Watch this machine "secondary" boot with relay suck up vocalist, measure the main switching power supply voltage of + B, boot the instantaneous output voltage has a + B, then relay release, + B voltage disappeared. Relay "secondary" boot off, and then release, doubt is to protect the circuit, microprocessor, the standby protection action. Measure the "C" voltage protection circuit, boot moments for the low level, measure "B" in the protection circuit voltage boot moments for the high level, the judgment is triode Q854 caused by the protection. cFAservice manual download site
 cFAservice manual download site
Because "B" external multiple protection circuit, adopt the method of measuring various protection circuit isolation diode voltage determine the scope of the fault, when measuring + B over-current detection circuit isolation diodes D859 when the anode voltage, as the high level, measuring D859 voltage on both ends is forward biased, so when is 10 B caused by over current detection circuit protection. cFAservice manual download site
 cFAservice manual download site
In order to determine the line is the output short circuit caused by the over current protection circuit, or a + B over-current detection circuit element metamorphism caused by error protection, USES the disconnect D859, remove + B over-current protection method. Boot measurement + B voltage on the low side, from 144 v to 100 v normal, grating to narrow, brightness is reduced, measuring line level output current is controlled in 1 a, line output tube heating. Measuring line output circuit of resistance within the normal range, estimation is line output transformer or deflection coil exists partial open circuit fault, caused by a + B output over-current protection. Change after the line output transformer, voltage + B and grating returned to normal, restore protection circuit D859 also no longer protection, troubleshooting.cFAservice manual download site