LSi-15 partial meltdown??

nooshinjohn

I was pushing my LSi's pretty hard today and after about 20 minutes worth of Aerosmith, I started to get this wierd melted wire smell from both towers. My Sunfire Cinema 425/5 is still fairly cool to the touch and both speakers were sounding just fine, but I shut everything off just to be safe. I pulled the crossover out of one of them and it looks fine, but hot to the touch. Did I pull the plug in time? Any ideas on this one before I plug them back in?

mole'

that sucks man

good luck

Maximus666

Do the speaker drivers function at all? Are the tweeters shot?

How much "real", RMS power does your amp source? Does it have a heavy transformer with nice, high voltage rails from the power supply? Just wondering if your amp was clipping, which can kill tweeters.

Or perhaps the crossover components blew. If you've got warranty then good for you!
If the warranty has expired on your units then you *could* pull out the crossovers and look for signs of charring, especially on the resistors. I've seen pics from crossover mod projects that showed blackened resistors, which are actually white-coloured wirewound jobs.

Maximus666

Sorry, didn't read your post fully. I think the Sunfire amps are "beefy", and you mentioned that the components on the xovers are fine.

Good luck man!

nooshinjohn

They have been cooling their heals for about 45 minutes now. I plugged them back in after testing the drivers for free movement and checking the crossovers for damage. They all checked out ok and appear no worse for wear. I knew they were sounding rather warm.


All is good. Just glad I caught it before damage was done.

kawizx9r

Did you trace the wires within the speaker as well? You could've melted the jacket on it. I know I did once in an older car of mine, I had dual Rockford Fosgate Power HE2 subs (they were their high-end subs back then) pushing hard and the wire jackets on mine had melted right then and there. It made such a mess that I replaced the carpet in my vehicle. :eek:

Maximus666

Do you still sense that burned smell? Heheh... can you put your nose inside the individual cabinets?

Anyways, I think those boxes used "smaller" guage wire (16 or narrower). I've wondered how much power they could really handle. The specs said 125W, so perhaps 10% higher is still safe...?

Once I start really living in my new house I'll probably attack that. Already replaced some crossover caps. Next I'll bring the xovers into shoeboxes (external) and beef up the cables all around. Maybe even use silver. <gasp!>

Yeah, and then replace the drivers, rebuild the cabinets... essentially upgrade to LSI-25's. ;-)

nooshinjohn

They must have been seeing 700wpc from the Sunfire at the volume I had them at. There was no clipping at all from them, just to much juice. They appear to be ok. As far as the smell is concerned, yes, there is still some being pumped out of the ports, but I expect that will begin to fade over time

Maximus666

700WPC. LOL. Yep, Bob rocks.

Here's a good one: did the smell remind you of burnt plastic, or of burnt electronics? I think that the smells are a bit different. I've smelled burnt epoxy packages in the lab... always gets people sniffing their own equipment to see if something blew. ;-)

You say that the crossovers looked fine. Did you have good looks at the capacitors and inductors, or even the epoxy (which should be kinda clear, I think)? Perhaps you just cooked some of the epoxy that holds some of the components to the PCBs. Also, check out the electrolytic caps. The metal tops are kinda like JiffyPop containers: if they get damaged, then they can blow their tops literally.

F1nut

I seriously doubt you were getting anywhere near a steady 700wpc. Anyway, the issue was most likely one or more of the resistors. There have been reports from other folks about cooking LSi resistors. A search might pull up something on that matter.

F1nut

Maximus666 wrote: »

Anyways, I think those boxes used "smaller" guage wire (16 or narrower).

16 gauge is more than sufficient.

Face

Those amps are made in the same factory as Emotiva, there was no way you were putting out 700wpc.

nooshinjohn

F1nut wrote: »

I seriously doubt you were getting anywhere near a steady 700wpc. Anyway, the issue was most likely one or more of the resistors. There have been reports from other folks about cooking LSi resistors. A search might pull up something on that matter.

I agree Jesse about the wpc. The volume was almost maxed out on the Rogue, but I have not seen anything about resistors... Thanks man, I will do some homework.

SolidSqual

nooshinjohn wrote: »

I agree Jesse about the wpc. The volume was almost maxed out on the Rogue, but I have not seen anything about resistors... Thanks man, I will do some homework.

Seriously? How the fack are you doing that? You are going to destroy your ears. Jesus man, I know you listen loud (me too), but that's just ridiculous.

nooshinjohn

SolidSqual wrote: »

Seriously? How the fack are you doing that? You are going to destroy your ears. Jesus man, I know you listen loud (me too), but that's just ridiculous.

I was working in the garage...:p

Maximus666

Hi Finut,

Regarding power output: Yeah, power ratings are suspect.

You could always open up the amp and see what kind and how many output devices are present per channel, plus measure the DC rails from the power supply. That might lead you to some reasonable guesstimate. (Knowing the VA rating of the transformer may not always help due to the efficiency of the amp.) I once had both a Carver TFM-45 and a Sunfire 300. They were both rated at 500WPC into 4ohm loads. The max power supply rails on the Carver were around 113V. I didn't measure the Sunfire because of the Tracking Downconverter. I think that both amps had at least 8 output devices per channel. So it's *possible* that, with the right transformer, the amps could have reached those levels... maybe.

My XPA-5 is rated at 300WPC into 4 ohms all driven. So that's 1500W, hopefully RMS. The power supply is rated at 1200VA, and I'm guessing the amps are not 100% efficient because they're class A/B. So definitely something amiss there.

The Spectron amps might actually meet their ratings, as they're driven from the A/C rails. Yep, they're special.


Regarding the 16-guage wire:

I like to hedge my bets with larger guage copper (fine) stranded, however, rather than spend hundreds of dollars on cable with special physics.


But I guess this conversation should probably be in a different forum. :-)

Face

I have some old wire out of an LSi15 here, it does appear to be stranded 16ga.

Vette C6.r

Guilty - I cooked the 15 XO when I was having a party. The place I got them replaced them under warranty. Got to love buying all your stuff from the same small place. They take care of ya.

TECHNOKID

nooshinjohn wrote: »

They must have been seeing 700wpc from the Sunfire at the volume I had them at. There was no clipping at all from them, just to much juice. They appear to be ok. As far as the smell is concerned, yes, there is still some being pumped out of the ports, but I expect that will begin to fade over time

F1nut wrote: »

I seriously doubt you were getting anywhere near a steady 700wpc. Anyway, the issue was most likely one or more of the resistors. There have been reports from other folks about cooking LSi resistors. A search might pull up something on that matter.

If in fact the resistors were affected it may appear OK but it is not OK as they are now weakened and their life span are definitely affected. The resistors may look good externally but this is no garantee that they fine. You might want to use an ohmeter and do some value comparision between the 2 Xos. Resistors can change value rather than short or open and this can cause stress on other components leading to more serious damage.

Cheers!
TK

nooshinjohn

^^ I will be pulling them out and doing the crossover mods on them after the TL's are done. A closer inspection reveals that a couple of those white rectangular blocks have burned on both speakers. are those the resistors? I have never seen one like that.

TECHNOKID

nooshinjohn wrote: »

^^ I will be pulling them out and doing the crossover mods on them after the TL's are done. A closer inspection reveals that a couple of those white rectangular blocks have burned on both speakers. are those the resistors? I have never seen one like that.

Not sure but I think you are talking about the ceramic resistors. Those are of higher watage capability and often they are the ones that are affected due to the high current going though them. I would suggest (if you are good with soldering iron) that you un-solder one legg and use your multimeter to check the value and compare with the written value on the resistor. Most of the time, when ceramic resistors blow the is no physical appearnce and measuring them is the way to detect if bad. When measuring them, depending on the resitor value a few ohms difference is OK (tolerance) but an extreme variation can be serious (however, the common problem is an open and rarely variation).

nooshinjohn

TECHNOKID wrote: »

Not sure but I think you are talking about the ceramic resistors. Those are of higher watage capability and often they are the ones that are affected due to the high current going though them. I would suggest (if you are good with soldering iron) that you un-solder one legg and use your multimeter to check the value and compare with the written value on the resistor. Most of the time, when ceramic resistors blow the is no physical appearnce and measuring them is the way to detect if bad. When measuring them, depending on the resitor value a few ohms difference is OK (tolerance) but an extreme variation can be serious (however, the common problem is an open and rarely variation).

Thanks man... one of them is clearly burned and has actually darkened the board under it.

McLoki

There have been multiple instances of getting the resistor in the tweeter circuit hot enough that it literally desolders itself from the crossover.

(As a matter of fact, this happened to Opus and I had to solder it back on for him - so I have seen it first hand if not heard it)

I have heard of it happening in the bookshelves and LSiC, but this would be the first I had heard of it happening in one of the towers....

Just something to pay attention to.

Michael

Edit - yes, the white blocks are the resistors....

McLoki

I stand corrected...

Resistor issue with the LSi15 (and carver by chance)

LSiC resistor issue...

I am sure there are others, but that is from a quick search....

TECHNOKID

Do they look like any of the below?

This is scary, those are all Chines manufacturing crap :eek: At times, I thing it wasn't a bad idea to move away from repair...

The 3 first pics (left to right) are typical OEM ceramic resistors while the last one is often used as aftermarket resistor for repairs. The 3rd one could possibly be seen in Xo since it is NON inductive.

nooshinjohn

My burned resistors are the same ones as in the picture on that thread, and I have the SAME AMP!


Coincidence... Does a bear **** in the woods?

F1nut

nooshinjohn wrote: »

A closer inspection reveals that a couple of those white rectangular blocks have burned on both speakers. are those the resistors?

I wouldn't steer you wrong.

I don't know what the value is, but if possible replace them with something better than the ceramic block type resistor and of a higher watt rating.

TECHNOKID

McLoki wrote: »

I stand corrected...

Resistor issue with the LSi15 (and carver by chance)

LSiC resistor issue...

I am sure there are others, but that is from a quick search....

Interesting threads. You know, tolerances aren't actually too too bad (5%) as I've seen higher in consumers equipment (but this is Polk, right ). Once you confirm them bad, I would suggest you install mil standard ( 1 or 2% tolerance). Ceramic resistors don't have to be OEM, in fact you pay much more for OEM and they are not necessary of better quality.

one of them is clearly burned and has actually darkened the board under it.

Then, you will have to clean the burned area and scape some varnish of the run at 2 points and measure to ensure there isn't any open in the run. When un-soldering your resistors, you will need more heat than typical resistor however, too much can damage the soldering pad as it is probably weakened (un-glued from the board) and could potentially break and come off. The long lead aftermarket resistor could be a good fix since you can simply fold the long lead on the board to mate with the broken run (scrape varnish and solder lead over exposed run).

TECHNOKID

F1nut wrote: »

I wouldn't steer you wrong.

I don't know what the value is, but if possible replace them with something better than the ceramic block type resistor and of a higher watt rating.

Higher wattage rating is a hazard for other components. I would prefer having an innexpensive and easily replacable ceramic resistor than replacing smaller and potentially more expensive electronic parts surrounding the resistor. In the repair shop, I always considered replacement of ceramic resistors as freebee. Readily available, easy to replace and innexpensive :cool:

Just thank God you are not replacing surface mount :eek:

NOTE: Resitors are usually like fuses, if you replace with different wattage, you go lower never higher unless specified in a mod by the manufacturer.

McLoki

F1nut wrote: »

I wouldn't steer you wrong.

I don't know what the value is, but if possible replace them with something better than the ceramic block type resistor and of a higher watt rating.

Assuming it is the one in the tweeter circuit - it is a 2ohm - 5 watt resistor.

I would replace it with a 2ohm - 12watt mills resistor. (you can get them a bunch of places including sonicraft and parts express)

Just so you know - there are 3 - 2ohm resistors (1 for the tweeter and 1 for each mid-woofer) and 1 - 3.5 ohm resistor for the 8" woofer per speaker. While you are in there, you might as well replace them all - after all, their cheap.....

Michael

McLoki

TECHNOKID wrote: »

Higher wattage rating is a hazard for other components. I would prefer having an innexpensive and easily replacable ceramic resistor than replacing smaller and potentially more expensive electronic parts surrounding the resistor. In the repair shop, I always considered replacement of ceramic resistors as freebee. Readily available, easy to replace and innexpensive :cool:

Just thank God you are not replacing surface mount :eek:

NOTE: Resitors are usually like fuses, if you replace with different wattage, you go lower never higher unless specified in a mod by the manufacturer.

May be true if there are transistors in the circuit, but in these crossovers, all there is, is resistors, caps and coils. The 5 watt resistor (specifically in the tweeter) seems to be the weak link. I have not heard of anyone doing an upgrade (or mod) to the resistors in a crossover that did not use the same values of a higher wattage.

In almost all cases - it seems to be the 12 watt mills is the weapon of choice.

To each their own though.

Michael