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systems_glitch

Bell 1A2 551C KSU Arrived Today!

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I finally found a real Bell 1A2 KSU to play with! Fortunately the seller was nearby, and it's a 551C enclosure, so shipping wasn't too much. It mostly survived UPS handling (the ring supply got one end smashed, but still works, and one of the modules got banged up). I uploaded pictures to my gallery:

http://www.binrev.com/forums/index.php/gallery/album/2713/198-bell-system-551c-ksu/

I tested the ring supply first thing, to ensure it wasn't ruined in shipping. Jumpering its outputs to pins 39 and 40 of my 2500-series 1A2 key phone produced ringing, so it should be fine. I'll start with the cleaning and testing of the power supply tonight.

Eventually, this will end up in the telephone/network closet of the house, connecting my key phone to an Asterisk PBX and some other planned goodies (more on that later). Once I've gotten it figured out, I want to test some of the spare modules I have and build a smaller KSU for use at work.

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Well, it seems to work! There's currently a huge pile of wires and telephone parts sitting on my workbench, but it seems that everything is functional -- no doubt a testament to Western Electric's quality control. Currently the telephone is plugged into an old SCSI connector (50-pin telco AMP connector is the same mechanical connector as oldschool SCSI) with jumper wires for the first circuit ran onto the 66-type punchdown block.

The mechanical interruptor had me confused for a while. I powered it on, only to have it spin a few revolutions and stop. It would start again with a nudge to one of the drive gears, but would stop at the same point again. It was only when I was testing the wink-lamp-on-hold feature that I realized the interruptor isn't /supposed/ to run unless a line card is calling for one of its functions!

Also, different line cards appear to have different ring voltage tolerances. Two of the cards will detect ringing while the other two won't. I don't know if this is something that is jumper-configurable (there are wire jumpers on the line cards), or a symptom of not having the ground lug attached to anything. I can't imagine it's line loss or noise, since the "line" is 25 feet of RJ-11 telephone cable.

The 3 Amp fuse for the 10 VAC lamp and motor supply is blown...they're funny little phenolic fuses that look like a piece of cut circuit board with the fuse wire visible in a hole in the middle. Apparently these are "Type 24" fuses, which no online parts house stocks directly. eBay turns up a few different compatible-looking fuses, but all the wrong amperage. Someone does have 1.5 Amp fuses, so I suppose I could solder two together, or just stack them on the screws. Any suggestions for sources?

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