle slightly to see if there was a slight misalignment which I could overcome. Unfortunately, the connector was held to the PCB with epoxy which didn't hold very well, as the connector tilted up and came free.

UART connector at top right, spot at lower left where main USB connector came off

Glob of epoxy on bottom of the connector that came off

Cable end at left and broken off connector at bottom - these two will NOT mate
I was able to verify with the separated connector and the cable that the two did not mate, no matter how I worked them together, nor did the cable mate with the other (UART) microUSB connector on the board. I have to assume it is a badly made cable end, although I will check it with other devices just to rule out problems with the board connectors.

However, this did force me to address the front panel USB connection change I had been pondering, now that the microUSB connector is broken off the board. I will carefully attach the leads of the enclosure cable to the pads on my fpga board, such that I can program and use it without opening the enclosure or touching the fpga board directly.

It won't be tonight, as there is almost no daylight left to do the fine soldering necessary, but I can take this on tomorrow. of course, the test is also postponed due to this unexpected issue.

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