2 Jaguar consoles with problems 1: no sound 2: black screen - any ideas?

hi all

i have a couple of jags with issues and would really like to sort them as they look like new!

1: console 1: works fine but no sound! any ideas where i should start to look?

2: console 2: black screen when switched on with cartridge inserted, power LED ok, so dead board?

thanks..