boss amplifier

[cris13fdz]

hi to any1 that takes time to read this
1 my english it's no so great
2 i remember a little of electronic from junnior and high schools 12
years ago so after saying that to the main ponit XD
a few months ago i bougth a boss amplifier to be more acurate phantom ph2.800 then the warranty expired now a few days ago the amp die having no reason cuz i check the power,the remote,the ground,fuses and inc audio but only to find nothing was wrong then i open the amp only to find 3 transistors irz44n and another 2 low signal transitors and 3 resitences where burn some how. any way im thinking just to replace, but from what i remember from school trasistors whit 3 terminal (irz44n) need schematics right or im a wrong ? if so where can i get it ?? if not should i just replace it ?? i dont have any experience but since im unemployed now i can really save some money adn kill some time till i get a job hehe besides nobody will die if i learn something ned like ( repair amplifier ) thx very much for help and if y guys want a pics let me know

[m4ick]

Pics are always good.

Digikey.com has the IRFZ44NPBF, they're the same just lead free. Those are the power supply mosfets.

If three failed you should definitely replace them all. The ones that look good are almost always toast (or will soon be toast). Same for the resistors, they are cheap and it will save you headaches if you replace them all.

The two small signal transistors are probably the drivers for the power supply mosfets. Post their part numbers. In my experience they are usually KTA1266Y or KTA1266GR (the KT is not written on the transistor). If so Taydaelectronics.com usually has them.

Most of the time shorted output transistors are the reason the power supply fries. With your multimeter to diode check (looks like an arrow with a line across the tip) check the transistors on the other side of the board (closer to the RCAs usually) that are mounted to the heat sink. Does anything read anywhere near 0 ohms between any of the 3 legs?

If you remove ALL of the power supply parts (all Z44Ns, gate resistors, and those two drivers) do you see approximately 5v coming from pins 9 and 10 of the TL494 when you power it up? DO NOT TOUCH TWO PINS AT ONCE!

[cris13fdz]

Originally Posted by m4ick

Pics are always good.

Digikey.com has the IRFZ44NPBF, they're the same just lead free. Those are the power supply mosfets.

If three failed you should definitely replace them all. The ones that look good are almost always toast (or will soon be toast). Same for the resistors, they are cheap and it will save you headaches if you replace them all.

The two small signal transistors are probably the drivers for the power supply mosfets. Post their part numbers. In my experience they are usually KTA1266Y or KTA1266GR (the KT is not written on the transistor). If so Taydaelectronics.com usually has them.

Most of the time shorted output transistors are the reason the power supply fries. With your multimeter to diode check (looks like an arrow with a line across the tip) check the transistors on the other side of the board (closer to the RCAs usually) that are mounted to the heat sink. Does anything read anywhere near 0 ohms between any of the 3 legs?

If you remove ALL of the power supply parts (all Z44Ns, gate resistors, and those two drivers) do you see approximately 5v coming from pins 9 and 10 of the TL494 when you power it up? DO NOT TOUCH TWO PINS AT ONCE!

thx for the answer
i did change all 3 irfz44nn and i change the resistors and the 2 low signal ( pnp ) and the 1 that u mention early are the 1s i change thx for that. any way i put it back light them on and bamm the same irfz44n instantly frie again so i quick disconect. for what i can see i have a big inc of power and 1 or 2 resistors arent working maybe 1 diode too this are the pics of the amp before i fix it ( for a few mins cuz it burn again ) i have to come back to the board again and i will be checking again o BTW i found a local electronic place the parts aren't to expencive, but its worth cuz if i buy it in the internet i have to wait this way i may not save money but speeds up the process of learning and geting it fix thx... HOOO!! 1 more thing if u can copy my pics and post it back and if u can mark it... in your experience what parts i have to check on priority tha will be very nice,and if u can do it, if its not to much to ask . thx again but some how i got tired of trying for 2 hours upload photos -_-

[Perry Babin]

There won't be an odd number of power supply FETs. It's likely that there are 3 on each side. If that's true, the ones on the other side may have been shorted and would have caused the new ones to have failed. If you can't upload the photos, email them to me and I'll be better able to help.

babin_perry@yahoo.com

[Perry Babin]

Looking at the photos...

Yes, there are 3 FETs/side.

You need to confirm that all 6 gate resistors are within tolerance.

The amp may have shorted output transistors. They are the larger transistors (4/side).

Before you apply power (after replacing all know defective parts), clamp all transistors to the heatsink and insert a 15 amp fuse in the B+ line. If the fuse blows, there are additional problems. Do not use a larger fuse.