atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems Western Electric 620 KSU Questions

Hello, I've been doing a lot of learning via this forum, a little reverse engineering, and a lot of guessing but now I need some help from the experts...

I have a WE 620A2 KSU with a 79B5 power supply that I've cobbled back into partial operation just for fun. There are a mix of 400D, G, and H cards that appear to work. I've been using some San/Bar line cards for experimenting since I can't track down jumper settings for the 400G and H cards.

I'm having a hard time getting the ringing to work the way I want. If I jumper the San/Bar line card to "constant ringing" it works just as expected, the phones ring without any pauses. Now when I jumper to "interrupted ringing" - no ringing.

Here is the odd part... when the jumper is on "interrupted ringing" it puts out interrupted 10 VAC 60 Hz lamp voltage as the ring signal. For fun, I hitched up a buzzer and it buzzes that, but I want the bells to ring! :bang:

I started tracing wires and both the 30 Hz uninterrupted and interrupted ring voltage does make its way back to the top terminal on the KSU. However, the interrupted 30 Hz never goes to the line cards.

Is there some kind of jumper in the 620 KSU that lets you change between interrupted 10VAC 60Hz buzzer ringing or high voltage 30 Hz bell ringing?

I should also add that the terminal wiring on the top of the 620 looks like somebody might have messed with it. There are some ugly "blobulous" looking solder joints on those wires.

Thanks for taking the time to read through this. I'm sure I will have a bunch more questions.
-Ryan

The pink 66 block field is divided into quadrants, one for each line card slot. The very top row should have (from left to right), pins 4 and 5 strapped together. The second row should also have pins 4 and 5 strapped together. This will restore the original factory wiring that provided interrupted ringing. Sorry for the crude depiction of how it should look, but here goes. I hope it makes sense:


_ 1 2 3 4__5

T - - - -<>- (<> means these should be strapped together).
R - - - -<>- (<> means these should be strapped together).
T - - - - -
R - - - - -
A - - - - -
A1 - - - - -
LG - - - - -
L - - - - -
RG - - - - -
RN - - - - -

It sounds like the top row has pins 3 and 4 strapped which would be 10VAC signaling.

This strapping is done at the factory with a piece of green wire. If it has been changed, it's probably either with a different-colored wire or with a bridge clip.

Thanks Ed for that lightning fast reply! You're the man! :toast:

I'll rearrange the straps tonight and see how it goes.

-Ryan

You may find that instead of a piece of green wire, there is a metal bridging clip performing the same function.

Ed/Arthur: There were bridging clips and I moved them all to match what you drew, Ed. It works great now! Thanks guys!

I assume you guys are familiar with Bell System Practices? I did some digging and I think I have the right BSP numbers for schematics of these units?:

KTU 400G and H ==> BSP 518-215-400?
620 KSU ==> BSP 518-215-419?

All I managed to find was an index but not the actual BSP documents. I'm not too familiar with how the BSP documents are organized. Do I need to find a whole book with "518-215" or can I get them separately?

-Ryan

I've got a whole box of ITT 1A2 keysets and parts, you are welcome to them if you want them. They are all in various stages of dissasembly, but you should be able to put together at lesat 2 working keysets.

Most of what you will need is in "Key Systems Service Manual, Volume 2". You are correct on the BSP numbers.

OK, I'll keep my eyes open for that manual on eBay etc. Some dealers also list it but it looks fairly pricey.

Matt: I do have a few sets that work, but I might take you up on your offer.

Right now I'm just tinkering 'cause I like messing around and learning about phone stuff. Its all sprawled out in the basement with the KSU and power supply on the workbench and a rats nest of wires to rig it up for testing.

-Ryan

If you just need copies of those pages, I'm sure that we can work something out. There's no sense in buying the whole manual for just that hardware.

Ed, what is the second set of T and R contacts for?
Also what is RG and RN?