Sony D98 chassis Operation Manual page 18

Troubleshooting Hints
See attached FLOW CHART to confirm if is really an HV/Protect Circuit issue.
No HV / No Power
Perform basic checks of Q901 and Q902 first. If both Q901 and Q902 were not broken, check the HV Drive pulse at the gate
of Q901. If no pulse, check R911 and D903. Otherwise, check R910, D901 or try changing IC805.
No G2 Voltage
Check R918 and D906.
Protect Malfunction
To see if HV Prot or ABL Prot are suspect check the Shutdown Log data at the Shutdown Log register. Refer to Shutdown
Log Table below.
When an HV Shutdown is indicated, check all N board connections, R917, R921 and D905 or, replace T901 (FBT).
Where ABL Shutdown is indicated, check the voltage T901 pin#11.
If it is higher than 0.5v immediately prior to shutdown, check connections all the way to N board. Should the voltage reach
and remain at the 0 volt level, even after the first 2.0 seconds of Power On, check D909 and 904 or check White Balance.
SHUTDOWN LOG TABLE
Bit Register value Shutdown Mode
bit7 128
bit6 64
bit5 32
bit4 16
bit3 8
bit2 4
bit1 2
bit0 1
7. Protection Circuitry Overview
Overview
The 19D98 chassis was developed with protection circuits other than HV/ABL.These protection circuits are controlled by
the N board mounted Microprocessor(IC1001);
- B+ Shutdown: Activates when the secondary of the power supply is overloaded.
- S Cap Switch Shutdown: Activates when any of S-Cap Switching FETs are broken.
- V Scan Shutdown: Activates when Vertical Deflection signal is absent or of insufficient level or of a distorted nature.
- H Scan Shutdown: Activates when Horizontal Deflection signal is absent or of insufficient level or of a distorted nature.
Troubleshooting Hints
B+ Shutdown
Refer to POWER SUPPLY section.
S Cap Switch Shutdown
In the event of failure of any S-Cap Switching FETs, and Remote or AC Power switch was turned Off/On, the Micropro-
cessor detects FET gate damage and goes into shutdown mode. For these conditions, refer to the section of H Linearity
Circuit.
Vertical Scan Shutdown
If the V FBP feedback at pin #42 the Microprocessor becomes less than +2.5V, a Shutdown will be initiated. Power Supply
problems may also produce a similar type failure. For these conditions, refer to the V Deflection Circuit or the Power
Supply section.
Horizontal Scan Shutdown
If the H FBP feedback at pin #32 of the Microprocessor becomes lower than +2.5V, Shutdown will be initiated. Some
power Supply problems may also produce a similar type failure. For these conditions, refer to the H Deflection Circuit or
Power Supply sections.
Comment
N/A
B+ Shutdown Explained later
S cap Shutdown Explained later
ABL Shutdown Hardware Controlled
HV Shutdown Hardware Controlled
HV U Shutdown Not Used
No Vertical Explained later
No H Pulse Explained later
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18
N/A
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