Hi everyone, I'm new here, this is my first diy build and spent the last two weeks reading this thread, buying components, building my gssl (basic, no mod apart of the hpf on a switch with a 100nF cap) and troubleshooting.
As for my actual problem I spent a noticeable amount of time on searching for this issue already sorted out, but haven't managed to get it clear so I thought I give it a try asking it.
Audio passing through the unit is barely recognizable in the form of a heavily distorted audio signal. After a thorough check I'd say all the components are in the right direction (caps,diodes,opamps,vcas, bridge diode, voltage regulators)
So I started to measure voltages at points mentioned in the thread to check. The results seem fine at most of the measured points
at the +15V and -15V jumper = +15,28V and -15,41V
at the 7815 pin 3 = +15,26V and 7915 pin3=-15,42V
at the 7812 pin 3= 12,13V
at the 78L12 pin 1= +11,9V pin 3=14,72V
at the 79L12 pin 2= -15,03V pin 3= -12,48V
+/- 12V at TL074(pin 4 and 11) and TL072 (pin 4 and 8)
+/- 12V at sidechain VCA (pin5 after the 5k1 resistor and pin 7)
+/- 15V at Left ad Right VCA (pin 5 and pin 7)
+/- 15V at 5534 for left and right VCA (pin 4 and 7)
What I found strange, are the following values:
5534 at left and right VCA (DBX emulation circuit) has +12,8V on pin 1 and 8 - I’m not sure if this is OK
And the I/O section op amps shows this:
5534 pins - 5532pins
1 +14,85V - 1 +14,48V
2 +2,48V - 2 +2,13V
3 -1,82V - 3 +1,31V
4 +2,02V - 4 +2,03V
5 -3,88V - 5 +1,05V
6 +4,53V - 6 +0,95V
7 +15,24V - 7 +14,47V
8 -15,03V - 8 +15,24V
So I suppose the cause of the distorted sound is somewhere in the I/O section on the PCB am I right? where should I go from here?
Thanks a lot in advance and if it is an already existing and sorted problem sorry for the long post, then please turn me into right direction ( page).
David