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Old 21st Jun 2021, 7:57 pm   #1
HMV 1120
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Default Troubleshooting a 332.

After a decade of living on a narrow boat (a vintage one at that ) SWMBO and I find ourselves shore side again. This means we can have ordinary people things like a washing machine, hot water from a tap and a telephone line. I've elected to take charge of the latter and have picked up a 332 that was last in use ten tears ago on a BT line and is already fitted for PST.

Lifting the handset produces a very weak dial tone in the receiver. On dialing in we have an excellent ring which ceases as the handset is lifted, but the ringing tone continues to be heard in the receiver.

Any advice on where to start gratefully received!

Robert.
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Old 21st Jun 2021, 8:37 pm   #2
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Default Re: Troubleshooting a 332.

Let’s have some good photos of the internal wiring, please.
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Old 22nd Jun 2021, 6:50 am   #3
Dave Moll
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Default Re: Troubleshooting a 332.

It's also worth laying some suspicion in the direction of the carbon granule transmitter. If the granules are no longer making good contact with one another, the resistance may be too high to make a loop. If you take out the inset and give it a firm rap, there is just a possibility of effecting some improvement if it's not too far gone.

You make no mention of outgoing calls from the 332. What results do you get attempting this?
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Old 22nd Jun 2021, 1:15 pm   #4
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Default Re: Troubleshooting a 332.

The ringing tone in the receiver when you lift the handset could be dirty cradle-switch contacts causing leakage in the receiver by making the loop at a high resistance. You'll need to remove the inner chassis, then after locating the contact sets where the plungers sit, you'll need to clean them by drawing a bit of rough paper (blotting paper?) back and forth between them. Could even be dirty dial-pulse contacts at the dial.

Start as Dave says by checking out the mic insert (easiest!). Just remove the capsule and short out the terminals for now (or do this on the terminal block under the base, terms: 4 & 5) and ring in. See what happens when you lift the handset then. When doing this check your receive-level to see if it's stronger.

If receive level has improved then you're sorted. If not, remove the earpiece by unscrewing it and gently slide off the stalloy diaphragm beneath. Check it for rust, dirt and flatness and note if it is attracted magnetically to the pole-pieces: if it has a 'pull' factor.

Then report back.
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Old 22nd Jun 2021, 6:14 pm   #5
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Default Re: Troubleshooting a 332.

Shorting out terminals 4 and 5 has no effect on the receiver audio, and the call remains 'unanswered'. The diaphram has a brown dusting but seems fine, certainly the income buzz is loud enough.

Lifting handset ceases the bell but does not answer the call - is a path through the transmitter required for this?

Dialing out does not function, all noise in the receiver ceases whilst the dial is in motion but returns when it parks itself. Our provider is Now TV, an offshoot of Sky and supposedly using a BT line, but I have not yet asked if pulse dialing is supported (if I can find someone who understands the question ). in any event, I would be happy if we can just accept incoming calls for the time being. I believe the dial can be disconnected and the phone operated in CB mode?

I make the wiring out to be:

Line Red:1, strapped to 2 via resistor (bell circuit?).
Line yellow:10, strapped to 11 and 12.
Line Green: 9, strapped to 8.
Line Blue: Not connected

Handset:

White: 4
Green: 5
Red: 6


Thank you all so far,

Robert
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Old 22nd Jun 2021, 8:05 pm   #6
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Default Re: Troubleshooting a 332.

Looking at your image, I note that your line cord uses a colour convention with which I am not familiar.

For your wiring to work, you need to ensure the line is connected across T1 (A leg) and T8 (B leg).

If using the internal bell capacitor, then T8 and T9 should be strapped (as they appear to be in your image).

If using a third (bell) wire from a master socket, either the strap between T8 and T9 or that between T10 and T11 need to be removed (to disconnect the internal capacitor) and the third (ring) wire needs to be connected to T11/T12.

Given the above,
red needs to be the A leg (furthest pin of BT plug from the locking clip)
green needs to be the B leg (nearest pin to clip)
and yellow needs to be the ring wire (next pin to above)
(I am assuming four pins in the plug. If there are six, then ignore the outer two.)
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Old 22nd Jun 2021, 8:36 pm   #7
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Default Re: Troubleshooting a 332.

I have continuity between red and A, yellow and ring. Green and B appears to be open circuit. I shall come back when I have fitted a new line cord and report the results.

Many thanks,

Robert
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Old 23rd Jun 2021, 7:51 am   #8
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Default Re: Troubleshooting a 332.

Quote:
Originally Posted by HMV 1120 View Post
Green and B appears to be open circuit.
That may well explain the symptoms you're encountering, as the ringer and receiver can operate without making a loop, whereas the transmitter and dial will only operate once a loop is made across the A and B legs.
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Old 25th Jun 2021, 6:27 pm   #9
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Default Re: Troubleshooting a 332.

I fitted a new line cord this evening according to the instructions found here and the phone is now working. It rings and picks-up, received audio sounds fine although the outgoing has a somewhat limited frequency response, albeit perfectly intelligible. I suspect the carbon transmitter is past its best.

The dial returns at the correct speed but we get line noise in between the numbers, so it looks as if pulse dialing is not supported. I shall be fitting a pulse to tone converter.

Many thanks for your pointers,

Robert
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Old 25th Jun 2021, 7:10 pm   #10
Dave Moll
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Default Re: Troubleshooting a 332.

It's good to know the problem was simply a faulty line cord.

When you say you "get line noise between the numbers", I assume you mean you continue to get dial tone after a digit is dialled - which, as you say, implies that loop disconnect dialling is not being recognised.

If you're really concerned about speech quality from the carbon-granule transmitter, you could replace it with an electronic Transmitter 21A. The version with a red outer casing can be fitted in a 332 if you remove the red outer casing from the transmitter (which simply unclips) and the centre pin from the transmitter housing of the handset. Preferably tape the pin inside the handset to retain it for possible future re-instatement. I also understand that the red outer casing of the transmitter inset can be modified to provide a snugger fit than the inner unit (which requires some packing).

As a matter of interest, what pulse-to-tone converter are you intending to fit? If using the Rotatone internal unit, take very seriously the warning about ensuring that your dial pulsing contacts are as clean as possible. It's surprising how much dirt one can get away with when they are operating at line current, but the miniscule switching current in a Rotatone is insufficient to break through. I know, I've been there! Personally, I prefer an external unit such as the Australian Dialgizmo that simply plugs in between the telephone and the line.
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Last edited by Dave Moll; 25th Jun 2021 at 7:14 pm. Reason: link to a sample supplier of transmitter 21A added
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Old 25th Jun 2021, 7:38 pm   #11
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Default Re: Troubleshooting a 332.

Dialing out now works, apparently we had an unspecified issue with setting up our new line that resulted in us being "temporarily unavailable".

A tone converter would still be useful for number options and future proofing down the line, so it looks like an external unit is the way to go.

Robert
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Old 12th Jul 2021, 9:04 pm   #12
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Default Re: Troubleshooting a 332.

A bit late to the party , but for future use, here's a copy of N diagram 432 ( GPO diagrams for phones always added 100 to the phone title). ( worth keeping in mind if you end up with other old phones). I never really worked on them as in my subs app days, we just swapped them out for a 700/740 series.
http://www.samhallas.co.uk/repositor.../0000/N432.pdf
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