See pic. Is that possibly bad inductior? Having issues with low output from mid and hi. Close up is one in question. Other pic is good one. Also what are options for replacment? It is L2 on schematic for Jbl 4435. 1.0mH
Bad inductor on Jbl 4435 xover?
- Thread starter script56
- Start date
I LIKE MUSIC
Super Member
It does look like it has been hot. Depending on how how hot, especially internally, it might have some shorted turns that might not show up with a basic DC resistance measurement.
While I do not know the history of this, a quick look at the schematic makes me want to also take a look a C11 and C12.
While I do not know the history of this, a quick look at the schematic makes me want to also take a look a C11 and C12.
dshoaf
That high voltage buzz
@w1jim's advice is a good start. Please compare that reading to the same component in the other crossover.
Generally, I'd be more concerned about _why_ the inductor got hot enough to discolor. This indicates a fair amount of heat being generated for a period of time. This didn't happen quickly. And why just the inductor? I'd also expect to see some other resistors suffering as well.
What's the whole crossover schematic look like? I couldn't tell much from the snip.
Until proven wrong, I'd suggest you're looking at a symptom - not the root cause yet.
There's been plenty of advice about that big rotary switch being a pain on that model. I'd suggest cleaning it first and then re-evaluating the symptoms.
Cheers,
David
Generally, I'd be more concerned about _why_ the inductor got hot enough to discolor. This indicates a fair amount of heat being generated for a period of time. This didn't happen quickly. And why just the inductor? I'd also expect to see some other resistors suffering as well.
What's the whole crossover schematic look like? I couldn't tell much from the snip.
Until proven wrong, I'd suggest you're looking at a symptom - not the root cause yet.
There's been plenty of advice about that big rotary switch being a pain on that model. I'd suggest cleaning it first and then re-evaluating the symptoms.
Cheers,
David
Zonker92
All shiny and chrome
I replaced mine with these:
https://www.parts-express.com/jantzen-audio-10mh-16-awg-copper-foil-wax-coil-crossover-coil--255-515
However, you could instead use one of these:
https://www.parts-express.com/Search.aspx?keyword=1.0mh&sitesearch=true
But check the DCR spec on each one; as I recall, it should be around 0.4 ohms to be close to the original.
https://www.parts-express.com/jantzen-audio-10mh-16-awg-copper-foil-wax-coil-crossover-coil--255-515
However, you could instead use one of these:
https://www.parts-express.com/Search.aspx?keyword=1.0mh&sitesearch=true
But check the DCR spec on each one; as I recall, it should be around 0.4 ohms to be close to the original.
I would suggest that someone was biamping it and put a lot of power to the woofers for a while. The 18mH inductor appears to stay in the circuit even in bi-amp mode and I would think this to be the burned inductor.
If you put an ohm meter across it (with at least one leg out of the circuit), the resistance should be so low as to almost read as a short circuit. If the meter reads infinity, the coil is burnt open.
If you put an ohm meter across it (with at least one leg out of the circuit), the resistance should be so low as to almost read as a short circuit. If the meter reads infinity, the coil is burnt open.
audiomagnate
Addicted Member
They impede the flow of high frequencies. They rarely go bad in my experience. BTW Script, you zeroed in too close on the schematic to show what it's really doing.
audiomagnate
Addicted Member
Or... the insulation could be melted causing shorts within the windings, bringing the effective number of turns down and lowering the value.
Zonker92
All shiny and chrome
The inductor in question is L2; 1.0 mH. It's part of the horn circuit, and parallel; not in series. The bass inductors are mounted outboard of the PCB.
toxcrusadr
Omelette au Fromage
I second the motion to check the caps in series with that driver, too. An inductor parallel to a mid or tweeter is not directly in the circuit path, it's there to shunt lower frequencies that came through the cap(s), thus making the curve drop off more steeply from the crossover point. The caps are in series and normally upstream of such an inductor so they would have carried all the current that went through the inductor, and more (since some - most - goes through the horn itself). If those caps had drifted to higher values, that could allow more bass into the circuit, which then gets directed through the inductor. Definitely check those caps, and if at all possible, measure the inductor before replacing it.
