They still support and do repairs last time my mates DM70’s went down, about a year ago.
Pick your country. http://halcro.com/dealers
Not much good news for you unless you live in Australia.....
Halcro did go out of business and despite at least two attempts (to my knowledge) to re-establish themselves....are still defunct.
You can open both the DM10 and DM58-68 amps by way of allen key screws accessed through the slots between the vertical aluminium heatsinks on the side of the amps.
But this is what you will find inside
PCBs covered with resin to protect the proprietary circuit design that Halcro owns. And despite the fact they are defunct...they will not release the designs to enable others to work on these circuits.
Here are the contact details of the original circuit design engineer in Adelaide who still services the Halcro gear:-
Independent Technical Consultant
+618 405 16 39 39