Repairing an MTX TE1501d

[Suicide Bobb 5,000+ posts]

My buddy wants me to fix this amp for him...I have good enough skills with a soldering iron, but no skills with electrical components. I don't know how to test transistors, resistors, etc. I have a radioshack dmm to work with.

He told me that the amp went up in smoke on him, and sure enough, there were 5 roasted transistors inside. They are 75339p transistors. It doesn't appear that they blew up the surrounding resistors, but I know that looks can be deceiving.

My question: What else on the board should I check to see if it's blown, how do I check them, and what should I replace the bad transistors with?

Click to read more...

 

[Bassin Buick]

you should replace them with 75339p transistors. LOL

 

[Bassin Buick]

set your meter on ohms and check the reading on those 5 resistors right inline with the fets. make sure they all read the same.

 

[Bassin Buick]

also check those insulators for damage , if the new fet's ground out because of a bad insulator you will be buying more fets.

 

[Suicide Bobb 5,000+ posts]

After I cleaned the top side:

 

[Bassin Buick]

why is it missing caps? 2 large ones are missing from the board , yet the board is clearly marked for them.

 

[Suicide Bobb 5,000+ posts]

also check those insulators for damage , if the new fet's ground out because of a bad insulator you will be buying more fets.

The reason I asked which fets to replace them with is because sometimes there are different fets that will do the same job but are more reliable/cheaper/easier to find.

I will go check the resistors now.

What are the insulators?

 

---------- Post added at 10:38 PM ---------- Previous post was at 10:37 PM ----------

 

why is it missing caps? 2 large ones are missing from the board , yet the board is clearly marked for them.

Like MMats, they use the same chassis and different boards for that specific line of amps.

 

[Bassin Buick]

The reason I asked which fets to replace them with is because sometimes there are different fets that will do the same job but are more reliable/cheaper/easier to find.
I will go check the resistors now.

What are the insulators?

 

---------- Post added at 10:38 PM ---------- Previous post was at 10:37 PM ----------

 

Like MMats, they use the same chassis and different boards for that specific line of amps.

the pieces of what looks like medical tape covered in thermal compound , it seperates the backs of the fet's from the metal heatsink , allows heat transfer without grounding the fets.

 

[Suicide Bobb 5,000+ posts]

All resistors around the fets read 10.5 //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

---------- Post added at 10:44 PM ---------- Previous post was at 10:43 PM ----------

 

the pieces of what looks like medical tape covered in thermal compound , it seperates the backs of the fet's from the metal heatsink , allows heat transfer without grounding the fets.

OH

What should I replace them with that is easy to get ahold of?

 

[Bassin Buick]

All resistors around the fets read 10.5 //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif 

---------- Post added at 10:44 PM ---------- Previous post was at 10:43 PM ----------

 

OH

What should I replace them with that is easy to get ahold of?

just inspect them for burnthough or slices from too much mounting pressure. If you cant see any rips or holes they should be fine.

 

[Suicide Bobb 5,000+ posts]

just inspect them for burnthough or slices from too much mounting pressure. If you cant see any rips or holes they should be fine.

Oh alright.

So if the resistors measure normal and the insulators are fine, all I need to do is replace the fets? I heard in a different forum that I also need to readjust the bias afterwards...

 

[Bassin Buick]

probably do , i never thought of that , could be why my usacoustics has a turn on pop in the channel i repaired. Hmm??? you got me thinkng i may check all of my amps now , it made a HUGE sq difference in my home reciever.

 

[Suicide Bobb 5,000+ posts]

I'm having a helluva time finding those transistors...on this site, I believe it's saying that the HUF75339P3 is a suitable replacement: 75339P datasheet, Pinout ,application circuits 75A, 55V, 0.012 Ohm, N-Channel UltraFET Power MOSFETs

 

[Bassin Buick]

just thought of something , thats the power supply section you are working on not the output section. bias shouldnt need touched.

 

---------- Post added at 01:53 AM ---------- Previous post was at 01:52 AM ----------

 

try the cross reference dealy on parts express

 

[Suicide Bobb 5,000+ posts]

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