LSI25 amp problem

So yesterday I picked up a pair of Polk LSI25 speakers at my local goodwill, and when I fired them up this morning, the sub in the right speaker wasn’t working. I decided to pull the amp board and take a look inside. The fuse was blown so I replaced it and plugged it in, and immediately one of the things that are the actual amps (can’t remember what they are called all of the sudden, it is one of the four pieces on the side of what I believe is a heat sink) began smoking. I don’t know if the amp powered on when I did that because I was paying to much attention the smoke, but does anyone know what could be the problem and how I could fix it?

Thanks,
Micah
2 channel
Speakers: Mission 770 Freedoms
Integrated amp: Technics SU-v75 and matching tuner
CDP: Technics SL-PC20
Cables: Monoprice, Monster, Acoustic Research, and a few generic ones
TT: Technics SL-3200, direct drive
Cartridge: Shure M97xE

Pc gaming setup
Receiver/amp: Yamaha RX-V665
Computer: Lenovo g50 (soon to be upgraded to a Dell Precision 690 which is far from stock!!)
Interconnects: Amazon basics HDMI, Acoustic Research HDMI, Monoprice speaker cables
Speakers: Boston Acoustics CR75s

Random equipment on standby:
Onkyo TX-v940, JBL woofers and tweeters, single Klipsch KG .5, Yamaha guitar amplifier, Peavey Rage 158 guitar amplifier, Kicker comp 12” subwoofer, single Bose 802 series II, a whole bunch of 1”-3” full range drivers, Infinity Crescendo 3007s (on sale), Polk LSi25s
txcoastal1 wrote: »

You don't tell her you read the manual, and you tell her you know what the problem is, and you fixed it, because that what men do, fix things
sure it has a flat response, and sure it has a lot of detail, and yes, it has good and clear lows. But is it enjoyable to listen to? Does it make you grin ear to ear? That’s what really matters.
Seen somewhere on AudioKarma (I think)

Comments

  • I think I posted this in the wrong place. Sorry!
    2 channel
    Speakers: Mission 770 Freedoms
    Integrated amp: Technics SU-v75 and matching tuner
    CDP: Technics SL-PC20
    Cables: Monoprice, Monster, Acoustic Research, and a few generic ones
    TT: Technics SL-3200, direct drive
    Cartridge: Shure M97xE

    Pc gaming setup
    Receiver/amp: Yamaha RX-V665
    Computer: Lenovo g50 (soon to be upgraded to a Dell Precision 690 which is far from stock!!)
    Interconnects: Amazon basics HDMI, Acoustic Research HDMI, Monoprice speaker cables
    Speakers: Boston Acoustics CR75s

    Random equipment on standby:
    Onkyo TX-v940, JBL woofers and tweeters, single Klipsch KG .5, Yamaha guitar amplifier, Peavey Rage 158 guitar amplifier, Kicker comp 12” subwoofer, single Bose 802 series II, a whole bunch of 1”-3” full range drivers, Infinity Crescendo 3007s (on sale), Polk LSi25s
    txcoastal1 wrote: »

    You don't tell her you read the manual, and you tell her you know what the problem is, and you fixed it, because that what men do, fix things
    sure it has a flat response, and sure it has a lot of detail, and yes, it has good and clear lows. But is it enjoyable to listen to? Does it make you grin ear to ear? That’s what really matters.
    Seen somewhere on AudioKarma (I think)
  • KennethSwaugerKennethSwauger Moderator Posts: 6,394
    Hello,
    The bass amplifier would have to be repaired or replaced, telephone Polk tomorrow at: 1-800-377-7655 select option 2 for parts.
    "And the house you live in will never fall down
    If you pity the stranger who stands at your gate" G.Lightfoot
  • Airplay355Airplay355 Posts: 4,153
    Somebody dumped Lsi25 at Goodwill? Lucky find, broken or not!
  • Ikr? I got them for $50!
    Thanks guys, I will
    2 channel
    Speakers: Mission 770 Freedoms
    Integrated amp: Technics SU-v75 and matching tuner
    CDP: Technics SL-PC20
    Cables: Monoprice, Monster, Acoustic Research, and a few generic ones
    TT: Technics SL-3200, direct drive
    Cartridge: Shure M97xE

    Pc gaming setup
    Receiver/amp: Yamaha RX-V665
    Computer: Lenovo g50 (soon to be upgraded to a Dell Precision 690 which is far from stock!!)
    Interconnects: Amazon basics HDMI, Acoustic Research HDMI, Monoprice speaker cables
    Speakers: Boston Acoustics CR75s

    Random equipment on standby:
    Onkyo TX-v940, JBL woofers and tweeters, single Klipsch KG .5, Yamaha guitar amplifier, Peavey Rage 158 guitar amplifier, Kicker comp 12” subwoofer, single Bose 802 series II, a whole bunch of 1”-3” full range drivers, Infinity Crescendo 3007s (on sale), Polk LSi25s
    txcoastal1 wrote: »

    You don't tell her you read the manual, and you tell her you know what the problem is, and you fixed it, because that what men do, fix things
    sure it has a flat response, and sure it has a lot of detail, and yes, it has good and clear lows. But is it enjoyable to listen to? Does it make you grin ear to ear? That’s what really matters.
    Seen somewhere on AudioKarma (I think)
  • While I was here I thought I would ask, I currently have a Yamaha amplifier that only is able to go down to 6 ohms, will this be a big problem that I have to fix ASAP or something that can wait?
    2 channel
    Speakers: Mission 770 Freedoms
    Integrated amp: Technics SU-v75 and matching tuner
    CDP: Technics SL-PC20
    Cables: Monoprice, Monster, Acoustic Research, and a few generic ones
    TT: Technics SL-3200, direct drive
    Cartridge: Shure M97xE

    Pc gaming setup
    Receiver/amp: Yamaha RX-V665
    Computer: Lenovo g50 (soon to be upgraded to a Dell Precision 690 which is far from stock!!)
    Interconnects: Amazon basics HDMI, Acoustic Research HDMI, Monoprice speaker cables
    Speakers: Boston Acoustics CR75s

    Random equipment on standby:
    Onkyo TX-v940, JBL woofers and tweeters, single Klipsch KG .5, Yamaha guitar amplifier, Peavey Rage 158 guitar amplifier, Kicker comp 12” subwoofer, single Bose 802 series II, a whole bunch of 1”-3” full range drivers, Infinity Crescendo 3007s (on sale), Polk LSi25s
    txcoastal1 wrote: »

    You don't tell her you read the manual, and you tell her you know what the problem is, and you fixed it, because that what men do, fix things
    sure it has a flat response, and sure it has a lot of detail, and yes, it has good and clear lows. But is it enjoyable to listen to? Does it make you grin ear to ear? That’s what really matters.
    Seen somewhere on AudioKarma (I think)
  • mlistens03mlistens03 Posts: 986
    Sorry to bump an old thread, but I decided that’s probably better than a new one :smile:
    I got to really looking at this amp yesterday, and I think I might have found a blown resistor, but I’m not 100% sure. It looks a little cooked, but then at the same time it looks like some [email protected] just got on it. Do you guys think this guys is blown?
    hoj80xrzpxzj.jpg
    I fall you think it is, do you know the values of this resistor? I can’t figure out how to read it, because everything I find on the interwebz doesn’t agree with what I see on that resistor.
    2 channel
    Speakers: Mission 770 Freedoms
    Integrated amp: Technics SU-v75 and matching tuner
    CDP: Technics SL-PC20
    Cables: Monoprice, Monster, Acoustic Research, and a few generic ones
    TT: Technics SL-3200, direct drive
    Cartridge: Shure M97xE

    Pc gaming setup
    Receiver/amp: Yamaha RX-V665
    Computer: Lenovo g50 (soon to be upgraded to a Dell Precision 690 which is far from stock!!)
    Interconnects: Amazon basics HDMI, Acoustic Research HDMI, Monoprice speaker cables
    Speakers: Boston Acoustics CR75s

    Random equipment on standby:
    Onkyo TX-v940, JBL woofers and tweeters, single Klipsch KG .5, Yamaha guitar amplifier, Peavey Rage 158 guitar amplifier, Kicker comp 12” subwoofer, single Bose 802 series II, a whole bunch of 1”-3” full range drivers, Infinity Crescendo 3007s (on sale), Polk LSi25s
    txcoastal1 wrote: »

    You don't tell her you read the manual, and you tell her you know what the problem is, and you fixed it, because that what men do, fix things
    sure it has a flat response, and sure it has a lot of detail, and yes, it has good and clear lows. But is it enjoyable to listen to? Does it make you grin ear to ear? That’s what really matters.
    Seen somewhere on AudioKarma (I think)
  • pitdogg2pitdogg2 Posts: 9,803
    edited May 19
    Which one are you referring to?
    Give us a number. Usually a cooked resistor is very easy to tell.
  • F1nutF1nut Posts: 39,600
    20k ohms 1%

    I don't think that resistor is cooked though.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."


  • txcoastal1txcoastal1 Posts: 9,602
    If I remember correctly, when my board went out it was around the rectifier
    2-channel: Modwright KWI-200 Integrated, Dynaudio C1-II Signatures
    Desktop rig: LSi7, Polk 110sub, Dayens Ampino amp, W4S DAC/pre, Sonos, JRiver
    Gear on standby: Melody 101 tube pre, Unison Research Simply Italy Integrated
    Gone to new homes: (Matt Polk's)Threshold Stasis SA12e monoblocks, Pass XA30.5 amp, Usher MD2 speakers, Dynaudio C4 platinum speakers, Modwright LS100 (voltz), Simaudio 780D DAC
  • mlistens03mlistens03 Posts: 986
    Sorry I forgot I’m looking at R80, looks like it either is slightly browned or has some form of crap on it.
    Where is the rectifier on the board? I’ve heard of that type of component before, but I don’t know what it is or looks like. Would this be the amp chips on the side of the heat sink?
    4t3z8bggtv42.jpg
    2 channel
    Speakers: Mission 770 Freedoms
    Integrated amp: Technics SU-v75 and matching tuner
    CDP: Technics SL-PC20
    Cables: Monoprice, Monster, Acoustic Research, and a few generic ones
    TT: Technics SL-3200, direct drive
    Cartridge: Shure M97xE

    Pc gaming setup
    Receiver/amp: Yamaha RX-V665
    Computer: Lenovo g50 (soon to be upgraded to a Dell Precision 690 which is far from stock!!)
    Interconnects: Amazon basics HDMI, Acoustic Research HDMI, Monoprice speaker cables
    Speakers: Boston Acoustics CR75s

    Random equipment on standby:
    Onkyo TX-v940, JBL woofers and tweeters, single Klipsch KG .5, Yamaha guitar amplifier, Peavey Rage 158 guitar amplifier, Kicker comp 12” subwoofer, single Bose 802 series II, a whole bunch of 1”-3” full range drivers, Infinity Crescendo 3007s (on sale), Polk LSi25s
    txcoastal1 wrote: »

    You don't tell her you read the manual, and you tell her you know what the problem is, and you fixed it, because that what men do, fix things
    sure it has a flat response, and sure it has a lot of detail, and yes, it has good and clear lows. But is it enjoyable to listen to? Does it make you grin ear to ear? That’s what really matters.
    Seen somewhere on AudioKarma (I think)
  • msgmsg Posts: 4,034
    M - was just curious, did you ever have this amp repaired? Are you having a problem with it now, or just having a look around?
  • mlistens03mlistens03 Posts: 986
    It didn’t work when I bought it, and I never got it repaired. I want to try fixing it now, so that it’s will work for the time being, and then they will be worth more when I sell them. I was just looking inside to see what I could see, and test caps/resistors and stuff.
    2 channel
    Speakers: Mission 770 Freedoms
    Integrated amp: Technics SU-v75 and matching tuner
    CDP: Technics SL-PC20
    Cables: Monoprice, Monster, Acoustic Research, and a few generic ones
    TT: Technics SL-3200, direct drive
    Cartridge: Shure M97xE

    Pc gaming setup
    Receiver/amp: Yamaha RX-V665
    Computer: Lenovo g50 (soon to be upgraded to a Dell Precision 690 which is far from stock!!)
    Interconnects: Amazon basics HDMI, Acoustic Research HDMI, Monoprice speaker cables
    Speakers: Boston Acoustics CR75s

    Random equipment on standby:
    Onkyo TX-v940, JBL woofers and tweeters, single Klipsch KG .5, Yamaha guitar amplifier, Peavey Rage 158 guitar amplifier, Kicker comp 12” subwoofer, single Bose 802 series II, a whole bunch of 1”-3” full range drivers, Infinity Crescendo 3007s (on sale), Polk LSi25s
    txcoastal1 wrote: »

    You don't tell her you read the manual, and you tell her you know what the problem is, and you fixed it, because that what men do, fix things
    sure it has a flat response, and sure it has a lot of detail, and yes, it has good and clear lows. But is it enjoyable to listen to? Does it make you grin ear to ear? That’s what really matters.
    Seen somewhere on AudioKarma (I think)
  • txcoastal1txcoastal1 Posts: 9,602
    The rectifier and heat sink I was speaking of, is between the blue capacitor S0143 and the brn/yel cable connector
    2-channel: Modwright KWI-200 Integrated, Dynaudio C1-II Signatures
    Desktop rig: LSi7, Polk 110sub, Dayens Ampino amp, W4S DAC/pre, Sonos, JRiver
    Gear on standby: Melody 101 tube pre, Unison Research Simply Italy Integrated
    Gone to new homes: (Matt Polk's)Threshold Stasis SA12e monoblocks, Pass XA30.5 amp, Usher MD2 speakers, Dynaudio C4 platinum speakers, Modwright LS100 (voltz), Simaudio 780D DAC
  • mlistens03mlistens03 Posts: 986
    I decided this was the thread I should post this in, I found this in my wallet from the LSis:
    9y5lfh7rtyps.jpg
    I guess I stuffed it in my wallet after buying them and forgot about it.
    I’m going to use this as an opportunity to say thanks so much for everything. Thanks for the help everyone, thanks Nightfall for the cartridge for my TT, and most importantly; thanks everyone for the memories.
    Micah
    2 channel
    Speakers: Mission 770 Freedoms
    Integrated amp: Technics SU-v75 and matching tuner
    CDP: Technics SL-PC20
    Cables: Monoprice, Monster, Acoustic Research, and a few generic ones
    TT: Technics SL-3200, direct drive
    Cartridge: Shure M97xE

    Pc gaming setup
    Receiver/amp: Yamaha RX-V665
    Computer: Lenovo g50 (soon to be upgraded to a Dell Precision 690 which is far from stock!!)
    Interconnects: Amazon basics HDMI, Acoustic Research HDMI, Monoprice speaker cables
    Speakers: Boston Acoustics CR75s

    Random equipment on standby:
    Onkyo TX-v940, JBL woofers and tweeters, single Klipsch KG .5, Yamaha guitar amplifier, Peavey Rage 158 guitar amplifier, Kicker comp 12” subwoofer, single Bose 802 series II, a whole bunch of 1”-3” full range drivers, Infinity Crescendo 3007s (on sale), Polk LSi25s
    txcoastal1 wrote: »

    You don't tell her you read the manual, and you tell her you know what the problem is, and you fixed it, because that what men do, fix things
    sure it has a flat response, and sure it has a lot of detail, and yes, it has good and clear lows. But is it enjoyable to listen to? Does it make you grin ear to ear? That’s what really matters.
    Seen somewhere on AudioKarma (I think)
  • FestYboyFestYboy Posts: 2,317
    That sounds very much like a goodbye...

    I hope I'm wrong.
  • mlistens03mlistens03 Posts: 986
    FestYboy wrote: »
    That sounds very much like a goodbye...

    I hope I'm wrong.

    Oh you are wrong! You are right that sounds like goodbye! Oops lol sorry everyone for not noticing that.
    2 channel
    Speakers: Mission 770 Freedoms
    Integrated amp: Technics SU-v75 and matching tuner
    CDP: Technics SL-PC20
    Cables: Monoprice, Monster, Acoustic Research, and a few generic ones
    TT: Technics SL-3200, direct drive
    Cartridge: Shure M97xE

    Pc gaming setup
    Receiver/amp: Yamaha RX-V665
    Computer: Lenovo g50 (soon to be upgraded to a Dell Precision 690 which is far from stock!!)
    Interconnects: Amazon basics HDMI, Acoustic Research HDMI, Monoprice speaker cables
    Speakers: Boston Acoustics CR75s

    Random equipment on standby:
    Onkyo TX-v940, JBL woofers and tweeters, single Klipsch KG .5, Yamaha guitar amplifier, Peavey Rage 158 guitar amplifier, Kicker comp 12” subwoofer, single Bose 802 series II, a whole bunch of 1”-3” full range drivers, Infinity Crescendo 3007s (on sale), Polk LSi25s
    txcoastal1 wrote: »

    You don't tell her you read the manual, and you tell her you know what the problem is, and you fixed it, because that what men do, fix things
    sure it has a flat response, and sure it has a lot of detail, and yes, it has good and clear lows. But is it enjoyable to listen to? Does it make you grin ear to ear? That’s what really matters.
    Seen somewhere on AudioKarma (I think)
  • FestYboyFestYboy Posts: 2,317
    Oh good.

    Now back to the task at hand: see if we can't get a service manual for that amp. Amps are fairly easy circuits, but when there's a preamp stage, filtering and shaping circuits, and power rectification, things can get weird and confusing quickly. Best to start on the power supply side, as it's the simplest circuit.

    I'll be getting knee deep in a NAD 7175PE's power circuit myself. It blows a 5A power switch fuse immediately, so a dead short is what I'll be after. From the sounds of it, the same is going to hold true for you.
  • mlistens03mlistens03 Posts: 986
    FestYboy wrote: »
    Oh good.

    Now back to the task at hand: see if we can't get a service manual for that amp. Amps are fairly easy circuits, but when there's a preamp stage, filtering and shaping circuits, and power rectification, things can get weird and confusing quickly. Best to start on the power supply side, as it's the simplest circuit.

    I'll be getting knee deep in a NAD 7175PE's power circuit myself. It blows a 5A power switch fuse immediately, so a dead short is what I'll be after. From the sounds of it, the same is going to hold true for you.

    Thanks! I think it is a dead short, because it blows the 5 amp fuse in about 2-3 seconds (I know it isn’t supposed to be 4 amps, but it was all we had on hand at the time). I’m slightly worried that the transformer is the problem, because according to the 3rd party repair guy’s eBay site, it isn’t the only part that can no longer be replaced.
    I have searched and searched the webs for a service manual, but I have yet to find one. Would Polk supplied me with one if I asked?
    Thanks,
    Micah
    2 channel
    Speakers: Mission 770 Freedoms
    Integrated amp: Technics SU-v75 and matching tuner
    CDP: Technics SL-PC20
    Cables: Monoprice, Monster, Acoustic Research, and a few generic ones
    TT: Technics SL-3200, direct drive
    Cartridge: Shure M97xE

    Pc gaming setup
    Receiver/amp: Yamaha RX-V665
    Computer: Lenovo g50 (soon to be upgraded to a Dell Precision 690 which is far from stock!!)
    Interconnects: Amazon basics HDMI, Acoustic Research HDMI, Monoprice speaker cables
    Speakers: Boston Acoustics CR75s

    Random equipment on standby:
    Onkyo TX-v940, JBL woofers and tweeters, single Klipsch KG .5, Yamaha guitar amplifier, Peavey Rage 158 guitar amplifier, Kicker comp 12” subwoofer, single Bose 802 series II, a whole bunch of 1”-3” full range drivers, Infinity Crescendo 3007s (on sale), Polk LSi25s
    txcoastal1 wrote: »

    You don't tell her you read the manual, and you tell her you know what the problem is, and you fixed it, because that what men do, fix things
    sure it has a flat response, and sure it has a lot of detail, and yes, it has good and clear lows. But is it enjoyable to listen to? Does it make you grin ear to ear? That’s what really matters.
    Seen somewhere on AudioKarma (I think)
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