La Scala Tweeter not working.

[Gregavi]

I have a pair of La Scalas from the mid 80s with a serial #8425978 if that matters. I replaced the crossovers a few years ago with a B&K Sound Xover and am very happy with the improved sound. Today I was fine tuning speaker levels after running Audyssey and noticed that one of the La Scalas sounded muffled. Upon more testing I discovered that the tweeter on the one that sounded muffled was not working. I disconnected it from the crossover and tested the ohms, which was reading at around 6. I did the battery test with a AA battery that puts out 1.2V and the tweeter produced the clicking sound I was taught to look for. Checked for any loose connections on the crossover board but didn't find any. 

Any advice on what my next step should be is appreciated.

Edited February 8, 2024 by Gregavi

[babadono]

So did you then hook it back up and it is still not working? I'm thinking maybe you had an oxidized connection at the crossover and now if you re connect it will work. Those tweeters are fragile beasts. Many of us have blown 1 or 2.

[Peter P.]

Since you have a voltmeter, set it to AC Volts and put the leads on the tweeter screws at the crossover board.

Play some music and you should see the numbers bounce around. Increase the volume and the bouncing

remains but the numbers are higher. It might help to have a couple clip leads to do this.

 

If you see no numbers, then a component in the crossover has failed or there is a bad connection somewhere in there.

[Gregavi]

14 hours ago, babadono said:

So did you then hook it back up and it is still not working? I'm thinking maybe you had an oxidized connection at the crossover and now if you re connect it will work. Those tweeters are fragile beasts. Many of us have blown 1 or 2.

I did and still not working.

[Gregavi]

8 hours ago, Peter P. said:

Since you have a voltmeter, set it to AC Volts and put the leads on the tweeter screws at the crossover board.

Play some music and you should see the numbers bounce around. Increase the volume and the bouncing

remains but the numbers are higher. It might help to have a couple clip leads to do this.

 

If you see no numbers, then a component in the crossover has failed or there is a bad connection somewhere in there.

I did this and it appears that the Xover is the culprit. On the speaker that is OK, the numbers jump around as you suggested. On the dead tweeter speaker, the number remained at Zero. BTW, on my volt meter I tried both V (volts) and mA (milliamps). The numbers went between 3 and 4 on V and of course higher numbers on mA. I checked most of the connections on the Xover board but I need to turn my speaker around to better access the Xover board. I will report back. 

Many thanks guys.

[Khornukopia]

18 minutes ago, Gregavi said:

I checked most of the connections on the Xover board but I need to turn my speaker around to better access the Xover board. I will report back

 

Can you take a picture of the board (and downsize the picture file) and post it here?

[Gregavi]

I took the X Over out, cleaned it up a bit, tightened all the connections and re-installed it. (I wish all speakers were as easy access). Still the tweeter is not working.

[Gregavi]

[babadono]

Is there a schematic for this B & K Sound crossover?

[Khornukopia]

At this point, I would remove the silent tweeter and connect it to the good La Scala for a listening test.

[OO1]

..bump

[DeanG Crossovers]

It’s an AL-3. 
 

Using your fully functioning La Scala, loosen the two screws for the tweeter and remove the tweeter connections. Now connect your non working tweeter to those connection points on the barrier strip. Play some music. If you hear the tweeter the other network has an issue.

[Gregavi]

I ran wires +/- from the known working xover tweeter connection to the non working tweeter and have verified that it is not the tweeter that has failed (the tweeter worked). Checked all the connections in the xover and they all seem to be tight.

Edited February 8, 2024 by Gregavi

[DeanG Crossovers]

Contact the vendor who built the networks. There is probably a label underneath with the contact information.  

[babadono]

[babadono]

This AK3?

 

[babadono]

So your meter responds to the tweeter terminals on the good crossover but on bad one shows nothing? Verify there is signal at first 2uf cap on the left, then follow through to the output.

[Peter P.]

It could be something as simple as a bad crimp connection. I would remove each spade terminal and test one at a time so you don't

confuse + and -. Test for continuity or low resistance from the spade terminal to the first 2uF capacitor like babadono suggests, and do

the same from the tweeter's - terminal to the other spade terminal. If those test good, then move on to testing the capacitors.

 

I say this because it's real easy for most people to replace a bad crimp connector.

[babadono]

I agree completely with @Peter P.. Bad crimp, cold solder joint under that heat shrink tubing, even a broken wire are all possibilities.

[DeanG Crossovers]

If I build something and it stops working, I expect the end user to send it back to me. I will stand behind my work, and there will be no charge, regardless of what I find. However, If they start poking around, etc. - all bets are off and they are going to get billed for the work.

 

I can’t really figure out this insistence on digging into this network when I’m pretty sure Michael would take care of it at no charge.