Optimus LX10 Linaeum tweeter dead - how to figure out what's broken?

[masofshad]

I've owned a pair of Optimus LX10 loudspeakers for about ten years now. About five years ago I noticed that the dipole ribbon tweeters on both speakers weren't producing any sound. The woofers were making noise just fine, just not the tweeters.

Fast forward to a couple weeks ago when I decided to try and fix them. I did some research on the interwebs and found a post on audioreview about a fuse on the circuit board inside the speaker that had a tendancy to blow.

I cracked one of the speakers open to check said fuse only to find that it is intact! Ok, lets check for leaky caps... nothing - it all looks good. What could be the problem here?

Do these tweeters go bad? I don't really understand how; I mean, they are a ribbon, magnets, and wiring - what component could fail?

Here is a picture of the circuit board. I have a digital multimeter, how can I test this circuit to check which component (if any) is defective?

 

[Cal Weldon]

Check the tweeter first. 🙂

 

[adason]

those dipole tweeters have actualy voice coils, except they are arranged in line, etched from copper foil
check those with ohm meter

 

[masofshad]

measurement results

I placed the multimeter's probes on the spade connectors for the dipole tweeter. I set the digital multimeter selector to the 20M OHM range and got .2 on the readout.

I'm guessing this means that the tweeter is shot as I should get a reading of 6 with the selector set to 200 OHM right?

Thanks for your help so far.

 

[masofshad]

dismantlement

I'm assuming I am correct in that the dipole tweeter is busted. Has anyone ever taken one of these things apart?

I don't see any screws anywhere, it actually looks like it was glues together; but I've been wrong about simpler things before 😱

Thanks,

Serge.

 

[adason]

Hi masofshad,

yes, at range 200 ohms the tweeter should measure close to 6 ohms. If it reads 0.2 ohms, than its shorted. If it reads 0.2 Mohms, than its open/burned. In any case its not a good sign.
I took some of those apart, but was not able to put them back!
Yes, they are glued together. Time to get new tweeters.

How about this one:
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=297-409
It's nice sit on top of the cabinet.

 

[sreten]

Hi,

It is very unusual for a tweeter to fail by going short,
it is nearly always a terminal open circuit failure.

🙂/sreten.

 

[masofshad]

If it reads 0.2 Mohms, than its open/burned.

Yup, it's 0.2 Mohms!

Hi,

It is very unusual for a tweeter to fail by going short,
it is nearly always a terminal open circuit failure.

🙂/sreten.

Indeed, it's open.

I think I'm going to take a stab and cutting it open with my deremel!!

WOOHOOO!!!

Thanks,

Serge.

 

[masofshad]

How about this one:
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=297-409
It's nice sit on top of the cabinet.

Thanks for the suggestion - the website is a great source for speakers!