here are the guts, sorry, my phone camera is crap
it was wired, i installed it, everything was working fine then all of a sudden i smell some thing burning, pull the REM of the amp and saw smoke, it was wired up rite, the amp does 1000rms @ 1ohm and the woofer was wired to 1 ohm, it was installed in a 300c and there batteries are in the back, i noticed the ground from the (-)BATT to car body looks really thin, like 8ga wire and i have 4ga on the amp.
it was wired, i installed it, everything was working fine then all of a sudden i smell some thing burning, pull the REM of the amp and saw smoke, it was wired up rite, the amp does 1000rms @ 1ohm and the woofer was wired to 1 ohm, it was installed in a 300c and there batteries are in the back, i noticed the ground from the (-)BATT to car body looks really thin, like 8ga wire and i have 4ga on the amp.
Ok, I cleaned up your photo and removed the clamps so you could see the transistors underneath. The 6 transistors on the left are the output transistors. You need to check them with an ohm meter to see if any read anything near zero ohms between any of the legs of any individual transistor. If you have any that read near zero ohms, they're defective.
These amplifiers also have a problem with broken leads on virtually all of the components that are clamped to the heatsink. You need to determine if any have broken leads where the lead goes into the body of the component. Gently push the component to the side. The component will have to be free to move (not clamped, not stuck to the insulator). If the lead is broken internally, the body will move but the lead will not follow. If any of the outputs have broken leads, all 6 should be replaced.
These amplifiers also have a problem with broken leads on virtually all of the components that are clamped to the heatsink. You need to determine if any have broken leads where the lead goes into the body of the component. Gently push the component to the side. The component will have to be free to move (not clamped, not stuck to the insulator). If the lead is broken internally, the body will move but the lead will not follow. If any of the outputs have broken leads, all 6 should be replaced.
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thank you SO!!!!! MUCH for the help, i took the heat sink off and there were 4 transistors that burned up, i will check them with a multimeter, also what could have been the cause? i did notice on a few of the toasted transistors the legs were broken, could that be what made the amp fail? a loose leg touching ground of something??
o ya and this line of LA amps are made by Fosgate, real nice quality and were tested to do 1,100 @ 1ohm, also i was wondering if it would make i difference if i put in beefyer FET's? and when i solder new ones in i noticed there was a piece of card board looking thing under the fets, they weren't on the bare aluminum, and there was no thermal past at all, will that help and should i remove the cardboard from under neath the fet's??
I'm not sure who made these amps but it was not Rockford. They don't even support the amps and could provide no information when I asked them for a schematic.
The semiconductors with metal tabs must be insulated from the aluminum heatsink. Generally, they use silicone insulators. You will need to replace the cardboard with a suitable insulator.
Which transstors were burned? You already showed photos of the power supply transistors. Were some of the output transistors damaged also? When the legs of the outputs break, they rarely burn. It's usually a clean break. When the power supply transistor fail, they often burn the third leg off.
When the first leg of the FETs breaks, it will allow the gate to charge (either internally or externally by the intermittently connected leg). When there is no way for the gate of the FET to be discharged, it can't be turnd off before the other FETs are turned on. This will cause the amp to fail. Sometimes it causes other transistors to fail and other times it causes the amp to go into protect.
The semiconductors with metal tabs must be insulated from the aluminum heatsink. Generally, they use silicone insulators. You will need to replace the cardboard with a suitable insulator.
Which transstors were burned? You already showed photos of the power supply transistors. Were some of the output transistors damaged also? When the legs of the outputs break, they rarely burn. It's usually a clean break. When the power supply transistor fail, they often burn the third leg off.
When the first leg of the FETs breaks, it will allow the gate to charge (either internally or externally by the intermittently connected leg). When there is no way for the gate of the FET to be discharged, it can't be turnd off before the other FETs are turned on. This will cause the amp to fail. Sometimes it causes other transistors to fail and other times it causes the amp to go into protect.
i wanted to know how i can test my mosfets with a multimeter? im new at this and have no clue, also i pulled them out, i can test them without them being soldered to the board? what do i look for if there ok? only 4 burned and i need 8 to replace all them, but the shop only had 5 so i replaced the burned ones, put power to the amp and one of the FETs i replaced didnt smoke but it popped.
Dougie085:
It was a joke. Even if I could have cleared it up, I could not have removed the clamps from the transistors.
doughboi916:
You can't replace only 4 of the 8. When the power supply fails, it's VERY rare that any of the FETs will survive. Just because there is no physical damage, that doesn't mean they're undamaged.
Go to the section labeled "Checking Field Effect Transistors" on page 97 of my car audio site. It will tell you how to check the FETs.
http://www.bcae1.com/
When you power up the amp, you need to insert a 10 amp fuse in the B+ line. This will help save the new parts if there are other problems. You also need to have the power semiconductors (FETs, rectifiers, regulators...) clamped to the heatsink before applying power.
You may also have defective driver transistors and defective gate resistors. Those should be checked. I'm not sure but the transistors Q405, Q406, Q407 and Q408 may be the drivers. If so, there will be continuity between the first leg and the gate resistors. One pair of drivers will go to 4 gate resistors and then to the gates of 4 FETs. The other pair will go to the other 4 FETs (via another 4 gate resistors). The 'A' (KTA1023?) driver transistors are most likely to fail.
It was a joke. Even if I could have cleared it up, I could not have removed the clamps from the transistors.
doughboi916:
You can't replace only 4 of the 8. When the power supply fails, it's VERY rare that any of the FETs will survive. Just because there is no physical damage, that doesn't mean they're undamaged.
Go to the section labeled "Checking Field Effect Transistors" on page 97 of my car audio site. It will tell you how to check the FETs.
http://www.bcae1.com/
When you power up the amp, you need to insert a 10 amp fuse in the B+ line. This will help save the new parts if there are other problems. You also need to have the power semiconductors (FETs, rectifiers, regulators...) clamped to the heatsink before applying power.
You may also have defective driver transistors and defective gate resistors. Those should be checked. I'm not sure but the transistors Q405, Q406, Q407 and Q408 may be the drivers. If so, there will be continuity between the first leg and the gate resistors. One pair of drivers will go to 4 gate resistors and then to the gates of 4 FETs. The other pair will go to the other 4 FETs (via another 4 gate resistors). The 'A' (KTA1023?) driver transistors are most likely to fail.
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