Hameg 604 No Second Channel Trace or Beam.

[mluhar]

Hi Members,
I have got a Hameg 604 Oscilloscope. I was given this scope by my brother-in-law. When I got it I switch it on and everything is working except channel two trace, (channel one fine). He also gave me a service manual. I would be very grateful if someone can direct me where to start looking for the faulty. I have a basic electronics knowledge. I don't know how the circuit works, if someone can explain to me that will be great. Look forward to hear something from someone.
Regards

[strawberry]

single beam scope
uses choper to switch/multiplex between channels(when turned on)

[mluhar]

Thank you for your reply sir. You couldn't explain to me how that circuit works? Your help will be appreciated. Thanks.