atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems Does anyone have an ITT 601A KSU in use?

Just out of curiosity, why hasn't anyone suggested replacing the A battery power supply with two 9V batteries? They certainly won't produce any hum and that would prove if it's a noisy power supply or if the hum is being introduced elsewhere. Just my $0.02 ...

I think that we haven't suggested that because he indicated that his tests were performed with nothing connected to the outputs of the A Talk supply. With nothing connected, there would be no introduction of noise from anywhere else.

Again, the filter design is dependent on the load characteristics. You can tweak the resistor value to get it closer to what the load resistance/reactance is presenting to the supply.

EV607797

I read the thread that you posted and I see more as to what he has tried to do. Unless I missed it, he never actually posted why he needs the AG AB source apart from the 601 needs and why it needs to be hum free. Filtering works, but, as I posted, it is dependent on the load characteristics.

Rcaman

RCAMan:

He's using a Teltone C-19 intercom that's external to the 601. It requires filtered "A" battery for the talk path, while the card that goes in the 601 has a certain amount of on-board filtering.

Got it. I wondered why the requirement for the low hum AG AB. Now it makes sense. It's been a while, but I distinctly remember that on "some" of those intercom units, you could not use AG AB and tie it to the BG BB. I tore apart an old TT unit once and found the commons were not "common."

I scoped the power supply AG AB on a 601 we have here and found the AC ripple to be around .2 VPP. I could hear it directly off the AG AB terminals, using a butt set, however, I hooked up a Melco IC unit and there was no detectable hum.

We do a lot of stage intercom work and I have used telco power supplies to replace the puny switch mode supplies that are installed with the ICs. On several occasions, I have used an auxiliary filter circuit, much as the one I described in this thread, to eliminate all the hum. If Matt1964 is still reading this, you may want to go to 5,000 mfd. on the capacitors and lead in with a 50 mH choke from the AG to the first capacitor.

Rcaman

OK, here's one that might even give Ed some trouble. Just opened my recently purchased 601. It has 3 K400E cards, a 401B and a K403A, two empty slots and one unmarked ITT card manuf. 3-85. My understanding was the 601 included the intercom so is the 401B an extra intercom? Isn't the K403A a buffer for MOH? And what could the unmarked card be? It is in the first slot from the top and doesn't look like any KTU card I've seen before. Some help, gentlemen?

Phonenut -

I only put in two of those 601s and that was about 20 years ago but as I recall they came with a printed circuit interruptor (that always burned out!) - that might be your unnamed card.

The 403 is a buffer for the MOH. It allows you to provide MOH to all lines without inducing xtalk into the system.

The prints for those 601s are floating around - I'll see if I can dig them up and let you know for sure.

Sam

The unmarked card is the interrupter card that provides lamp flash and interrupted ringing. That must be installed in the uppermost slot below the power supply. The 601 didn't include an intercom card, in fact it was a very expensive option.

The 401B is the ONLY intercom card that you have. It's not a dial-selective intercom unit. It just provides a talk path and relies upon manual button/buzzer signaling between stations.

The 403A is definitely the music on hold interface card and there is a dedicated slot near the bottom for that. It is the second one from the bottom.

Thanks Ed.

You saved me at least 2 hours hunting around in the pit of despair (my basement).

Sam

Ed, the 601's IC may have been expensive, but when you compared that to the cost AND the installation time of a Melco, etc, it was pretty much a push and using the 601 IC was a lot cleaner. We based our installs on $50/hour for the 1st man and $30/hr for additional men. Rounded up on time for each item and that meant $50 install for the Melco, plus materials and Melco cost. The 601 IC was a plug and play 2 minute install and wiring was simpler, after you'd done a couple. I suppose you will disagree, but I was the ops MGR and I didn't want 'stuff from here and stuff from there' and stuff that made the job cheaper and came back to haunt me for service. Any extra cost could be written off against serviceability. Yeah, I know I had great company owners! Seviceability was NEVER considered by most interconnects, AND came back to bite! But, that's all gone now. John C. (Not Garand)