# MTX Thunder 280 repair. Resistor identification



## kyleaudio (Jul 6, 2009)

Hi guys,

I've got an old broken MTX Thunder 280 that a friend gave me and I'd like to get it going again. I've identified a few shorted mosfets and there are a few burnt resistors on the board. 

Does anyone have one of these amps that could help identify the burnt resistors?

Thanks,
Kyle


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## truckerfte (Jul 30, 2010)

Not sure. Try tricky Ricky. Or sell it to me. Lol


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## kyleaudio (Jul 6, 2009)

Thanks truckerfte, I sent him a message.


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## TrickyRicky (Apr 5, 2009)

Hey truckerfte did I send you back your MTX amp's feet? I thought I did.

OP, you'll have to tell me what those resistors are tied to...I don't have that amplifier but have schematics for a MTX amp that utilizes the same PWM IC and amplifier design so hopefully I can be able to help you out.

PS: If you don't know what they are tied to, then just take a picture (hi res) of the bottom of the pcb so I can see the traces.


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## kyleaudio (Jul 6, 2009)

Hi TrickRicky,

Finally got a chance to sit down and trace out the circiut! Here's what I came up with.

Please let me know if you need any more of the circuit.

Thank you,
Kyle


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## kyleaudio (Jul 6, 2009)

Actually, I just realized that I don't need the values for R11, R12 and R13. I can just copy the values from the other channel. I just need R111 and R109.

Thanks,
Kyle


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## truckerfte (Jul 30, 2010)

Ricky..I don't think they had any. But if you have some I'll buy them off of you. I need a bunch.


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## TrickyRicky (Apr 5, 2009)

kyleaudio said:


> Actually, I just realized that I don't need the values for R11, R12 and R13. I can just copy the values from the other channel. I just need R111 and R109.
> 
> Thanks,
> Kyle


Am not 100% sure but they appear to be fuse-type 62ohm resistors.


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## TrickyRicky (Apr 5, 2009)

truckerfte said:


> Ricky..I don't think they had any. But if you have some I'll buy them off of you. I need a bunch.


I'll look for them, no need to pay for them as am pretty sure they were on your amps (and I thought I shipped them to you in an envelope...unless I find them of course).


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## kyleaudio (Jul 6, 2009)

Awesome, thank you!


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## TrickyRicky (Apr 5, 2009)

kyleaudio said:


> Awesome, thank you!


Make sure to power it up with an inline current limiter or a 5amp fuse just incase you have other issues present.


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## kyleaudio (Jul 6, 2009)

Yeah, don't want to blow the ass end out of another component! I'll power it up with a my 3 amp bench supply first before hooking it to a battery. Again, thank you for identifying those resistors. I'll post how things go once the parts get here.


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## kyleaudio (Jul 6, 2009)

The new components came in today. After soldering everything in, I powered it up. The first time I found that one channel that worked fine, but the other channel (the one that was blown) had about 19v DC offset!!! After a few measurements I found one sorted MPSW56 PNP transistor. I temporarily replaced it with a 2N3906 and now both channels work fine!


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## TrickyRicky (Apr 5, 2009)

kyleaudio said:


> The new components came in today. After soldering everything in, I powered it up. The first time I found that one channel that worked fine, but the other channel (the one that was blown) had about 19v DC offset!!! After a few measurements I found one sorted MPSW56 PNP transistor. I temporarily replaced it with a 2N3906 and now both channels work fine!


Congrats!!


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