Hi Salas
Last week I built and tested left channel and was rejoycing about it´s sound and absence of hum.
Yesterday I finished right channel, installed it and it works but the left one stoped.
I read -35mv in the output
Between R10 (4,7k) and Q2 I read only 0.3v instead of 7,9v I have on the working channel.
What can be wrong ?
Ricardo
Last week I built and tested left channel and was rejoycing about it´s sound and absence of hum.
Yesterday I finished right channel, installed it and it works but the left one stoped.
I read -35mv in the output
Between R10 (4,7k) and Q2 I read only 0.3v instead of 7,9v I have on the working channel.
What can be wrong ?
Ricardo
I have power 28v and the voltages in the first stage are ok.
The problem seems related with the riaa 2nd stage.
I have 26v on top of Q5 (output buffer) where I read 14v on the working channel
I have 0.3v on top of Q2 where I should have 7,9v
measuring R5 (without power on) I get 1M on the working riaa and 45k on the dead one. (I desoldered R5 and it measures 1M but in place it measures 45k)
Can there be a fault in C4 ?
Ricardo
The problem seems related with the riaa 2nd stage.
I have 26v on top of Q5 (output buffer) where I read 14v on the working channel
I have 0.3v on top of Q2 where I should have 7,9v
measuring R5 (without power on) I get 1M on the working riaa and 45k on the dead one. (I desoldered R5 and it measures 1M but in place it measures 45k)
Can there be a fault in C4 ?
Ricardo
I'm not up to date with all that you tried. But I think it's the transistors. If you haven't checked them, you should. For jfet just make sure with a 9V battery that you got the proper Idss, that's how I test them. For npn, it's enough to check with the diode tester between B-E and B-C pins, one way street 
I don't think a board that worked all of a sudden turns bad.
I don't think a board that worked all of a sudden turns bad.
yes... the strange part is that it played perfectly before I installed the second channel (right).
Now the new channel works with the lacquer... and the other one has strange behaviour in second stage..... I am wondering about the board because lifting one leg of R5 and using the dmm I get 1M. If I touch the board with the lifted leg, the reading goes down to 900 and if I insert it on the hole (without soldering) the reading goes to 400.
Now the new channel works with the lacquer... and the other one has strange behaviour in second stage..... I am wondering about the board because lifting one leg of R5 and using the dmm I get 1M. If I touch the board with the lifted leg, the reading goes down to 900 and if I insert it on the hole (without soldering) the reading goes to 400.