AMB Laboratories DIY Audio

[lgulyas]

Hi guys,

I am testing my new M3 and doing the initial check after ground OPAMP installed I got 11,4V between 4 and 7 pins. Between 4 and ground I got 8,1V and between 7 and ground I got 3,3V. What sould be the problem?

Thanks!

Laci

[lgulyas]

I found the problem. The initial check is done. Connecting the gamma 2 soon.

Thanks!

[lgulyas]

Okey, so the problem was that the Q5+ was placed reversly. Desoldered the transitor/redirected and than did the inital setup and it worked well. The sound was amazing! Then when I powered it on later I got no sound from the M3. I checked the voltages at the OMPamps and I got a reading of 0V everywhere(pin 4,7). My question is that how is it possible that the q5+ worked well after the redirection but after a later power on it died. Is it possible that other transitors/fet died there too? Tomorrow I ll get a spare part. I dont know how is it possible to work perfectly than die after power on.

Thanks,

Laci

[amb]

Maybe Q5+ or Q5- blew again. If you're working with the board and the C5+/C5- capacitors are charged up (they could remain so for quite some time after the power is off), and there is an inadvertent short circuit somewhere downstream from these transistors, they would be blown.

[lgulyas]

Okey, so if I understand you correctly, you are saying that the Q5+/Q5- are probably blown(because of being reversly mounted Q5+) and there is a chance that the C5- and Cr+(I don't know which is this one) are blown, too? How can I check that these capacitators are blown(I cannot see any visual error on them).
Thanks!

[amb]

Sorry that was a typo -- I edited the post after yours. It's C5+/C5-. No, those capacitors are not blown. One or both of Q5+/Q5- is probably blown again because the the C5s are charged up and an accidental short circuit happened when you're handling the board.

[lgulyas]

The thing is that it worked after I put everything in the box. And when I wanted to turn it on later it didn't work, when I touched the Q5+ it was really hot. So I did not touch it accidentally. Is it possible that when I accidentally reversly mounted Q5+(something happend with the transitor), It worked a little bit (when I tested the board and listened it) but later without any changes or accidental touch it blown?

Laci

[amb]

Just replace Q5+ and Q5- and re-test. If you're not getting voltage at the opamp sockets then that has to be the reason.

[lgulyas]

Today I changed the Q5+ worked well and sounded well but I think it blown again. My build:

https://plus.google.com/photos/107717019839837471340/albums/5703548785897938945?authkey=CPvA-5mrufHW0AE

The gamma 2 and the M3 is in one box. The gamma 2 output is connected to the m3 directly and also to the RCA out (KRK gp6 active monitor). So the M3 works till I connect the RCA innterconnect from the KRK. I can fill some current in my hands when I am connecting the interconnect cable. What could be the problem? I think there is something with the shared output of the gamma 2...


Thanks!

[MisterX]

Does the enclosure have metal or plastic end panels?