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Four, The other faulty
No color:
There are two main reasons that cause to no color: firstly, the signal is too weak that the automatic
color controls electric circuit and then close color degree passage; Secondly, vice carrier wave
creates electric circuit and decoding electric circuit.
If it is caused by the first reason, there will be obvious snowflakes on the general pictures, for which
we need to check first the tuner and
intermediate frequency circuit components, at the same
time we should test the electro circuit of Intermediate player, sound , etc. And it is also can be
caused because of the problem of High and Intermediate AGC electric circuit. The high AGC
voltage is general for 3V-4V, the medium AGC voltage may have some change for about 2V when
the signal varies. The no color problem will be resolved as soon as the weak signal raveled out.
During the period of decoding, feet 38 of IC301 have to produce a vice- carrier signal with a stable
frequency for 4.43 MHZ. Once this signal frequency changes greatly or abnormally, which will lead
to no color. Feet 39 is the colorful APC filter, would still have no color if outer capacitance
damaged.
Program Searching:
Program setting problems can be divided into two aspects: it cannot search program and the
automatic search cannot target.
There are a lot of reasons of searching no program, which is commonly caused by high frequancy
receiver and the related electric circuit .For this question we have to satisfy the priorities:
1. Power supply of high frequency receiver normally use
2. The 33V tuner voltage works normally
3. Wave band controlled by CPU switches well
4. Pre-Intermediate player and AGC are well used
During the maintaining these two electric circuits will be more easy to come into problems: shortage
of 33V tuner electric voltage, too low high put AGC voltage.
The problem that automatic search cannot target refers that we can search every program but the
channel number remains, and after searching it will has no programs. This is mainly caused by four
reasons:
1. Feet 31 of IC701 cannot identify the signal normally, which we often can resolve it by checking
CPU and related outer electric circuits;
2. AFT signal for Feet 10 of IC701 is abnormal
3. Feet 50 of IC301 outer capacitance electric is creepaged
4. The CPU and memory are damaged.
No remote controlling:
First please check whether the remote controlling itself can work well or not, which can be
conveniently judged from the reception or the way of substitution. If the remote control is good, but
without telecontrol, when we should check whether the receiver power of remote control is normal,
whether the signal arriving to CPU has already opened new roads etc, finally change receiver head
or CPU. Then we can settle the breakdown.
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