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
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.
Quote from: EBK on January 07, 2017, 09:18:15 PM
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
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.
Quote from: amptramp on January 07, 2017, 09:35:07 PM
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