Hydromat torch

Hello everyone. Last year I bought , secondhand from my friend the
jeweller, a Hydromat torch. It had no instructions and I have been
unable to track down any. I use a similar torch at work so I am not a
complete novice but I am not confident with it. It worked for a
while, but now every time I turn it on it won’t hold a flame so I use
my butane torch instead which is fine,but it does not solve the
problem. The Hydromat was serviced before I recieved it so it is easy
to see the water level is ok, but I really have no idea what is the
correct level for the MEK. Also it had developed a most disturbing
habit of emitting a single tone, a bit like someone blowing through a
reed, when it has been on for a while. This scary sound sends me
straight to the 'off ’ button. Can anyone out there help with this.
Thanks, Ruth in the uk.