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3Phase615V · 21st Oct 2019, 2:43 am

Hi Kevin,

Many thanks for replying to my post.

Looking at what you've suggested I guess I should have followed that track to the microprocessor before now.

I tested the voltages on Q953 and got the results below. So I pulled Q953 out of the board and tested it in my component tester and it appears to be okay.

Q953
E: 14.1 V
C: 0.8 V
B: 13.65 V

So then based on the collector voltage being lower on Q953 than stated in the SM (12V) I worked back to see if Q952 was functioning:

Q952
E: 0 V
C: 13.4 V
B: 0 V

Interestingly, the base is dead so I checked the voltage on the track leading from pin 20 (S/BY) on the microcontroller and it was 0V. I powered off the TV and connected up pin 20 to an analogue multimeter to monitor it on switch on. Immediately after powering the TV on the meter needle jumps to about 1.6V then immediately falls back to 0V. Just in case I checked the microcontroller was receiving sufficient power and it appears to be okay:

SAA5290 microcontroller
VDDM microcontroller power supply (pin 20) - 4.9V
+5 V analog/text power supply (pins 38/39) - 1.16V ( I assume these are not 5V as the TV is in standby)

So at this point I'm wondering if I need to pull out Q952 to test it's not the cause of the failure to switch on Q953?

Does that make sense?

21st Oct 2019, 2:43 am	#3
3Phase615V Tetrode Join Date: Nov 2011 Location: London, UK. Posts: 90	Re: Hitachi C1714TE stuck in standby Hi Kevin, Many thanks for replying to my post. Looking at what you've suggested I guess I should have followed that track to the microprocessor before now. I tested the voltages on Q953 and got the results below. So I pulled Q953 out of the board and tested it in my component tester and it appears to be okay. Q953 E: 14.1 V C: 0.8 V B: 13.65 V So then based on the collector voltage being lower on Q953 than stated in the SM (12V) I worked back to see if Q952 was functioning: Q952 E: 0 V C: 13.4 V B: 0 V Interestingly, the base is dead so I checked the voltage on the track leading from pin 20 (S/BY) on the microcontroller and it was 0V. I powered off the TV and connected up pin 20 to an analogue multimeter to monitor it on switch on. Immediately after powering the TV on the meter needle jumps to about 1.6V then immediately falls back to 0V. Just in case I checked the microcontroller was receiving sufficient power and it appears to be okay: SAA5290 microcontroller VDDM microcontroller power supply (pin 20) - 4.9V +5 V analog/text power supply (pins 38/39) - 1.16V ( I assume these are not 5V as the TV is in standby) So at this point I'm wondering if I need to pull out Q952 to test it's not the cause of the failure to switch on Q953? Does that make sense?