hye everybody ,
I am trying to repair a MTX amplifier wich doesn' t work anymore.
I think that the problem is located on the SMPS . One of the four 75339P is quite cooking . I haven' t got teh diagram of the circuit !
There is a TL494 wich drives 4 ( 2 * 2 ) 75339P Fets .
As i retired the cooking one it didn' t work better , the current was
continuesly incrising !
So what should i do now ? It is difficult for me to get the 75339P
drivers . Can i replace them by other components ?
On the amplifier output stages they use IRF540 . Can i try to replace two of the 75339P by the IRF ? The wiring is the same.
Thanks for answering my questions .
Best regards , Philippe.
I am trying to repair a MTX amplifier wich doesn' t work anymore.
I think that the problem is located on the SMPS . One of the four 75339P is quite cooking . I haven' t got teh diagram of the circuit !
There is a TL494 wich drives 4 ( 2 * 2 ) 75339P Fets .
As i retired the cooking one it didn' t work better , the current was
continuesly incrising !
So what should i do now ? It is difficult for me to get the 75339P
drivers . Can i replace them by other components ?
On the amplifier output stages they use IRF540 . Can i try to replace two of the 75339P by the IRF ? The wiring is the same.
Thanks for answering my questions .
Best regards , Philippe.
MTX Amps R Great
Sure. Replace ALL FOUR SMPS transistors with IRFZ48V and the output transistors with the IRF540. Adjust the bias accordingly after repair, because it's going to change a bit unless you use exact MTX replacement transistors (I have no idea why!!). Hope this helps!!
Sure. Replace ALL FOUR SMPS transistors with IRFZ48V and the output transistors with the IRF540. Adjust the bias accordingly after repair, because it's going to change a bit unless you use exact MTX replacement transistors (I have no idea why!!). Hope this helps!!
I just checked the only power devices left. TO220 IRF 540 mosfets 1 pair damaged but left, should be from the output stage. I guess thats part of that pure N-channel design... By the Bias you mean the output stage right, theres only one trim pot for each output set but I think that makes sense.
How do you adjust the bias? i have a mtx blue thunder taht uses 75339p and i´m going to replace the four with irf3205 they are similar, and the output fets are irf540
you shouldn't have to adjust the bias after fixing the power stage, but you do after messing about in the power stage.
You can replace those power supply fets with most any high current switching MOSFETs most of the time. Just make sure you replace ALL of them at the same time with the same kind (preferably from the same batch).
But I would check the output section first to see if something is sorted or otherwise causing the power supply to be loaded down much more than usual. Hint, check the voltage accross the source (and drain, in the pure N design) resistors on the outputs to measure the current through them.
Generally, if the output devices blow, you either get no sound on one channel, a hot running amp, and amp that pops it's fuse an/or smokes and/or gets really hot, but only when the remote line is switched on. The power supply MOSFETS most of the time will also cause problems as soon as the battery is connected if they are shorted. Sometimes the power supply MOSFETS will short out, and then pyrotechnically remove themselves from the amplifier.
You can replace those power supply fets with most any high current switching MOSFETs most of the time. Just make sure you replace ALL of them at the same time with the same kind (preferably from the same batch).
But I would check the output section first to see if something is sorted or otherwise causing the power supply to be loaded down much more than usual. Hint, check the voltage accross the source (and drain, in the pure N design) resistors on the outputs to measure the current through them.
Generally, if the output devices blow, you either get no sound on one channel, a hot running amp, and amp that pops it's fuse an/or smokes and/or gets really hot, but only when the remote line is switched on. The power supply MOSFETS most of the time will also cause problems as soon as the battery is connected if they are shorted. Sometimes the power supply MOSFETS will short out, and then pyrotechnically remove themselves from the amplifier.
Hi rhr9, i have an MTX BLUE THUNDER 1502, i want to repair and this amp uses the same fets than yours,and the output power is the same 150 x 2 @2 ohms, it uses two fuses of 30 A, i think this amp is similar the one you have, in my amp two resistors has blown and i do not know the values of them, they are conected in parallel, with the outputs, i mean between the positive and negative of each channel they are bigger than the others if you do not have a multimeter please just tell me the colors printed in this resistors, i will apreciate your help, i have boght the fets irf 3205, they are compatible with 75339p, the irfz48 is also a good replacement, but the irf 3205 can handle more current an will work cooler than the irfz48
the value of the resistor is all that i need to begin repairing the amplifier, thanks so much, i hope we colud help each other with the repair work of our Amps😎
the value of the resistor is all that i need to begin repairing the amplifier, thanks so much, i hope we colud help each other with the repair work of our Amps😎
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