Question about Legacy Audio American Legacy II LA290 Car Audio Amplifier

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No power plug amp up but no power. i`m wondering could it be the two power ic`s located on the heat sink

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Re: no power

Check the unit for any Fuses, Fusable Links etc, if they are OK proceede on to testing, I often troubleshoot these issues via a stereo head set, modify the leads so you can "Touch" them onto the Speakers Output Terminals, connect the "Shields" together, thats "Earth" and the other Two, are Left & Right... with a Sinal feed in & the Amp's volume turned to about 25% volume, connect up the Earth wires to the Chassis with a clip, under a srew etc, just make good contact... then touch the Left & right wires onto the output, ya should hear sound... if not most probably the Output device(s) may have gone faulty.

Posted on Aug 08, 2007

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The output IC mounted on the heat sink is the part that will burn
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have this amp, had this problem, had to crack it open to re-solder the RCA input jack as the soldered mount connections failed. Seems like the issue was the input spiking when those connections moved around, or it was caused by poor connection between the mosfets and heat-sink(causing near-instant overheat condition). There are 4 or 6, don't remember. They were attached to 2 slide rail looking pieces of aluminum that fit in the shell. I broke them free (as it made the job faster) and reattached with minimal heat-sink compound. Thing runs like a champ now. Get another 20 years out of it.

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Crunch 1500 went into protect mode, what do i do?

Hi ,
is an error code for short and overload. Once the power applied to the unit and shorts sensed by the processor, the unit will automatically turned to "protect" to avoid further damaged to other parts. Most shorts is in the supply voltage (B+, Vcc) line and most common caused is the sound output IC (mounted in heat sink). This part is responsible for amplifying the audio from the pre-amplifier stage and will feed to your speakers.

If you have a knowledge in disoldering and soldering technique, I would advice you to pull-out this part and then try the unit. If the "Amp Grd" error code is gone then you must replaced this IC with a new one to back your unit in normal operation again.
Before that, try to isolate first the speakers, if you have a shorted one, same symptoms will be encounter. Disconnect all the speakers from the unit and turned it on naked. If the symptoms is gone, then check for shorted speakers.

Hope I helped you.
Have a nice day!
Thanks for using Fixya.

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1 Answer

Protection light staying on & power light blinks on & off with no sound

Hi Charles,

Protect is an error code for short and or overload. This will appear once the processor sense a malfunction either on the power supply or on the load (high chance is the output IC). DIY steps are as follow to determine where the fault is : 1. Allow the unit to cool down for an hour. Give proper ventilation and keep away all obstruction from the vent to have a sufficient air flow. 2. Disconnect one at a time the speakers, inputs, from the unit while powering it on.

If the unit back to normal again then you've confirmed that any of the above caused the error code. If #1 is the caused, you have to check also the exhaust fan(if installed), clean it as much as possible, replaced if faulty. If #2 is the caused (speaker) check the wire and speakers for short, (input) check the RCA cord for short or replaced if necessary.

If the above simple fix didn't cure the error code, you can try the next steps if you are an electronicsenthusiast. Now after removing the cover, you have to concentrate first on the power supply board. Look for bulged electrolytic capacitor. Leaky capacitor will affect the regulation of the supply and will trigger the error code. Look for dry joints. Check it also in the pre-amplifier stage, main output board where a big heat sink is located. Next disable the output amplifier stage by disconnecting the supply. If the unit come out, make some re-soldering on the board, spot the cold solder and dry joints and then try to connect again. If the error code appear again, high chance that your output IC is faulty but still to be confirmed. Using the disoldering pump and soldering iron pull-out the output IC from the board then try the unit. If the error code disappear, confirmed that your IC is faulty.After trying the abovesteps-by-steps guide and still the symptoms persist this is the time for you to send it to repair shop. Remember that your unit has a lot of parts and only some basic steps have done, leave the expert to troubleshoot the entire unit.

Hope I helped you.

Have a nice day!

Thanks for using Fixya.

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2 Answers

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you have blown the actual filters that make the sound. a amp is basically a filter with the same filters on both channels on each side of the inside of the amp - channel 1 and channel 2, that pop was in the heat sinks of the amp usually. if you have replaced the fuse in this amp and you get no on light, the internal amp is in need of repair

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Hello nymnym999,

You did not specify which Fusion amp you have but if the insides looks like the Fusion PP-AM60020 image below, you'll have to "desolder" the transistor.

First remove the heat sink from the transistor case. You'll need a controlled heat soldering station, a desoldering vacuum tool commonly referred to as a "solder ******", and some desoldering braid. Be careful with the heat around other components.

After removing the transistor, use the desoldering braid to clean off any remaining solder from around and in the circuit board mounting holes. Position the new transistor and solder it to the board. Put a thin film of thermal compound on the heat sink and remount it to the new transistor. Use just enough of the compound to insure an air-free join between the transistor case and the heat sink. Reassemble the case and you're finished.

Hope this helps.

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1 Answer

Car amps

I think the originals may have been IR21844S. I've been using the IRS21844S and they have worked well.

The un-connected pads lift relatively easily on these boards. If you want to avoid lifting those pads and you have a soldering iron with a temperature control, use ChipQuik solder alloy to remove the ICs. Set the iron to ~450F as a starting point. Increase the temperature slightly if necessary.

If the amp has vertically mounted outputs, be careful when you reinstall them. The holes typically have a fair amount of slack. If the transistor isn't positioned correctly when it's soldered in, it will be too far from the sink and will not be able to mate (thermally) to the sink (the clamps aren't strong enough. If they are too close to the sink, they will rip the insulators when you slide the board back into the sink.

Let me know if you have any other questions.

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