JYE Tech Forum

Hello,
I soldered my dso138 oscilloscope and powered it. Everything booted up fine but the trace line is at the bottom of the screen and it doesn't react to any signals. I measured the voltages and they are not as they were supossed to be.
AV- : -4.42V
AV+ : +4.92V
+3.3V : 3,303V
+5V: 4.958V
V1: 0V
V2: -1.44V
V3: -2.77V
TLVL: 1.62V
At the positive end of D1 and L1: -5.58V
V-: 5.52V
The rest voltages(including at Q1 and Q2) seem to be allright.
Also U5 is getting slightly warm when powered.
I know the soldering isn't perfect but I can't find anything shorted or opened.
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The voltage at V1 should be +1.6. The problem is at U2C or the surrounding components.
Since V1 is 0 volts and is connected to U2 pin 10 you should have 0 volts there too.
If the op amp is working U2 pin 9 will be driven to match pin 10.

R10 and R11 try to pull pin 9 negative. The feedback through R9 should bring it up to 0 volts(matching pin 10). If you have good connections and resistors are in the right places U2 is defective.

The incorrect voltage at V3 is probably a result of the wrong voltage at V2