Panasonic CT-27D10B Service Manual

Also see for CT27D10DB - 27" COLOR TV: User guide

Panasonic CT-27D10B Service Manual Manual pdf 5 page image

- 5 -Service Notes (Continued)IMPORTANT: To protect against possible damage tothe solid state devices due to arcing or static discharge,make certain that all ground wires and CTR DAG wireare securely connected.CAUTION: The power supply circuit is above earthground and the chassis cannot be polarized. Use anisolation transformer when servicing the Receiver toavoid damage to the test equipment or to the chassis.Connect the test equipment to the proper ground ( ) or( ) when servicing, or incorrect voltages will bemeasured.WARNING: This Receiver has been designed to meetor exceed applicable safety and X-ray radiationprotection as specified by government agencies andindependent testing laboratories.To maintain original product safety design standardsrelative to X-ray radiation and shock and fire hazard,parts indicated with the symbol on the schematicmust be replaced with identical parts. Order parts fromthe manufacturer’s parts center using the partsnumbers shown in this service manual, or provide thechassis number and the part reference number.For optimum performance and reliability, all other partsshould be replaced with components ofidentical specification.Horizontal Oscillator Disable CircuitThis chassis employs a special circuit to protectagainst excessive high voltage and beam current. If, forany reason, the high voltage and beam current exceeda predetermined level this protective circuit activatesand detunes the horizontal oscillator that limits the highvoltage. The over-voltage protection circuit is notadjustable. However, if components indicated by thesymbol on the schematic in either the horizontalsweep system or the over-voltage protection circuititself are changed, the operation of the circuit should bechecked using the following procedure:Equipment needed to check the disabled circuit:1. Voltmeter (0 - 200V scale)2. High Voltage Meter (0- 50kV)3. Variac or Isolation TransformerProcedure:1. Tune in a station to verify that the horizontal isin sync.2. Obtain a Monoscope pattern or a signal generatorcrosshatch pattern3. Connect the voltmeter (-) lead to TPD2 and the (+)lead to TPD1 (junction of D55b anode, R556 &R557). Set Bright level to (0) and Picture for a 1.8volt reading on the voltmeter.4. Turn the Receiver OFF. Connect a jumper acrossIC803 pin 3 and pin 4. Apply +9V DC to cathode ofD001.5. Reduce the AC supply voltage to approximately45V. Connect the high voltage meter to the CRTanode. (H.V. button).Note: Use the Dag Ground (C10 on the CRT Board)to connect the (-) lead of the meter.6. Turn the Receiver ON. Slowly increase the ACsupply voltage and verify that the high voltagesdoes not exceed 37.1kV when horizontal; justbegins to pull out of sync. If the high voltage is notwithin the specified limit, the cause must bedetermined and corrected before the Receiver isreturned to the customer.