Testing reset IC ncp803sn293 & 2sc3052 NPN Transistor

Collapse
X
Collapse
 
  • Page of 1
  • Time
  • Show
Clear All
new posts
Previous template Next
  • Chaks
    Senior Member
    • Sep 2015
    • 115
    • India
    #1

    Testing reset IC ncp803sn293 & 2sc3052 NPN Transistor

    I am trying to trouble shoot the power-detect part of the circuit see attached images and my readings are as below. can anyone suggest me if the IC and NPN transistor is working properly. The TV resets automatically when switched on.

    Q7502 2sc3052 npn transistor has the following readings.
    Base +lead to emitter -lead = 0.6v
    Base +lead to collector -lead =0.6v
    Emitter +lead to base -lead =over limit
    Collector +lead to base -lead = over limit

    Collector +lead to emitter -lead = 0.98 volts
    Emitter +lead to collector -lead = 0.68 volts

    POWER DET circuit:

    IC 7509 ( ncp 803 sn293)

    Pin 3 vcc to ground of PCB is 3.5 volts
    Resistance between pin vcc and reset pin 2 is 100k ohms
    The TV resets when pin 1 gnd or pin 2 reset is touched by multimeter leads pos or neg.

    IC 7510 (ncp 803 sn293)
    Pin vcc to ground of PCB is 0.9 volts
    Pin 3 vcc to gnd pin 1 is 1.9 volts
    Resistance between vcc and reset pin is 355k ohms
    Pin 1 gnd and pin 2 reset pin (+lead) is 3.6 volts
    Reset pin to ground of PCB is 1.2 volts

    Is there anything faulty here? Power-det circuit is on page 35 of the service manual.
    The service manual of TV is also attached.
    Attached Files
    Tags: None
    Previous template Next

    Related Topics

    Collapse
    • Superbee_dad
      Sharp 80” long short flash backlight error - Help
      by Superbee_dad
      Hello Sharp TV experts
      Our Sharp LC-80LE642U displays one short one long flash error code which is a backlight error. I went into service mode and there were 8 lamp error counts recorded. I reset the count to 0 and did a reset. The last monitor error cause was 16 B00014639:12. 16 is the code for backlight error. I tried to power the tv up but went back into error mode.

      > I checked voltages on the power supply board and they all check out .. including 3.28 volts at the error pin.
      > There is power to the cpu and T-CONN and no faults found there. The cpu has a flashing...
      01-24-2025, 11:51 PM
    • Mcfeetroy
      Fishing bite alarm drains battery
      by Mcfeetroy
      Good day to all. The bite alarm drains 9-volt Krona batteries. Current consumption when switched on is about 50 mA. I wiped the board from oxides, I will attach a photo (on the board there is a j3y transistor and a 7533 stabilizer, the microcircuit is erased = (the 3.3-volt stabilizer heats up weakly. I replaced it, nothing changed. I unsoldered the microcircuit, the consumption disappeared. The resistance on the pins of the unsoldered microcircuit from the point clockwise is more than 2 megaohms, the 11th leg is presumably ground. I warmed up the microcircuit, the consumption does not change....
      Today, 03:52 AM
    • MisterAIL
      PS5 digital / No Power / No Beep / Good power supply
      by MisterAIL
      Hi everyone,

      Brought a non functionnal PS5. Apparently only a bad PSU...
      No beep, nothing.

      After some tests i found this :
      - PSU is fine (12 volts stable)
      - 12 volts line is shorted
      - DA9065 was fried, F7003 also => Replaced both of them, short is gone on 12 volts line, no dead short anywhere else.
      - By the way, nothing change. No signal, no power, no beep.

      Mesuring all rails with my workbench psu (12 volts input)
      - 0.00 amp drawing
      - 12 volts, 5 volts, 2 volts, 1,15 volts are presents (suppose new DA9065 do is...
      3.3v PMIC
      5 Photos
      03-12-2024, 03:24 PM
    • odie34
      Sony OLED XR-77A80J - 5 Flashes But Turn On After Hard Reset
      by odie34
      I am a hobbyist (not a professional) so please be gentle...

      I recently received an XR-77A80J that wouldn't turn on. (Repeating 5 flashes when plugged in.)

      I did a hard reset by holding the power button for about 30 seconds until the set powered down. I then tried to turn it on and it powered up, bringing me to the setup screen. There's not a lot of detail on the setup screen but the picture didn't have any distortions, so at least a cursory examination suggests no physical damage to the screen. The set appeared to be working normally, but it shut down after about 15 seconds,...
      02-18-2024, 09:11 AM
    • ictc
      Philips MDP 3380/12 Blu-ray Player – No Power, Reset Signal Always High
      by ictc
      I'm troubleshooting a Philips MDP 3380/12 Blu-ray player that shows no signs of life. The display remains off, and no buttons respond.

      Inside, the power supply is working correctly, and all expected voltages on the mainboard match the service manual specifications. The CPU warms up slightly (checked with a thermal camera), the crystal oscillator is functioning, but the reset signal remains high at all times.

      The reset circuit appears to consist of two NPN transistors, one driven by 5V VCC and the other by 3.3V STBY, as shown in the attached schematic. Should the reset...
      02-25-2025, 12:15 PM
    • Loading...
    • No more items.
    Working...