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

Hello -

If anyone has a 601A KSU, I was wondering if you could do me a favor.

I get hum when hooking a telephone across AB/AG.

However, if I hook the phone across the T/R terminals of the intercom, there is no hum.

I understand that normally you have AB for filtered voice, and BB for relays, etc - but the 601 only has AB/AG.

Having said that, the manual says that AB/AG can be used for voice, as well as relays, etc.

Ed is shipping me a power supply to see if that's my problem. However, I'd hate to take the chance that there is something wrong with my KSU that causes power supplies to go bad.

I've also replaced every component on the power supply board that I think could contribute to hum (capacitors and diodes). All that's left is the transformer, and from what I'm guessing a couple voltage regulators. (The voltage holds steady on all AC and DC outputs).

Of course, I'm by no means an electronics wizard; pretty much a parts swapper/hack in that area.

Anyway, if somebody has a 601 in use that you could hook a butt set or the tip and ring of a telephone across AB/AG on, and see if you get hum, I'd appreciate it very much.

Thanks
Matt

Well, there's hum and there's humm. Using a butt set you will detect some low level hum on a 601 power supply directly off the AB AG terminals. It should be low enough (approximately 1 VPP) to be audible across AB AG, however, when the voltage is applied to a card, there are additional filter capacitors that take out the ripple altogether. If you have a scope, check out the level of ripple that you have. It's all power supply. There is nothing else (except a defective card, which I assume you have already eliminated as a possible source of the ripple) that can cause hum in a 601.

Rcaman

Rcaman

Rcaman -

Thanks! I'd call it hummmmmm. It definately sounds like AC is present, it's "talk-overable", but annoying.

I don't have a scope

One thing - the voltage (-24vdc) is present on AB/AG with no line cards (K400E) installed. However I have 5 line cards, have tried each one anyway, to no effect.

I'm positive the intercom card must have the additional filtering you describe, becasue as I said, it's clean and clear across it's tip and ring.

I guess what I'm trying to figure out is if ITT never intended AB/AG to be used (directly) for voice - and that if you wanted to do that, then you would have to buy thier intercom card.

One thing I never mentioned - the hum is only present on AB/AG - not the CO lines.

Thanks
Matt

The CO line cards do not use the 24 VDC for talk battery. The line cards use the 24 VDC for relay operation. That is why you do not have any hum issues on the CO line cards. The ITT Intercom card does have additional filtering to reduce the ripple for the intercom.

If you want to use the supply for just battery, then I would suggest two 1,000 mfd. 50VDC capacitors connected together with a 100 Ohm 2 Watt resistor between the two electrolytic capacitors connected between the AG (+) and AB (-) terminals. Be careful of the polarity. This should wipe out all the ripple and give you a clean AG and AB.

Connect the positive terminal of capacitor 1 to the AG terminal. Connect the 100 ohm resistor to the same terminal. Connect the other end of the resistor to the positive terminal of capacitor 2. Connect both negative terminals of the capacitors to the AB terminal. Connect the load to the positive terminal of capacitor 2 (AG) and AB (-). The "nominal" ripple voltage on a 601 power supply is between .5 and 1 VPP AC. This setup should knock down as much as 10 VPP AC to less than .1 VPP AC. At that point, hum should not be detectable.

Rcaman

OK -

I did that, but only one 1000 mfd cap and no resistor.

Will give it a shot tonight.

Thanks!!!!
Matt

This needs a "pi" filtering network and what I gave you is a "Pi" RC filter for 60 to 120 Hz. There is math that can be used to determine the exact values of the resistor and capacitor values. What you have here is like using a shotgun to kill a fly. It works...but you can achieve good results if you know exactly what you are trying to filter. A scope or a good RMS VOM is essential.

A LC network is actually more efficient and provides better filtering, however, most people don't have a spare 100 mH choke lying around.

Rcaman

"I get hum when hooking a telephone across AB/AG."

You can't do this.. Intercom line cards are made for this. The trouble is simple. The A battery and A ground are two different applications. The Ag is the
ground in the crkt. Just as the B battery has a ground.

Grounds are not always common.

The AG completes the crkt. A batt B batt .

What you have is A battery then you have unfiltered B battery. Two separate crkts on the power supply. Don't confuse them. An don't make your grounds common when mixing them.


You need to understand that you are working with two different crkts. One is true DC and the other is supper imposed over a DC wave form.

Matt, you will always hear hum on talk battery supplies, because they are unbalanced. When you feed the talk battery through the "A" relay or equivalent of an intercom talk path, the balanced windings of the relay act as a retard coil, and filter out the noise. You are obsessing over squat, and I say that in the nicest possible way. Did you get the 2565HK cord I sent you for Christmas?

lol

Yep! got the xmas present today, just unwrapped it, and now am going to sing Xmas carols. In fact, I think I'll hand out candy canes for Halloween.

THANKS

(PS: Obsessive doesn't even begin to come close, but it's one of the nicer words used to describe me and at least one of my peronalities). It's what happens when you don't have a life.

Just ask Ed!

Someone said The CO line cards do not use the 24 VDC for talk battery. Bullshit they can be used.

If I press a button with 1a2 you would be surprised what I can't make work.

I see what you are saying, but this KSU has no B battery - Just AB and AG; which the manual says can be used for voice. But you answered my question - the intercom card does the filtering.

Thanks!
Matt

The funny part is that you don't hear any hum on talk battery suppiles unless it goes past 10000 ft.

Simple point. I will connect a ring down crkt with two car batteries.

The KSU has B Batt. Take your but sett and listen for it.

If this is a KSU 551 or greater they all have B battery.

This is how we wire the buzzers. 18-24 b batt.

DC does not run buzzers or bells.

You can create noise an a DC output. This should be a wakeup call on bad crkts within the network.

These older power supplies are unique.

Take your but set and connect one side to ground.

Then go across the power supply terminals to listen for the ac.

Now you have found the your ac crkt.

Sorry this is a lost art.

Hmmm

If it has a B battery, then all the documentation I have is wrong. The power supply schematic shows one 24 vdc output, one 18 vac output, and one 10 vac output. The 24 volt output runs directly to the AB terminal. Also, nowhere in any of the 50 pages or so of documentation is a B battery ever mentioned. Buzzers are fed from the 10 or 18 vac outputs, the lamps are fed from the 10v output.

My VOM can distinguish AC from DC; plus I have the schematic... no need to go searching.

Everything is as the documentation says it should be, with the exception that it says you can use AB for talk, and I get hum on it. The intercom card filters it out though, so the issue is resolved.

Thanks -
Matt

Matt said, He has a volt meter and never told us about how many 1a2 key systems that he has worked on.

Hey, Matt. The next time I need a volt ohm meter to work on 1a2 I will call you to waste my time.

A but set is a meter without a digital or analog meter such as a simpson meter.

If you spent years listening to electricity/capacity you don't need a meter.

It's kind of looking at it with a scope. The only difference is that your ears become your eye's.

SS, you missed it. He's using an ITT601 KSU and it has NO BB/BG. Doesn't need it, was a limited capability 1A2 KSU. Strictly CO lines and 10 Station IC. WE551's had more P/S and more flexibility, no question about it. Note that there were DC buzzers and bells used in the telco industry, early on. They became obsolete pretty quick, granted. Adjusting the contacts that made them work was probably the main reason, ya think! All that said, we are all having 1 h-ll of a good time watching Matt grow into the latest and greatest (And possibly the only)1A2 tech in the greater KC area. (Ahhh, the memories) John C. (Not Garand)

Station Specialties,

I said the CO line cards do not use the AG AB for talk voltage. The circuit works with Central Office supplied voltage. The BG and BB are used on the CO cards for relay operation and A lead control. In this case, the ITT 601 has NO BG and BB. The AG and AB is all that is supplied for both relay control and intercom talk battery.

If Matt1964 wants to use the AG AB for talk battery, he needs to filter it better than it is.

Rcaman

Which I just got the parts for, will update soon. Thanks RCA!

the b battery runs the lamps. from 10-24. The more sets you have to wire the B battery to 24 on the lamps is used based on dimming of lights based on the total number of sets off the power supply.

If you only have 5 or 7 sers then 18 on the b batt is correct..

If you are trying to connect a melco intercom forget how you wired the sets.

Forget what ever prints you have.

The melco has two inputs. One for A battery and one for singnal b battery...

The latch contact makes the switchhook contact in this unit.. If you wire it right you will hear the relay in the intercom unit click. The relay is now looking for audible volatage contacts.

If its a TT intercom you will hear the latch .. It has now made a second connection looking for B battery audible to ring or buzz the station.

OK....I have only been at this for 40 years, so I know I still have a lot to learn. However, my days at Bell Telephone taught me that if I hook up BG and BB to lamps, I'll have a lot of burned out bulbs as ALL line key bulbs are 10 volt in 99% of all 1A2 sets. BG and BB were designed as an unfiltered voltage source for operating relays. The AG and AB were designed as a fairly well filtered voltage source for talk battery for intercoms, etc. RG and RB were used for common ringing and SG SB for intercom buzzers.

I did not see any mention of a Melco intercom unit in any of Matt1964's posts.

Rcaman

The ITT 601 was even more flexible than a Weco 551.

601 had it's own ring generator buit in. The 551 was a plug in add on type transformer that had to be wired up to inputs on the shoebox 66 type panel.

I worked on a lot of weco key systems. The ITT was better. It didnt blow fuses as easy as a weco. When it did blow a fuse it usually fxxck up the line card unlike the Weco.

RCAMan:

The intercom unit was mentioned and illustrated in This thread. Scroll down and you'll see.

It looks to me to be a Teltone intercom, but the brand really wouldn't matter, nor be an issue in this case since it's not even connected yet.

If you worked on it for ten years every day it's enough to last you a lifetime. One can install it. Then there those who fix it.

When it doesn't work and to keep it going from bad keypads to dirty button contacts to water on the foor in a amp connector and a host of other basic electricity issues.

These old phone system are basic electricity.

Patients with 1a2 is a virtue. The best guys who work on this stuff are now 80 years old.

Let's move on to Tesla.


The best thing about 1a2 was that if you could fix the worst problem in a couple of hours the General Manager of AT&T needed you.

Matt, I think along with your VOM, you may need a BS detector.

If you need any more 1A2 advice, and don't necessarily want to be publicly abused and confused, just give me a call. You have my number.

RCAMan - sorry, still have hum. I'm giving up on this... I know the intercom card for this KSU presents a clean talk path, so I'm off to pursue my options there.

Arthur -

I hear ya.

Thanks
Matt

Thanks John! Gotta say I'm having just as much fun - glad to hear you guys are getting a kick out of it as well. This stuff just fascinates me for some reason.... looking at a bunch of wires and 66 blocks, wondering how in the h*** is this all going to come together, and then suddenly (in my case with a great deal of help) ... the light comes on. VERY satisfying. I think this is the first hobby I've had in years that I truly enjoy. Anyway, thanks for the kudos!

- Matt

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)

A Talk battery DC supply With nothing connected? there would be no introduction of noise from anywhere else other than cable pair or connection faults. This is again dc in it's true form. This what we talk on!!!!!! Hello

The noise??? Other than what?


ITT 601 is the same spec as a Weco. I give up.


Again, I'm funny and can fix it. The good guys are almost dead or on the real deal of dead low voltage and various apps in this subject.

I'm still pissed at all mistakes I made with IA2.

This keeps me going for the love of this business..


Charlie

I'm not sure about what you are asking here.

I didn't see anything about noise unless you are speaking of the original thread started last year. Those issues seem to have been resolved back in October.

Sorry to disagree, but the 601 was very, very different from WECO other than standard 1A2 functionality. Perhaps you are thinking of ITT's 501? That KSU was functionally and physically equivalent to WECO.

ITT came up with the 601 and WECO came up with the 551C about the same time, but they were very different in many ways.

I understand Ed .. I am only talking fixing 1a2 theory. ITT or Western does not matter.

The fuse potential was much worse on western electric key service units than the ITT

You should know this?

Thanks for the help, but I still have a question. I know the 401 cards are talk only, no dial capability. But why is the 601 considered having an intercom capability? Is it a separate card that plugs in?

Bill, the ITT 601 did have IC capability. As previously discussed, it warn't cheap. And if I recall correctly, you had to add a DTMF decoder card to make it work with touch-tone. And if you didn't protect both the CO lines and the AC power, the IC card would save the rest of the cabinet by dying first. I believe it went in the bottom slot. Some of the 601's came with a board layout glued inside the cover. Maybe you're 1 of the lucky ones. And if you peek all around the card slots, I believe they were marked in some way also. Been too long, sorry. John C. (Not Garand)

"I know the 401 cards are talk only, no dial capability."

Let me be mistaken the 401 cards are a family of cards..I don't get the question?

The Intercom card is simular to any 401. Although, one would need to wire talk batery in to the KTU 400 TR intercom card off a DC source from the power supply. Again we talk on DC supper imposed. Once you begin to talk the wave is now AC.

Hope this helps you?

I only know of the 401A and 401B. Is there another part of the family I don't know about? My understanding of the 401 card is that it only allows a talk circuit when the button is pushed, there is no type of dial capability with this card. So to make it functional you would have to have a separate paging or signaling system to let someone know you wanted to talk to them on the intercom.

Yes used to use manual signal and buzzer system.

Jim & Phonenut are correct. The 401 A required an 'A' lead; the 401B did not. They both provideded the same thing - a filtered talk path. You would use them with a button & buzzer system or with a matching transformer (WMT-1) as an access to a PA system (there was a contact closure that worked really well for muting the BGM.

Sam

There is no type of dial capability with this card.?

If you connect the right DC voltage, again talk battery to the card it will DTMF.. The A lead is a off hook through the switch hook and dial pad..

Options might have to be changed in the set.


If you need a weco 400 intercom card let me know..

My point is that you can Use a Viking product with any exsisting line input of a 400d if you don't have this intercom card.

We are discussing a 401A/B manual intercom card; a simple private talk path using button/buzzer signaling.

The discussion is that the 401 series of cards lacks any intelligence, as in deciphering tone or pulse dialing.

Yes, if you want to split hairs, you can use the CO Tip/Ring of the standard 400 card to provide access to an external product made by other manufacturers, but most do not require a 400-type line circuit in order to do this.

So to make it functional you would have to have a separate paging or signaling system to let someone know you wanted to talk to them on the intercom?


I'm trying to figure out what you need to accomplish? loudspeaker paging and station signaling or both?

The Intercom card is the way to go. Only because it has a voice coil built in. But you don't really need it. It depends on the application.


You need to know first that you will have to unscrew the pin on one of The chosen Buttons for the signal feature. This is for starters. No programing involved

You can build both. One button held for page and one button to signal intercom buzz or even page. Or even dial access to both with a Melco. The later option is a bit more expensive based on todays technology. Still you can do both if you have two extra line buttons on a 2564 set?

If you have 10 buttons it's even better.

I have built what I think you are trying to do.


So, if I pull two pins from two line buttons and wire it correctly to a secondary relay source I created fun and games with 1a2?


Email me for help.