How to repair tweeters for AR11 / AR10pi

[kj2005]

 

I have with success been able to repair one tweeter where the incomming wire from the plus side was disconnected. 

Before I delete some of the pictures please find the tweeter repair at a amateursite I am about to make.  Under my profile you can find my website , URL

regards

Kim Hansen

[kj2005]

I have just changed the address to my new amateur site.  

Profile shows my website , URL.

[kj2005]

The AR10pi tweeter: The inner diameter of the aluminum coil mold is 1,945 cm  or approx 0,765748 inch ?  and I have measured the wire thickness to 0,1 mm ..... the thickness of the coil mold is 0,1 mm. I have measured the DC resistance to 3,4 Ohm ..It should be possible to get someone to wind new coils for old magnet units? rgds Kim

[kj2005]

One important issue to take care of is the use of ultra-thin 2 seconds glue (cyanacrylate) on the edge of area where the spider is glued to the aluminium coil form. It was necessary to loosen the spider from the very thin (0,1mm) alu coil mold in order to be able to draw approx. 1,2 cm out from existing cobber vindings on the coil. Don't loosen the spider all the way round but only enough to be able to draw a short peace of the wire out.

The old brown glue AR used that kept the spider in place was a very hard type of glue. I thought that cyancrylate could do the job as well. I used a tooth-plastic-pin to get the right amount of glue in place.  See the marks where to add the cyanacrylate at the purple circle...and the soldering at the red circle.

 

[kj2005]

When the voicecoil is situated and back in place use a little amount of waterbased contact glue close to the edge of the magnet air gab ( but no glue on the pole piece)

I used several 6 mm wide paper strips formed like arrows in the air-gap in order to center the voice coil. AR used a tiny little amount of magnetic oil at the voice coil and the paper strips takes a small part of the oil away by doing this. But it's ok!

Make a pressure on the double-glue-tape so that the tape once again connects to the magnet coverplate. After this use two pieces of clear thin tape to isolate the two thin wires from the magnet coverplate. The voltage meter shows 4,1 Ohm . The test wires has 0,7 Ohm resistance so we have a standard 3,4 Ohm working voicecoil again ☺️  rgds kim

[kj2005]

The last action is to glue the dome-cap back in place. The original brown hard glue is replaced with a tiny amount of cyanacrylate, but in order to keep the dome-cap in centerposition I used just a few tiny drops of waterbased contact glue. When the contact glue after some time has hardened enough, then use the tooth-pin and some tiny drops of cyanacrylate on the edge of dome-cap and the alu-coil-form.

Then I could use some advice concerning the rubber-foam originally used by AR on the tweeter frontplate? What does the members use as replacement? thanks in advance

Rgds Kim 

[kj2005]

Repair of AR dome tweeters?  I thought this was a great issue to many AR11 and AR10pi owners, as direct replacement tweeters are not available any more and very hard to find.

... no comments...?

If one looks at Ebay for AR11/AR10pi tweeters  prices has gone up for old used units, so why not try to repair the AR tweeters? Normally it's the wire path comming in towards the plus side of the coil  that melts and disconnects.

Rgds. Kim

NB. I used the same method with paper-strips to center a AR11 woofer cone,  where the original AR production "cut-off" of the aluminium tube-coil made some edges on the aluminium tube that scraped on the pole piece. I took a while to clean off the old woodring without doing any harm to the woofer spider.

[dxho]

I think it's quite an accomplishment! Thank you for detailing the process. You might be the first
person, to my knowledge, who did so. I think a couple of reasons (and probably others, no doubt)
for no response: there is one person, maybe two, who are now offering repair services here, and
there's finally a reasonably close-in-sound aftermarket replacement available. Nevertheless, I
may finally drag out the dead tweeters I've been hanging onto for several years and see if they can
be revived.

[kj2005]

4 hours ago, dxho said:

I think it's quite an accomplishment! Thank you for detailing the process. You might be the first
person, to my knowledge, who did so. I think a couple of reasons (and probably others, no doubt)
for no response: there is one person, maybe two, who are now offering repair services here, and
there's finally a reasonably close-in-sound aftermarket replacement available. Nevertheless, I
may finally drag out the dead tweeters I've been hanging onto for several years and see if they can
be revived.

Hi Thanks. You may have a point with the aftermarket replacement tweeters like Hivi Q1R and similar, because it's less difficult to change the old tweeters with new types.

I have worked with magnifying glasses and lenses for low vision /weak sighted people for more than four decades, and I am used to work with microscope. With a wire thickness of only 0,1mm you need magnifying glasses to be able to clean off the isolation lacquer from the copper-wire when you are going to solder the two wire-endings together.

The best advice for us older people with projects like this: use maximum light led 10-13W = 100Watt = 1000 ~1250 Lumen ( 3000K warm white has the best relaxation for our (normal)eyes, red/green/blue rod and cones) Yellow becomes visible by a combination of red and green spectral colours fired from the second ganglion cell layer to the vision center in the back of the brain. 3000 Kelvin is ok.

This is important knowledge if one are about to choose light type. White light is has many different combinations taken out from visible spectrum (400nm ~ 70nm)... bit off topic

Take the magnifying glasses and focus on the incomming wires both plus and minus and see, whether you can locate the melting point on the wire...you need at least +6,00 ~ +8,00D in the glasses :-))   You need a scalpel to scratch the wire with!

[GD70]

Excellent work! Only the last couple years the original tweeters for the 3a are being successfully repaired, once thought when they were dead, they were paper weights or ready for the trash can! The 3's tweeters are a bit easier to repair, but the mids are now being repaired as well, and brought back close to new sound output! This is very exciting for us vintage AR owners! 

[kj2005]

Thanks for the roses. At first sight I would consider the 3a tweeters to be a bigger problem as far as repair is concerned. The 3a tweeter dome is made of some sort of  paper-maché or compressed paper layers ( I don't know the correct word in english for "papmaché") and glued upon a coilform that looks like fenol-paper. I find it more difficult to separate the paper-dome from the very sensitive coilform on the 3a tweeter. I have tried once:-)

I am happy to know that we have some hifi people around with the same interest as me to keep the old midranges and tweeters going for the next decades to come? Edgar's invention....

[Glenn E]

Very nice work. I have a tweeter out of AR93s (and other models) which needs fixing. I am inspired to have a go. Glenn

[kj2005]

10 minutes ago, Glenn E said:

Very nice work. I have a tweeter out of AR93s (and other models) which needs fixing. I am inspired to have a go. Glenn

well nothing can go wrong with your tweeters because they are already to use as book supports or just for the trash can.....you can try to visit my amateursite for details, and feel free to ask if any questions occurs  rgds Kim