aleph 30 troubleshooting tips

[pcnreddy]

Hi,

I am building my first diy amp. I chose to build an aleph 3. The boards are from Kristijan. I did the power supply also as specified by Kristijan.

I powered up the amp and I had smoke in one channel. The
polarity was given wrong to that channel. I corrected the polarity and now there is no smoke. But, now for that channel, the LED
glows but there is no sound. The smoke came from the eight 0.47 ohm 5watt resistors. These are R16 to R19 and R21 to R24 on the PCB.

The other channel is working fine.

When I touch the input for the channel that is not working, I get a hum in the speaker that slowly dies down to a silence within 5 seconds or so. If I connect an input there is no sound output at all though.

The PCB details are available here:


kristijan aleph3


I had attached the parts list that I used.

Looks like the service manuals are now taken off from the web. Please give me detailed troubleshooting tips to get this channel also working.

Thanks,
chinna

[pcnreddy]

Hi,

The other channel is working now. The sound is very very good. Thanks a ton to Mr. Pass for sharing the circuits and designs.

One of the transistor was bad. Once I replaced it, the amp worked.

I don't have any expertise in amplifier circuit design/building or troubleshooting. Basically I had one channel working and the other not working. I just took the multimeter and started checking all the resistors using the ohm meter. I checked each component on both the boards to see if anything is different on the bad board. Then I checked the resistance across the capacitors. Then in my multimeter there is a setting to check diodes in the ohm meter section. I used that to just check different pins of each of the mosfets, and transistors. One of the transistor showed different values between the working board and the non-working board. I just changed that, and the amp started working.

I am not sure if this is a valid troubleshooting technique or whether I was just plain lucky.

Checking all the parts didn't take much time since there are not that many parts overall. It took about an hour.

Just wanted to put this info in here so that it may be useful for people who don't know much about amp design.

Again thanks to Mr Pass for sharing the design.

Thanks,
chinna