Category 5
Well-known member
My second Seventh Circle N72 has failed to work.
I put the second N72 together the same as the first (which worked fine), except
maybe a bit cleaner (nicer solder joints, etc).
I don't have a current meter so I just plugged it up and tested Q6 like I did with
the first one. I get .469v at Q6 collector regardless of where r39 is.
I then proceeded to test the other transistors. My values are within less than
1 volt on Q1 Q2 and Q3, but at Q4 and Q5 things start to go awry.
Q4 reads 1.145v col, .4v em, and 5.ma at the base. Q5 reads .469v on both the emitter
and collector, and 1.144 on the base.
Of course, Q6 reads .469v on the base too, but I didn't write down the other readings.
Apparently, something is going wrong between the 2 gain stages. I did solder the
conn 3 jumper in place, and I tested to make sure it shorted siccessfully between
pins 1 and 3, but not pin 2.
There are no blatant shorts, and no apparent broken PCB traces, so what could it
be?
Could one or more of the BC184 transistors be bad?
Could I have ruined a cap by keeping heat on it too long? How do I test for this
and where do I start?
Thanks!
Shane
I put the second N72 together the same as the first (which worked fine), except
maybe a bit cleaner (nicer solder joints, etc).
I don't have a current meter so I just plugged it up and tested Q6 like I did with
the first one. I get .469v at Q6 collector regardless of where r39 is.
I then proceeded to test the other transistors. My values are within less than
1 volt on Q1 Q2 and Q3, but at Q4 and Q5 things start to go awry.
Q4 reads 1.145v col, .4v em, and 5.ma at the base. Q5 reads .469v on both the emitter
and collector, and 1.144 on the base.
Of course, Q6 reads .469v on the base too, but I didn't write down the other readings.
Apparently, something is going wrong between the 2 gain stages. I did solder the
conn 3 jumper in place, and I tested to make sure it shorted siccessfully between
pins 1 and 3, but not pin 2.
There are no blatant shorts, and no apparent broken PCB traces, so what could it
be?
Could one or more of the BC184 transistors be bad?
Could I have ruined a cap by keeping heat on it too long? How do I test for this
and where do I start?
Thanks!
Shane