OPENING HIGH VOLTAGE SECTION, DISCOVERING A MESS
The area of the power supply that carries 208/230 and 115VAC was enclosed with a metal cover. Outside of it, there were only wires to the transformer primaries of the 48VDC/20VAC supply and the usage meter supply. All else was low voltage components covered by a wire mesh. I opened the wire mesh to begin testing the big capacitors and the rectifier diodes.
I noticed the characteristic rust stains on the metal enclosure that I saw when other machines had suffered sustained large scale rodent infestations. I also saw some shells amidst the power supply components.
I opened the cover to examine the high voltage section, uncovering a compartment jammed full of bedding. The lowest sections were darkened from urine corroding the metal floor and walls. I began removing it to see whether we had any visible damage such as chewed wires.
I did come across a mummified rodent carcass as I excavated the bedding and shells.
I had to pull the 'wool' out with forceps, avoiding wires and buried components. I then made use of a small shop vacuum to remove as much as I could otherwise.
The bolts that hold the two metal sides to the bottom plate are so rusted that they can't be removed to gain more access. If I do need to get into here, the bolts will need to be drilled out and replaced.
TESTING LARGE ELECTROLYTIC CAPACITORS AND DIODES
The power supply has four 11,000 uF capacitors in parallel to filter the 48VDC. A transformer with a pair of diodes as a half wave rectifier feeds these capacitors. This supply drives the carriage motor as well as the solenoids for printing a character on each of the 120 print columns
One of the capacitors was at the specified 11,000 uF level while the other three were substantially higher, around 16,000 uF on average. The rectifier diodes checked out good as well. Germanium diodes with a .425V diode drop.
NO TESTING FOR 20VAC LAMP SUPPLY
The 20VAC section is directly from the transformer with no filtering.
ENERGIZING RELAY AND CONTACTOR WITH 24VAC
When the main 1130 system has its power switch turned on, it delivers 24VAC over the cables to its peripherals. The 1132 uses this power to energize a relay K2 and a contactor K1. One end of the 24VAC runs up through the Motor Power toggle switch on the 1132 front panel and back down as the 24 VAC SEQ COM wire. I connected my Variac to the terminal block terminals 9 and 10 to verify that the relay and contactor would energize.
The relay pulled in nicely however the contactor didn't budge. The coil terminals had 24VAC across them, so the problem is in the contactor itself. I removed the part from the machine and began testing.
The coil was open. This has happened in other relays that were subjected to rodent urine, so it was not a complete surprise, but without the contactor, the printer won't turn on when the 1130 system does.
I noticed that one of the two terminals for the coil looked particularly funky and corroded. If that was were the break occurred, near the outside, there was hope of repairing this part. If not, I would be searching for a substitute.
EXCAVATING WHERE CORROSION SUGGESTED THE CONNECTION HAD BROKEN
I pulled apart the contactor and removed the coil from the rest. I dug out the tar-like coating around the coil and confirmed that the wire was eaten away. I found the intact end and confirmed with a meter that it had continuity to the other terminal.
I soldered a wire to the end inside the pit on the coil and hooked up the 24VAC to test the operation.
The contactor snapped on and off satisfactorily. I will be epoxying the wire down to ensure the end doesn't snap off from flexing, then it will be ready to reinstall.
TESTING CONTACTS ON RELAY AND CONTACTOR
I also used an ohmmeter to check the contacts on both K1 and K2. They needed to have a low resistance. Often they will oxidize with the decades and bad environments such as mouse urine vapors.
The relay K2 contacts were low resistance, needing no work. The contactor surfaces had quite a bit of oxidation from mouse urine vapors. I will burnish them to restore conductivity after I get the contactor reinstalled.
