By power on the dvr only beep. No start up. The motherboard have a IC with 5 pin U65 (ATV... I don't know the part No.) This IC make start up reset signal for U2 controller and more ICs over U64 hex inverter.
No start-up by external high signal too.
By first diagnostic: U2 contorller is bad. -> replace the IC but nothing change.
The dvr beep continually.
Very difficult the diagnostic without shematic.