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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment |
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15th Nov 2017, 6:40 pm | #61 |
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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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15th Nov 2017, 9:34 pm | #62 |
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Re: GPO 332 transmitter issue
That's a start. what happens when you fit the T21 mic?
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15th Nov 2017, 9:35 pm | #63 |
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Re: GPO 332 transmitter issue
Same result
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15th Nov 2017, 11:35 pm | #64 |
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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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16th Nov 2017, 12:01 am | #65 |
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Re: GPO 332 transmitter issue
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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16th Nov 2017, 8:27 am | #66 |
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Re: GPO 332 transmitter issue
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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16th Nov 2017, 1:24 pm | #67 |
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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.
Regards Last edited by bigus01; 16th Nov 2017 at 1:33 pm. |
16th Nov 2017, 1:49 pm | #68 |
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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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16th Nov 2017, 1:51 pm | #69 |
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Re: GPO 332 transmitter issue
Yes, read an article which suggested this method. Just had it "free floating" whilst testing.
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16th Nov 2017, 2:34 pm | #70 |
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Re: GPO 332 transmitter issue
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16th Nov 2017, 2:42 pm | #71 | |
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Re: GPO 332 transmitter issue
Quote:
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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16th Nov 2017, 2:46 pm | #72 |
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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.
Regards Last edited by bigus01; 16th Nov 2017 at 3:02 pm. |
16th Nov 2017, 3:06 pm | #73 | |
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Re: GPO 332 transmitter issue
Quote:
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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16th Nov 2017, 3:07 pm | #74 |
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Re: GPO 332 transmitter issue
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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Mending is better than Ending (cf Brave New World by Aldous Huxley) Last edited by Dave Moll; 16th Nov 2017 at 3:09 pm. Reason: quote inserted for clarity as Russell's post intervened |
16th Nov 2017, 3:09 pm | #75 |
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Re: GPO 332 transmitter issue
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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16th Nov 2017, 3:26 pm | #76 |
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Re: GPO 332 transmitter issue
No, works fine like this.
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16th Nov 2017, 3:32 pm | #77 |
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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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Mending is better than Ending (cf Brave New World by Aldous Huxley) |
16th Nov 2017, 3:42 pm | #78 |
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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. |
16th Nov 2017, 3:53 pm | #79 |
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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. |
16th Nov 2017, 4:09 pm | #80 |
Octode
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Re: GPO 332 transmitter issue
Contact 3 should be connecting to Contact 4 when DON is closed. Try swapping the Brown and Pink wires around.
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