Hey everyone, I'm new here and have a question.
I have a Power Acoustik 2400 watt "supposily" 1-ohm bridgeable amp that was given to me a few years ago. Guy was just going to throw it away, so I took it.
The history on the amp is it has two inputs for the power supply. (Two seperate B+, Rem, Gnd.) Kinda weired, but at one time, one side was hooked up backwards, and that pretty well ended one side of the amp.
When received the IRFZ44N were blown on one side, which I assume was the side that was hooked up wrong. So I replaced all of them on that side. Also I checked the resistors that were on the gate (I think) and they all checked out ok. I can't remeber if they were 10 ohm, or 100 ohm, but they all checked out ok.
So when I powered up the amp, it played fine at low volume, but the side I replaced the IRFZ44N seemed to be getting extremely hot! I decided what the heck and give it some more volume, and then two of the IRFZ44N blew again. So obliviously there is something else wrong with it.
Also it was just one channel that blew, the other channel kept playing, but didn't sound to clean.
What else can I check? Could I have a problem with some of the electrolytic capacitors?
Also I have access to a DVM, and oscilloscope if needed!
I have a Power Acoustik 2400 watt "supposily" 1-ohm bridgeable amp that was given to me a few years ago. Guy was just going to throw it away, so I took it.
The history on the amp is it has two inputs for the power supply. (Two seperate B+, Rem, Gnd.) Kinda weired, but at one time, one side was hooked up backwards, and that pretty well ended one side of the amp.
When received the IRFZ44N were blown on one side, which I assume was the side that was hooked up wrong. So I replaced all of them on that side. Also I checked the resistors that were on the gate (I think) and they all checked out ok. I can't remeber if they were 10 ohm, or 100 ohm, but they all checked out ok.
So when I powered up the amp, it played fine at low volume, but the side I replaced the IRFZ44N seemed to be getting extremely hot! I decided what the heck and give it some more volume, and then two of the IRFZ44N blew again. So obliviously there is something else wrong with it.
Also it was just one channel that blew, the other channel kept playing, but didn't sound to clean.
What else can I check? Could I have a problem with some of the electrolytic capacitors?
Also I have access to a DVM, and oscilloscope if needed!
Ok all the amp has on it far as model goes is "1-Ohm 2400-2"
Here are some pics with captions. Sorry if the pics are bad, cell phone is all I have.
View of the amp
Here are the two power inputs. It seems this amp is almost two amps built into one.
Ok, here is all the good stuff. There is a board on there with I have marked with SEE POST. It's just some break out board that is covered in some potting compound! They really didn't want you to see or work on this?? Any ideas?
Back side of amp.
Here is a pic of the toasty irfz44n.
Here are some pics with captions. Sorry if the pics are bad, cell phone is all I have.
View of the amp
An externally hosted image should be here but it was not working when we last tested it.
Here are the two power inputs. It seems this amp is almost two amps built into one.
An externally hosted image should be here but it was not working when we last tested it.
Ok, here is all the good stuff. There is a board on there with I have marked with SEE POST. It's just some break out board that is covered in some potting compound! They really didn't want you to see or work on this?? Any ideas?
An externally hosted image should be here but it was not working when we last tested it.
Back side of amp.
An externally hosted image should be here but it was not working when we last tested it.
Here is a pic of the toasty irfz44n.
An externally hosted image should be here but it was not working when we last tested it.
Pull the 8 FETs in that half of the amp. With the amp powered up, measure the DC voltage on the gate's solder pads (all 8 gate pads). Place the black meter lead on the ground terminal of the amplifier when taking the readings. Post the voltage read from the pads.
The gate pad is the solder pad where the first leg of the FET is soldered to the board.
You need to insert a 10 amp fuse in the power line feeding the amp to help prevent damage. You should have the amp clamped to the sink while testing. If that's not possible, closely monitor the temperature of the components that are normally clamped to the heatsink.
The gate pad is the solder pad where the first leg of the FET is soldered to the board.
You need to insert a 10 amp fuse in the power line feeding the amp to help prevent damage. You should have the amp clamped to the sink while testing. If that's not possible, closely monitor the temperature of the components that are normally clamped to the heatsink.
I pulled all 8 FETS, and connected the amp to a 14.4v supply just like if it was running in a car.
All 8 gates read a voltage of 4.2v. I measured the good side, it they were only reading .38v. So then I traced the gates through the 100 ohm resistors, and they all go to two pins on the board that is covered in a potting compound. (I was afraid of this!)
This board has one of these on each side. So I took measurements from the good said, and bad side, and here is what I got.
Good Bad
pin1= .87v------ .9v
pin2= .38v------ 4.2v (GATES)
pin3= .38v------ 4.2v (GATES)
pin4= 13.8v-----13.8v
pin5= gnd------- gnd
pin6= gnd------- gnd
pin7= gnd------- gnd
pin8= 13mv----- 16mv
pin9= 23mv----- 23mv
pin10= 35.4v----- 1.08v
pin11= 11.8v----- 1.08
pin12= 0v--------- 0v
pin13= 1.02v----- .87v
pin14= 1.25------ .1.05
I believe my problems might stem from this board. What do you think?
If so, I'll try to find a way to remove the potting compound from this board so I can try to access it. For some reason they didn't want you getting in there.
All 8 gates read a voltage of 4.2v. I measured the good side, it they were only reading .38v. So then I traced the gates through the 100 ohm resistors, and they all go to two pins on the board that is covered in a potting compound. (I was afraid of this!)
An externally hosted image should be here but it was not working when we last tested it.
This board has one of these on each side. So I took measurements from the good said, and bad side, and here is what I got.
Good Bad
pin1= .87v------ .9v
pin2= .38v------ 4.2v (GATES)
pin3= .38v------ 4.2v (GATES)
pin4= 13.8v-----13.8v
pin5= gnd------- gnd
pin6= gnd------- gnd
pin7= gnd------- gnd
pin8= 13mv----- 16mv
pin9= 23mv----- 23mv
pin10= 35.4v----- 1.08v
pin11= 11.8v----- 1.08
pin12= 0v--------- 0v
pin13= 1.02v----- .87v
pin14= 1.25------ .1.05
I believe my problems might stem from this board. What do you think?
If so, I'll try to find a way to remove the potting compound from this board so I can try to access it. For some reason they didn't want you getting in there.
It appears that the amp has regulated power supplies. The 4.2v on the output of the board is a good thing. It means the drivers are probably intact. The good side probably has a lower reading because the duty cycle has been reduced. The duty cycle is reduced as the rail voltage reaches its target voltage (which appears to be ~35v here).
If there are no gate resistors that are out of tolerance, the drive circuit feeding the FETs appears to be OK.
Generally, when the power supply blows, it's due to excessive current draw from the secondary side of the power supply. This can be caused by shorted/leaking outputs, shorted rectifiers, broken connections in the bias circuit or a defective transformer. If you replace all 8 FETs and the amp still draws excessive current, you need to check all of the above.
You can do a quick check of the output transistors. Measure the resistance between the legs of each transistor. There should be no transistors that read near zero ohms between the legs of an individual transistor. You can compare the readings between the good and bad channels. Do this with no power applied to the circuit.
After replacing the FETs, insert a 10 amp fuse in series with the B+ line. If it blows, the amp is likely drawing excessive current and you need to do more troubleshooting. Have the transistors clamped to the sink when you power it up initially. If they're not clamped to the heatsink, it takes only seconds for the FETs to fail if there is a problem.
If there are no gate resistors that are out of tolerance, the drive circuit feeding the FETs appears to be OK.
Generally, when the power supply blows, it's due to excessive current draw from the secondary side of the power supply. This can be caused by shorted/leaking outputs, shorted rectifiers, broken connections in the bias circuit or a defective transformer. If you replace all 8 FETs and the amp still draws excessive current, you need to check all of the above.
You can do a quick check of the output transistors. Measure the resistance between the legs of each transistor. There should be no transistors that read near zero ohms between the legs of an individual transistor. You can compare the readings between the good and bad channels. Do this with no power applied to the circuit.
After replacing the FETs, insert a 10 amp fuse in series with the B+ line. If it blows, the amp is likely drawing excessive current and you need to do more troubleshooting. Have the transistors clamped to the sink when you power it up initially. If they're not clamped to the heatsink, it takes only seconds for the FETs to fail if there is a problem.
You can use fewer than 4 per bank. It will be easier to blow them (compared to 4/bank) but all you need is 1/bank. If you use a 10 amp fuse and clamp the transistors to the sink, 1/bank may survive even if there is excessive current draw.
Don't try to re-use the power supply FETs that were in the amp when it failed. It's VERY rare that any of the FETs survive when the supply fails.
The TIP35c/36c are the output transistors.
Don't try to re-use the power supply FETs that were in the amp when it failed. It's VERY rare that any of the FETs survive when the supply fails.
The TIP35c/36c are the output transistors.
Those are pretty cool amps for power acoustik. My friend had the version that is half that size and he killed it once by hooking it backwards. After I repaired it and hooked it up for him it kept going. It actually ran the load without overheating, I was pretty amazed. Pretty sure it only runs 1 ohm per channel and 2 ohms bridged though, that's what his was rated for. Looks just like yours but shorter.
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