I have a driver that needs fixed, an Usher midwoofer from an S520. One of the tinsel leads has come adrift from the voice coil lead-out wire. Here's a picture:
The voice coil lead-out wire is glued to the cone, which is clear plastic of some sort. I plan to use a scalpel to scrape the lead-out wire to expose a little more copper, and also to lift the end of it clear of the cone, before attempting to solder the tinsel lead back onto it.
The tinsel lead has a big blob of yellowish glue on the end, which was supposed to hold it in place. That'll need to be removed, and when I've resoldered the wires together, I'll need to glue the joint down onto the cone with a fresh blob.
Have I got all that correct? Any advice? What type of glue would be best for regluing the joint to the cone?
The voice coil lead-out wire is glued to the cone, which is clear plastic of some sort. I plan to use a scalpel to scrape the lead-out wire to expose a little more copper, and also to lift the end of it clear of the cone, before attempting to solder the tinsel lead back onto it.
The tinsel lead has a big blob of yellowish glue on the end, which was supposed to hold it in place. That'll need to be removed, and when I've resoldered the wires together, I'll need to glue the joint down onto the cone with a fresh blob.
Have I got all that correct? Any advice? What type of glue would be best for regluing the joint to the cone?
Last edited:
If you have to remove enamel from copper wire scraping might do the job if the wire is thick enough. If it is not sufficiently thick and you are able to free the wire far enough, this is a trick to remove enamel.
Take a white Paracetamol pill (yes, the headache killer). Put the wire on the pill and your soldering iron tip on top of the wire. The pill starts to melt with the wire embedded in the smelt. After a few seconds your wire is clean. This also works for stranded enamel wire (Litze). As far as I know it is the only way for stranded wire.
You want to keep your head far away from the fumes. I don t know what is in it but I cannot imagine it is healthy.
The glue appears as hot glue to me. On a paper cone I use hot glue. On a plastic cone I am not sure. Silicone would do as well. Both have the advanage to be reversible. Hot glue more so.
Take a white Paracetamol pill (yes, the headache killer). Put the wire on the pill and your soldering iron tip on top of the wire. The pill starts to melt with the wire embedded in the smelt. After a few seconds your wire is clean. This also works for stranded enamel wire (Litze). As far as I know it is the only way for stranded wire.
You want to keep your head far away from the fumes. I don t know what is in it but I cannot imagine it is healthy.
The glue appears as hot glue to me. On a paper cone I use hot glue. On a plastic cone I am not sure. Silicone would do as well. Both have the advanage to be reversible. Hot glue more so.
I'd be wary of attempting to scrape the enamel off the thin voice coil wire with a scalpel for fear of damaging the wire.
That makes jlinkels' interesting enamel removing method sound very inviting.
For a polypropylene cone like that of the Usher S520, this particular silicone adhesive may prove more effective than hot glue:
https://www.halfords.com/motoring/p...97*MTczNTgyNzQwNS4xLjAuMTczNTgyNzk2OC4wLjAuMA..
That makes jlinkels' interesting enamel removing method sound very inviting.
For a polypropylene cone like that of the Usher S520, this particular silicone adhesive may prove more effective than hot glue:
https://www.halfords.com/motoring/p...97*MTczNTgyNzQwNS4xLjAuMTczNTgyNzk2OC4wLjAuMA..
I'd also be wary of any normal silicone that includes acetic acid. That kind is not typically used on delicate electronics since it can corrode copper. If you're going to use silicone, look for one that specifically says it's electronics grade.
That would be a 'neutral cure' silicone which releases alcohol on drying rather than an 'acetoxy cure' silicone which releases acetic acid.
I've used the silicone sealant to which I linked. It is suitable for electrical connections.
I've used the silicone sealant to which I linked. It is suitable for electrical connections.
Thanks all, those are really helpful responses.
I'd not heard of the paracetamol trick before, but it sounds good. I'll get some, and some neutral cure silicone, and give it a go, hopefully tomorrow. I might take a couple of paracetamol first. 😆
I'd not heard of the paracetamol trick before, but it sounds good. I'll get some, and some neutral cure silicone, and give it a go, hopefully tomorrow. I might take a couple of paracetamol first. 😆
I've just looked out my tube of Granville silicone adhesive and it does smell vinegary - so best avoid when there is direct contact with copper.
Oh... Also: Nail polish remover often contains oils that are left behind once the acetone evaporates. That's probably good for nails, but not so hot if you're looking to solder to the wire after.
If acetone is what you're after, you're better off finding a small bottle of it in the paint department of your local home improvement store. Acetone is a pretty aggressive solvent, though. I'd try a few things first before reaching for the acetone.
Tom
If acetone is what you're after, you're better off finding a small bottle of it in the paint department of your local home improvement store. Acetone is a pretty aggressive solvent, though. I'd try a few things first before reaching for the acetone.
Tom
Thanks for those points. I am reluctant to try to put any liquid solvent in there - space is very restricted, and if there was any bleed or run, it could be nasty. I'm not even sure I can squeeze a big enough piece of a paracetamol tab in there, to be honest. I'll head out to the workshop shortly to try.
True enough, but the description of the planned repair wouldn't/shouldn't require touching it.
Yep, currently having to take max dosage daily, though wasn't aware of its versatility.
Yes, all that I've used had oil, though didn't pose any problems, though in retrospect always used very high wattage irons, so basically boiled it off and yes; the industrial acetone I've used is much too aggressive IME for VC tinsel repair and didn't mean to suggest it per se.
Well, good news - I think I've managed to fix it.
I didn't use paracetamol after all: when it came to the crunch, there just wasn't enough room to try it safely.
So in the end, having lifted the end of the lead-out wire off the cone, I just scraped the raised portion with the scalpel very gently. I managed to get a decent area of exposed copper quite quickly. I feel a bit of a numpty for not following any of the advice offered, but the scalpel felt like the least risky option.
The thing that took longest was getting the tinsel lead positioned correctly, in a way that still allowed the soldering iron safe access to the joint. The key was lots of practicing with the iron cold, until I was confident that I could get the solder and the iron into position without the tinsel lead moving. And when heat was finally added, everything stayed steady and the job was done in a flash. Here's a pic of the result:
And here it is with some neutral cure silicone added (courtesy of my local Screwfix 😄).
The voice coil is measuring a steady 5.2 ohms, at the terminals. I'm going to let everything cure overnight. Tomorrow I'll put the speaker back together and try it out with some music. Fingers and toes crossed!
I didn't use paracetamol after all: when it came to the crunch, there just wasn't enough room to try it safely.
So in the end, having lifted the end of the lead-out wire off the cone, I just scraped the raised portion with the scalpel very gently. I managed to get a decent area of exposed copper quite quickly. I feel a bit of a numpty for not following any of the advice offered, but the scalpel felt like the least risky option.
The thing that took longest was getting the tinsel lead positioned correctly, in a way that still allowed the soldering iron safe access to the joint. The key was lots of practicing with the iron cold, until I was confident that I could get the solder and the iron into position without the tinsel lead moving. And when heat was finally added, everything stayed steady and the job was done in a flash. Here's a pic of the result:
And here it is with some neutral cure silicone added (courtesy of my local Screwfix 😄).
The voice coil is measuring a steady 5.2 ohms, at the terminals. I'm going to let everything cure overnight. Tomorrow I'll put the speaker back together and try it out with some music. Fingers and toes crossed!
Attachments
Last edited:
Good job!
Since that glue support gave up the ghost, it may be worth reinforcing the still intact one.
I await the stress test!
Since that glue support gave up the ghost, it may be worth reinforcing the still intact one.
I await the stress test!
I added a bit more glue (and some on the other wire junction, as @Galu suggested), just to improve the chances of everything holding together in the longer term. I gave them another 24 hours for the silicone to cure, and I've now had them playing for a couple of hours, low volumes at first, then more normal. All seems fine. The Ushers sound like decent little mini-monitors, going by what I'm hearing so far.
I suggest your next task would be to reinforce the wire junctions of the other speaker of the stereo pair - if you haven't already done so.
Unfortunately, there's still a problem. After a couple of days playing the Ushers, (and marvelling at how good they are!) I started to get a buzzing noise from the repaired woofer last night, on bass tones.
I've removed the woofer from the speaker, this morning, and had a poke at it. The silicone blob seems rather loose and floppy. It's possible to wiggle the soldered joint around a bit, despite the silicone blob, which concerns me I'm wondering if there's an adhesion issue: polypropylene has 'low surface energy', apparently, and many adhesives, including silicones, don't stick well to it. On the other hand, it could just be that the silicone, a low-modulus type, is too floppy. I don't know exactly what's causing the buzz, but I think I need to have another go at this repair.
I'm planning to cut away the silicone blob. If I can get the cone clean of it, I'm thinking it might be smart to apply a dab of a suitable plastic primer to it, before re-gluing. Maybe this primer: https://www.amazon.co.uk/Rust-Oleum...xt&ref_=fplfs&psc=1&smid=A3P5ROKL5A1OLE&gQT=1 It's normally used prior to painting, rather than gluing, but it does at least seem to be suitable for use on polypropylene.
To re-glue, I'm wondering if I should invest in a little hot-melt gun, and try that. The hot-melt blobs on the other leads seem very firm, compared to the silicone - maybe that's the way to go?
I've removed the woofer from the speaker, this morning, and had a poke at it. The silicone blob seems rather loose and floppy. It's possible to wiggle the soldered joint around a bit, despite the silicone blob, which concerns me I'm wondering if there's an adhesion issue: polypropylene has 'low surface energy', apparently, and many adhesives, including silicones, don't stick well to it. On the other hand, it could just be that the silicone, a low-modulus type, is too floppy. I don't know exactly what's causing the buzz, but I think I need to have another go at this repair.
I'm planning to cut away the silicone blob. If I can get the cone clean of it, I'm thinking it might be smart to apply a dab of a suitable plastic primer to it, before re-gluing. Maybe this primer: https://www.amazon.co.uk/Rust-Oleum...xt&ref_=fplfs&psc=1&smid=A3P5ROKL5A1OLE&gQT=1 It's normally used prior to painting, rather than gluing, but it does at least seem to be suitable for use on polypropylene.
To re-glue, I'm wondering if I should invest in a little hot-melt gun, and try that. The hot-melt blobs on the other leads seem very firm, compared to the silicone - maybe that's the way to go?
Following on from the above, another option for primer would be Loctite SF 770, which is intended as a primer for cyanoacrylate glues, but might work in this application too.
Other glue options: I'm concerned that the low-modulus silicones are too flexible to do the job here. The glue blob needs to hold the end of the voice-coil wire (and its soldered connection to the tinsel-lead) firm, so it moves with the cone as one, rather than flexing. The tinsel lead is where the flexing should happen.
However I can't find any high-modulus neutral cure silicones. So I'm thinking hot-melt, as I mentioned above, or alternatively how about these options: (a) a high-modulus polymer sealant/adhesive such as Arbomeric MP20 (https://www.arbo.co.uk/products/modified-polymer-sealants/arbomeric-mp20) or maybe even (b) Sugru (https://www.tesa.com/en-gb/consumer/repairing-tapes/sugru)
Any thoughts?
Other glue options: I'm concerned that the low-modulus silicones are too flexible to do the job here. The glue blob needs to hold the end of the voice-coil wire (and its soldered connection to the tinsel-lead) firm, so it moves with the cone as one, rather than flexing. The tinsel lead is where the flexing should happen.
However I can't find any high-modulus neutral cure silicones. So I'm thinking hot-melt, as I mentioned above, or alternatively how about these options: (a) a high-modulus polymer sealant/adhesive such as Arbomeric MP20 (https://www.arbo.co.uk/products/modified-polymer-sealants/arbomeric-mp20) or maybe even (b) Sugru (https://www.tesa.com/en-gb/consumer/repairing-tapes/sugru)
Any thoughts?
Last edited:
I think the silicone may have left a residue preventing any other glues from adhering. The trouble is that you need pretty strong solvents (or commercial silicone removers) to remove it and they might damage the cone. But hopefully I'm wrong.
FYI, that yellow stuff definitely looks like hot glue and coincidentally I only recently looked at a pair of Peerless woofers (with polypropylene cones) in a pair of DIY speakers I made years ago, and they also had the same glue in that position. (I thought there was an issue with the wires but there wasn't).
You don't need to buy a glue gun. You can buy glue sticks and heat them with a flame, quickly transferring the glue to the leads using (say) a heated screwdriver to keep it melted. The gun might not fit anyway. I have a gun but use hot glue like this on occasion.
Those Ushers got really good reviews in UK HiFi World when they were released.
FYI, that yellow stuff definitely looks like hot glue and coincidentally I only recently looked at a pair of Peerless woofers (with polypropylene cones) in a pair of DIY speakers I made years ago, and they also had the same glue in that position. (I thought there was an issue with the wires but there wasn't).
You don't need to buy a glue gun. You can buy glue sticks and heat them with a flame, quickly transferring the glue to the leads using (say) a heated screwdriver to keep it melted. The gun might not fit anyway. I have a gun but use hot glue like this on occasion.
Those Ushers got really good reviews in UK HiFi World when they were released.