sundance-communications.com/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems Manual needed for 551KSU

Bill:

Remember how there was a metal strip that went from one of the output grounds on the front of the power supply to one of the cabinet screws? That was how the output and input grounds were kept separated when required.

If that strap was removed, then 400D's didn't have a ground to reference. Unless a separate ground was connected to the ground screw a the bottom of the KSU, there was no ground on the low-voltage side at C.O. potential. 400D line cards were tripped by ring-to-ground, not across tip-ring like with later card versions. A missing third prong on the power cord and no local ground conection was usually the culprit.

They had that strap because at the time of manufacture, there were some local electrical codes that didn't allow input and output grounds to be common. I think that was more a Canadian issue than in the U.S.

I don't remember all the details, but I do remember troubles, ringing and others, if no external ground. Some day Ed the light will come on that says "yeah, I remember that"...until then the 51a will just flash..have a good night.

Ok I checked i have 10 VAC on MB/MG and LB/LG I do not have a ST term on the block but I know the Interupter is good I have tested it with holding calls. Here is what I am doing to test: I am connecting the ring gen to the first line on the CO side. I hear the 400D buzz I beleave its the reed relay and nothing elese hapens, I have tried it with 4 other 400D cards and same result.

I am still pretty sure that your KSU's ground and the ring supply you are using are not common. One side of the ring generator output must be grounded (as well as the KSU) or 400D cards won't detect incoming ringing.

Remember that standard ring generators and CO line simulators have a "floating" output, that is, neither of the output terminals is grounded. There's a very long story behind that and I am sure you don't need to hear it. Just connect either of the ring generator's output terminal to the same ground your KSU is using and you should be able to start the ringing cycle on the 400D.

Do you have any 400G, H or ITT 400E cards to use for a test? If you don't, I will be glad to send one to you to try. Just let me know.

Ed I was wondering if you still had that manual for the 551-C KSU?

I have the manual, but it's in hard copy version and very fragile. I might be able to copy the pages and fax them to you for a small fee. Please send me a PM or e-mail if you are interested and I'll get the pages to you.