long beep in tvt dvr

[ERANG1000 0]

hello evryone

i have some tvt dvr thet get virus.. one day 6 pcs dvr installed in difrunt places are only when power one long beep and no screen

i heared thet have in pcb board rest function for riper this problem

[evolution977 0]

same problem i face 20 dvrs total anyone know the reason please advice