Hello every body, am new in this forum, and this is the second time I tray to fix a car amplifier and no luck, right now am tray to fix my Kenwood kac-8401. I was working fine but two weeks ago stop working so I take it out of the car and I use a pc power supply just to test it and the red led turns on, so I did i research on the internet and I read that went that happens is because the amp is protect mode, so I open it and I did no fund any transistor mosfet burn, so I measured whit digital multimiter and I think I found two fets bad so I replace it and I test it again on pc power supply and no luck the blue led turns on but turns of right away, so I thut maybe there is more transistors bud and I replace four more on the same line and now no power the led tray to turn on but turns of rig away. I don’t really know how to measure or test the transistors mosfet but I just notice that there is some deferent then the others, am getting crazy I really want to learn to fix my amp this is the second time that happens and I don’t want to throw this amp again so if somebody know and want help me to fix this problem i will really appreciated
Connect a voltmeter(Multimeter) to the speaker terminals and then power the amp without the speakers.
Repeat it for each channel starting from 'Connect.... speakers.'
If one of the channel is faulty, u will read increasing dc voltage at the speaker terminals.
Then u will have to rectify that channel.
Other reason could be the faulty internal PSU.
Gajanan Phadte
Repeat it for each channel starting from 'Connect.... speakers.'
If one of the channel is faulty, u will read increasing dc voltage at the speaker terminals.
Then u will have to rectify that channel.
Other reason could be the faulty internal PSU.
Gajanan Phadte
There should be two different size transistors. The larger ones will be the output transistors. Measure the resistance between the second and third legs of each individual transistor. If you find any that read near 0 ohms, they need to be removed and checked. If they still read near 0 ohms, they are defective.
am wander if any body know what it`s the order to place the transistors npn and pnp back in to the pcb like i tell you guys im in the lerning process and went i teke it out of the boar i did not put atencion and now i just dont know, same problem whit the diodes y have two i dont know what goes first . please help me
sounds like you need a schematic. does anyone out there have a schematic for a kenwood kac8401 ? i may have a simmilar around to look at but pictures of yours would help.
If somebody tells a noob to remove this and that and test it, it is a totally wrong approach. I am sure the copper has already come off the laminate.
We seem to forget our first attempt at electronics and the mess and mistakes we made, and take things for granted after being experienced. This is where we miss things and the moderators are very good in explaining such details. I envy that.
It is not a big secret that u will explain on a pm but doing it on the open lets detailed- minded to give u a flawless advice and precautions.
Just a suggestion that is good for all.
Gajanan Phadte
We seem to forget our first attempt at electronics and the mess and mistakes we made, and take things for granted after being experienced. This is where we miss things and the moderators are very good in explaining such details. I envy that.
It is not a big secret that u will explain on a pm but doing it on the open lets detailed- minded to give u a flawless advice and precautions.
Just a suggestion that is good for all.
Gajanan Phadte
i have offered the original poster to come by my place so that i can help him troubleshoot but i have not told him to remove anything yet. he did that on his own. any advice you can give him would still be of great help.
lalo01
Do u have a multimeter, what type -digital or analog.
What are the numbers of the transiators(3 lead devices) out of the circuit.
A picture or a sketch of the pcb.
Gajanan Phadte
Do u have a multimeter, what type -digital or analog.
What are the numbers of the transiators(3 lead devices) out of the circuit.
A picture or a sketch of the pcb.
Gajanan Phadte
lalo01 and i are still trying to get this amp up and running but it was bought at a swap meet and looks like it was refurbished. some of the devices had different date codes and even slightly different part numbers. it is now pulling high current at power up. the output devices were changed as well as new power supply mosfets. we found 2 bad outputs and 1 bad irfz46n in the power supply section. it still pulls 20+ amps when powered on.
does anyone have a schematic for this or can anyone tell us what fets were originally in this for the outputs and power section and where exactly they go. lalo01 originally took parts off without noting where they went
but i think i have them back in the proper order.
ch1. n-ch. fet/p-ch. fet repeated for channels 2-4. does this sound correct?? at first he had all p's on one side and all n's on the other side of the amp and the rectifiers reversed as well. what damage would this do? is it worth salvaging after all this and some lifted pads? i got good readings from the controler with the power supply fets removed and no high current.😕
does anyone have a schematic for this or can anyone tell us what fets were originally in this for the outputs and power section and where exactly they go. lalo01 originally took parts off without noting where they went
but i think i have them back in the proper order.ch1. n-ch. fet/p-ch. fet repeated for channels 2-4. does this sound correct?? at first he had all p's on one side and all n's on the other side of the amp and the rectifiers reversed as well. what damage would this do? is it worth salvaging after all this and some lifted pads? i got good readings from the controler with the power supply fets removed and no high current.😕
If this is like audio sections of most other amps, the center leg of the N-channel FET will go to the positive rail. The center leg of the P-channel FET will go to the negative rail.
You can confirm that it's like most other amps of the third leg of the audio output FET is connected to the speaker terminal.
You can confirm that it's like most other amps of the third leg of the audio output FET is connected to the speaker terminal.
oh really? and this is for a kenwood kac8401? the outputs are the same size as the power supply fets. are there bjt's that size? 😕 this may be too far gone for me to handle without a service manual.
The manual I have is for the amp in the attached photo.
Is the name spelled correctly? I've never seen a knock-off with the name spelled correctly. I have seen a couple that looked very similar and had similar names. There was a kingwood amp that looked a lot like these amps.
Is the name spelled correctly? I've never seen a knock-off with the name spelled correctly. I have seen a couple that looked very similar and had similar names. There was a kingwood amp that looked a lot like these amps.
Attachments
the cover says KENWOOD Subwoofer power amplifier 1000w maximum power. i don't think it is exactly a subwoofer amp and 1000 watts is pushing it. plus on the back it says made in japan. i thought all the new kenwood amps were either made in mexico or china or is it korea??
After looking at all of the photos, I think you're right. It appears to be a counterfeit amp.
I've never seen kenwood use black fixative/adhesive. It's always been white (as far as I can remember).
I've never seen them use the cheap clamps either. They almost always clamp the transistors with a screw through the hole in the semi.
The toroidal transformer would also be new/different.
I can't remember any Kenwood amps using the audio output transistors in the TO-220 package either.
I guess if they can lie about the power ratings, the country of origin printed on the label could also be incorrect.
I've never seen kenwood use black fixative/adhesive. It's always been white (as far as I can remember).
I've never seen them use the cheap clamps either. They almost always clamp the transistors with a screw through the hole in the semi.
The toroidal transformer would also be new/different.
I can't remember any Kenwood amps using the audio output transistors in the TO-220 package either.
I guess if they can lie about the power ratings, the country of origin printed on the label could also be incorrect.
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