Sometimes it is also possible to just solder the Flash ROM chip from a board of a known good HDA to the PCB being tested. If a drive with a known good HDA and a tested PCB functions without errors, then the problem is not in the controller board. Then you should write back the original firmware (or return the ROM chip) and proceed to searching
for HDA defects. However, if the PCB does not function on a normal HDA and acts in the same manner (identical to its connection to the malfunctioning HDD being tested) then it is the source of problems and you should try to find the malfunction and eliminate it. Data recovery does not require PCB repair; instead, you should just install to the "patient" HDA a known good board (having recorded to its Flash ROM firmware from the patient's PCB or having soldered its ROM chip onto the normal PCB) and copy user data.