I've got a cheapo "planet audio" amp that blew the large 200v caps on the output end as well as the small blue square cap that is in series with a resistor that measures about 1100 ohms. There are also two other blue square caps that read 224j100 that got hot and melted down closer to the power supply. I tried ampguts but the only similar amp I could find was a power acoustik and the pics aren't clear enough for me to zoom and check the part number for the tiny blue cap on the output. I'm also wondering how 200v 105c caps on the output end would give out when the 80v power supply caps are fine. ????? So I need to verify the tiny output cap p/n and possibly the actual capacitance of the 224j100 caps. I believe they are 100v, but need a refresher on how to use the 224j to get the capacitance measurement. Thanks for any help
Pic of the output terminal section. The tiny blue cap is gone that is supposed to be to the right of the large resistor, it was basically disintegrated, but there was a small piece of the blue plastic. I've also already removed the 4 200v caps.
And here are the two blue caps that melted and exploded, I cleaned most of the mess off of the board
Pic of the output terminal section. The tiny blue cap is gone that is supposed to be to the right of the large resistor, it was basically disintegrated, but there was a small piece of the blue plastic. I've also already removed the 4 200v caps.
An externally hosted image should be here but it was not working when we last tested it.
And here are the two blue caps that melted and exploded, I cleaned most of the mess off of the board
An externally hosted image should be here but it was not working when we last tested it.
The blue caps are 0.22uf/100v/5%. The resistor is supposed to be 1000 ohms.
If you still have switching noise on the outputs, you may have a shorted inductor. Move the inductors to see if the noise changes. The inductors fail when the insulation wears through. The problem generally occurs where the lead winding passes over the top/inside of the other windings. This is VERY common on ALL of the amps that use this design.
The shorted (possibly intermittently shorted) inductors could have caused the capacitors to fail.
The capacitors (particularly the smaller caps) fail because they receive too much voltage. As the capacitance of the electrolytic caps decreases (often due to overheating caused by shorted inductors), the output voltage on the inductors goes WELL above rail voltage and will cause all of the caps on the output to fail.
Is R101 near the RCA jacks intact?
If you still have switching noise on the outputs, you may have a shorted inductor. Move the inductors to see if the noise changes. The inductors fail when the insulation wears through. The problem generally occurs where the lead winding passes over the top/inside of the other windings. This is VERY common on ALL of the amps that use this design.
The shorted (possibly intermittently shorted) inductors could have caused the capacitors to fail.
The capacitors (particularly the smaller caps) fail because they receive too much voltage. As the capacitance of the electrolytic caps decreases (often due to overheating caused by shorted inductors), the output voltage on the inductors goes WELL above rail voltage and will cause all of the caps on the output to fail.
Is R101 near the RCA jacks intact?
Wow, thanks for the info, Perry. The noise isn't really loud, just a little louder than the noise you can hear on most class d amps if you have the volume down and put your ear close to the woofer. And R101 looks fine, no signs of overheating. It reads at 217 ohms.
Would you recommend any specific type or tolerance for replacement of the .22 caps? Mylar, polyester, ceramic, etc... 5%,10%,20%...? I'll check the windings and see if the noise changes. They all seem to be firmly attached to the board.
Would you recommend any specific type or tolerance for replacement of the .22 caps? Mylar, polyester, ceramic, etc... 5%,10%,20%...? I'll check the windings and see if the noise changes. They all seem to be firmly attached to the board.
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