I have a Hameg HM203-6 20 MHz analog 'scope I bought from a flea shop. There's about 20% mismatch of the readings of the two channels, with CH1's vertical amplification being about 20% higher than CH2 when both are at the "CAL" positions of their respective variable amplification knobs. Using a reliable 5V DC source, I've checked that CH2 shows about 5 volts exactly, whereas CH1 is close to 6 volts. On this model, the "CAL" position is at maximum CCW, and sensitivity cannot be reduced below the calibrated one.
So I assume the "calibrated position" must be recalibrated. The problem is that there's no mention on how to do this in the manual I was able to find. I see those "CH1/CH2 balance" holes on the underside of the case, but they serve a different purpose.
I'm also almost sure that the sensitivity can be calibrated through the VR703 ("Y-GAIN CH1") pot, slightly below the center in this photo.
So my questions are,