Tip & How-To about Audio Players & Recorders

Amplifier Repair Trick

So, you've replaced some parts in an amplifier, but are afraid they'll blow again if you missed something...
Here's a rig that's saved a lot of amps from a second death!
Build a box where you have the main power coming in from the outlet, and on this box, put a lightbulb socket, and a power outlet.
Wire these in SERIES.
plug the box into the wall, and plug the amp into the box.
The lighbulb will not only dampen the turn-on power surge, but if something is overloading in the amp, the lighbulb will start glowing as it drops the voltage to the amp - and in doing so, saving the fuses and components.

If the light is glowing bright with no signal going in, the amp is using way too much current - pull the plug, something surely is wrong...but you just saved a fuse! and probably several components!

At turn on, the light should light partially for a very brief period of time then go out essentially becoming nothing but a wire, and allowing the amplifier to operate normally.
For most amplifiers, I recommend about a 60W - 100W bulb at 120V for Canadian and US units.

NOTE**** If the amp is blowing fuses even with this rig in place, lower the wattage of the bulb. ****

Remember, if you see that bulb glowing steady, PULL THE PLUG.
Better yet, incorporate a light switch into the unit (also in series) so you can turn the power on and off at a moments notice !

Now to burn in your amp once it's working...
They are hard to find, and you may have to make your own by wrapping transformer wire around an aluminum rod or some such thing, but either find or make an 8 OHM coil. Use this rather than speakers to run high volume tests.
The lighbulb should start glowing to the beat.
At this point, scope the outputs to see if they are clean and not distorted or riding a DC voltage.
If all looks good, shut down, plug it into the wall, and go back to your high volume testing.
CAUTION - your resistor may get very hot! DO NOT run this test unattended!!!!!
After 30 minutes or so of stress testing the amp, check again to make sure the outputs are clean and DC free.
If everything looks OK, check the impedance of your speakers to make sure they aren't blown. Open or less than rated impedance means a blown or partially blown (and likely defective) speaker !
If the speakers check out, go ahead and hook them back up, and enjoy the sound of victory!

(c) Please do not copy/paste this tip anywhere outside of the FixYa community as I am posting this for our internal benefit to our customers and experts. The information contained within this document are the property of the author and FixYa.

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1 Answer

A/C blows hot, not out of freon. What's the problem?


Watch the clutch on the compressor while the AC is on to see if it is engaged. There are pressure sensors, relays and fuses in concert that operate the clutch. A low pressure from an improper amount of freon will cause it too. It may start for a minute then stop to save the compressor from damage. Lots of things to check for proper operation.

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amp is blowing inline fuse everytime i connect the pos.&neg. wires


Hi thetexster74,
Blowing of fuse indicated of shorted parts inline with the supply voltage. Most common shorted parts is the sound output IC which is mounted in the heatsink. If your handy with electronics, have knowledge in soldering and desoldering technique, pull-out this IC to the board and then try the unit. If the fuse does not blow this time, you must replace this IC and your unit will back to normal again.
Let me know if the symptoms still persist after you've done the above solution.
Hope I helped you.
Thanks for using Fixya.

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hi,my peavey amplifier cs 4080 hz blew the transistor and number for the transistor part G30N60C3D ,how can it cost me


Ouch! That is an expensive one... a little over $7 here:

http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&WT.z_homepage_link=hp_go_button&KeyWords=g30n60c3d

The BAD news is that USUALLY other things go at same time or cause the failure. If you miss replacing a second part that is degraded, then you blow out the new one. Pay particular attention to the gate limiting Zener diode... it may be blown open and would result in instant failure again. Also ALL parts associated with the gate drive of that transistor.

The circuitry for this amp is rather complicated and a lot of other parts need to be checked for damage before putting full power on the unit again.

When firing this up, put a 250 Watt lamp in series with the power input to act as a resetable fuse to avoid blowing out the part again... It is good to use a variac to slowly bring up the voltage at first. If the lamp stays lit, better keep looking for bad parts.

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1 Answer

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Sounds like the amp is shorting somehow. You are obviously shorting out somewhere between the battery and the amp. Are you sure you grounding location is a good one? is the fuse blowing only when you turn the stereo on? Something is not hooked up correctly.

If the fuse at the battery is blowing then it's a short.

If the fuse on the amp is blowing then its probably a bad amp.

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