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Old 13th Jun 2012, 12:26 pm   #1
ted_ntsx
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Default ATM 332 very low earpiece volume

Hi,
I have just acquired a vintage ATM 332 phone. It appears to be a genuine original. Inside looked undisturbed. Dust of ages, etc. This is the first antique phone I have worked on, so I am new to it all.

After some initial cleaning, I converted/rewired it as per the very clear instruction on the antiquephones.blogspot.co.uk web site.

It worked but the dial tone was very quiet. My wife then made a test call from her mobile and it rings very well, and transmits my voice at good volume, but the receive audio is also extremely quite. I assume it is likely to be a faulty/dunged up earpiece?

I wanted to check out the earpiece, but unfortunately I can't remove the earpiece cover as is jammed (possibly cross threaded). It already has a hairline crack in it, so I am reluctant to use any force on it as it will probably just break.

So...
Is there anything else that might cause very low received volume that I could check first?
Are there any known "receive volume problems" with phones like this?

Ted.
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Old 13th Jun 2012, 1:59 pm   #2
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Default Re: ATM 332 very low earpiece volume

Quote:
Originally Posted by ted_ntsx View Post
I can't remove the earpiece cover as is jammed (possibly cross threaded).
Have you tried allowing some sort of penetrating lubricant to soak into the thread of the earpiece cover? I have had more than one jammed solid that has responded (eventually) to this treatment - it does require a bit of patience, as it can take a day or two for the lubricant to soak into the thread.

It should be possible to judge visually whether it really is cross-threaded, but it is probably simply gummed up. It takes very little in the way of foreign particles in the thread to effect a significant increase in friction.
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Old 13th Jun 2012, 3:29 pm   #3
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Default Re: ATM 332 very low earpiece volume

Quote:
Originally Posted by ted_ntsx View Post

So...
Is there anything else that might cause very low received volume that I could check first?
Are there any known "receive volume problems" with phones like this?

Ted.
You could always disconnect one of the receiver wires from the terminal block (the one that isn't common with the microphone) and clip a modern balanced armature receiver, or a pair of lo-Z headphones across it to check audio at the terminals.

If audio present, look at the handset receiver - including wiring. If no, or weak audio present, report back.
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Old 13th Jun 2012, 4:24 pm   #4
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Default Re: ATM 332 very low earpiece volume

Quote:
Originally Posted by ted_ntsx View Post
Hi,
I have just acquired a vintage ATM 332 phone. It appears to be a genuine original.
I would agree, although the dial looks a bit Indian to me, with that thin style of finger stop. Could be wrong though.

Nick.
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Old 13th Jun 2012, 10:47 pm   #5
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Default Re: ATM 332 very low earpiece volume

I have one of these in normal daily use. Try cleaning the diaphragm in the earpeice, (or turn it over) and make sure there is no swarf stuck to the magnet inside.

I don't think mine is an Indian one-and presumably the OP's, but more likely a non GPO(public network) one, such as was used on a switchboard or private network. Mine came from a Bristol hospital.

Quote:
I wanted to check out the earpiece, but unfortunately I can't remove the earpiece cover as is jammed (possibly cross threaded). It already has a hairline crack in it, so I am reluctant to use any force on it as it will probably just break.
Could you warm it with a hairdryer or something? A rubber glove might give you a little more grip.....
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Old 14th Jun 2012, 8:33 am   #6
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Default Re: ATM 332 very low earpiece volume

Quote:
Originally Posted by Dave Moll View Post
Quote:
Originally Posted by ted_ntsx View Post
I can't remove the earpiece cover as is jammed (possibly cross threaded).
Have you tried allowing some sort of penetrating lubricant to soak into the thread of the earpiece cover? I have had more than one jammed solid that has responded (eventually) to this treatment - it does require a bit of patience, as it can take a day or two for the lubricant to soak into the thread.

It should be possible to judge visually whether it really is cross-threaded, but it is probably simply gummed up. It takes very little in the way of foreign particles in the thread to effect a significant increase in friction.

I did put some lubricant on it last night. No sign of any movement this morning, but I will add a bit more and give it some more time to soak.

Ted.
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Old 14th Jun 2012, 8:36 am   #7
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Default Re: ATM 332 very low earpiece volume

Quote:
Originally Posted by russell_w_b View Post
You could always disconnect one of the receiver wires from the terminal block (the one that isn't common with the microphone) and clip a modern balanced armature receiver, or a pair of lo-Z headphones across it to check audio at the terminals.

If audio present, look at the handset receiver - including wiring. If no, or weak audio present, report back.
Good idea. I will give that a try, thanks.

Ted.

Last edited by Dave Moll; 14th Jun 2012 at 10:46 am. Reason: quote fixed
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Old 14th Jun 2012, 8:46 am   #8
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Default Re: ATM 332 very low earpiece volume

Quote:
Originally Posted by Nickthedentist View Post
Quote:
Originally Posted by ted_ntsx View Post
Hi,
I have just acquired a vintage ATM 332 phone. It appears to be a genuine original.
I would agree, although the dial looks a bit Indian to me, with that thin style of finger stop. Could be wrong though.

Nick.
I did wonder about the dial being wrong, but there does seem to be a-thousand-and-one variants of the 332 phone about.

Inside the phone, the capacitor is stamped "GPO batch tested" (the stamp is smudged, but the GPO part is clear) and the impressed stamp on bottom cover appears to be a normal ATM mark. All wiring and soldering looks original and untouched. The paper label on the front of the dial has the Plessey symbol on it, so I assume it was one of their internal phones.

Ted.
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Old 14th Jun 2012, 8:51 am   #9
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Default Re: ATM 332 very low earpiece volume

Quote:
Originally Posted by Tim View Post
I have one of these in normal daily use. Try cleaning the diaphragm in the earpeice, (or turn it over) and make sure there is no swarf stuck to the magnet inside.

Could you warm it with a hairdryer or something? A rubber glove might give you a little more grip.....
If I can get it off I will try cleaning it.

I will try warming it (I have now put some lube on it to soak in as well) but as it has a hairline crack in the cover I am concerned that any force will cause the thin threaded part it to shatter.

Ted.
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Old 14th Jun 2012, 11:02 am   #10
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Default Re: ATM 332 very low earpiece volume

One of those strap wrenches would be useful here, often sold for removing oil filters: http://www.toolstation.com/images/li...bbig/67000.jpg

Should the worst happen, spares do crop up on eBay etc. at reasonable prices.

Nick.
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Old 14th Jun 2012, 11:32 am   #11
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Default Re: ATM 332 very low earpiece volume

Quote:
Originally Posted by ted_ntsx View Post
Quote:
Originally Posted by russell_w_b View Post
You could always disconnect one of the receiver wires from the terminal block (the one that isn't common with the microphone) and clip a modern balanced armature receiver, or a pair of lo-Z headphones across it to check audio at the terminals.

If audio present, look at the handset receiver - including wiring. If no, or weak audio present, report back.
Good idea. I will give that a try, thanks.

Ted.
<Later>
Just tried it, and the dial tone is quite a reasonable volume in a cheapo headphone, so it does look like it is the earpiece that is the problem. I'm still working on getting the cover off!

Ted.
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Old 14th Jun 2012, 3:53 pm   #12
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Default Re: ATM 332 very low earpiece volume

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Originally Posted by ted_ntsx View Post
I'm still working on getting the cover off!

Ted.
One of those grippy rubber sheets used for pickle-jar tops, etc... may work best, or the back of a latex glove. Attempt to tighten the earpiece first - but not too far - then try unfastening it.
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Old 14th Jun 2012, 5:20 pm   #13
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Default Re: ATM 332 very low earpiece volume

SUCCESS!

I finally got the earpiece cover off, and in one piece!

After a long soak with some lube, a latex glove gave me the required grip. The real trick was the suggestion by Russell W. B. of attempting to tighten it slightly first. I then felt it move slightly, and was then able to unscrew it.
The problem with the low volume was immediately obvious. The diaphragm had rusted to the magnet poles. A good clean-up worked and the volume is now just fine.

Many thanks to everyone with their suggestions. I now have a good working phone, apart from a slightly "jumpy" dial which I will now tackle.

Ted.

Last edited by Dave Moll; 14th Jun 2012 at 7:28 pm. Reason: broken quote of preceding post removed
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Old 14th Jun 2012, 6:15 pm   #14
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Default Re: ATM 332 very low earpiece volume

Pleased it worked, Ted, and you got sorted. You could put a little french chalk dust around the threads and it'll come apart easier next time.
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