MACHINE 3 PARTIALLY FIXED, WAITING ON PINFEED FORMS
The keyboard was properly adjusted and was the typing unit distributor and selector properly serialized and deserialized the typed characters. The type quality was excellent with the new ribbon installed. This machine has a form feed option where it takes forms with sprocket holes, the inner forms are 8 1/2 x 11 in side.
The form feed mechanism was initially frozen in place, but eventually loosened. The machine would take cycles for Line Feed character but not for Form Feed, also it was not yet advancing one line or form with that cycle. The rest of the typing functions seemed fully operational.
The owner has ordered a roll of the paper but chose to put the machine aside until we have the proper paper with which to continue testing and adjustment. As a result, we didn't finish the line/form feed fixes, nor work on the paper tape reader and punch parts of the machine.
ASR/33 READER POWER SUPPLY FIXED FOR MACHINE 1
The ASR reader makes use of 150V DC to power the solenoid that tests the holes and advances the tape on sprocket hole. This was blowing fuses when we last worked on it. After some false leads of the root cause of the overload, where we replaced the rectifier diodes and main filter capacitor, we discovered that we had some gunk on the PCB that was conductive enough to pull more than 1A even with no load wired to the supply. With that fixed, the supply worked great.
USING EXTERNAL 20MA TO RS232 ADAPTER ON MACHINE 1
We had initially worked on the machine in Local mode where the output of the keyboard is looped back to the typing unit so that each keypress results in typing or other functions on the machine in front of you. More typically, these are attached so that the key presses are sent out over lines to a remote teletype or computer, while data from that remote location comes back to the typing unit to be printed. This is Line mode.
The owner brought a small box that supplied 20ma to the typing unit and read the keyboard side, using a RS-232 serial connection on the other end. With that we used an oscilloscope to watch the well formed serial data stream during keypresses and then looped the RS-232 RX-TX for local printing of what we typed.
MACHINE 1 MOST PROBLEMS RESOLVED
We had a list of problems for machine 1 when we began this weekend, among them were failure to line feed, carrier return not getting all the way to the left margin leaving the carriage unlocked, printing only the right edge of each character, and the reader wasn't operating.
The line feed issue needed a small adjustment to pull down far enough to rachet the platen up one line. In addition, the line feed operations triggered most time but not every time an LF was sent. That will involve a minor adjustment of the triggering mechanism, but we didn't get to it this time.
The carrier return latching issue was due to crude on the piston and cylinder on the left side which cushions and slows the carrier as it returns. A long spring provides the energy to pull the carrier to the left once it is unlatched. As the piston seats in the cylinder a projection on the carrier moves a mechanism to relatch the carrier. When the piston didn't seat all the way, the carrier didn't relatch so we would type characters atop each other with no rightward carrier movement.
I cleaned and oiled the piston and cylinder, cleaned the rod upon which the carrier travels, and lubricated the rollers and bearings that support the carrier. With that done, the carrier return would completely enter the cylinder and relatch.
The adjustment for the partial printing is to loosen the nut holding the type cylinder in place, turn it slightly to make the full character face the platen, then tighten it up. We did see the type quality improve greatly, but the cylinder would soon slip out of position. A new lockwasher didn't improve this enough, so it will need to be attended to in the next session.
Inside the paper tape reader is a microswitch that turns on the reader. There are two types of readers on ASR-33 teletypes, automatic and manual. This machine had the simpler manual version which just reads continually as long as the lever is turned to the on position of the reader. A pin pops up to sense whether there is paper tape in the reader, if not it blocks the contact even though the lever is set on.
When the lever is on and the pin detects paper, the reader closes a solenoid inside the typing unit which trips the distributor clutch and the large solenoid in the reader pushes spring loaded pins up in the eight data positions across the tape. Everywhere there is a hole, the pin goes up and makes electrical contact.
As the distributor clutch cycle begins, a microswitch interrupts the large solenoid power to the reader, which pulls the tape to the next sprocket hole position. When the distributor cycle completes, having serialized the character from the tape, the microswitch again allows the big reader solenoid to be energized.
Thus we have a synchronizing dance of the little solenoid triggering the distributor clutch to transmit a character, the microswitch releasing the big reader solenoid to advance the tape on position, and then the microswitch reconnecting at the end of the current character to read the next.
We were not seeing the big solenoid pull and release but all the voltages and contact circuits were working properly. The solenoid shows as the 100 ohm DC resistance that is expected, so our next session will first verify that the magnetic field is generated before we begin readjusting the solenoid to properly move the mechanisms in the reader.
140,000 PUNCHED CARDS PICKED UP BY NEW OWNER
Since I had reliably read and archived all the card contents of my large collection of 1130 oriented punched cards, it was time to free up the room in my workshop that they took up. The new owner arrived with a box truck and collected them all on Saturday.
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