Help! One Of My Regulator Get Warmer Than The Other

[Agung Kurniawan]

Hi everyone,
I have DIY amp and it use +/-15V with 78xx and 79xx for supplying the preamp, filter and EQ section. The power amp get +/-25 non-regulated.

Yesterday I found my amp to be noisy(like a buzz for me), when I open the amp chasis and touch the +15 regulator, It's hot. But the -15 regulator just at it's normal temperature. When I check the 7815 voltage, it's drop at 5V ( Im using analog multimeter, its hard to me to read it)
And then I replace the 7815 with the new one. But now the regulator a bit warmer than the 7915. And my amp a bit noisy. But when I check the voltage, it's say right at +15V.
Im using 25-0-25 3A for supplying the regulators

I didn't know what's going on, please anyone help me debugging this anoying problem..
Thanks

[EBK]

You have a heat sink on those?  If so, is it big enough? I believe the 78xx have thermal shutdown protection.  Dropping from 25-ish volts to 15 volts is going to create a lot of heat.  If it cant dump the heat fast enough it will give you problems. 

[Agung Kurniawan]

You have a heat sink on those?  If so, is it big enough? I believe the 78xx have thermal shutdown protection.  Dropping from 25-ish volts to 15 volts is going to create a lot of heat.  If it cant dump the heat fast enough it will give you problems.

Yep, not so big but effective. I was using this amp for 2 weeks and the regulator never get heat before

Before this problem came out, that was kind of pop sound out from the amp. After that, the amp going noisy imediately

[amptramp]

That kind of sound can come from a bad electrolytic capacitor at the regulator output.  If the very thin aluminum oxide film shorts out, it can go to a high leakage mode that draws a lot of current.  Check if anything else is overheating - you may be able to diagnose the problem by feel.

[Agung Kurniawan]

That kind of sound can come from a bad electrolytic capacitor at the regulator output.  If the very thin aluminum oxide film shorts out, it can go to a high leakage mode that draws a lot of current.  Check if anything else is overheating - you may be able to diagnose the problem by feel.

I can smell like a fried on something around the 7815 regulator