Hello. You have a short within the amp. If you can't locate it yourself, take it to any autoelectric repair shop where they have the diagnostic tools to locate it quickly. J.
This makes me believe that there is a short circuit at the fet's output stage (maybe not a direct short circuit but maybe a closed capasitor...)
Let me try to locate the manual and take a look for yourself.
I'll be back.
Thanks and regards
Stelios
direct FixYa link: http://www.fixya.com/users/technical114
thank you would be awsome also not sure if the last question i asked went to you
can i use a higher rated fet same votlage and everything just a higher amp rating?
First of all let me tell you something: you will not get more power if you replace the fets with higher voltage fets. As far for IRFB42N20D this one is a part of the power supply section for your amp. Unfortunately I didn't manage to locate a diagram for your model. I'll keep on trying but if you already have one it would be a save of time to send it at my e-mail [email protected].
Regards
Stelios
direct FixYa link:http://www.fixya.com/users/technical114
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Sounds like some bad caps or resistors in there that are sending the wrong voltage. Did you make sure fuse was pulled out when connecting everything, then pushed in when all connected?
yes an inline fuse and i replaced the caps
Do make sure you use the same size caps or you could end up burning up the entire board including your resistors and everything else.
No i used a higher uf rating someone told me it would give the amp more power when it needed it the voltage is the same the uf was like maybe +100 on one size and like +1400 uf on the other
i could only see the gate resistors where blown 2 of them on the mosfet IRFB42N20D side on one of the amps and the other amp had blown caps and gate resistors and blown fets on the orther side i dont see any other resistors blown one amp worked a little after i replaced everything but one of the rf power cokes would get hot and cause one of the thermal cut offs to trigger i replaced the rf cokes didnt help so i pulled the board off again to check if anything looked fried it looked fine i put some thermal compound on all the fets the heat sink tape was kinda ripped i spots could the artic silver 5 caused a short a ground?
someone sent this to me how do i do what there talking about? rebulid the power supplies?------The main power supply is easy The secondary low V power supply and the output drive sections are unique and complicated. They don't follow a pattern when they go, each time taking out different parts across the board. You throw new FETs in it without rebuilding drive and sec power supplies & it will blow up every time. ---------
I recommend repacing all resistors, and fets and manually test each capacitor with an analog meter.
all what resistors? there prob 100+ surface mounted i replaced the gate resistor
maybe diodes? and if so where and what resistors to check?
also am i able to use a fet of the same voltage and charitors but higher amp rating?
the 75339p3 is hard to find its a 55v 75a i found a irf3205 but its 55v 110a its very close to the same thing
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Check the short in the circuit first with a continuity.Test the connections again.Check if you have connected any electrical part in reverse order.This same thing occurs many times if the electrical component is not connected properly or connected properly but not soldered properly.The particular component overheats when the current passes through it.reconnect everything back then check again .Be careful.
Thanks.
Hi.
I am afraid you will have to do a bit of work at component level. Any fault in the gate section (eg an open resistor), can blow the FETs. If any of the FETs blow, the rest will blow because of the load, often almost immediately.
Check the gate drive, that is the section that prevents the FETs from blowing. If the 75339 keep blowing it is usually something wrong in gate.
Double check the resistors, ensure that they are factory specs.
Do not check only impedance, but also tolerance.
There should be capacitors near the FET, check them out to see if they look fine.
Check the zener diode connected the gate. That will cut off if load is too big. If a diode is shorted, then zener will blow.
Generally inspect the board for cold joints.
Check the PSU section.
I do not have precise schematics for this model. If you need to know the value of components (eg. the different gate resistors before FET), then the best thing to do is contacting MTX and getting the the component specs .
See:MTX Audio.
ok well i have replaced the resistors gate sesistors there 39.2ohm
i noticed some of the capacitors where bloated so i replaced them the 4 250v ones but the uf i replaced with was about 120uf higher and the larger 100v caps i replaced with maybe a 2500 to 3000 higher uf would that make something go wrong or would it just have more storage for when power is needed
could it maybe be bad ic fet driver? if so where is it located at?
and i used actic silver heatsink compound on fets and some of the heatsink pads for the fets and rips could it have caused a ground or short?
and also for some reason the chokes that are right inline with the power input where the power runs thru them then the power goes to the board they make a whining buzzing noise i took them out and replaced them mtx said there special made in china and i could take them apart and mesure lenth and gauge of magnet wire and hand wind new ones and i did but still made noise sigh these chokes are the small ones and one has a thermal cut off in middle of one
i have two of these amps same prob with all this on both please let me know how to fix
What are the values of the choke?
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Jun 08, 2010 - ok well i have replaced the resistors gate sesistors there 39.2ohm
i noticed some of the capacitors where bloated so i replaced them the 4 250v ones but the uf i replaced with was about 120uf higher and the larger 100v caps i replaced with maybe a 2500 to 3000 higher uf would that make something go wrong or would it just have more storage for when power is needed
could it maybe be bad ic fet driver? if so where is it located at?
and i used actic silver heatsink compound on fets and some of the heatsink pads for the fets and rips could it have caused a ground or short?
and also for some reason the chokes that are right inline with the power input where the power runs thru them then the power goes to the board they make a whining buzzing noise i took them out and replaced them mtx said there special made in china and i could take them apart and mesure lenth and gauge of magnet wire and hand wind new ones and i did but still made noise sigh these chokes are the small ones and one has a thermal cut off in middle of one
i have two of these amps same prob with all this on both please let me know how to fix
ok well i have replaced the resistors gate sesistors there 39.2ohm
i noticed some of the capacitors where bloated so i replaced them the 4 250v ones but the uf i replaced with was about 120uf higher and the larger 100v caps i replaced with maybe a 2500 to 3000 higher uf would that make something go wrong or would it just have more storage for when power is needed
could it maybe be bad ic fet driver? if so where is it located at?
and i used actic silver heatsink compound on fets and some of the heatsink pads for the fets and rips could it have caused a ground or short?
and also for some reason the chokes that are right inline with the power input where the power runs thru them then the power goes to the board they make a whining buzzing noise i took them out and replaced them mtx said there special made in china and i could take them apart and mesure lenth and gauge of magnet wire and hand wind new ones and i did but still made noise sigh these chokes are the small ones and one has a thermal cut off in middle of one
i have two of these amps same prob with all this on both please let me know how to fix
Sounds like some bad caps or resistors in there that are sending the wrong voltage. Did you make sure fuse was pulled out when connecting everything, then pushed in when all connected?
Jun 10, 2010 - yes an inline fuse and i replaced the caps Jun 10, 2010 - Do make sure you use the same size caps or you could end up burning up the entire board including your resistors and everything else. Jun 11, 2010 - No i used a higher uf rating someone told me it would give the amp more power when it needed it the voltage is the same the uf was like maybe +100 on one size and like +1400 uf on the other
i could only see the gate resistors where blown 2 of them on the mosfet IRFB42N20D side on one of the amps and the other amp had blown caps and gate resistors and blown fets on the orther side i dont see any other resistors blown one amp worked a little after i replaced everything but one of the rf power cokes would get hot and cause one of the thermal cut offs to trigger i replaced the rf cokes didnt help so i pulled the board off again to check if anything looked fried it looked fine i put some thermal compound on all the fets the heat sink tape was kinda ripped i spots could the artic silver 5 caused a short a ground?
someone sent this to me how do i do what there talking about? rebulid the power supplies?------The main power supply is easy The secondary low V power supply and the output drive sections are unique and complicated. They don't follow a pattern when they go, each time taking out different parts across the board. You throw new FETs in it without rebuilding drive and sec power supplies & it will blow up every time. ---------
i got the 42n20 fets its the other ones im not looking for more power just something to replace them with will it be ok to use a higher amprage?
and no i dont have a diagrham ive been looking for one belive me
hey as i asked before like days ago no one has answered me on i used artic silver heatsink compound on the fets and some of the termal tape had ripps in it would that cause a short?
thank you so much Joshua
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