Transcript HA2500trn
UNIVERSAL HORIZONTAL ANALYZER (HA2500) TRAINING HA2500 Universal Horizontal Analyzer Universal Horizontal Analyzer Tests Load Test checks H.output -chassis off Dynamic Hoirz Output Meter Test output current from H. Driver stage Substitute B+ voltage to Horiz. Output stage Load Test & Sub Drive Frequency Adjust Ringer Test Detects shorted turn in IHVT, yokes, coils Substitute H. Drive to Horiz. Output Transistor HORIZONTAL STAGES IN HI-RESOLUTION CRT VIDEO DISPLAYS 1. Horizontal Output - Produces current in flyback and/or yoke resulting in HV and/or deflection 2. B+ Power Supply - Powers horizontal output & driver stages with voltage ranging 30-190 volts. 3. HV/Deflection Regulator - Varies B+ to horizontal output to keep HV and/or deflection constant. 4. Horizontal OSC/AFC - Generates sync-locked drive at the horizontal scanning frequency. 5. Horizontal Driver Stage - Amplifies weak drive to level needed by the horizontal output transistor. 6. X-Ray Shutdown - Disables horizontal output stage by removing drive or B+ when the HV is at an unsafe level. Basics of Horizontal Output Stage Horizontal Output Stage in Multi-Resolution CRT Video Display Horizontal Output Stage in Hi-Resolution CRT Video Displays Horizontal Output Stage Types In Hi-Resolution CRT Video Displays S-Capacitor and Linearity Coil Switching H. Deflection Regulated B+ T503 Q519 HST + D511 Horiz. Drive H. Yoke C538 HLC Linearity Coil L506 + 15 V S-Capacitors Select C523 Q518 Q520 Q522 Q523 Q527 Q524 C554 Switched by mode control as horizontal scanning frequency (resolution) increased. 2.2uFd Understanding Horizontal Troubleshooting Difficulties Technicians indicate more than 50% of failures are horizontal related. * Excessive horizontal current (loading) decreases the SMPS output voltage (limiting) or damages SMPS circuitry. * Excessive horizontal output current stresses or burns out, HOTs, HV/defl. Regulator & SMPS components. * A flyback or horiz. yoke shorted turnor flyback secondary circuit short cause excessive current (loading) not evident with ohmmeter. * HV/deflection regulator interacts with horizontal output stage. * Horiz. Drive defects cause horizontal output transistor heating often resulting in failures. * Flyback pulses feed back to AFC, these circuit loops can cause unusual drive and picture symptoms. * X-ray shutdown results in momentary operation with no effective means to make measurements to isolate the cause. HA2500 Universal Horizontal Analyzer Features * Chassis Off Horizontal Output Stage Load Test: Isolates defects with power off (PS loading, shutdown, HOT burn outs). * Dynamic Horizontal Output “METER”: Tests output operation & finds horizontal drive and B+ supply problems. * Exclusive Horiz Driver Test: Measures driver stage output current- detects weak drive or intermittent drive. * Horizontal Output Transistor Base or Gate Sub Drive:Subs missing or suspect drive to prove output stage good or bad. * Substitute B+ Power Supply: Subs chassis B+ supply to isolate SMPS, HV/Defl. Regulator, X-ray, or output stage. * Flyback, Yoke & Coil Ringer Tester: Determines is component good or bad from a shorted turn(s). Horizontal Output Load Test Introduction Provides a functional test of the horizontal output stage at the proper frequency & 1/10th B+ voltage to detect loading (high B+ current) and defects that do not permit power on testing. Benefits: Identify horizontal output stage defects before replacing and burning out replacement output and P.S. parts. Quickly determine if horizontal output stage defects exist before applying AC voltage. Determine if the horizontal output stage is the cause of PS defects or improper operation. Block Diagram of Load Test and Connections To Horiz. Output Stage Orange clip to B+ Input to Flyback Yellow clip to Collector of H.O.T. Black clip to Horiz. Circuit Ground Load Test Setup Load Test Setup Guides you to setting frequency & 1/10 B+ voltage to test the horizontal output stage. Confirms proper load test with VPP readout. 1. Remove AC to chassis - start with LOAD TEST B+ VOLTS at “MIN.” 2. Connect the LOAD/RINGER test leads to proper chassis points. 3. Set the LOAD & RINGER TEST Switch to “LOAD TESTS SETUP.” 4. Set the HORIZONTAL FREQUENCY COARSE and FINE Controls for a frequency near the displays highest horizontal scanning frequency. 5. Increase the LOAD TEST B+ VOLTS Control to approximately 1/10 of the normal B+ to the horizontal output stage. 6. Read the VPP readout - 1/10 of normal - 100VPP typical. Load Test Connections & Readouts ANALYZING THE HORIZONTAL OUTPUT STAGE Load Tests Readouts Interpreting Load Test Readings Typical uS range or horizontal pulse times for multi-frequency (resolution) video displays. A display’s pulse time should be in the range of its highest horizontal scanning frequency or scan format capability. Relationship of flyback pulse to horizontal blanking interval in underscan and overscan displays. Horiz. Flyback pulse is retrace time which occurs during video horiz. blanking interval. Ringer Test Provides a test to determine if the flyback or yoke has a shorted turn defect. * Confirms if flyback, yoke or coil must be replaced. * Saves time replacing components and doing added testing to determine flyback, yoke or coil is defective. * Proves the flyback, yoke or coil does not have a shorted turn and repair is likely feasible. Ringer Test Ringer Test Detects Shorted Turns To Ringer Test a Flyback 1. Remove AC to the chassis 2. Set the Load & Ringer Tests Switch to “Yokes & Flybacks.” 3. Connect the Ringer/Load Test leads to the primary winding. (Use the orange and black test lead clips) 4. Read the rings indicated by the HA2500 center display. Note: 10 or more rings indicates the flyback does not have a shorted turn. Rings less than 10 indicate a shorted turn. DYNAMIC TESTS - METER Provides automatic measurements at horizontal output transistor to ID horizontal drive, B+ supply or horizontal output stage symptoms and defects. Check horizontal drive VPP and Freqeuncy. Check for missing or improper B+ volts. Check for horizontal output stage flyback pulse VPP. Check flyback pulse time in uS automatically. Collector Or Drain METER Readouts Base Or Gate METER Readouts To Use the Dynamic Tests Meter 1. Remove AC to the chassis 2. Connect the Dynamic Tests Leads 3. Set the Dynamic Tests Switch to “Collector Or Drain.” 4. Apply AC to the chassis. 5. Read the DCV, VPP and uS readouts in the center display. 6. Set the Dynamic Tests Swtich to “Base or Gate.” 7. Read the kHz and VPP readouts in the center display. Horizontal Driver Test A measurement of the output current capability of the horizontal driver stage. The test simulates a base/emitter HOT junction and measures output current during positive drive cycle. Benefits * Determines if the base drive current is adequate for normal HOT function. *Indicates when driver stage is suspect of HOT heating or repeat failures. * Displays drive current to ID intermittent drive defects without damaging replacement horizontal output transistors. HORIZONTAL DRIVER & OUTPUT STAGE The horizontal driver stage produces output drive current to the base/emitter junction of the horizontal output stage. Defects reduce this current causing H.O.T. heating, failures and improper horizontal output stage operation. Methods used to control driver stage output current with horizontal scan frequency changes. Adjust V+ to Driver Stage Switch resistance in base of H.O.T Horizontal Driver Test - Push & Hold Red Test Button How To Perform the Horiz. Driver Test 1. Remove AC voltage - unsolder H.O.T. base or open base circuit path. 2. Connect Dynamic Test Leads 3. Set DYNAMIC TESTS Switch to “HORIZ. DRIVER TEST.” 4. Apply AC voltage to chassis - Push Power switch to ON. 5. Push & Hold the HORIZ DRIVER TEST OR SUB DRIVE Pushbutton. 6. Read the mA reading & compare to typical mA range chart. Block Diagram of Horiz. Driver Test Base Sub Drive & Gate Subdrive Provides substitute horizontal drive, optimized to drive the base (bipolar output) or gate (MOSFET output) transistor. Subs for missing or suspect horizontal drive to test the horizontal output stage or to isolate subtle reduced deflection, noises or unusual picture horizontal tearing defects. Display Before & During Base or Gate Sub Drive Be sure Frequency matches signal source. Be sure B+ voltage is proper or regulated. During Subbing collector DCV, VPP puse uS readings are displayed. Substitute Horiz. Drive To The Base or Gate of Horizontal Output Transistor (Base -Bipolor, Gate - MOSFET) Block Diagram of HA2500 Base Sub Drive Output drive current is dynamically adjusted. Gate Sub Drive Block Diagram To Substitute Base Drive to the Horizontal Output Transistor (Bipolar) 1. With AC power removed unsolder the Horiz. Output transistor base or open base circuit path. 2. Connect Dynamic Test Leads - Blue to base of H.O.T. Yellow to H.O.T collector, Black to Horiz. Ground. 3. Set the Dynamic Test Swtich to “Base Sub Drive.” 4. Apply AC to the chassis and read the DCV readout to confirm proper B+. 5. Read the display kHz readout to confirm the proper drive frequency. 6. Push & hold the Horiz. Driver Test or Sub Drive push button. 7. Read the DCV, VPP and uS readouts to test the horizontal output stage. Note: Proper readings indicate normal output stage operation. Synced With Generator A Locked Picture Appears SUBSTITUTE B+ SUPPLY A variable DCV power supply to substitute for the B+ voltage to the horizontal output stage or to the HV/Deflection regulator. Determines if the horizontal output stage is good or bad by subbing for a dead or suspect B+ power supply. Isolates defects to B+ supply, regulator, or horizontal output stage. Permits slowly increasing B+ voltage to isolate HV breakdown failures, troubleshoot current shutdown and regulation defects. Isolate X-ray or HV shutdown symptoms.I Typical B+ Voltage Path In Multi-Frequency CRT Display Using The Substitute B+ Supply To Substitute B+ Voltage To a Horizontal Output Stage 1. Remove AC to the chassis and open a jumper wire, coil or resistor in the B+ power supply path to the flyback. 2. Set the HA2500 VOLTS Control to “off” and the POWER LIMIT control to 1/2 scale (40W). 3. Connect the B+ Supply Leads to the chassis. 4. Connect the Dynamic Test Leads to the chassis horizontal output transistor. 5. Set the Dynamic Tests Switch to “Collector Or Drain.” 6. Apply AC Power to the chassis. 7. Increase the VOLTS Control to apply substitute B+ volts. (Increase the B+ sub voltage until the Collector Or Drain meter indicates normal VPP for the chassis) B+ Substitution to the Input of HV/Deflection Switching Regulator Using the Substitute B+ Supply and Sub Drive Together Congratulations- You are now an experienced Universal Horizontal Analyzer (HA2500) User!