Hi everyone!
I was given an Altec Lancing inMotion IM7 a while back and I shorted the subwoofer amplifier accidentally trying to mod it. One of the IRF7379 chips caught fire and burned up two small parts near it.
The IRF7379 I replaced:
The two smaller parts: (One of them says "KA2" and the other says "Z 2")
So far what I have done:
1) I replaced the IRF7379 that burned up. (Amp worked but had crackling noises)
2) I removed the two smaller parts and replaced them with others from another channel's amp, sound improved but horribly distorted at high volumes.
3) Removed the two replacements, put them back where they came from, and left the solder pads empty. No crackling but horribly distorted at high volumes.
^This is where its at now. What are the two little parts and where can I find them? Ive looked all over and don't have a clue. Also, what else could be wrong and causing the distortion?
Thanks in advance! If its totally screwed I guess I'll just have to buy a shiny new IMT810 haha.
I was given an Altec Lancing inMotion IM7 a while back and I shorted the subwoofer amplifier accidentally trying to mod it. One of the IRF7379 chips caught fire and burned up two small parts near it.
The IRF7379 I replaced:
The two smaller parts: (One of them says "KA2" and the other says "Z 2")
So far what I have done:
1) I replaced the IRF7379 that burned up. (Amp worked but had crackling noises)
2) I removed the two smaller parts and replaced them with others from another channel's amp, sound improved but horribly distorted at high volumes.
3) Removed the two replacements, put them back where they came from, and left the solder pads empty. No crackling but horribly distorted at high volumes.
^This is where its at now. What are the two little parts and where can I find them? Ive looked all over and don't have a clue. Also, what else could be wrong and causing the distortion?
Thanks in advance! If its totally screwed I guess I'll just have to buy a shiny new IMT810 haha.
I've done a lot of googling and I can't find any schematics for this amp board. Does anyone have any ideas of what could cause the distortion?
IM7 distortion
Have you made any progress on this? I have an IM7 with a similar issue. I ran it at high volume for several hours last summer and it was great. Next time I turned it on, all I got was a loud bass thump and no audio.
I tried it a few months later and now it works again but easily distorts at volumes just above background level. The EQ seems to be a contributing factor as despite the ability to still adjust them with the remote, the sound is overly bright and too bass-y.
Thanks for those photos. I haven't opened mine yet - are there any pitfalls and suggestions about what might be wrong?
Have you made any progress on this? I have an IM7 with a similar issue. I ran it at high volume for several hours last summer and it was great. Next time I turned it on, all I got was a loud bass thump and no audio.
I tried it a few months later and now it works again but easily distorts at volumes just above background level. The EQ seems to be a contributing factor as despite the ability to still adjust them with the remote, the sound is overly bright and too bass-y.
Thanks for those photos. I haven't opened mine yet - are there any pitfalls and suggestions about what might be wrong?
The smaller parts are marked D20 and D21 ... these are diodes. I would guess these together with the two resistors between R103 and R10x (cant see the last digit) form the gate input circuit. Seems that the two diodes are the same (make sense) marked KA2 .... Try to google for this markin ... would think it's some kind of 1N4148 ... Vishay maybe ....
Cant read the marking on the bigger chip (U28) behind the big cap ... it's probably the driver/class-d modulator ... can you state it here?
Best regards Baldin 😉
Cant read the marking on the bigger chip (U28) behind the big cap ... it's probably the driver/class-d modulator ... can you state it here?
Best regards Baldin 😉
Diodes:
http://www.diodes.com/datasheets/ds12003.pdf
but any MMDB4148 or IMDB4148 would brobably do .... you can also just try a 1N4148 leaded first if you can fit it ... change both diodes
http://www.diodes.com/datasheets/ds12003.pdf
but any MMDB4148 or IMDB4148 would brobably do .... you can also just try a 1N4148 leaded first if you can fit it ... change both diodes
You are way ahead of me, I have not figured out how to remove the rear panel for disassembly. How about a hint.
Hi,
Never late than never:
I saved and zoomed the pictures, and did some google searches...
If i'm not mistaken, U20 chip is a simple Quad AND gate SN54/74ACT08, driven by a simple quad comparator OP AMP LM339A... This is discrete D Class amplifier, old design but efficient!
It can be upgrated with other output MOSFETs and higher voltages, to transform IM7 into big 5kilowatt RAVE BEAST lol
Never late than never:
I saved and zoomed the pictures, and did some google searches...
If i'm not mistaken, U20 chip is a simple Quad AND gate SN54/74ACT08, driven by a simple quad comparator OP AMP LM339A... This is discrete D Class amplifier, old design but efficient!
It can be upgrated with other output MOSFETs and higher voltages, to transform IM7 into big 5kilowatt RAVE BEAST lol
Hi everyone.
I have the same problem as AudioAudio stated.
Poor soon on medium frequencies.
Just purchased the speakers but I think the problem came because of high volume functioning.
Does anyone own a repair manual ?
do you have any advice for me?
thank you.
I have the same problem as AudioAudio stated.
Poor soon on medium frequencies.
Just purchased the speakers but I think the problem came because of high volume functioning.
Does anyone own a repair manual ?
do you have any advice for me?
thank you.
I'm also having trouble removing the rear white panel with the handle, one end
will not budge and there are no screws I can find anywhere that might be holding it.
One online tear down instruction says to pry but it is clearly going to crack if I use
enough force.
This unit worked great for a few weeks, then stopped working and will not power up.
OK got it, there is a slot that is glued in, pry from underneath the plastic.
There is some of that brownish/black glue that looks like it caused oxidation
around some of the ceramic caps, scraped that and now it works but I'm not
convinced that it won't come back.
Some of this glue is known to become conductive with age, anyone know of
a good solvent to remove it from the circuit board?
This thing sounds great when it works.
There is some of that brownish/black glue that looks like it caused oxidation
around some of the ceramic caps, scraped that and now it works but I'm not
convinced that it won't come back.
Some of this glue is known to become conductive with age, anyone know of
a good solvent to remove it from the circuit board?
This thing sounds great when it works.
Hi, I'm hoping someone here might be able to help me to open up my own iM7.
The DC barrel is faulty and I'm hoping to replace it, but the iM7 seems to be glued together at every stage!
I've got both side speakers unscrewed (following this iFixit guide) but the two halves just will not separate (see Step 7).
It sounds like one or two of you have managed to reach the circuit board inside the iM7 - do you have any words of advice on prising it apart?
The DC barrel is faulty and I'm hoping to replace it, but the iM7 seems to be glued together at every stage!
I've got both side speakers unscrewed (following this iFixit guide) but the two halves just will not separate (see Step 7).
It sounds like one or two of you have managed to reach the circuit board inside the iM7 - do you have any words of advice on prising it apart?
Attachments
Did you remove the mesh grilles over the speakers, not sure but I think that they
hook over the other half.
I don't actually remember the trick to open it.
I wrote this in post #11 but I don't have the unit in front of me so I'm not
sure about the details:
"OK got it, there is a slot that is glued in, pry from underneath the plastic."
I don't remember if the slot was some sort of cover or if there are screws in the slot, sorry.
hook over the other half.
I don't actually remember the trick to open it.
I wrote this in post #11 but I don't have the unit in front of me so I'm not
sure about the details:
"OK got it, there is a slot that is glued in, pry from underneath the plastic."
I don't remember if the slot was some sort of cover or if there are screws in the slot, sorry.
Last edited:
Thanks for taking the time to reply.
I've removed the grille from the back but not the front. I wasn't sure if it should be removed, as the plastic surround around the iPod 'holder' felt like it didn't want to come out.
If that's a step I've missed then I'm happy to give that another go.
(I'm only so doggedly determined to fix the speakers because they have sentimental value. We used them as speakers at our wedding... a few years ago now!)
I've removed the grille from the back but not the front. I wasn't sure if it should be removed, as the plastic surround around the iPod 'holder' felt like it didn't want to come out.
If that's a step I've missed then I'm happy to give that another go.
(I'm only so doggedly determined to fix the speakers because they have sentimental value. We used them as speakers at our wedding... a few years ago now!)
