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Silent tweeters - Crossover broken

B

BeezyP

New Member
Hi all,

I recently inherited some german speakers (Magnat All-Ribbon 4). When I received them, everything worked fine. However, after a few hours of moderate listening, the tweeter of one speaker went silent.

I thought I might‘ve blown the tweeter. However, today I measured 6 ohms of dc resistance (supposed to have 8 ohm impedance) which gave me some hope. I them switched both tweeters and sure enough the supposedly „broken“ one turned out to be just fine.

I then suspected a cap or resistor might‘ve broken, so I pulled out the crossover. Visually, the caps and resistors are just fine. Also, there‘s a fuse in the terminal which is also fine (measured continuity). I now want to diagnose which components are broken.

How do I do just that? Do I have to desolder one leg of each part, then measure resistance/capacitance? Any smart way to do this without too much desoldering?

Thanks for any tipps or tricks!
 
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Resistors can be checked in circuit.
Caps usually need to be removed from the circuit to accurately test.

In my limited experience it's usually the resistors that leave an open circuit (no sound), whereas the caps usually just drift their values and change the xover frequency.
 
painttoad said:
try clipping leads on either end of the fuse holder and wiggling the fuse and watch your meter. loose fuses/dirty fuse holders are a potential problem
Click to expand...
I put my multimeter on the fuse leads that are connected to the crossovers. It measbures continuity even when wiggling so I can‘t detect any loose contact. Good hunch tho!
 
swechsler said:
Also check the tweeter terminals for oxidation. It's possible that just switching the leads scraped off enough oxidation so that the tweeter is working again.
Click to expand...
The tweeter is soldered in place and I couldn‘t see any bad solder joints. However I‘ll try reconnecting the tweeter and see if it magically works by now before desoldering the caps.
 
kmagnuss said:
Resistors can be checked in circuit.
Caps usually need to be removed from the circuit to accurately test.

In my limited experience it's usually the resistors that leave an open circuit (no sound), whereas the caps usually just drift their values and change the xover frequency.
Click to expand...
When checking the resistors, all except for one showed the value they‘re rated at. There was a 15 ohm one that only showed 3 but probably because it‘s in parallel with some others - didn‘t figure out the schematic yet. However none of them was open. I‘ll probably start with desoldering one lead of the caps and measure them, starting with the smallest one. However I agree, if the caps were the fault, they‘d probably need to have no continuity or change their capacitance for there to be no tweeter sound at all.

I‘ll keep you posted.
 
BeezyP said:
When checking the resistors, all except for one showed the value they‘re rated at. There was a 15 ohm one that only showed 3 but probably because it‘s in parallel with some others - didn‘t figure out the schematic yet. However none of them was open. I‘ll probably start with desoldering one lead of the caps and measure them, starting with the smallest one. However I agree, if the caps were the fault, they‘d probably need to have no continuity or change their capacitance for there to be no tweeter sound at all.

I‘ll keep you posted.
Click to expand...
Try adding a little fresh solder to all the solder points. The speaker may have developed a periodic broken or cold solder, which can be hard to isolate.
 
Hi all,

i desoldered all caps and measured them. The ratings are around 20% off on all of them, which I‘d say is expected and fine given the age of the speakers (they‘re rated at 10%). The resistors are all good, I just touched up the solder joints and screwed everything back together. I also inspected the voice coil of the tweeters, looking for any obvious damage but found none. I then didn‘t know what to do anymore so I just screwed everything back together.

I then tested the speakers again before admitting defeat and voilà - They are alive again. The tweeter wrongly declared dead before still is a bit quieter/not as detailed as the other good one. Nevertheless they work at least and it‘s barely noticeable in Stereo.
In the long run I might get a replacement tweeter and do some recapping, but for now I‘ll just leave it as is.

Another thing I noticed - The speaker with the crossover I touched up now has a very slight crackling noise when turning the volume up/down rapidly. It‘s noticeable when no music is played but AUX is connected and the knob is turned. It‘s only on the one touched up speaker, but not the other. Any idea why that is? Maybe some soldering mistakes?

Anyways, I‘m happy they work again without a dollar spent in repairs. Thanks for all the great help.
 
BeezyP said:
Hi all,

Another thing I noticed - The speaker with the crossover I touched up now has a very slight crackling noise when turning the volume up/down rapidly. It‘s noticeable when no music is played but AUX is connected and the knob is turned. It‘s only on the one touched up speaker, but not the other. Any idea why that is? Maybe some soldering mistakes?
Click to expand...
Try some Fader Lube on the volume control (in the receiver or pre-amp). The pot channel on the noisy speaker's side may be oxidized.
 
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