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Old 3rd Jun 2019, 3:14 pm   #1
Shmason
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Default GPO planset with external extensions

Hi Everyone,

Thank you for accepting me into your group! I kept coming across one of your old posts regarding someone wanting to get a planphone working and have the lights working for display only. I saw some very knowledgeable replies so I am appealing for some help!

My good friend has spent a large amount of time putting together a working Planset system complete with two 'external' extensions and original power supply and ringing converter. He has installed it for me over the weekend and it works a treat! The only issue I can see is that if the main phone is switched as 'extn to exch' the main phone does not ring. Similarly at either extension you can no longer make contact with the main in this condition as the main buzzer does not operate.

From doing a Google search I believe the buzzer should sound instead of the bell in the main when the exchange line is switched through and I find it hard to believe if the exchange is switched through to the extensions the extensions can no longer contact the main!

My plea to you all is what is the missing piece of the puzzle? Has my Dear friend missed something that can correct this condition?

Very many thanks to you all.

Best regards

Jason
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Old 3rd Jun 2019, 4:46 pm   #2
TonyDuell
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Default Re: Gpo planset with external extensions

My first thought (without really working through the circuits) is the 'earth' connections. Each extension needs to be earthed, so does the planset _and it depends on the 'a' wire of the telephone line being earthed at the exchange_.

You can simply link the earths together, and back to the A wire (using 3 core cable to the extensions) rather than using true earth (which may cause problems if your telephone line is wired the other way round).
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Old 3rd Jun 2019, 8:18 pm   #3
JohnBHanson
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Default Re: GPO planset with external extensions

Some versions of planset use a transistor to detect the extension being off hook rather than a relay. This makes it polarity sensitive.

Also external extensions use need an earth to work ringing the main.
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Old 3rd Jun 2019, 8:42 pm   #4
Shmason
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Default

Thank you very much Tony for getting back to me. I should have also mentioned I know little about telephony and wiring! But that said, I have looked inside the junction boxes and found the following:

Both extensions - Green from phone cord wired to green with white stripe AND white with green stripe. These all terminate (ie 4 cables) under terminal 13 on the plan phone terminal block. Then a brown cable runs from terminal block into base unit. It appears red and white of line cord into main phone are used and blue and green are not.

Hope this means something to you!

Many thanks

Jason

Quote:
Originally Posted by JohnBHanson View Post
Some versions of planset use a transistor to detect the extension being off hook rather than a relay. This makes it polarity sensitive.

Also external extensions use need an earth to work ringing the main.
Thank you John. This is a very late model if that helps determine if transistor or relay use? Sounds like you can hear a relay though when extension calls main whilst the exchange line is switched through (ie instead of hearing the buzzer you can hear a click)
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Old 3rd Jun 2019, 10:35 pm   #5
WayneL74
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Default Re: GPO planset with external extensions

Are you sure the extensions have been wired as "external" extensions? I have just had a look at the appropriate N diagram (N4507 - page 3) & according to that the only thing connected to "Block Terminal No 37" terminal 13 should be a connection to terminal 1 of "Convertor Ringing 9A".

As Tony has said you are best off wiring these as 3-wire extensions. (I have done this for a set I have created & can provide details if required)

I have attached the appropriate N diagrams which I obtained from Sam Hallas's excellent site - http://www.samhallas.co.uk/repositor...rams/index.htm

You can usually ascertain which version of the Planset you have by looking at the base plate of the Planset. It usually says whether it's a mark 1, 2 or 3. Failing that you can take off the base plate & comparing the circuit layout with the pictures on diagram N625. If you do have a mark 1 be careful that the power supply or connected with the correct polarity as if not I believe it blows the 2 transistors in the Planset base.

Also reading you note about only red & white being used in the cable to the main. Do you mean the cable from the terminal block to the Planset base? This should be quite thick & have 18 wires in it.

If it helps post some pictures of the connections & we will take a look & advise.

Regards,

Wayne
Attached Files
File Type: pdf N4507.pdf (368.9 KB, 24 views)
File Type: pdf N625.pdf (817.2 KB, 18 views)

Last edited by WayneL74; 3rd Jun 2019 at 10:44 pm. Reason: Corrected Planset cable capacity
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Old 4th Jun 2019, 11:29 am   #6
Shmason
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Default Re: GPO planset with external extensions

Hi Wayne,

Thanks for getting back to me. Yes there are 3 wires in use on the extensions, the third I presume is earth (green wire on extensions).

Perhaps he has made a mistake, and I will check tonight not but I am fairly sure it was terminal 13 the earth wires were connected to. It is strange though that all other functions of the system seem ok; intercom mode works when all buttons released on the planset, external bells ring when switched through etc.

Thanks so much for the diagram links. I believe he worked off N4507 and left a copy with me but he didn't leave me N625 so perhaps he didn't have it.

Mine is a Mark 3 planset. My friend had mentioned this recently and I think I saw it underneath. It is certainly a very late model as it has REN 1 stamped underneath and the approved for use on network sticker that appeared in the 80's.

The red and white cabling I referred to is from the telephone socket to the planphone terminal block. Sorry I didn't make that very clear. This matches what I saw on 'British Telephones' website so perhaps he used this to assist him.

Thank you again. Happy to do some photos if they will help.

Best

Jason
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Old 4th Jun 2019, 3:52 pm   #7
TonyDuell
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Default Re: GPO planset with external extensions

I don't think terminal 13 is earth, it should go to the ringing converter only.

Looks like terminal 7 (in the N diagram, 'BT' means 'Block, Terminal') is earth. But I have an idea that it assumes the A wire is earthed at the exchange too. So try a link between 6 and 7?
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Old 4th Jun 2019, 4:27 pm   #8
Shmason
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Thumbs up Re: GPO planset with external extensions

Thank you I will check this tonight. I am very keen to get this up and running correctly. If this doesn't work I'll write out how he has wired it up.
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Old 4th Jun 2019, 9:27 pm   #9
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Default Re: GPO planset with external extensions

Hi, from the memory of the Planset that was installed where I once worked, I don't think the MAIN phone should ring when switched through to an external extension, the buzzer operates in sympathy with the ringing cadence instead.

I think that there is a modification to the strapping and ringing converter to allow the main to ring when switched through to an external extension however it may only be applicable to Plan 7, which only has one external extension and not plan 5 which has two extensions.

There's a load of information here and the N diagrams can be found here

Feel free to PM me if you require any additional help

Regards

Andrew
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Old 4th Jun 2019, 10:50 pm   #10
Shmason
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Default

Hi All,

Thanks for all your replies! To confirm, earth is not connected to 13, it is correctly connected to 7- the TB is the 'wrong' way up compared to ringer converter and power supply (mounted on a wooden base)! Also, as far as I can see terminals 6&7 are already bridged inside the base unit.

I have had a look at the terminal block wiring and my findings are attached. I appreciate it is hard to tell just from this, especially in my novice descriptions, but I thought maybe it might highlight something obvious. I guess my next step will be to see where wires terminate inside the base unit?

Andrew I agree with you; from what I have googled I think the buzzer should ring in the main when exchange is switched to extension.

Thanks again!

Jason

Just a thought, and I think this will be a red herring but will mention it anyway... the planphone has a bell on/off switch which seems to be working fine. I think it is a three wire switch but the third wire (brown?) is just loose inside the case. Not sure if this would have any bearing on anything!
Attached Files
File Type: xlsx PLANSET.xlsx (10.4 KB, 18 views)
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Old 5th Jun 2019, 2:07 pm   #11
AndiiT
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Default Re: GPO planset with external extensions

Hi again,
The N diagrams should show you where the wires need to be on the terminals inside the Planset and also on the extensions and ringing converter.

If your Planset has a Bell on/off switch it suggests that it may have originally been installed where there was an additional phone (Plan 1A or similar) or bell and may well have its connections strapped for an internal and not an external extension.

I haven't read back through your thread before posting this message, you are aware that if the external extensions aren't located a great distance away that the Earth connections can be a physical wire and not true earth aren't you?

Did you manage to obtain thermistors for the external extension bell circuit to prevent bell tinkle when dialling?

Regards

Andrew
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Old 5th Jun 2019, 2:17 pm   #12
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Default Re: GPO planset with external extensions

Quote:
Originally Posted by Shmason View Post
........ if the exchange is switched through to the extensions the extensions can no longer contact the main!...
Apologies, I have just read this part - in the original Plan 105/107 set up with external extensions the external phone(s) had to be on hook when the 'Call Main' button was depress to operate the buzzer in the Planset (via the relay in the ringing convertor), as a result there were no 'recall main' facilities provided when an exchange to extension or an extension to extension call was in progress.

The official operating procedure was that an external extension user should depress the call main button once after their handset was replaced to alert the main to release the Planset's keys to their idle state, I don't know of anywhere who had a Planset installed that actually did this though.

You must remember that these systems where designed for small offices or businesses where it was unlikely that a call going to an extension would have the need to be transferred back to the main.

Regards

Andrew
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Old 5th Jun 2019, 6:41 pm   #13
TonyDuell
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Default Re: GPO planset with external extensions

OK, I think it's time to go through this logically. I am working from the diagrams on pages 6 and 7 of N4507 (from Sam's site).

Now we have Exch-to-Extn operated, so contact KE5 is open, disconnecting the 'main unit' bell. KE1 is changed over, so the B wire (terminal 4 in the main unit) goes out on terminal 1 to the relay coil in the ringing converter. Contact A2 (part of the relay inside the plinth) should be open as relay A is not energised, so the relay coil is not shorted out. The other side of the relay coil comes back on terminal 9, then via KA1 or KB1 (both not operated) to the bells in the extensions, then to earth (and thus back to the A wire which is assumed to be earthed at the exchange)

The relay in the ringing converter has one contact. This conects the +v side of the PSU to one side of the buzzer, the other side of the buzzer goes to the -ve side of the PSU via contact A3.

OK. Now I believe you said the extensions do ring in this mode So there must be a path from the B wire to the appropriate line of the extension, the to 'earth' and back to the A wire.

So there seem to be several possibilites :

1) Contact A2 is closed for some reason, shorting out the relay coil

2) The relay in the ringing converter is not operating for some reason.

3) Contact A3 is open for some reason

4) The buzzer is faulty

5) The PSU is defective.

Start by taking the cover off the ringing converter. The relay is obvious. Now have an incoming call. Does it operate? If not then either relay A is operated for some reaso or the wiring is wrong.

Maybe the line current sense reed relay LS has stuck closed? That would cause A to be energised.
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Old 5th Jun 2019, 11:22 pm   #14
Shmason
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Default Re: GPO planset with external extensions

Tony,

Thanks for the detailed response. I appreciate it is frustrating when you are not with the equipment and dealing with a novice who doesn’t really understand circuit diagrams.

Tonight’s revelation is that the ring conv relay will operate the buzzer when pressed manually. I also disconnected the two wires leading to its coil and applied an independent power source; the relay activated and buzzer sounded. So I think it is fairly safe to say finding out why the ring conv relay doesn’t activate is key to all this. I have copied your earlier message below and will comment in capitals to save time with formatting. I’M NOT SHOUTING!!!

Now we have Exch-to-Extn operated, so contact KE5 is open, disconnecting the 'main unit' bell. KE1 is changed over, so the B wire (terminal 4 in the main unit) goes out on terminal 1 to the relay coil in the ringing converter. Contact A2 (part of the relay inside the plinth) should be open as relay A is not energised, so the relay coil is not shorted out. The other side of the relay coil comes back on terminal 9, then via KA1 or KB1 (both not operated) to the bells in the extensions, then to earth (and thus back to the A wire which is assumed to be earthed at the exchange)

WHEN EXCH TO EXTN DEPRESSED, MAIN RELAY (PRESUME THIS IS A) IN PLINTH IS NOT OPERATED. HOWEVER, IT DOES OPERATE WHEN SOMEBODY LIFTS ONE OF THE EXTENSIONS AND PRESSES THE CALL EXCHANGE BUTTON.
YOU MENTION TERMINAL 4 AND 9, IS THAT ELECTRICALLY CONNECTED DUE TO THE SWITCH AS MINE IS NOT HARD WIRED THIS WAY (SEE FURTHER DOWN).

The relay in the ringing converter has one contact. This conects the +v side of the PSU to one side of the buzzer, the other side of the buzzer goes to the -ve side of the PSU via contact A3.

OK. Now I believe you said the extensions do ring in this mode So there must be a path from the B wire to the appropriate line of the extension, the to 'earth' and back to the A wire.

So there seem to be several possibilites :

1) Contact A2 is closed for some reason, shorting out the relay coil

2) The relay in the ringing converter is not operating for some reason.

3) Contact A3 is open for some reason

4) The buzzer is faulty

5) The PSU is defective.

ARE THE CONTACTS A2 & A3 WITHIN ‘MAIN’ RELAY A IN PLINTH? THIS RELAY ACTIVATES WHEN EXCH TO EXTN IS DEPRESSED & MAIN HANDSET IS LIFTED OR AN EXTENSION HANDSET IS LIFTED & CALL EXCHANGE BUTTON IS PRESSED. OTHER THAN WITH MANUAL INTERVENTION I HAVE NOT SEEN RING CONV RELAY OPERATE UNDER ANY CONDITION OF PLANSET OPERATION. BUZZER SOUNDS WHEN RING CONV RELAY PRESSED MANUALLY OR WHEN EXTENSIONS CALL MAIN WITH ALL BUTTONS RELEASED. PSU PRESUMED OK.

Start by taking the cover off the ringing converter. The relay is obvious. Now have an incoming call. Does it operate? If not then either relay A is operated for some reaso or the wiring is wrong.

AS STATED IT DOES NOTHING. RELAY A (AGAIN, ASSUMING THIS IS THE COMPLEX RELAY WITHIN PLINTH) IS NOT OPERATED ON AN INCOMING EXCHANGE CALL.

Maybe the line current sense reed relay LS has stuck closed? That would cause A to be energised.

PLEASE ADVISE WHERE REED RELAY LS CAN BE FOUND. AS STATED RELAY IS ENERGISED WHEN EXTENSION PRESSES CALL EXCHANGE BUTTON BUT DOES NOT APPEAR TO BE ON AN INCOMING CALL.

Using page 3 of N4507 I have tried to trace the ring converter wiring back to terminal block. It seems correct, though it was made more difficult to check as the wires which should have been white/green, white/orange etc were all just plain white!

In my own simple terms, here is how the ring converter relay coil is connected. Perhaps the next step would be if you could see if you agree and then perhaps suggest some further testing?

4 of ring conv goes to 14 on TB which then goes to 1 on plinth using green/brown wire. (This has 2x blue wires feeding off it.)

5 of ring conv goes to 9 on TB which then goes to 9 on plinth (and bridged to 10) using green/red wire. (This has white/brown and white/green wires feeding off it.)

Apologies once again I have had to simplify things and probably not answered all your questions. This is very much a learning curve for me. I much appreciate the time you have all spent with your responses, thank you.

Jason
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Old 6th Jun 2019, 5:20 am   #15
TonyDuell
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Default Re: GPO planset with external extensions

To answer some of your comments :

Yes, Relay A is the relay in the plinth. I think on a Mk3 Planset it's one of those little 'continental cradle relays' as RS used to call them. The convention on GPO diagrams is to give the coil a letter (here 'A') and the contacts operated by it the same letter followed by a numner so 'A2' is a contact operated by the relay coil A

The LS reed relay is a long cylindrical thing in the plinth. But that all seems to be working correctly, the relay 'A' is operating as I would expect. And the fact that the buzzer operates when you press the armature of the relay in the ringing converter confirms this.

And yes, the problem is that the relay in the ringing converter is not operating on incoming calls with Ext-to-Exch pressed. The wiring of this relay coil to the plinth seems correct.

Can you confirm that the extensions ring on an incoming call with Ext-to-Exch pressed? If they don't then there is possibly a problem there (the extension bells are in parallel, that combination is in series with the relay coil essentially).

If the extensions do ring on an incoming call, try (temporarily) disconnecting one of the relay coil wires at the ringing converter terminals. Does this stop the extensions from ringing? It should do as it would open the circuit to their bells. But if it doesn't there's a short or misconnection somewhere.

Another silly thought... It's not the diode in parallel with the relay coil in the ringing converter its it? If that diode is open-circuit I have an idea the relay will not respond to the AC ringing signal. It will burn out if you test the relay on DC of the wrong polarity.

Last edited by TonyDuell; 6th Jun 2019 at 5:27 am. Reason: Added a silly thought
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Old 6th Jun 2019, 9:06 am   #16
Shmason
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Default Re: GPO planset with external extensions

Thanks for clarifying those points for me. I have had a quick look whilst waiting for the breakdown people to look at my car (it's been that sort of week).

In answer to your questions yes extensions ring when switched through but they stop when I remove one relay coil wire.

As the relay has never operated in my possession there is a chance it could have blown from the get go. Is there a way of testing, ie approx resistance values if ok or if burnt out?

Many thanks
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Old 6th Jun 2019, 12:26 pm   #17
AndiiT
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Default Re: GPO planset with external extensions

Quote:
Originally Posted by Shmason View Post
.....they stop when I remove one relay coil wire.
They will as the ringing current goes through the relay coil which in turn proves that....
Quote:
Originally Posted by Shmason View Post
....it could have blown.....
The relay coil must be OK


Andrew
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Old 6th Jun 2019, 1:07 pm   #18
Dave Moll
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Default Re: GPO planset with external extensions

... unless it has shorted turns.
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Old 6th Jun 2019, 3:02 pm   #19
Shmason
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Default Re: GPO planset with external extensions

Quote:
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... unless it has shorted turns.
I removed the two coil wires from the ring converter wiring block and applied a separate 9v source to the relay - it worked ok so fingers crossed the coils all fine.
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Old 6th Jun 2019, 4:48 pm   #20
TonyDuell
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Default Re: GPO planset with external extensions

Did you read my last comment?

There is a diode in parallel with the relay coil in the ringing converter. Desolder it and check it. If it is open-circuit then the relay will not respond to the AC ringing signal I think.

Diagram N626 is the one for the ringing converter. The diode is D1 on the circuit diagram. It says the relay coil should be 400 ohms, but you wouldn't pick up a few shorted turns like that (not that I think that is the problem). It's a special 'slugged' relay so you would have problems getting a replacement...
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