Bench test of 1132 printer power box - part 3

COMPLETED REWIRING OF POWER SUPPLY BOX

Most of the wires had ring terminals on each end. It was easy to put new terminals on new wire of the same length. However, one wire was soldered at one end and ran directly into the transformer on the other end. It was the 20VAC supply that was adjustable by the potentiometer it was soldered to. That allowed the lamp brightness to be adjusted to have the photocells on the timing disk produce the best pulses. 

I had to splice a new wire onto part of the existing wire, the section that came into the metal box from the transformer. The other end was soldered onto the pot. This was the last damaged wire to be replaced. 

I had disconnected about nine wires in order to get the metal plate to tilt out far enough, so I had to very carefully validate where they were to be reattached before doing so. At the same time, I reinstalled the contactor. Because one of its two coil terminals was corroded and fell off, I had a wire coming out instead of a terminal to attach the two ring terminals from other parts of the circuitry. I installed a small terminal block with just one position, put a ring terminal on the loose wire from the coil and thus all three were attached to the new block.

BURNISHING CONTACTOR CONTACTS BEFORE CLOSING UP METAL BOX

I used a burnishing tool to establish a good electrical connection for the contactor points. The K1 side connects the 208/230VAC from the CE Switch to the fuses F3 and F4. The K3 side connects the +48VDC filter capacitors to the rest of the circuitry that uses 48V. The middle section, K2, is unused on this machine. 

I purchased some new screws in order to reassemble the metal box in preparation for power on testing. The reassembly was uneventful with the new hardware. 

TEST 48VDC AND 20VAC POWER SUPPLY OPERATION

Hooking 230V to the power supply main transformer, with the main motor and usage meter isolated, let me check for proper 48V to operate all the solenoids and that lamp voltage was developed by the 20VAC side. 

There are five fuses on the power supply box. F1 and F2 control power to the utility outlet. F3 controls power to the main motor and the usage meter power supply. F4 controls power to the transformer for the power supply portion we are testing. F5 controls 48V power from the power supply portion we are testing out to the carriage motor. 

For this test only F4 was inserted. The output is measured across TB2-2 and TB2-4 for the 48V supply and across TB2-5 and TB2-6 for the 20VAC supply. The contactor had to be energized to route the 48V out of the power supply; pushing down on it with a nonconducting tool closed the points without requiring me to hook to 24VAC. 

The outputs were right on the money - 48VDC and 21 VAC. The latter is adjustable via the potentiometer R5 in case we want a bit less or a bit more than 21V for the lamp that shines through the timing disk into the photocells. 

CLOSED UP THE POWER SUPPLY, READY TO PUT IT BACK INSIDE THE 1132 PRINTER

I put the metal enclosure together since the power supply is functioning correctly. A picture below shows it with the 230V input still attached via white power cord, before the metal mesh was installed prior to movement.