REPAIRING AND NOT THROWING AWAY

REPAIRING AND NOT THROWING AWAY

Richtige Fernseher haben Röhren!

Richtige Fernseher haben Röhren!

In Brief: On this site you will find pictures and technical information about Service Modes, Circuit Diagrams, Firmware Update procedure, Disassemble procedure, Universal remote control set-up codes, Troubleshooting and more....

If you go into the profession, you will obtain or have access to a variety of tech tips databases HERE IT IS Master Electronics Repair !.

These are an excellent investment where the saying: 'time-is-money' rules. However, to learn, you need to develop a general troubleshooting approach - a logical, methodical, method of narrowing down the problem. A tech tip database might suggest: 'Replace C536' for a particular symptom. This is good advice for a specific problem on one model. However, what you really want to understand is why C536 was the cause and how to pinpoint the culprit in general even if you don't have a service manual or schematic and your tech tip database doesn't have an entry for your sick TV or VCR.

While schematics are nice, you won't always have them or be able to justify the purchase for a one-of repair. Therefore, in many cases, some reverse engineering will be necessary. The time will be well spent since even if you don't see another instance of the same model in your entire lifetime, you will have learned something in the process that can be applied to other equipment problems.
As always, when you get stuck, checking out a tech-tips database may quickly identify your problem and solution.In that case, you can greatly simplify your troubleshooting or at least confirm a diagnosis before ordering parts.

Happy repairing!
Today, the West is headed for the abyss. For the ultimate fate of our disposable society is for that society itself to be disposed of. And this will happen sooner, rather than later.

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..............The bitterness of poor quality is remembered long after the sweetness of todays funny gadgets low price has faded from memory........ . . . . . .....
Don't forget the past, the end of the world is upon us! Pretty soon it will all turn to dust!

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Friday 15 March 2019

PROJECTION TV_ZENITH_ST-BY POWER SUPPLY SHUT-DOWN CAUSES & DEFLECTION_ SCHEMATIC [CIRCUIT DIAGRAM]

PROJECTION TV_ZENITH_ST-BY POWER SUPPLY Shut-Down Causes & DEFLECTION_ SCHEMATIC [Circuit Diagram]


DEFLECTION CIRCUIT
ST-BY POWER SUPPLY CIRCUIT
POWER SUPPLY SHUTDOWN EXPLANATION
Shut down occurs when the shutdown SCR QP01 is activated by gate voltage. When QP01 receives gate voltage of 0.6V, the SCR fires and give a ground path for the pin (5) of Connector PQD2 called PROTECT. This Low is routed to the Sub Power Supply PWB and is impressed on the base of the Relay Driver Transistor Q911 turning it Off. When Q911 turns Off the Relay S901 will disengage and remove the AC source from the Deflection Power Supply.
VOLTAGE LOSS DETECTION
1. Shorted 220V (DP31 and DP32) Inverted by QP03 then through DP22 The cathode of DP31 is connected directly to the 220V line. If it shorts this circuit is activated and pulls the base of QP03 low. This output High is routed through DP22 to the gate of the Shut Down SCR QP01.
2. Shorted SW+8V (DP33) Inverted by QP03 then through DP22 The cathode of DP33 is connected directly to the SW+8V line. If it shorts this circuit is activated and pulls the base of QP03 low. This output High is routed through DP22 to the gate of the Shut Down SCR QP01.
3. Shorted 28V (DP30) Inverted by QP03 then through DP22 The cathode of DP30 is connected directly to the 28V line. If it shorts this circuit is activated and pulls the base of QP03 low. This output High is routed through DP22 to the gate of the Shut Down SCR QP01.
4. Shorted Side Pin Cushion Circuit (D760 and Q754) then through DP34 The Side Pin Cushion circuit is comprised of I651, Q652 through Q657 If a problem occurred in this circuit that creates a Low on the cathode of D760, the low will be routed to the base of Q754, turning it
Off. This output High is routed through DP34 to the gate of the Shut Down SCR QP01.
5. Shorted Deflection Transformer or Misoperation (D756 and Q754) then through DP34 The Deflection circuit generates the actual Drive signal used in the High Voltage section. If a problem occurs in this circuit, the CRTs could be damaged or burnt. D757 is connected to D759 which is normally rectifying pulses off the Deflection Transformer T753. This rectified voltage is normally sent through D757, D756 to the base of Q754 keeping it On and it’s collector Low. If the Deflection circuit fails to produce the pulses for rectification, the base voltage of Q754 disappears and the transistor turns Off generating a High on its collector. This output High is routed through DP34 to the gate of the Shut Down SCR QP01.
6. Heater Loss Detection (DH26, DH27,QH07 and DP34).  This voltage does not go to the CRTs.The Flyback Transformer TH01 generates a pulse called Heater. (Note: This does not go to the CRTs as heater voltage, it’s used for Excessive High Voltage Detection. If a problem occurs
in this circuit, the Excessive High Voltage Detection circuit wouldn’t operate. It would be possible for there to be High Voltage but the circuit detecting Excessive High Voltage couldn’t work. DH26 is connected to DH24 which is normally rectifying pulses off the Flyback Transformer TH01. This rectified voltage is normally sent through DH26, DH27 to the base of QH07 keeping it On and its collector Low. If the Heater Pulse fails to produce the pulses for rectification, the base voltage of Q754 disappears and the transistor turns Off generating a High on its collector. This output High is routed through DH30 to the anode of DP34 to the gate of the Shut Down SCR QP01.
NEGATIVE VOLTAGE LOSS DETECTION:
7. -M28V Loss Detection (DP23, DP24) RP31 (18K ohm) is connected to the negative –M28V line and RP30 (22Kohm) is connected to the positive +29V line. The Cathode of DP23 monitors the neutral point where these two resistors are connected. If the negative voltage disappears, the zener DP23 fires. This high is routed through DP24 to the gate of the Shut Down SCR QP01 and Shut Down occurs.
8. SW-8V Loss Detection (DP28, DP29) RP26 (3.3K ohm) is connected to the negative SW-8V line and RP25 (3.3Kohm) is connected to the positive SW+8V line. The Cathode of DP28 monitors the neutral point where these two resistors are connected. If the negative voltage disappears, the zener DP28 fires. This high is routed through DP29 to the gate of the Shut Down SCR QP01 and Shut Down occurs.
EXCESSIVE CURRENT DETECTION:
9. 120V Deflection Power Supply (RP17, QP02, DP15, DP16 and DP18) If an excessive current condition of the Deflection B+ is detected by RP17 a 0.47 ohm resistor, the base of QP02 would drop. This would turn on QP02 and the high produced at the collector would fire zener DP15. This High would be routed through DP16 through DP18 to the gate of the Shut Down SCR QP01 and Shut Down occurs.
10. 28V Vertical IC I601 Power Supply (R645, Q609, D615, and DP34) If an excessive current condition of the Vertical B+ is detected by R645 a 0.68 ohm resistor, the base of Q609 would drop. This would turn on Q609 and the high produced at the collector would be routed through D615 through DP34 to the gate of the Shut Down SCR QP01 and Shut Down occurs.
VOLTAGE TOO HIGH DETECTION:
11. Excessive High Voltage Detection (DH31, RH54, RH55 and DH24). Sensed from the Heater Voltage generated from pin (5) of the Flyback Transformer TH01. Also, (DH42) sends a high command to the Horizontal Driver IC IH02, to defeat Horizontal Drive Output The Flyback
Transformer TH01 generates a pulse called Heater. (Note: This does not go to the CRTs as heater voltage, its used for Excessive High Voltage Detection). If this voltage goes too high indicating an excessive High Voltage condition, the voltage divider comprised of RH54 and RH55 would impress a high on the cathode of DH31.  This high is routed through DH34 to the gate of the Shut Down SCR QP01 and a Shut Down occurs.
12. Side Pincushion failure generating a High. (D754, and D753) The Side Pin Cushion circuit is comprised of I651, Q652 through Q657 If a problem occurred in this circuit that creates a High on the cathode of D754, the High will be routed through D753 to the gate of the Shut Down SCR QP01.
13. Deflection B+ Too High. (DP17, RP21 and RP22 RP21 and RP22 form a voltage divider. The top side of RP22 is monitored by DP17. If this voltage goes too high, zener DP17 will fire. This high is routed through DP18 to the gate of the Shut Down SCR QP01 and Shut Down
occurs.
14. Heater Voltage from the Deflection Power Supply Too High Detection. (DP27 and DP28) The Heater Voltage for the CRTs filament is generated in the Deflection Power Supply. This voltage is monitored by DP27. If this voltage goes too high, zener DP27 will fire. This high is routed through DP28 to the gate of the Shut Down SCR QP01 and Shut Down occurs.
Posted By: FRANK at 06:21
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