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Old 14th Nov 2017, 6:07 pm   #21
ThePillenwerfer
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Default Re: GPO 332 transmitter issue

Quote:
Originally Posted by bigus01 View Post
Get o/c across T4 &T5 if I disconnect green wire from T6.
Regards
Unless you've altered the wiring in the handset the WHITE wire should be on T6.

Going on the photos I'd agree with Russell that the connexions should be:—

T4 - Red Wire - Bottom Left Handset Terminal (The one with the spike)
T5 - Green Wire - The Two Linked Right Handset Terminals (M1 and R2)
T6 - White Wire - Top Left Handset Terminal (R1)

The only other straw I can clutch at is suggesting you test for resistance between M1 and the hole at the extreme right where the curved fork thing goes that touches the back of the original transmitter.
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Last edited by ThePillenwerfer; 14th Nov 2017 at 6:15 pm. Reason: Typo and addition.
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Old 14th Nov 2017, 6:17 pm   #22
bigus01
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Default Re: GPO 332 transmitter issue

Update - I have now tried disconnecting dial. Still have the same resistance.
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Old 14th Nov 2017, 6:21 pm   #23
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Default Re: GPO 332 transmitter issue

Configured as it is in the photos that will be the resistance of the receiver, though it's higher than I'd expect. It may be different on a Handset 184 though.
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Old 14th Nov 2017, 6:34 pm   #24
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Default Re: GPO 332 transmitter issue

Quote:
Originally Posted by ThePillenwerfer View Post
Unless you've altered the wiring in the handset the WHITE wire should be on T6.

Going on the photos I'd agree with Russell that the connexions should be:—

T4 - Red Wire - Bottom Left Handset Terminal (The one with the spike)
T5 - Green Wire - The Two Linked Right Handset Terminals (M1 and R2)
T6 - White Wire - Top Left Handset Terminal (R1)

The only other straw I can clutch at is suggesting you test for resistance between M1 and the hole at the extreme right where the curved fork thing goes that touches the back of the original transmitter.
The handset wiring has remained the same, does not work with this wiring configuration. There is no resistance between M1 and horseshoe. Thanks for the input.
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Old 14th Nov 2017, 6:47 pm   #25
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Default Re: GPO 332 transmitter issue

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Originally Posted by ThePillenwerfer View Post
Configured as it is in the photos that will be the resistance of the receiver.
I believe Bigus rewired the handset at the telephone terminal block as I suggested in post #10 (he may have put it back, of course) So I'd disconnect the handset from the telephone terminal block, leave the dial disconnected and chase for 150 ohms round the loop from across terminals 4&5.

If you get a resistance here, then there's your fault. You may need to snip one of the wires to the 0.1uF cap as they're soldered on. It's not unknown for wires to snag and touch at switch contacts or the ASTIC.
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Old 14th Nov 2017, 6:51 pm   #26
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Default Re: GPO 332 transmitter issue

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It may be different on a Handset 184 though.
The 184 is a four-terminal handset, but it looks from the photograph that the green wire is used as a 'common' M/R wire by joining handset terminals M1 and R2 together. The pintle and mount for the carbon mic is from a Handset 164 as it is stamped M/R2, being the common connection on a 164 handset.
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Old 14th Nov 2017, 7:31 pm   #27
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Default Re: GPO 332 transmitter issue

You're right, the wiring has all been returned to as per the photo's which is how it was bought and how it works with carbon transmitter. Just clarify if you will that you suspect the the square capacitor?
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Last edited by bigus01; 14th Nov 2017 at 7:44 pm.
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Old 14th Nov 2017, 7:55 pm   #28
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Default Re: GPO 332 transmitter issue

I do indeedy! Neither capacitor (both are contained in the same case) is critical to its operation given that you're on a plug-in connection. The telephone bell uses the cap in the master LJU.

Be warned, though... If that's how the telephone handset was wired, it's wrong. It's effectively connecting the receiver in series with the mic. Passing d.c. through the receiver will eventually damage it. When you do find your spurious 150 Ohms, connect the handset as I suggested earlier, and as the drawings show.
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Old 14th Nov 2017, 8:02 pm   #29
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Default Re: GPO 332 transmitter issue

Thanks for that. Any ideas on where to obtain spares? When I left the handset wiring as it was and altered the phone wiring as you advised it would not work.
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Old 14th Nov 2017, 8:34 pm   #30
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Default Re: GPO 332 transmitter issue

You'll need to clear the fault first. Whatever is shorting your mic with 150 Ohms is pulling down the current in the 21A mic, but allowing sufficient current to flow thrugh the carbon mic. When we were kids we would wire a couple of handsets in series mic-rec -some wire-battery-some more wire-rec-mic and we'd have an intercom. Wrong thing to do (because of the need to keep d.c. out of the receiver), but it works.

Right... I've just had a look in the few telephones I have with Handsets 184. The metal plate behind the centre pintle does indeed say 'M/R2'. But this only applies on a handset 164 and is most probably down to economies of manufacture and interchangeability (telephone manufacturers are very good at that).

However... Rest assured that, on your handset, the two receiver terminals are the ones marked R1 and R2 in the bakelite. The two microphone terminals are the centre pintle and plate, and M1 in the bakelite. The two mic terminals marked M/R2 and M1 are not in any way connected inside the handset to the two receiver terminals marked R1 and R2.

As I said earlier, it looks like the common connection to mic and rec has been made from the green wire on yours.Attached, for your confusion ( ) is how a 164 handset connection looks, where the common connector is the centre pintle.

I wouldn't worry about a spare 0.1uF capacitor. Your telephone will work fine without one.
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Old 14th Nov 2017, 8:45 pm   #31
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Default Re: GPO 332 transmitter issue

So, in essence, if I disconnect capacitor it should clear the fault and work OK? Please excuse my ignorance on the subject, it is 30 years since I was in the electrical trade and never in telecoms.
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Old 14th Nov 2017, 8:52 pm   #32
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Default Re: GPO 332 transmitter issue

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So, in essence, if I disconnect capacitor it should clear the fault and work OK?
Well, it might... If it doesn't, there's a fault on your wiring that will require more in-depth investigation. But it can be done.

Now you're this far, start with the telephone chassis and find the fault. Then once you've found it, connect the handset as suggested (making sure the terminals 4 and 5 on the dial strip on top of the chassis are shorted together) and see if your mic works when you plug the telephone onto the line. Start with the carbon mic then try your T21A.

Then connect your dial as you disconnected it and see if it still works.

Then case it up.
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Old 14th Nov 2017, 8:56 pm   #33
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Default Re: GPO 332 transmitter issue

Will give that a go tomorrow, thanks again for all the advice.
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Old 14th Nov 2017, 9:29 pm   #34
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Default Re: GPO 332 transmitter issue

I've just read your post #20 and am guessing you reconnected the handset as you had it originally before measuring across T4 and T5. I should've made clear that you should've either disconnected the handset from the phone or left it wired as I suggested. In the original state there'd've been 150 Ohm through the receiver and the ASTIC.

I suggest you check out your handset wiring for continuity and ensure there are no shorts between wires. Then wire the handset so you have three clearly identifiable handset wires available for connection to the telephone terminal block:

* A common mic / receiver wire to connect to terminal T5.
*A receiver connection to connect to terminal T6.
*A microphone connection to connect to terminal T4.

Leave it in this configuration, then we'll take it from there.
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Old 14th Nov 2017, 10:38 pm   #35
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Default Re: GPO 332 transmitter issue

Quote:
Originally Posted by ThePillenwerfer View Post
Configured as it is in the photos that will be the resistance of the receiver, though it's higher than I'd expect. It may be different on a Handset 184 though.
An older 1L receiver is 80 Ohm; a more modern 2P is about 56 Ohm. I've commented on this on post #34 as I'd overlooked a comment about reversion to how it was wired originally (there being a path back through receiver and ASTIC as a result).

If Bigus craved authenticity the wiring could be put back with the colours as you suggest, but it's a bit of a fiddles rewiring inside the bakelite mic bowl on the handset. I think I'd be getting the thing to work first!
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Old 15th Nov 2017, 9:21 am   #36
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Default Re: GPO 332 transmitter issue

Bigus,

Before proceeding with this fault (we'll get there ), I have two comments:

*Are you using this as your main telephone? If so, I suggest you use another tele instead and lay this one aside so you can work on it at leisure.

*I'm assuming that your 332 telephone is 'sound' as far as the chassis wiring is concerned. But this may not be the case. Your instrument is fitted with a 184 handset, which is the handset normally used on a local battery telephone where the rec and mic circuits have to be kept separate. It really should have a 164 handset. It will still work with a 184 handset fitted, as long as it's wired as suggested, so don't worry.

So maybe there have been other wiring modifications in your telephone that we're currently unaware of? To this end, it would be better if we repair this fault step-by-step: when one step is completed, we'll move on to the next step. It's up to you.
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Old 15th Nov 2017, 9:35 am   #37
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Default Re: GPO 332 transmitter issue

OK, I have wired as per Russell W.B's instructions and put a strap between T4 & T5 on the dial contacts terminal. This has the result of reversing the polarity in the handset and increasing voltage to 9v dropping to 5. Again the carbon inset works fine, but not the electret.
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Old 15th Nov 2017, 10:10 am   #38
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Default Re: GPO 332 transmitter issue

Assuming that the 5V is what's measured across the electret unit itself, then it should work fine at this voltage, as I successfully run field telephones with 21A transmitter insets from 4V batteries.
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Old 15th Nov 2017, 10:15 am   #39
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Default Re: GPO 332 transmitter issue

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OK, I have wired as per Russell W.B's instructions and put a strap between T4 & T5 on the dial contacts terminal. This has the result of reversing the polarity in the handset and increasing voltage to 9v dropping to 5. Again the carbon inset works fine, but not the electret.
Inside the handset I now have M1, R1 and R2 all -ve and M1 +ve.
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Old 15th Nov 2017, 10:28 am   #40
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Default Re: GPO 332 transmitter issue

There is a box of 5 telephone microphones for sale on the auction site if that helps, I don't know if they are the right ones, telephones are beyond my ken.
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