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Old 15th Nov 2017, 6:40 pm   #61
bigus01
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Default Re: GPO 332 transmitter issue

Test works as you suggest, dial tone plus side tone. Just checked and the is a connection between capacitor and T1 of dial strip.
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Old 15th Nov 2017, 9:34 pm   #62
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Default Re: GPO 332 transmitter issue

That's a start. what happens when you fit the T21 mic?
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Old 15th Nov 2017, 9:35 pm   #63
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Default Re: GPO 332 transmitter issue

Same result
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Old 15th Nov 2017, 11:35 pm   #64
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Default Re: GPO 332 transmitter issue

Oh, goody. You now have a working telephone that you can speak on and will receive calls. Just need to sort the dial now. The wiring colours look OK: T1, 2, 3, 4, 5 being blue, slate, brown, orange and pink respectively.

Pink and orange (4, 5) are the dial pulse terminals.

Brown and pink (3, 4) are one set of DON contacts.

Blue and slate (1, 2) are the other set of DON contacts.

I see yours is the older 'slipping cam' dial. Terminals 2 and 3 are linked on the newer 'trigger' dials. You could try linking 2 and 3 on yours. Attached is a schematic of a trigger dial, but it shouldn't be too difficult to work out which are the right connections on your dial. I'd remove all the wires from the actual dial and check out which connections are which.

Don't forget to remove the link between T4 and T5 on the dial strip when ready to use the dial!

The 0.1u cap should be connected to T4 on the dial strip, not T1.
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Old 16th Nov 2017, 12:01 am   #65
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Default Re: GPO 332 transmitter issue

Quote:
Originally Posted by russell_w_b View Post
Attached is a schematic of a trigger dial, but it shouldn't be too difficult to work out which are the right connections on your dial.
Here's a better paster diagram that's more appropriate for your 332 (I think it'll be a Mk:I).
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Old 16th Nov 2017, 8:27 am   #66
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Default Re: GPO 332 transmitter issue

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Originally Posted by bigus01 View Post
Both visually and with a meter.
Regards
Just curious... How come you have the pulse contacts shorted out AND the three remaining DON contact wires in place? Did you not dis these three wires for the test? Or is the photo taken after you reconnected them and before you took the pulse contact links out?

Because if it works like this, it's likely to be H/R pulse contacts that's causing you problems!
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Old 16th Nov 2017, 1:24 pm   #67
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Default Re: GPO 332 transmitter issue

Hi, yes photo was taken after testing was complete. Terminals 2 and 3 are already linked at the back of the dial strip. Is the link at 4 & 5 a permanent link, as without it I have no mic.
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Old 16th Nov 2017, 1:49 pm   #68
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Default Re: GPO 332 transmitter issue

How are you mounting your T21A mic insert in the handset? I've done a few but I've always kept them in the red case, having cut out a slot in the edge to accommodate the moulded bakelite protrusion that carries the mic contact to the springy crescent connection.

I noticed your handset still had the rear pintle connection fitted. Did you remove the little square mic capsule from the case?
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Old 16th Nov 2017, 1:51 pm   #69
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Default Re: GPO 332 transmitter issue

Yes, read an article which suggested this method. Just had it "free floating" whilst testing.
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Old 16th Nov 2017, 2:34 pm   #70
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Default Re: GPO 332 transmitter issue

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Originally Posted by bigus01 View Post
Yes, read an article which suggested this method. Just had it "free floating" whilst testing.
The wires that seem to connect across the pulse contacts appear to be pink and slate. I have no contact across 4 & 5 without the wire link, does this make sense?
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Old 16th Nov 2017, 2:42 pm   #71
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Default Re: GPO 332 transmitter issue

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Is the link at 4 & 5 a permanent link, as without it I have no mic.
Regards
No. This link is currently shorting out your dial pulse contacts, and allowing current through the telephone line loop of dial pulse contacts, mic, ASTIC primary winding, gravity-switch contact and return line.

It sounds like your dial pulse contacts, which are normally closed, are high-resistance and not allowing sufficient current through to power your T21A mic. You'll need to clean them. Over the years they'll've become pitted with sparking.

I would use a thin strip of rough paper (blotting paper) and, with your fingers gently squeezing the contacts together, draw the paper through back and forth a few dozen times. But ensure that they are actually making contact when the dial is at rest.

Another thing it could be is a dodgy pink or orange wire between dial and dial terminal strip, especially the little bound loop connectors at the ends. They may be hanging on a thread or so or otherwise H/R. I've known me having to change some of them out. Your telephone, being the older model, has cotton-covered insulation rather than PVC.

That's the area to focus on next. It can be magnifying-glass stuff!
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Old 16th Nov 2017, 2:46 pm   #72
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Default Re: GPO 332 transmitter issue

I have already cleaned contacts which give a good reading with meter. Should these contacts do the same job as the wire link? See previous post. I have also tested continuity off all 5 cables, which are fine. All I can get is the sound of my own voice in the receiver, no sound transmitted. Think I'm nearing the point of putting everything back to original and accepting it.
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Last edited by bigus01; 16th Nov 2017 at 3:02 pm.
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Old 16th Nov 2017, 3:06 pm   #73
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Default Re: GPO 332 transmitter issue

Quote:
Originally Posted by bigus01 View Post
The wires that seem to connect across the pulse contacts appear to be pink and slate. I have no contact across 4 & 5 without the wire link, does this make sense?
It does, but it's wired incorrectly. Look at the paster diagram I posted earlier and you'll see.

Looking down at the dial terminal strip, the terminals are numbered 12345 left-to-right. The colour order is as follows:-
1 = Blue
2 = Slate
3 = Brown
4 = Pink
5 = Orange.

Don't get hung up on the colours, though - it's been known for them to have been swapped out in the past. But the pulse contacts should go to 4 and 5 on the dial terminal strip.

The other terminals are confusing and there's a conflict between what is shown on a dial No: 10 (like yours) and on the explanatory diagram. Here's what I'd do...

*Disconnect your dial entirely and determine which are both sets of DON contacts.

*Check to see if any of these contacts are connected to each other internally on the dial springs.

*After deducing the aforementioned, draw out and post on here how your dial contacts interact with each other, and we'll take it from there.
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Old 16th Nov 2017, 3:07 pm   #74
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Default Re: GPO 332 transmitter issue

Quote:
Originally Posted by bigus01 View Post
Should these contacts do the same job as the wire link?
As Russell says, when the dial is at rest, these contacts should be closed, thus making the loop in the same way as your temporary link when it was in place. When the dial is turned, the contacts will open (thus causing a Loop Disconnect) the required number of times to pulse out the digit dialled.
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Last edited by Dave Moll; 16th Nov 2017 at 3:09 pm. Reason: quote inserted for clarity as Russell's post intervened
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Old 16th Nov 2017, 3:09 pm   #75
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Default Re: GPO 332 transmitter issue

Quote:
Originally Posted by bigus01 View Post
All I can get is the sound of my own voice in the receiver, no sound transmitted.
Is this the case with all the dial terminal strip contacts physically removed and terminals 4 and 5 on the dial strip shorted together?
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Old 16th Nov 2017, 3:26 pm   #76
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Default Re: GPO 332 transmitter issue

No, works fine like this.
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Old 16th Nov 2017, 3:32 pm   #77
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Default Re: GPO 332 transmitter issue

With the dial in place, but with the shorting link removed, what resistance reading do you get between terminals 4 and 5 on the dial strip? It should be approximately zero.
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Old 16th Nov 2017, 3:42 pm   #78
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Default Re: GPO 332 transmitter issue

Below is how I've got a Dial No 10 connected in a 332, which also has a Transmitter 21A.

No matter how many I do I STILL get in a mess with dial connexions so you aren't alone.
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Old 16th Nov 2017, 3:53 pm   #79
bigus01
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Default Re: GPO 332 transmitter issue

Right, here goes;
Contacts 1 (blue) &2 (slate) make contact with DON closed.
Contact 3(orange) makes contact with 5 when pulse contact open & DON closed.
Contact 4 (brown) makes contact with 5 (pink) when pulse contact closed.
The numbers are those of the terminals.
Make sense?
Regards

Last edited by bigus01; 16th Nov 2017 at 4:11 pm.
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Old 16th Nov 2017, 4:09 pm   #80
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Default Re: GPO 332 transmitter issue

Quote:
Originally Posted by bigus01 View Post
Contact 3(orange) makes contact with 5 when dial contact open & DON closed.
Contact 3 should be connecting to Contact 4 when DON is closed. Try swapping the Brown and Pink wires around.
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