My mate has a 2 way speaker and in the photo of the crossover the 10ohm 50w resistor has blown hardcore and I reckon the cap was ok but the resistor popped so hard it shot a flame out and scorched the cap. Does that look like what happened? and what could cause this? It's the second time that resistor has blown :O
HF diaphram is open circuit but not burnt actually it still looks new.
HF diaphram is open circuit but not burnt actually it still looks new.
Are you sure the amp is not defective? Otherwise there must have been severe overdrive of the speaker.
That resistor is more like only 5W without being mounted on a large heat sink.
That resistor is more like only 5W without being mounted on a large heat sink.
The second time? That doesn't look standard and that isn't the normal way to mount such a resistor. I'd have to wonder whether there was damage to the board which wasn't detected first time around.
The capacitor needs to go, and all traces of carbon cleaned off the board and then everything checked including the board, speakers and amp.
You don't mention how it was being used at the time?
The capacitor needs to go, and all traces of carbon cleaned off the board and then everything checked including the board, speakers and amp.
You don't mention how it was being used at the time?
It claimed to be a 50w but who knows. The original was a 50w ceramic and it blew also. The other speaker blew that same ceramic resistor too.
They said it was background music but they could have over driven it and not said anything. They are using other speakers on the amp and they work fine apparently.
LF driver is fine, HF driver is open but still looks new no over excursion or discoloration of coil.
I'll get them to check the crossover thoroughly and clean of carbonation.
They said it was background music but they could have over driven it and not said anything. They are using other speakers on the amp and they work fine apparently.
LF driver is fine, HF driver is open but still looks new no over excursion or discoloration of coil.
I'll get them to check the crossover thoroughly and clean of carbonation.
None of what you say disproves anything.
So far it's not known why it's necessary to have a 50W resistor, whether the circuit is susceptible to amplifier problems that others may not be. Have you checked the board for shorts? Have you measured the DC offset of the amp? Have a schematic?
Have you checked the coils for shorts? Are you prepared to hardwire a replacement crossover?
So far it's not known why it's necessary to have a 50W resistor, whether the circuit is susceptible to amplifier problems that others may not be. Have you checked the board for shorts? Have you measured the DC offset of the amp? Have a schematic?
Have you checked the coils for shorts? Are you prepared to hardwire a replacement crossover?
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............and why I've only used industrial and/or mil-spec power resistors in business and DIY.
That's a high quality Dale wirewound resistor that was severely over powered.
The rating is only 20W if it is not attached to a large heat sink.
https://www.digikey.com/en/products/detail/vishay-dale/RH05010R00FE02/1166306
First question, is where the resistor is in the circuit? Is it before the crossover parts caps and coils or is it after, and is it a shunt component? If it's not a shunt component and it's after the crossover both of those would stop this from being someplace that would heat up terribly on a tweeter circuit. Further information a shunt component in front of the crossover without having a voltage divider will see the entire bandwidth that the crossover would normally filter out. This means the resistors are directly across the amplifier's output and can run hot, and not only that, produce a very low impedance measurement for the system.
This compounded by having a rating of 5 to 10 watts without being on a heat sink, would really be a reason it would get hot. You can see the charring on the resistor case. It was really hot!
Yes DC offset very well could be another cause of it getting warm as well.
I have ran those kind of Dale resistors before without heat sinks in Tweeter circuits and never had them get remotely that warm. 5 to 10 watts is usually pretty reasonable on a tweeter circuit in most home hi-fi designs.
If it's not an amp problem and it's not a circuit problem then somebody wasn't careful with the volume knob.
This compounded by having a rating of 5 to 10 watts without being on a heat sink, would really be a reason it would get hot. You can see the charring on the resistor case. It was really hot!
Yes DC offset very well could be another cause of it getting warm as well.
I have ran those kind of Dale resistors before without heat sinks in Tweeter circuits and never had them get remotely that warm. 5 to 10 watts is usually pretty reasonable on a tweeter circuit in most home hi-fi designs.
If it's not an amp problem and it's not a circuit problem then somebody wasn't careful with the volume knob.
OK, thanks! So grossly misapplied in this case, but my point is to use components designed/rated for catastrophic failure containment. Aware of plenty of 'popped' resistors around the world in my time of designing industrial power & controls apps when no upstream short ckt. protection was used, but that's where the damaged ended when the proper resistor(s) were used.
This begs the question though of why aren't 'we' still promoting basic short ckt. protection like for prosound for high power potential DIY speakers?
This begs the question though of why aren't 'we' still promoting basic short ckt. protection like for prosound for high power potential DIY speakers?
Reason I've quit buying power resistors from newark, digikey, mouser, alliedelec RS etc. The rating of their power resistors includes a $$$ aluminum heatsink they don't sell as a package. I've been buying large wirewounds from surplus houses, since the major distributors want to push snake oil. This is the first place I've seen the implicit heat sink even mentioned. electric bicycles, ac inverters, battery chargers, solar power, I need resistors that dump power to the air, not to another $$$ component.
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Ok, so a heavy hand on the volume knob is the likely problem. Maybe them, maybe their kids when they're gone.
Add an external 2A fuse to the resistor. And get them a couple of boxes of fuses, they'll need them.
The bulbs eminence uses in their crossovers work very well for driver and xover protection. They are also fairly inert in regards to SQ. A polyswitch works too, but they degrade over time and increase in resistance everytime they are tripped.
I suspect the capacitor shorted first and that put the resistor directly across the amplifier. Just guessing at the schematic. Replacing the resistor likely repeated that experiment. Replacing both the resistor and capacitor will likely solve the problem. How the driver survived? Who knows. Is the driver or wiring to it shorted? A schematic would help a lot. When I've seen things like this from my friends, there was always drinking involved. Ha
Both speakers are blown. And the amplifier still works. Somebody cranked up the volume all the way.
When the rat bit into it? Aliens! That's it. Aliens. Time to form a crossover CSI team.
Yeah, someone's heavy handed on the volume. I've seen film caps short before, but both crossovers being affected means it was likely abuse or a resistor power rating design issue.