As there is no video output only, so the fault should be in video processing and output circuit, the circuit shown in the appended drawings. Video signal by the integrated block IC1411 (sp) M50558-108 character/synchronization signal processing/video switch from 12 feet after the output, then the Q1404, Q1530 two level wideband amplifier is divided into two after the road: a path R1535, C1535 to video output socket PG153110 feet; Another path R1535, R1537, C1534 sent to Q1531 b, shot by the buffer amplifier, then by C1535 sent to radio frequency converter, mixed with the audio signal, and then by radio frequency socket output rf signal. EYeservice manual download site
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Via checking, IC1411 12 feet have video signal waveform, but no signal waveform PG153110 foot, apparently failure in PG1531 10 feet to 12 feet IC1411 circuits. Therefore, decided to go against the signal and lookup. Traces found R1535 Ω (75) have burned black, the measured resistance has been increased to 390 Ω, measuring buffer amplifier tube Q1530 sa933 (2) c - e has breakdown, still no video signal output, after replacement measure Q1530b great video signal output, according to the signal to always check the Q1404e, still did not see the video signal waveform. EYeservice manual download site
But have video signal waveform, Q1404b very doubt Q1404 damage, but under the welding test was normal. So doubt its bias circuit has a problem, as Q1404e no 12 v voltage, check the QF871 (ICP - N5) left side has 12 v voltage, and the voltage of the right to zero, QF871 is a tube of two-terminal device shaped like a small power, is rated current of 250 ma is insurance device, has been open. Playing at 250 ma insurance tube for QF871 welding circuit back after commissioning, troubleshooting.EYeservice manual download site