I hgave this car amplifier, it has a SMPS supply for each channel, using the
classic TL494 and IRFZ44 design.

the outputs were shorted, and the IRF were blown apart. i replaced the
outputs and the IRF, along with the gate drive resistors to the mosfets.

the amp functioned after that, and had no DC offset, amp was running
reletively cool, and sounded nice. then the outputs shorted again out of
nowhere and blew out the power suppl yagain.

so i replaced all those parts again, and this time i changed the drivers to
the outputs on that channel.

it ran for 4 days working nicely, and bam, ouputs go again.

im at a loss, i dunno whats up. i checked all the resistors and transistors
in that side of the amp. come up wiht nothing. :-(

Mike wrote:

I hgave this car amplifier, it has a SMPS supply for each channel, using the
classic TL494 and IRFZ44 design.

the outputs were shorted, and the IRF were blown apart. i replaced the
outputs and the IRF, along with the gate drive resistors to the mosfets.

the amp functioned after that, and had no DC offset, amp was running
reletively cool, and sounded nice. then the outputs shorted again out of
nowhere and blew out the power suppl yagain.

so i replaced all those parts again, and this time i changed the drivers to
the outputs on that channel.

it ran for 4 days working nicely, and bam, ouputs go again.

im at a loss, i dunno whats up. i checked all the resistors and transistors
in that side of the amp. come up wiht nothing. :-(



did you replace the TL494 ? sounds to me that it's running wild.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

no becuase the same TL494 runs both channels. there are 2 SMPS supplies, the
smae TL494 runs both. the right channel is fine.


i just did some volt measurements. its about +/-45 on both channels. :-)



"Jamie" t wrote in message
...
Mike wrote:

I hgave this car amplifier, it has a SMPS supply for each channel, using
the classic TL494 and IRFZ44 design.

the outputs were shorted, and the IRF were blown apart. i replaced the
outputs and the IRF, along with the gate drive resistors to the mosfets.

the amp functioned after that, and had no DC offset, amp was running
reletively cool, and sounded nice. then the outputs shorted again out of
nowhere and blew out the power suppl yagain.

so i replaced all those parts again, and this time i changed the drivers
to the outputs on that channel.

it ran for 4 days working nicely, and bam, ouputs go again.

im at a loss, i dunno whats up. i checked all the resistors and
transistors in that side of the amp. come up wiht nothing. :-(



did you replace the TL494 ? sounds to me that it's running wild.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

Mike wrote:

no becuase the same TL494 runs both channels. there are 2 SMPS supplies, the
smae TL494 runs both. the right channel is fine.


i just did some volt measurements. its about +/-45 on both channels. :-)



"Jamie" t wrote in message
...

Mike wrote:


I hgave this car amplifier, it has a SMPS supply for each channel, using
the classic TL494 and IRFZ44 design.

the outputs were shorted, and the IRF were blown apart. i replaced the
outputs and the IRF, along with the gate drive resistors to the mosfets.

the amp functioned after that, and had no DC offset, amp was running
reletively cool, and sounded nice. then the outputs shorted again out of
nowhere and blew out the power suppl yagain.

so i replaced all those parts again, and this time i changed the drivers
to the outputs on that channel.

it ran for 4 days working nicely, and bam, ouputs go again.

im at a loss, i dunno whats up. i checked all the resistors and
transistors in that side of the amp. come up wiht nothing. :-(




did you replace the TL494 ? sounds to me that it's running wild.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5




to save your self some parts, replace the parts again only this time.
get your self a couple of 200 watt incandescent lamps, series the
power throw them on that one channel and let it sit on the bench and
run for a bit.
Allow the unit to short.
the bulbs will absorb the current and not burn out your components
while you can probe in to see where the short is talking place.

It's possible you may have an oscillation channel or maybe your
output is getting shorted in the car?


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

Mike wrote:

I hgave this car amplifier, it has a SMPS supply for each channel, using the
classic TL494 and IRFZ44 design.

the outputs were shorted, and the IRF were blown apart. i replaced the
outputs and the IRF, along with the gate drive resistors to the mosfets.

the amp functioned after that, and had no DC offset, amp was running
reletively cool, and sounded nice. then the outputs shorted again out of
nowhere and blew out the power suppl yagain.

so i replaced all those parts again, and this time i changed the drivers to
the outputs on that channel.

it ran for 4 days working nicely, and bam, ouputs go again.

im at a loss, i dunno whats up. i checked all the resistors and transistors
in that side of the amp. come up wiht nothing. :-(




Further information is needed.

On car amps, you have to know the EXACT load. I have seen too many times
units loaded down below there recommended specs. CUstomers don't have
a clue a lot of the time. Or bridging amps when they should not be.
Or hooking up a working amp to speakers that are damaged.
You need the woofers box in to verify the load and verify the voice
coils are ok and not rubbing.

Things to look for: mica insulators on the amps that are damaged.
I have seen torroids that are intermittently shorted from primary
to secondary. Filter caps that break off a Leeds on the pc board
from mechanical fatigue of the amp vibrating it. The list goes on.

Also, check the car for good power and ground. I cannot count the times
i have seen an amp in the truck with the ground wires stuck under the
trunk hinge or such with no good mechanical connection. Or the hot wire
jammed into the battery connector up front.

Bob

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ok the speakres are pioneer 450watt 12s they are brand new, and are rated 4
ohms.

the amp says its stable to 2 ohms, but i doubt it.

i replaced the parts and am testing it on my bench, everything appears
normal.

the quesent current for each channel is drawing about an amp or so.

i think the amp had this problem before my buddy got it, becuase when my
buddy got it, the left channel was blown already. it just blew again twice.
so its definatly internal.

the rails on th eleft and right channel are holding steady at about +/- 45v

but at peak load ive seen the power supply draw around 15 to 20 amps. weee
lots of current.

as for the car, the amp is bolted on the back of the speakerbox. the
speakerbox is a bandpass box that that has 2 speakers, one hooked to each
channel. the speaker that was hooked to the channel that blew, the coil is
burned up from the DC before the power supply blew on the left channel, so
he had to replace that speaker


"Bob Urz" wrote in message
...


Mike wrote:

I hgave this car amplifier, it has a SMPS supply for each channel, using
the classic TL494 and IRFZ44 design.

the outputs were shorted, and the IRF were blown apart. i replaced the
outputs and the IRF, along with the gate drive resistors to the mosfets.

the amp functioned after that, and had no DC offset, amp was running
reletively cool, and sounded nice. then the outputs shorted again out of
nowhere and blew out the power suppl yagain.

so i replaced all those parts again, and this time i changed the drivers
to the outputs on that channel.

it ran for 4 days working nicely, and bam, ouputs go again.

im at a loss, i dunno whats up. i checked all the resistors and
transistors in that side of the amp. come up wiht nothing. :-(




Further information is needed.

On car amps, you have to know the EXACT load. I have seen too many times
units loaded down below there recommended specs. CUstomers don't have
a clue a lot of the time. Or bridging amps when they should not be.
Or hooking up a working amp to speakers that are damaged.
You need the woofers box in to verify the load and verify the voice
coils are ok and not rubbing.

Things to look for: mica insulators on the amps that are damaged.
I have seen torroids that are intermittently shorted from primary
to secondary. Filter caps that break off a Leeds on the pc board
from mechanical fatigue of the amp vibrating it. The list goes on.

Also, check the car for good power and ground. I cannot count the times
i have seen an amp in the truck with the ground wires stuck under the
trunk hinge or such with no good mechanical connection. Or the hot wire
jammed into the battery connector up front.

Bob

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