Need help fixing speaker of my classic corded phone

Hello everyone, hopefully it's the correct place to ask this question. The speaker of my corded phone broke down a couple of days back & it's a really old and a unique one so, i want to fix it.

I opened the handset & removed the speaker. Here is what the tiny speaker looks like: (http://imgur.com/oX2Zk18)
There are 4 connecting points in it, which I have marked as 1,2,3 & 4. I used a digital multimeter to check the continuity & when i touch the point 1 & 2 with the red & black prongs/probes of the multimeter, I get the beep. Same happens for the point 3 & 4. I do not get the beep when I touch point 1 & 4 or any other combination. Since I am getting the beep, does that mean the speaker is fine?

Also, i am 90% sure that the 2 wires (yellowish and black) were soldered to the points 1 & 4. Is there a way to determine & make sure via the multimeter which points need to be soldered with the wires?

Also, is it possible to check the polarity of the points (+ve and -ve) via the multimeter & the wires too, so I connect them correctly ?

Here is a picture of multimeter I am using: (http://imgur.com/XtD63NC)
Hope I have not asked too many questions You all are having a wonderful Sunday & thanks in advance.

Hi,
I believe 1&2 are directly connected, likewise 3&4.

Two of them (2 & 3, from what you say) will be used to connect the ends of the louspeaker voice coil, then the other two are for the external wires. That's to avoid the joints to the extremely fine coil wire being disturbed when the external connections are added.

There should be some level of resistance between the two sides, anything from a few ohms to possibly a hundred ohms, depending on the speaker design. As there is no connection there, it has failed.
Note that you may not get a continuity beep even if it is OK, you need to look at the resistance reading on the 200 or 2000 ohms range.

Have a look for the ends of the coil wires using a magnifying glass if required & see if there is a visible break in either?

rjenkinsgb said:

There should be some level of resistance between the two sides, anything from a few ohms to possibly a hundred ohms, depending on the speaker design. As there is no connection there, it has failed.
Note that you may not get a continuity beep even if it is OK, you need to look at the resistance reading on the 200 or 2000 ohms range.

Click to expand...

Hi, thanks a ton for replying back. Can you explain this a bit more to me & how to do it via the multimeter i posted above? So, i put the probes on point 1 and 4 and look for resistance reading, right? Which setting should i set the dial to on my multimeter while doing it?

Have a look for the ends of the coil wires using a magnifying glass if required & see if there is a visible break in either?

Click to expand...

I could do that, do you think i should replace the speaker itself, in case the coil is broken from inside? From the naked eye i can't find any breaks.

Again, thanks for replying back.

rjenkinsgb said:

There should be some level of resistance between the two sides, anything from a few ohms to possibly a hundred ohms, depending on the speaker design. As there is no connection there, it has failed.

Click to expand...

Hi, I just set the dial to 200 ohms & checked the resistance between 1 & 4, the reading stayed at 1 and did not change. The resistance between 1 & 2, 3 & 4 at 200 ohms showed up as 0.7.

Also, on the back it says 100Ω 0.25W. It's a plastic shell speaker, i might be able to procure a similar speaker (same diameter, plastic shell) but 16Ω 0.25W or 8Ω 0.25W. Do you think, it will work with the device having same wattage but low resistance?

You need a 100 ohms speaker to be a telephone earphone in its handset. An 8 ohms or 16 ohms speaker will not work.

audioguru said:

You need a 100 ohms speaker to be a telephone earphone in its handset. An 8 ohms or 16 ohms speaker will not work.

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OK, point noted. Thank you.

It's dead, if no reading on the 200 Ohm range.

Can you post some more pictures and the dimensions of the speaker? the one photo is rather dark and the size is not obvious.

Also, what make and model of phone is it? There are quite a few old telephone handsets that should have the earpiece included, on ebay, eg.

rjenkinsgb said:

It's dead, if no reading on the 200 Ohm range.

Can you post some more pictures and the dimensions of the speaker? the one photo is rather dark and the size is not obvious.

Also, what make and model of phone is it? There are quite a few old telephone handsets that should have the earpiece included, on ebay, eg.

Vintage Western Electric Handset UNTESTED As Is parts or repair | eBay

As-is see photos.

www.ebay.co.uk

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Hi Thanks again for replying back. The earlier pic looked dark, because a thick black piece of square sponge was glued to the backside of speaker to keep it in place on the handset. I unglued and took another pic of the back here:

(http://imgur.com/JJatbp4)
Here is the front side of speaker, notice that it has got some rusted color inside the outer protective film, so it's almost impossible to spot any break at the end of coil wires. Can i remove that plasticky protective film and look for break in wire?

(http://imgur.com/PFiTqIy)
The diameter of the speaker is almost 26mm.

The maker of the phone is Beetel, can't spot the model no. as the labels have peeled off.

I was looking for speakers online, and i was able to spot a similar sized plastic shell speaker but with specs of 32Ω 0.25W. Do you reckon it could work or do I need to keep looking for 100Ω 0.25W?

Cheers!

rick.laguy said:

Can i remove that plasticky protective film and look for break in wire?

Click to expand...

The plastic is the speaker diaphragm; don't try to remove that.

Would one of these fit? 27mm appears to be a standard size.

rjenkinsgb said:

The plastic is the speaker diaphragm; don't try to remove that.

Would one of these fit? 27mm appears to be a standard size.

Best-selling mylar cone loudspeaker for headset 27mm speaker drive 100 ohm

Best-selling mylar cone loudspeaker for headset 27mm speaker drive 100 ohm Specification Speaker Mylar speaker Model 27PM100 Diameter 27*8.3(H)mm Rated power 0.02 watt Max 0.03watt Nominal Impedance 100 Ohm±15% Lowest Resonance Frequency 150±20% HZ Output Sound Pressure Level(S....

www.soundbuzzer.com

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Yes, I think it will fit, but it's wattage seems to be 0.02 watt, would it not be an issue?

These one seem to be exact same specs and measurement, but I can't order from Alibaba, so i have to look for these in local electronic shops

Possibly look at model railway suppliers? I keep seeing references to 100 Ohm miniature speakers for use in model train sound systems.

Do you use the very old phone? Does it have a rotary dial?

audioguru said:

Do you use the very old phone? Does it have a rotary dial?

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Hi, sorry for the late reply. No, it's not a rotary dial one, it has buttons, it's a very old one & has worked for a long time & I do not want to throw it away.