Mmats d class

[bigtymer2306]

ive recently been working on a couple amps... i have 2 d200hc's and 1 d300hc.. im new to trying to fix this myself so i need some help.. i replace all the mosfets in each of them.. and figured that was their problem seeing how there was scars on the d200hc's where they blew up... now the dont go straight into protection, they power up and go into protection after about 5 seconds (both d200hc's)... now i replace all the mosfets in the d300hc at first and used 3025 instead of 3710 and it powered up until the mosfets blew... so i replace them with the correct 3710 and then it didnt come out of protection...

now im working with a cheap multimeter (1.5v in diode mode, etc) but im willing to try anything as this is a good experience for me.. so any guidance yall can give me would be greatly appreciated. thanks

[luka]

first find out where are shorts... most times input and/or output fets blow. If so, you will need to remove them, until you won't have short no more. its good to know also how did the amp die. it can be as simple as user connecting positive and negative backwards. in such case you can have short on input by internal diode, that is put there just for that...

once you don't have short no where, you try to power up, the IC of supply, checking if it has right voltages on pins and so on

and you might want to use current limited supply, or resistor in series, just to make things safer if there is still a problem

[bigtymer2306]

Hmm I've already replaced all the fets on power and output...

[bigtymer2306]

Any other suggestions???

[luka]

time to bring out scope
still have shorts? or just nothing happens

[nigelwright7557]

Originally Posted by bigtymer2306

Any other suggestions???

You could have wiped out the class d chip when the mosfets went.