Failure analysis: computer control system, as long as there is an operational functions properly, the circuit for this function to be used to in other working conditions can work properly. This is because regardless of what control function are to through coding, decoding recognition, find program, Executive program of full process, just in interface circuit Shang has separate, manual selected Taiwan can lock, and only is automatically selected Taiwan cannot lock, just two a entered interface different just, manual by press signal lost people, and automatically is is by in the put AFT circuit sent to of instruction (Dang tuning right Shi, AFT output for 0, computer is according to this principle to judge tuning of right or not) according to this machine fault phenomenon, AFT is not computer tuned correct instructions. Should consult the AFT signals is appropriate.


Repair techniques: check the AFT measured signal-see also color 2013 Scarlett TV schematic diagram of IC001 (41) AFT-foot signal input (voltage change) so check way leads are lost, this search method does not find the essence of things, cause there is no find, need to open another path. Then check again starting from the static failure, checking of IC001 (11) leg static output, press works, when you select search (11) foot in no case there should be high level, when there is a low level, the measured (11) feet high and with up to 8V. Beyond computer of work power voltage, this voltage impossible is computer sent out, should finds is interface circuit fault, so check (11) feet interface circuit, measuring have Q007b very also up to 8V, and e very OV, such can concluded that Q007be knot has open, split Xia Q007, (11) feet is up to 8V, by circuit analysis known: only Dang C031 breakdown or PCB leakage or take Tin Shi (11) feet only appeared high level. According to principle should first remove the easy issues before the tough ones C031 (breakdown) put on new, troubleshooting, root cause to find out.

Analysis: starting so detours, suspicion still fail and automatically sets cannot be latched and AFT relevant, but wrong in it. The trouble lies in not gotten, is there are two contradictions, there is a major contradiction. For two faults of public positions in the AFT circuit, intellectually speaking, pretty good. Public site trouble-free in practice, it should be viewed from two symptom check up found AFT of effective and manually is also effective, it is necessary to check the static failure, in order to find the fault really lies, namely Q007be junctions break due to electrolytic breakdown, high voltage reverse into IC001 (11 per cent), resulting in the internal part of the interface circuit is abnormal.

Addition, dang IC001 (11) feet voltage up 8V Shi, IC001 of power voltage also up to 8V, if by simulation circuit overhaul, will wrong sentenced due to power voltage high caused computer work errors, and from power started, but to note: computer as long as has a operation function normal, remaining function also should normal, computer should no fault, so must from another a phenomenon started, without from power Shang find causes.