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 Post subject: Dead speaker
PostPosted: Sep Sat 18, 2021 11:44 pm 
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Hello,

I got a speaker out of a Japanese 6 transistor radio, it's 8 ohms and 0.2 watts. It is completely dead, however. does not work at all on the radio nor does it click when I press a 9v battery to the contacts. Its physical condition is fine however, no tears in the speaker everything looks intact. My meter just stays in infinite when I try to test it.

I don't like to throw parts out, anyone knows what the issue may be?

Thanks,
Henry

Oh and replaced this dead speaker with an 8 ohm 200 milliwatt speaker of the exact size in the radio. Volume is still low after a recap, performance isn't all there either could this be a cause of the new speaker? Could just be a bad transistor, however.


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 Post subject: Re: Dead speaker
PostPosted: Sep Sun 19, 2021 12:02 am 
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How do the flex-wires on back side of speaker look ? Sometimes battery leakage will contaminate and corrode them...

John


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 Post subject: Re: Dead speaker
PostPosted: Sep Sun 19, 2021 12:20 am 
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Thanks, John

No, they look fine. Show continuity as well...

Henry


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 Post subject: Re: Dead speaker
PostPosted: Sep Sun 19, 2021 5:41 pm 
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I have had a few small PM speakers wind up DOA, even looking brand-new. I have taken them apart (destructive dissection) to find the cause. I have found the common issue was where the super fine wire of the voice coil is soldered to the "flex-wire" attaching to the paper cone. This connection breaks, resulting in a useless and unrepairable speaker. Some I could not figure out. It is possible that the wire in the voice coil had severed? Only solution is to replace the speaker.

Jeff


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 Post subject: Re: Dead speaker
PostPosted: Sep Sun 19, 2021 5:44 pm 
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Another possibility with Henry's speaker - voice coil is "frozen" and unable to move. Might try tapping the end of a screwdriver against the magnet to possibly free it up? Just a thought.....

Jeff


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 Post subject: Re: Dead speaker
PostPosted: Sep Sun 19, 2021 6:12 pm 
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whfh99 wrote:
does not work at all on the radio nor does it click when I press a 9v battery to the contacts.


Did I understand correctly that you attached that battery to the contacts of the speaker itself? Then you burned the coil even if it was still intact ...

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 Post subject: Re: Dead speaker
PostPosted: Sep Sun 19, 2021 7:39 pm 
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Jeff, I will have to try that, thanks!

Vlad, I have done that with another 8-ohm speaker and it still works fine. It probably doesn't do any good to the speaker, I must have thought it was a way of testing it...


I have plenty of other speakers though, so not a big deal.



Henry


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 Post subject: Re: Dead speaker
PostPosted: Sep Sun 19, 2021 7:45 pm 
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I recently managed to tidy up a terribly wheezing speaker by wetting the paper of the diffuser in the area of the cap with isopropyl alcohol and then gently pushing the diffuser several times. Something fell into place or cleared and the diffuser moved easily.

I've heard people take the speaker apart and take out and change the coil, but I've never done it myself. I think you can try that.

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 Post subject: Re: Dead speaker
PostPosted: Sep Mon 20, 2021 2:03 pm 
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whfh99 wrote:
I got a speaker out of a Japanese 6 transistor radio, it's 8 ohms and 0.2 watts. It is completely dead, however. does not work at all on the radio nor does it click when I press a 9v battery to the contacts. Its physical condition is fine however, no tears in the speaker everything looks intact. My meter just stays in infinite when I try to test it.
9 volts applied to an 8-ohm speaker will draw 1.125 amps. The voice coil will try to dissipate around 10 Watts! That's far too much for a speaker rated for only 200 mW and could easily be damaged or go open. Even a 1.5 volt battery will produce 280 mW which is more than the speaker's power rating.

Dave


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 Post subject: Re: Dead speaker
PostPosted: Sep Sun 26, 2021 2:37 pm 
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Dave Doughty wrote:
whfh99 wrote:
I got a speaker out of a Japanese 6 transistor radio, it's 8 ohms and 0.2 watts. It is completely dead, however. does not work at all on the radio nor does it click when I press a 9v battery to the contacts. Its physical condition is fine however, no tears in the speaker everything looks intact. My meter just stays in infinite when I try to test it.
9 volts applied to an 8-ohm speaker will draw 1.125 amps. The voice coil will try to dissipate around 10 Watts! That's far too much for a speaker rated for only 200 mW and could easily be damaged or go open. Even a 1.5 volt battery will produce 280 mW which is more than the speaker's power rating.

Dave


A quick zap will do no harm. Done it a zillion times. Now, if you connect it and leave it ........

RRM


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 Post subject: Re: Dead speaker
PostPosted: Sep Sun 26, 2021 6:49 pm 
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Or use a weak battery to minimize the risk even further.

Magnet size and mounting can sometimes be an issue with replacements if it must fit into a hole in the circuit board or mount a certain way. Otherwise small speakers are common; a substitute might be found in the junkbox or online for cheap.

As an exercise, I've dissected a few. Acetone might loosen the edge glue and spider glue to remove the cone intact. Not caring how it looked or turned out, I just sliced it out with a sharp #11 exacto blade.

Very tiny wires and almost impossible to repair and reassemble in working order. Sometimes the break is at the connecting point on the rear of the cone where it is soldered to the tinsel wire and then sealed with the black stuff. You can sometimes scritch the coating away enough to try resoldering. Or the solder might fail at the speaker terminals, an easier fix. Next stop is where the tinsel wire joins to the coil itself. If the break is within the voicecoil winding, "it's Dead, Jim."

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 Post subject: Re: Dead speaker
PostPosted: Sep Sun 26, 2021 10:30 pm 
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whfh99 wrote:
Hello,

I got a speaker out of a Japanese 6 transistor radio, it's 8 ohms

My meter just stays in infinite when I try to test it.

Which means it's open somewhere. As suggested, check the wire connection to the voice coil.

And an easy piece of test gear for this would be two clip leads connected to an earphone plug. Then simply clip to a speaker to be tested, plug into any convenient Transistor radio's earphone jack, turn it on, and either the speaker sings or it doesn't.

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 Post subject: Re: Dead speaker
PostPosted: Sep Mon 27, 2021 6:57 pm 
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Commenting on a comment, 9V can maybe put over an amp thru 8 DC ohms, but a typical 9V battery ain't gonna be able to make that kind of current. Still a 1.5 V battery would be better for low resistance speakers, a 9V would be safe with a hi impedance speaker or headphones(think 20s 30s vintage). As for transistor radio speakers, there is no use saving dead ones. Bust off the magnet and save that. The only exception would be if you got some time to waste and want to attack the problem for fun and experience, or if it is a unique speaker in a rare radio, maybe. Most Japanese transistor speakers are about visually identical and functionally equivalent. The exception might be very early sets. Some US made transistors use oddball speakers. I got some small ca. 62 GE radios and they have a rather high resistance and are constructed like early PM speakers. Armature driving a pin, no standard voice coil.

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