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Old 6th Jun 2019, 7:35 pm   #21
Shmason
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Default Re: GPO planset with external extensions

Ok I don't want to jinx it but I think we are getting close! I have removed the diode and put a meter across it both ways and there is zero resistance reading both ways. The relay coil does measure 400 ohms or there abouts. I put the meter in voltage mode and put it across the two relay terminals in the ring converter then called the phone from my mobile with the line switched to extension. The needle in the meter happily danced in tune to the phone ringing in the other room. So therefore current is reaching the relay coil and the diode is the culprit?

Further more, with the help of my partner I have discovered with the diode removed the extensions can successfully buzz the main whilst the exchange line is switched through. I am really chuffed about this as this was the main thing I wanted to acheive.

Finally, I remembered years ago my friend gave me some diodes for a clock application (this is my main hobby). I have just fished them out the garage. As far as I can see they read 1n4002. Will they be suitable or if not could you please advise what I may require? Thanks so much!
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Old 6th Jun 2019, 7:41 pm   #22
TonyDuell
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Default Re: GPO planset with external extensions

Do you mean zero resistance (meter needle swings all the way to the right) or infinite resistance (needle doesn't move at all) when testing the diode?

The 1N4002 is rated at 100V. That's a bit low for this application, I would try something like a 1N4007. But with the relay coil in parallel the voltage across it probably won't be that high actually, Give it a go, it may work (and if it does, at least you know the diode was the problem).
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Old 6th Jun 2019, 8:20 pm   #23
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Default Re: GPO planset with external extensions

Sorry, yes needle doesn't move whatsoever.

I have tried a diode and nothing happened so perhaps I'll order 1N4007 and give that a go.

Many thanks
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Old 6th Jun 2019, 8:31 pm   #24
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Default Re: GPO planset with external extensions

If the diode reads open-circuit (infinite resistance) on the meter, the fact that removing it causes the relay to work presumably means that it breaks down with the ringing current passing through it, effectively shorting out the relay coil.
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Old 7th Jun 2019, 12:31 pm   #25
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Default Re: GPO planset with external extensions

I have had various suggestions of diodes from different people so have ordered a few of 4 different types. Hopefully one of the blighters will solve the issue!

I did a final test; in a box of junk I have a 746 chassis and I wired the bell circuit to the wires that should activate the ring conv relay. I called the house with my mobile and with exch to extn switched through it rang perfectly. Therefore the issue has to be diode related??
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Old 7th Jun 2019, 4:41 pm   #26
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Default Re: GPO planset with external extensions

A couple of quick things to do.

1) Test one of you new 1N4002 diodes to make sure it appears to conduct one way only. This will verify you can test diodes with your meter.

2) Now test the 1N4002 you fitted to the rigning converter. Does it still test good? It's possible there's a fault that is burning the diode out.

I beleve you can get the relay in the ringing converter to operate by the buttons on the extensions. Connect your multimeter (DC volts range) between terminals 4 and 5 of the ringing converter (those numbers are the terminal numbers in the ringing converter), +ve lead to terminal 5. 'Buzz' from an extension and check the meter reads normally (should be about 9-12V). If it reads backwards then you have a wiring fault which could damage said diode.

Make sure the diode is fitted with the banded end connected to terminal 5 in the ringing converter.
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Old 7th Jun 2019, 4:52 pm   #27
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Default Re: GPO planset with external extensions

Many thanks. Away for weekend but will try all that ASAP.
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Old 7th Jun 2019, 6:17 pm   #28
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Default Re: GPO planset with external extensions

Another question. I assume you can ring the extensions (that is, the bells in said telephones will ring) using the 2 keys in front of the labelled keys on the plinth.
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Old 8th Jun 2019, 12:25 pm   #29
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Default Re: GPO planset with external extensions

Yes that's correct both extensions can be rung fine.
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Old 9th Jun 2019, 3:26 pm   #30
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Default Re: GPO planset with external extensions

Ok here goes!

1. I presume this means you will only get a resistance reading with the leads one way round, if so yes.

2. It has the same reading as an unused one.

3. With no switches pressed down, you get reading of approx 11v when extension calls main.

With extn to exch depressed needle moves wrong way. Possibly like this a long time hence dead original diode.

Swapping red and white BT line wires remedies this, ie in both conditions I get correct reading on meter. Buzzer works for internal call but still not for external. Is it ok to leave red and white wires swapped or is this asking for trouble?
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Old 9th Jun 2019, 3:41 pm   #31
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Default Re: GPO planset with external extensions

Are you saying that when you press 'ext to exch' (and everything is on-hook), you get a DC voltage across the relay coil? Because I don't think you should. Try (temporarily) disconnectng the wires to the extensions at terminals 3 and 12 of the Block Terminal. Do you get that DC voltage across the relay (don't worry about the polarity for the moment) with no extensions connected? With just one extension connected (say the wite removed from terminal 3 but the one on terminal 12 in place)? With just the other extension connected?

The telephone line wires go to terminal 4 and 6 of the Block Terminal. Terminal 6 (the 'B wire') should be the -ve one. That is, your meter should read normally with the red probe on 4 and the black probe on 6
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Old 9th Jun 2019, 5:05 pm   #32
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Default Re: GPO planset with external extensions

I get the DC voltage when an extension if off the hook and the press button on that extension is pushed. With all on hook no voltage present.
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Old 9th Jun 2019, 5:07 pm   #33
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Default Re: GPO planset with external extensions

Ah, OK, that makes sense.

Have you checked the line polarity at terminals 4 and 6 of the Block Terminal? Connect the red and white wires whichever way round makes it correct.
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Old 9th Jun 2019, 5:40 pm   #34
Shmason
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Default Re: GPO planset with external extensions

Ok. Having red on terminal 6 makes the polarity incorrect at the TB but correct across 4 and 5 of the ring conv. Switching white and red on the TB obviously does the reverse. But if I switch incoming wires 4 and 5 of the ring conv the polarity is correct when switched as extn to exch but incorrect when all buttons released!!
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Old 9th Jun 2019, 5:56 pm   #35
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Default Re: GPO planset with external extensions

This makes no sense to me, and I have read and re-read the circuit diagram.

Let's start with the basics. You have the meter probes in the right sockets. If in doubt, check a battery or something. The meter should read normally (pointer swinging to the right) on DC volts ranges when the red probe is positive.

Connect the red and white line cord wires so that terminal 4 in the block terminal is the +ve one.

Now check the polarity of the 'local' DC power supply. This goes to terminals 1 and 2 of the Block Terminal. Terminal 2 should be the +ve one.

When sounding the buzzer, check between terminals 4 and 5 of the ringing converter. Terminal 5 should be +ve
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Old 9th Jun 2019, 7:05 pm   #36
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Default Re: GPO planset with external extensions

Putting red back to 4 on TB that is all correct if NO buttons are pressed on the main phone. However if you press extn to exchange the polarity is reversed across 4 and 5 on ring converter.
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Old 10th Jun 2019, 5:03 am   #37
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Default Re: GPO planset with external extensions

Yes, I understand that. What I want to know is the exact polarities (at the the Block Terminal) of the line (red may or may not be +ve here) and the DC power supply.
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Old 10th Jun 2019, 9:14 am   #38
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Default Re: GPO planset with external extensions

Sorry, to clarify terminals 2 and 4 of main TB are +ve.

On ring converter, 4 is +ve when extn to exch is depressed and call main is pressed from an extension and polarity changes and 5 becomes +ve when all plinth buttons released and call main pressed from an extension.
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Old 10th Jun 2019, 6:09 pm   #39
TonyDuell
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Default Re: GPO planset with external extensions

Terminal 2 should be the +ve one. But terminal 4 (Labelled 'B' on the N diagram) should be the -ve line wire, with terminal 6 the +ve line wire. Connect it like that.

Now try terminals 14 and 9 in the Block Terminal when doing 'call main' from an extension in with 'extn to exch' pressed and also when it is released. In both cases terminal 9 should be the +ve one. And then in the Ringing converter check terminals 4 and 5, where terminal 5 should be the +ve when doing 'call main'

It sounds like the last part is correct, all you have is the line wires the wrong way round.
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Old 10th Jun 2019, 8:37 pm   #40
Shmason
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Default Re: GPO planset with external extensions

Ok, line wires swapped and in switched through and released conditions all polarities are correct to your last message.

Two questions on the diode please. Because we have been changing the polarities during experiementing I have removed the diode during testing then wired back in at an appropriate time to stop potential damage. If everything is correct does the diode work immediately or does it require being connected to current for a while?

So terminal 5 is +ve on ring conv. Am I correct that on diode end with silver stripe it is cathode which is negative so needs to go to terminal 4.

Many thanks
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