Author Topic: Field exchange SB-22/PT  (Read 3028 times)

Offline dsk

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Field exchange SB-22/PT
« on: November 15, 2019, 03:21:17 AM »
SB 22/PT is made in several versions during the years.
The first ones had a heavy metal case, the later plastic.  The older operators packs had that retractable cords, but no jack for resting the plug. That rest jack on the newer ones had an extra switch cutting transmitter power to prevent discharging of the battery.
Later models could have trunck-packs for connecting to CB lines, in addition could it be a keypad.

Mine is one of the older ones, I have modified a line -pack to a trunk-pack and use a rotary dial for dialing.
I have not been willing to pay for those expensive parts,  shipping and customs to Norway of several 100 dollars.
When I served, we used a handset, but a headset was the standard. In my setup I took another handset more suitable for my use.
dsk

PS I modified to use some rechargable batteries I have.  (18650 lithium battery)   DS
« Last Edit: November 15, 2019, 03:31:40 AM by dsk »

Offline RB

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Re: Field exchange SB-22/PT
« Reply #1 on: November 15, 2019, 12:25:24 PM »
sweeet! I like the handset, and the dial mount ! :)

Offline dsk

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Re: Field exchange SB-22/PT
« Reply #2 on: November 16, 2019, 12:44:53 PM »
sweeet! I like the handset, and the dial mount ! :)

I like to improvise, and the Dial was an old Antwerp dial, on witch I did put belt clip on the back side and a logo in the dial-center.
The handset was on I had without anything else but it has press to talk it is comfortable to hold and has a good receiver (equal to most German receivers) and a good electronic transmitter-capsule suitable here, but polarity sensitive.  The handset has a logo with the brand  Gfeller, (Albiswerk AG, Gfeller AG ?)  (logo pictured)

dsk
« Last Edit: November 16, 2019, 01:01:10 PM by dsk »

Offline countryman

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Re: Field exchange SB-22/PT
« Reply #3 on: November 16, 2019, 02:59:42 PM »
"in 1896 Christian Gfeller founded a mechanical workshop for telephones and railway signals in Bümpliz.(...) 1984 Gfeller AG* and Autophon AG merged.(...) 1987 Autophon, Hasler and Zellweger merged to Ascom."
(http://www.query.sta.be.ch/detail.aspx?ID=546950)
It seems Gfeller was a major supplier for fhe swiss army.

*AG = Swiss public company.

Offline dsk

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Re: Field exchange SB-22/PT
« Reply #4 on: January 06, 2020, 12:22:49 AM »
Due to the limitation in how lagre uploads we may put here a good pdf manual is located here: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKEwiLkJv7nO7mAhXU5KYKHbjACl4QFjAAegQIAxAC&url=https%3A%2F%2Fradionerds.com%2Fimages%2Fb%2Fbe%2FTM_11-5805-262-12.pdf&usg=AOvVaw0sZaZ0gRvkW12Nq5p5Cdwc

More info about the SB22 is here and ther e on the net:
http://www.prc68.com/I/SB22.shtml

dsk

PS attatched the PDF where the late pages are removed, this waas only blank pages, and forms ti fill out ...    DS
« Last Edit: January 06, 2020, 12:45:09 AM by dsk »

Offline dsk

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Re: Field exchange SB-22/PT
« Reply #5 on: April 16, 2020, 03:25:15 PM »
Since it seems to be impossible to get the original DTMF unit for the cordboard, and my trunkpack also is a DIY version, I did get inspired of the German WWII solution: http://www.classicrotaryphones.com/forum/index.php?topic=22478.msg226592#msg226592


But of course I would like to have touch tone too, so I found a scrap phone with tone/pulse selector.   I did put in a jack, and some components.   I prefere the transformer to get the systems isolated from each other, the small transformer does not like the DC components, so I did put e capacitor in series on the CO side, and added a 470 ohms resistor to keep the DC path without loosing to much of the signal. On the SB-22 side I also added a capacitor to prevent it from stealing all the ring off power.

The diagram sketch shows how I wired it.  And ofcourse you have to see how small the transformer actually is.

The best of all, it woorks great on first try.
dsk

Offline countryman

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Re: Field exchange SB-22/PT
« Reply #6 on: April 16, 2020, 03:38:12 PM »
Bookmarked for later use...

Offline dsk

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Re: Field exchange SB-22/PT
« Reply #7 on: November 17, 2020, 09:44:31 AM »
Maybe not impossible, but at least extremely expensive to get a trunk-pack, so I made one a year ago, and modified it today with a LED  Depending on line polarity the led will light up when I am off hook, and it will flash during ringing.  Since we sometimes do not want the light (in the war close to enemy etc) it will not light up if I switch tip and ring wires.

It works well on my old SXS and on ATAs. 

dsk

Offline Key2871

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Re: Field exchange SB-22/PT
« Reply #8 on: November 17, 2020, 12:15:52 PM »
Great idea! Nice work.
KEN

Offline dsk

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Re: Field exchange SB-22/PT
« Reply #9 on: December 03, 2020, 02:55:54 PM »
Working on this and kinda missing the touch tone pad for the SB/22-TP-A with trunk line. As you see earlier in this thread it works with my other D.I.Y. solutions, but what may solve that, --  What about a regular push button phone like a W.E. 2500, and wouldn't it be OK to use that as the operators handset too?    The solution is of course to connect it to the pair 15 (EMG OPER) just as the keypad, but we need to power it by a battery, but not sending DC out on the line.   A capacitor of 2-5 uF will block DC and let voice trough  Then a battery across the line will supply power, but to limit the loss of voice signal a coil (or a resistor) in series helps, a diode helps too when the the phone is on hook and you use the regular handset/headset.  A suitable coil is of course depending on what you have, but the higher resistance the more volt you need on the battery.  Just a guess, but less than 100 ohms, and a 9V battery will do a great job.  Here is the simple diagram: ( I had a 90 ohm coil, 9V battery diode and  ringer capacitor of 2.2uF and that works.  )

Offline RB

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Re: Field exchange SB-22/PT
« Reply #10 on: December 03, 2020, 04:08:32 PM »
Nice work Sir! as usual.
Now, how did you add that switch blade???
That stack is a monster!

Offline dsk

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Re: Field exchange SB-22/PT
« Reply #11 on: December 03, 2020, 05:06:11 PM »
Redesigning the line unit to a trunk unit without the right parts is a challenge, and will not last without service far as long as the originals.  Here you see that I used a relay as a coil and added a micro-switch to sense that the plug is out. The extra contact on the jack is just a metal piece and will last as a real contact with silver ..  Glue is good for a project, but not the right thing to fix the relay...
As usual, it is a (well) working prototype.
dsk

Offline dsk

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Re: Field exchange SB-22/PT
« Reply #12 on: December 18, 2020, 04:13:51 PM »
I actually discovered at least one error in the manuals schematics.  It is probably more, if we look at that witch has been distributed unchanged for more than 60 years, it is surprising me.

I have only made one important correction of the last page here: https://www.scribd.com/document/488629535/TM-SB-22-PT

A little green wire from the bottom wire and up to the switch  P304 contact D3.

dsk

Offline dsk

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Re: Field exchange SB-22/PT
« Reply #13 on: December 26, 2020, 05:56:15 AM »
We have another thread too: http://www.classicrotaryphones.com/forum/index.php?topic=20588.msg244657#msg244657
Where we may find these:


and this:

Now I have used it for a while, and it was definitely not 100% OK, but it took time to discover some of the problems.

The first I had to do was to change the cord and plug, the cord was weared out.  (6)
The next was some problems I believed was in the switches so I measured and got some resistance.  (5) Cleaning with plain paper dipped in alcohol and keep the contacts closed.  Helped a lot!

Some later I found that the ring and sleeve had no connection.  The fault was the switch inside the generator (4)
What else have I heard others having problems? The Capacitors (2) and (3)  are also weak points, First aid suggestions: The no C301 (2) will just remove the anti sidetone, and you will probably barely notice it.  C302 (3) will make you loose the contact to the handset.  Without using a tone sender or field telephone to the contacts "EMG OPR" it will probably mean nothing to short C302 until it may be replaced of any unpolrized capacitor of 2-4 uF  rated at least 50V  If you can not get power to the transmitter it is most likely in outside the operators pack, often in the battery holder, and somtimes in the handset/headset with cords.  I can see a possible problem in the rest jack, but find that not so reasonable since those jacs are tough.
dsk
PS I really hope it works OK from now  DS



I also have to say thank you to Brooke Clarke who has great pages with information:
https://prc68.com/I/SB22.shtml

He actually also links to us.  :)

dsk

Offline dsk

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Re: Field exchange SB-22/PT
« Reply #14 on: December 26, 2020, 08:18:03 AM »
This one is definitely right, but not easy to read.

I hope this will be more easy to read and that I have got all the details here too.