atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems 1A2 and some old WECO stuff

Yesterday was The Day!

551C KSU from 1981 is converted to 230V, wired and made operational. Now in more details.

I managed to find a matching size power transformer with necessary secondary voltages. Original Western Electric 110V transformer is on the left (removed) and the new one is on the right (installed).



Below is a new transformer in closer look. I was lucky enough to find this one on eBay here in Germany. The dimensions are really very close to original WE one, it is only slightly narrower so I have to drill another hole for fixing it. One may see now the original small hole in the power supply unit faceplate, however it will be used later for a lamp indicating activated ring generator.

The transformer has 3 secondary coils: 10V, 18V and 24V. Later one is used to provide DC 24V output for signalling and talk. I've installed a precision regulated power board (behind the transformer) as I use 24V AC coil of transformer to provide power for 24VDC circuits (551C scheme requires common ground on positive side of DC and one of the sides of AC voltages, if 18VAC and rectified 24VDC are taken from the same secondary coil, then diode rectifier bridge need to be modified to 3 diodes scheme instead of 4 diodes full bridge. I've decided not to bother with that and install a precision DC power supply board to have regulated and precise 24VDC). Original filter capacitors block has been removed from service to save space within the power supply unit.

Also installed Siemens & Halske power varistors for 20V and 14V to protect buzzer and lamps outputs from possible transformer's inrush current or other bad things. They are soldered directly to the 8-pin blue Amphenol connector of power unit (see upper left corner of the photo below).



A small bonus - I've ordered on eBay a regulated power board with no LED, as I don't need it and don't want to waste energy. However, I received an alternative model with blue LED indicating power on state. Decided not to cut it out for now. It actually gives a nice deep blue background in the power unit making it look fun.



New transformer fits well the housing of 28D2 power unit, have some space inside for ring generator board and potentially control unit for audibles.



If I were a marketer of Western Electric / Bell System I would have called it "Mystery Blue" and probably would charge customers $1.99 per month for this additional feature. Mention the small hole behind the blue voltage selector wire (it is not used any longer, just left it for cosmetic purposes to keep the look of original unit). This is the original transformer mounting point. New one is slightly to the right from it. I will later use this hole to bring up on the panel a miniature lamp, which will be run in parallel with ring generator, so lamp will indicate when the ring generator is powered on (I don't want to power it continuously, it takes power in idle state and also goes warm. So it will be controlled by a power MOSFET transistor from interruptor's motor start lead. Thus ring generator will receive power - rectified 10VAC which is 12VDC - only when interruptor is activated, and this is when ringing voltage is needed).



Siemens & Halske power varistors on the Amphenol output connector within the power supply unit. I have become superstitious to line transformers after an integrated rectifiers bridge in my 108A loudspeaker unit of 4A speakerphone has been killed by a secondary 18VAC coils of a big transformer (the one which will be used for powering 584C panel later) presumably during power on/power off cycle. Now varistors are everywhere and Zenner diodes are in stock to provide more precise protection (not installed in this version).



Nitty-gritty wiring job on KSU's 66 block. I'm happy I've got a punch down tool, since I planned originally to install wires manually. What a pleasure I had with a punch tool instead for $8.50. This is really a great thing for dealing with 66 blocks. I was surprised that limited space for cabling within 551C KSU is in reality more than enough to make a neat termination. For now only two 25-pair cables with female Amphenol end are terminated here, I plan to add two more when they arrive. These ends are made from old Amphenol male-female extender cables with plastic ends. I've ordered some cables with original metal shell female Amphenol plugs. I will re-terminate these cables as well with metal Amphenols. Strange enough, but female Amphenols are in much bigger shortage than their male counterparts. I have a supply of plastic black AMP connectors here for ~$2.50, but I like original metal ones more. And those are possible to find as male, but female almost not exist on eBay.

I managed to find a Western Electric gray color insulation tape (of course it is not WE brand, I'm only talking about the color. Lines pairs are divided by this tape. So if anyone needs a grey insultaion tape I can mail it from the nearest Bauhaus (this is a German construction outlet like Home Depot in States).

Small rust brown unit in the right cable tray is PowerDsine 3W ringing generator (12VDC to 70VrmsAC). This tiny unit is the heart of my 551C KSU audibles. It will power all ringers in my telephone sets and as well Western Electric Chime bell to provide service of central ringer. This is a highly recommended unit, small and powerful it is potted in ceramic providing necessary protection and heat dissipation properties. It can be powered from 10VAC lamp battery via a rectifier (red and black wires). Output 70VAC ringing voltage (white and blue wires) is routed to RG and RB terminals of 551C KSU. I sourced these units from a guy in Israel were they were produced till 1996. This is a NOS supply, looks they produced more than they could sell at that time.



Four 400-series line cards (San/Bar 4000F) are installed into line card jacks of the KSU. I like San/Bar more as they are well designed and made, and suitable for repair. WE 400D are good, but they are on the metal board and really look like from stone age. I have some in stock, but they will be used on 584C panel. Haven't tried yet WE 400H cards on solid state circuits, which originally came with this KSU. Those should operate silently, since they have no magnet coil relays (all is solid state) and only one reed relay, but that one is with mercury wetted contacts and only can be installed vertically. So I can mount those cards only when KSU is on the wall.



For the nearest future the following improvements are planned:

1) Produce and install ringing generator power control board and install it into the KSU, so that ringing generator is activated by motor start voltage of interruptor and shut down after ringing cadence is not needed any longer.

2) Produce a feature block based on one 4-switching contacts relay to be able to easily switch between common audible based on ringers to buzzers and back across the whole network. This is an easy task, I plan this switch to be activated by pressing a signal key on any of the telephone sets connected.

3) Extend 551C KSU service to 5 lines. There is indeed a designed place for 5th line card below the standard cards slots. This space has thread holes for a jack and even mounting holes for a retaining bracket like on upper card slots (of course there is no bracket provided). I will take 18-pin line card jack from 584C panel (I don't need 13 lines there and 13 is not a good number, I like 12 much more) and wire it up. The only engineering reason I see from finally abandoned idea to furnish 551C KSU with 5 lines service (which would have been fantastic, since these combined commercial/residential shoe box in this case would have matched the most popular layout of 1 hold and 5 pick up buttons of standard 1A2 telephone sets) is that they could squeeze in a 66 block with enough terminals for all 5 lines. And this reason is stupid for me. I've ordered a 6-pin small additional 66 block and will terminate line 5 there (will need to figure out where to place this additional block - probably on the bracket above the interruptor where 118A ringer generator is installed, since I don't need a 118A generator.

Trouble encountered:

Somehow have problem with Tip and Ring polarity. San/Bar 4000 line cards are not sensitive to CO line polarity, however they don't want to detect ring when I put polarity correctly (tip is positive to ring). Reverse polarity works well for ring detection, so I have to keep it as is ("plus" of CO line is on ring terminal). However this cause a problem with one of my 565 telephone sets - touch tone dials is inoperative in this condition. Reversing CO line polarity to normal allows dialing out but disables ringing detection by all four line cards. If anyone has an assumption of possible cause, would be great to know.

Here's the first video of 1A2 system testing on 2872A2M and 564HK telephone sets. Will keep you posted on updates. Comments and recommendations are welcomed.

[video:youtube][/video]

Not sure why the San Bar cards are doing that. Don't recall that ever being an issue. Have you tried reversing polarity on the line INSIDE the set?

I seem to remember that there was a provision on ITT sets to disable the polarity guard by cutting a strap on the back of the Tone Dial. I don't know if that would apply to WECO sets, I'll have to look.

Nice job on the shoebox!

Sam

Awesome project!

Update on the project:

551C KSU has been mounted to the wall next to my Ascom 2030 ISDN PBX (4 analogue lines run from this PBX to the KSU), connected to common ground and commissioned to regular service.

Control board for PowerDsine ringing generator has been made - I simplified it versus originally planned design. It actually takes only rectifying bridge, one filter capacitor and a protective 300 Ohm 3W resistor for the output 70Vrms circuit. As planned I've added a miniature lamp to indicate active state of ring generator - it flashes whenever ringing signal is sent to the common audible pair. Right side of the board is not needed actually, but I've decided not to cut it for the time being as I may need to place an additional relay on it in the future.



All mounted on the metal bracket from the construction supermarket. Back side of wiring board is potted into hotmelt glue to protect from short circuits. Only 2 pairs coming out: 10VAC in from interrupted common audible (white-red) and 70VAC output (white-yellow) for ringing signal to the system common ringer pair. They are terminated to 551C KSU's 66 block.



Bracket is mounted using one of the original holes for ringing generator mounting bracket (the unobtainable one). It covers part of the 66 block, however if needed it can be turned up or down from this position to open access to corresponding terminals of 66 block. I could turn it around to position it above the interruptor, but I don't want to occupy space for 5th line card in the 551C KSU, since it will be added later.



Miniature 12V lamp is connected in parrallel with ringing generator to the output of integrated rectifying diode bridge. So it lights up following the cadence of ringing signal.



With full uncut board KSU cover still perfectly fits - so everything is left as it is now. Probably I will make one day an Issue 2 control board with improved appearance and functionality. For now this works perfectly.



I have finally opted for using existing switching relay in Ascom 2030 PBX instead of installing additional one into the KSU. This relay has one set of contacts (normally closed and normally opened), which is activated by a button on the system set or via phone code. I wired this relay to switch common audibles from ringers (via control board and PowerDsine ringing generator) to buzzers (10VAC) and back. So now I can instantly switch between these two modes by dialing special code 12-75 on any of 1A2 sets connected. Very handy function for keeping the system flexible.

Software

Now when the stage one hardware works have been completed on my 1A2 system, I've spent some time programming the Ascom 2030 PBX to deal properly with 4-lines wired into KSU:

Hunting group has been created to cycle the extension numbers in the KSU. PBX provides extension 40 (Line 1), 41 (Line 2), 42 (Line 3) and 43 (Line 4). Now if any of called extensions is busy, the next line button will ring. Group is circular, so if Line 4 (extension 43) is busy, system will come back to Line 1 or any free line button available.

With incoming external calls it looks cool: first incoming call on my external number appears on Line 1 button. If I occupy this button and somebody calls my number at the same time, this call will appear on Line 2 button. If both are busy, then it will hunt further and indicate call on Line 3 button. Finally if I have 3 lines in use (on hold or in conversation), next incoming call will appear on Line 4 button. This is how business telephone system should work in my view: incoming line should never be busy (unless I occupy all 4 lines).

I could extend it to Line 5 button, however it is reserved for mobile phone integration via Bluetooth gate in the next release.

2872A2M Touch-A-Matic update:

Battery repair. Each 2872A2M Touch-A-Matic set is equipped with 1200 mAh 5V Ni-Cd battery. Nominal life cycle of this battery is 4 years according to BSP. My set has battery dated 1980, so no chance to hope old cells can give anythings after 37 years. Actually this battery already started to leak, creating some damage to the connectors and metal base around the battery. See picture of RJ11 connector on the battery.

Battery housing is sealed, so I have to saw it around the seam to get access to accumulator cells.



Inside the black box I have found four 1.5V cells mounted on hotmelt glue, all in salt and electrolyte. Quick search on eBay revealed exact size battery pack used for AEG portable vacuum cleaner. Difference is that it is Ni-MH and hence has slightly higher capacity of 1600 mAh. So Touch-A-Matic can withstand longer power outrage than with the original battery.



My guess was correct and ordered batteries fit perfectly into the original box.



First step of repair - RJ11 connector has been changed to a new one. No cleaning would have helped with the damage from leaking battery.



Wires have been soldered to the new battery terminal and it has been assembled back with sealing the perimeter with hotmelt glue. 2872A2M has a lockout to prevent using the autodial function without battery connected. In reality this lockout is only 2 black wires bridged together and connected to the negative terminal of the battery pack.



That's it - battery is installed back to Touch-A-Matic set and tested for memory retention without the AC power. I don't know how energy efficient memory circuits are in this 1980 telephone set, but this accu pack can power a vacuum cleaner for couple of hours I believe. So I can only imagine how long memory chips would eat all this 1.6 Ampere-hours to run it to zero.

Still looking for somebody in the possession of Touch-A-Matic set with speakerphone function. I would appreciate just some pictures of this option board to be able to produce it on my own.

I am on the trail of either (1) a set of the two circuit boards required for "one-touch" dialing with speakerphone, or (2) the SD's for those two boards. I will let you know as soon as I am in possession of either or both.

Arthur,

I really appreciate if you'd manage to find it. I even can take the whole old Touch A Matic for parts if the boards are there.

Konstantin

Touch-A-Matic repair is completed:

New beige handset installed, new directory sheet with matching typeface and key designation tabs are produced.



Waiting for a matching color Western Electric 4A speakerphone to complete this wonderful station set.

After last hunting on eBay I feel like a kid in a toy store.

Bell Chime F1A ringer from 1962 in ivory. Bells are cleaned today utilizing musical brass polishing technology.



Difficult to believe that it it is from 1962, but the ringer marked that date as well as same year molded on the plastic cover inside.

A labor of love! Nicely done.

Sam

You could have simply used a 220/120v step down transformer. That would have saved you a lot of needless work and kept everything original. Just sayin...

-Hal