# Need 4 Transistors



## OldSchoolAudioandVideo (Nov 14, 2011)

Im trying to fix an amp
The power supply has 4 transistors that need to be replaced. One was burnt. and it was dangling by a leg.

There are 2 others on the opposite side of these that are fine

The part numbers I got off the 4 are
NX
psmn015
100p
pem 0827
7842



And Im not to great at fixing amps but do know a little bit. 
Im great with a soldering iron. I have a multimeter.
And I have the mental capacity to learn.

The amp blows fuses when it powers up.
I asked a tech that said the power supply is out. Sure enough its burnt.
It also looks like the left side of the amp, ( left channels ) were replaced. I had to redo the soldering. They all seem fine.

So, Any tips and links to the product I need would be much appreciated.
Its for a really nice expensive amp I got from here. 
Id like to try fixing it before I pay $225 to have someone else do it.
It doesnt look bad. The worst part is the terrible soldering job , which I think shorted out the legs on the transistors in the power supply. 
Looks like a 5yo tried to solder everything.


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## ATOMICTECH62 (Jan 24, 2009)

I think those are some off brand generic replacement parts.Are these in the power supply?


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## OldSchoolAudioandVideo (Nov 14, 2011)

ATOMICTECH62 said:


> I think those are some off brand generic replacement parts.Are these in the power supply?


yes these are in the power supply.
between each of these is a surface mount resistor of about 10 ohms. one is measuring 30 ohms. should i replace the 30 ohm to a 10 ohm ?


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## ATOMICTECH62 (Jan 24, 2009)

Yes they all have to match.The most common power supply mosfet is the irfz44.
Are these the to220 case or the larger to247?
How many watts is the amp?What model is it?


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## OldSchoolAudioandVideo (Nov 14, 2011)

ATOMICTECH62 said:


> Yes they all have to match.The most common power supply mosfet is the irfz44.
> Are these the to220 case or the larger to247?
> How many watts is the amp?What model is it?


The amp is a MMats SMT4090. Its a 90 wattx4 amp.
The 4 transistors are To 220's

About the resistor. Should I replace it with the same surface mount type? Or can I use a 10 ohm quarter watt? If so then I can go ahead and replace all 4 surface mount resistors with 10 ohm quarter watts. Is that ok? Cause its gonna be tough soldering them little things in place.

Thanks for the help


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## OldSchoolAudioandVideo (Nov 14, 2011)

THIS is what I found about the 4 transistors that were in the amp. 
I think these will work.
From what I can see, the soldering job was the reason they burnt. The legs were slightly soldered together.
After they burnt, maybe the small resistor got too hot and changed value.


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## ATOMICTECH62 (Jan 24, 2009)

I doubt you be able to get by just replacing the mosfets and the resistors.
The drivers for the mosfets and possibly the PWM IC is also damaged.
Trace back from the 10 ohm resistors and see what drives them.look for a 16 pin chip with # like tl494-594 ,sg3525.that is the PWM IC.and it might drive 2 or 4 small transistors.


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## OldSchoolAudioandVideo (Nov 14, 2011)

ATOMICTECH62 said:


> I doubt you be able to get by just replacing the mosfets and the resistors.
> The drivers for the mosfets and possibly the PWM IC is also damaged.
> Trace back from the 10 ohm resistors and see what drives them.look for a 16 pin chip with # like tl494-594 ,sg3525.that is the PWM IC.and it might drive 2 or 4 small transistors.


Theres an sg3525ap and 2 small transistors next to it.


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## ATOMICTECH62 (Jan 24, 2009)

I would replace them before you power the amp or the mosfets will blow again.
Have you checked the output transistors in all 4 channels for shorts?
Do you have a scope?


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## OldSchoolAudioandVideo (Nov 14, 2011)

ATOMICTECH62 said:


> I would replace them before you power the amp or the mosfets will blow again.
> Have you checked the output transistors in all 4 channels for shorts?
> Do you have a scope?


no scope. i just compared the transistors using a diode check on the dmm and they are all the same.
and
i didnt find any shorts 

looks like the driver and small transistors were not replaced. this may also be why the amp burned up again.

wondering why they replaced all the left channel outputs?

they all measure good. 

as well as the e factory ones that werent replaced.


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## envisionelec (Dec 14, 2005)

OldSchoolAudioandVideo said:


> Im trying to fix an amp
> The power supply has 4 transistors that need to be replaced. One was burnt. and it was dangling by a leg.
> 
> There are 2 others on the opposite side of these that are fine
> ...


$225!!!

Man, that's ridiculous!

IRF3205 is a good replacement. Don't need the high voltage in the primary side.


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## OldSchoolAudioandVideo (Nov 14, 2011)

envisionelec said:


> $225!!!
> 
> Man, that's ridiculous!
> 
> ...


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## OldSchoolAudioandVideo (Nov 14, 2011)

Ok. So I retested the output transistors. What i get this time is
some are measuring 1.2volts and most are measuring .6volts.
Its cause some are IRF540 and some are IRF9540

Maybe I should send it in. LOL

Man i feel like Im gettin in over my head here. LOL
But its fun


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## RiLoWa (Nov 9, 2011)

Use your DMM set to Ohms and find out if Pin #11 or Pin #14 of the SG3525 is directly connected to one side of the FET gate resistors on the burned up side.

If either of them are, I would replace the SG3525.

If either of them are not, you will need to find all of the FET drivers and check them. There is probably more than two of them. Follow the traces from pins 11 & 14 or trace back from the FET gate resistors.


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## sundownz (Apr 13, 2007)

envisionelec said:


> $225!!!
> 
> Man, that's ridiculous!
> 
> IRF3205 is a good replacement. Don't need the high voltage in the primary side.


I have a bunch of IRF3205 transistors if he needs some.


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## OldSchoolAudioandVideo (Nov 14, 2011)

I decided to send it to MMats
I have no idea why but they decided to fix it for $150
I think the guy that answers the phones there isnt too swift on the pricing.
Maybe the amp models are on a scale and mine fell into the $150 range. IDK
I sent it off.
Its over my head.
When I get it back it should be all nice and ready to Jam. Like new is what they said.
And that price is including shipping back to me.
So, for a super rare amp , with high SQ , I went ahead and paid the $150. Thats the usual and I was already willing to pay that anyway. 
Even if I decide to resell later, the amp will have great value.


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## envisionelec (Dec 14, 2005)

OldSchoolAudioandVideo said:


> I decided to send it to MMats
> I have no idea why but they decided to fix it for $150
> I think the guy that answers the phones there isnt too swift on the pricing.
> Maybe the amp models are on a scale and mine fell into the $150 range. IDK
> ...


Wow. It would have been $85 plus parts from me. 

Oh well...next time, huh?


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## OldSchoolAudioandVideo (Nov 14, 2011)

Next time .. wink


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## OldSchoolAudioandVideo (Nov 14, 2011)

The Amp is on the way back.
They fixed it on one day.. Thats pretty bad ass... Cant wait to hear it.


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## OldSchoolAudioandVideo (Nov 14, 2011)

Got the amp back today. This thing sounds really good. Id have to say it sounds more neutral than any amp Ive heard. Not too bright not to warm not to sweet or mellow. Ive heard all those kinds of amps. It also isnt over powering or even fatiguing. Its just an amplifier that amplifies. LOL 
I think Im gonna keep this one. Ill be on the look out for another MMats amp for bass.
This amp was worth the money to fix.


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## TrickyRicky (Apr 5, 2009)

OldSchoolAudioandVideo said:


> Got the amp back today. This thing sounds really good. Id have to say it sounds more neutral than any amp Ive heard. Not too bright not to warm not to sweet or mellow. Ive heard all those kinds of amps. It also isnt over powering or even fatiguing. Its just an amplifier that amplifies. LOL
> I think Im gonna keep this one. Ill be on the look out for another MMats amp for bass.
> This amp was worth the money to fix.


How much was the total price you had to pay (with the repair fees and shipping fees)?


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## OldSchoolAudioandVideo (Nov 14, 2011)

TrickyRicky said:


> How much was the total price you had to pay (with the repair fees and shipping fees)?


The repair was $150. Shipping is included BUT I did have to pay to send it there so it was like $170.

When i first called them, the dude that answered the phone said $225. I was like.. O hell no. But then i called back and just asked for someone to setup an RMA just to see if the price was right. Well, when I set up the RMA the dude, a different dude, said it was $150. SO Im guessing there may be a sliding scale based on the amp model IDK.
They fixed it the same day !!! They sent it back UPS in a nice MMats box nicely packaged and included a receipt and the new Flyer for there products.
I opened up the amp to see what they did. Man they did a good job. 
They replaced ALL the outputs. We are talking 16 outputs here. They also changed the power mosfets and the surface mount resistors. They may have checked other components but from what I see thats all they changed. 
The solder job is nice and neat and shiny. The components look to be updated and in place not all cocked and looking like a cheap job some kid did.
And it works !!!! 
So all together I paid $100 for the amp and $170 to get it fixed. So $270.
The amp looks mint. Its works like new and now I have a super rare MMats amp that was serviced by the manufacturer. 
It really does sound nice. The gains are really sensitive. Just the way I like it. You can tune in on the sound like precision. Yet there is no coloring such as extra highs or mids or lows from the amp.
I compare all amps to the JL 300/4 because I think that amp , to me sounds best. BUT now I think I have a new standard cause this amp sound a tad bit better.
The JL had what i called a plastic sound. But it had a nice soundstage and you could crank it up and have no distortion. Well this amp has no sound. It just amplifies what it passes through. I read a couple of reviews saying this amp is actually preferred over a Mcintosh 4 channel amp. Although I havent heard a McIntosh amp, I can say Im really happy with it.
Every other amp Ive heard always gave the sound some kind of addition to it. The Xtant amps had a brighness I didnt like. The Soundstreams also had a brightness but a certain clarity that made up for it. The Boston amps I had , had a really good sound stage but they sounded thin. And for some odd reason sounded like they has a BBE processor in them so they also has a bit of distortion with brightness that made tweeters spit and hiss. I had Sony XES and ES amps and I can say they actually had very little to no problems but did tend to distort when used with cheap speakers. I have no idea why but the SOny amps just sounded there best when using them with Image Dynamics speakers. 
So far this MMats SMT4090 sounds like what Id call default. As in, this is where an amp should start. Then if you want to add treble or whatever you can use a eq. I found it really odd that the amp doesnt really need any time delay either. The Boston amp I had would drastically change in sound when using time delay. This amp stays about the same. 
I also notice other amps didnt really "listen" to what settings I sent it from a EQ. They exagerrated it or just didnt want to cooperate. This amp does what you tell it to do. It s like I said. it passes the sound through and just amplifies it. ANd what also striked me after a few minutes of listening is that it didnt hurt or give me ear fatigue like the other amps. And Im comparing this to even the nicest of amps like the SOundSTream Class A Reference. Im really now believing the Class A thing is all ********. Every one Ive heard is nothing spectacular. Special yes cause of the way it sounds but not better. In my opinion of course. 
All amps sound different. People will argue about this but for real Its true. They all have a signature. Id say this amp has less of a signature than any amp Ive heard. Pretty crazy.... LOL
It also plays things I havent heard. I hear fingers on guitar strings better.
And it the sound stage a bit farther beyond the speaker now. Its also powerful. 
IDK whats in the amp to make it sound so neutral. I think the preamps are the same ones used in the SQ series. Only difference is these use a defferent output transistor. The SQ series uses T03 outputs and uses one per channel. This amp uses 4. 
If I was looking for a NEW amp that has been recently made Id actually give MMats some attention. I gambled on this old broken amp. But this gamble came out a winner !!!


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## TrickyRicky (Apr 5, 2009)

OldSchoolAudioandVideo said:


> The repair was $150. Shipping is included BUT I did have to pay to send it there so it was like $170.
> 
> When i first called them, the dude that answered the phone said $225. I was like.. O hell no. But then i called back and just asked for someone to setup an RMA just to see if the price was right. Well, when I set up the RMA the dude, a different dude, said it was $150. SO Im guessing there may be a sliding scale based on the amp model IDK.


Post pics of guts (before and after).


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## OldSchoolAudioandVideo (Nov 14, 2011)

All I got is a cell phone camera. It wouldnt come out too good.
Plus I already installed the amp.
Sorry man. I know you wanted to see it. Maybe in the near future Ill get a good camera and update this thread with pics.


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## OldSchoolAudioandVideo (Nov 14, 2011)

Mothr F77ker
So Ive had this amp now for about 1 week.
Ive cranked it up and tweaked it and it did sound good. Till today
I had the volume down low and was listening to Talk radio


Booof !!!!


I smell it


Sound stops


I pull over and the trunk is full of smoke.


F77K !!!!!!


I disconnect the amp

I get home and open it up.
What do I see?
The same gotdam power mosfets burnt.
So I check out the job they did but inspect it closer..
They replaced the power mosfets ( the ones in the power supply )
with IRF3205 and the surface mount resistors were changed to what seems to be a 20 ohms. The 4 measure between 22 and 20 ohms.
Then drivers for the mosfets and the PWM IC was not replaced.
So Im pretty sure, from what AtomicTech62 said, this is why the amp blow up again. 

I need some help here guys. WTF do I do about this?
I really dont want to spend another dime on MMats. They should have replaced those $1 parts. 
I shoulda known they did a half ass job cause it was "fixed" in less than a day. 
When i got it back the dials were not even moved. They just tested it for power up but not output.


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## envisionelec (Dec 14, 2005)

OldSchoolAudioandVideo said:


> Mothr F77ker
> So Ive had this amp now for about 1 week.
> Ive cranked it up and tweaked it and it did sound good. Till today
> I had the volume down low and was listening to Talk radio
> ...



That sucks. MMATS should take care of it AND pay return shipping.


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## OldSchoolAudioandVideo (Nov 14, 2011)

envisionelec said:


> That sucks. MMATS should take care of it AND pay return shipping.


Yea. Ill have to call them.
But
I shoulda sent it to you 
Seems you know what youre talking about.

You think its the driver stage and chip?


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## OldSchoolAudioandVideo (Nov 14, 2011)

Im sending it back. They give a 30 day warranty.. So
they will fix it again and not charge anything

Now I dont have an amp...
Sux
But I decided to buy another amp to play with.
All the fluff about the Twister amps got me curious so I got one
If I like it Ill buy a smaller one for the mids and highs.

The MMats amps are expensive even used. Finding a decent priced bass amp made by MMats is hard to do. There resale value is high.
probably cause not only are they smaller per watt but sound good. 
So after I get this one back I may sell it. Use the money to get another Twister amp.


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## envisionelec (Dec 14, 2005)

OldSchoolAudioandVideo said:


> Yea. Ill have to call them.
> But
> I shoulda sent it to you
> Seems you know what youre talking about.
> ...


Maybe. Could also be loop instability since it happened at low volume.

Thanks for thinking of me. I do 1 year warranties for most stuff.


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## apotelyt (Nov 5, 2009)

OldSchoolAudioandVideo said:


> Im sending it back. They give a 30 day warranty.. So
> they will fix it again and not charge anything
> 
> Now I dont have an amp...
> ...


How do you like the Twister amp compared to the Mmats? Which model Twister did you get?


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