Toshiba 40L310U with potential control board issue


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Toshiba 40L310U with potential control board issue

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frogcm
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Jul 25, 2017, 2:48 AM

Post #1 of 4 (4377 views)
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Toshiba 40L310U with potential control board issue	Can't Post

I've got a Toshiba 40L310U that is not powering on.

When disconnected from the control board, the power supply board has +5V on, ~3.3V on the PWON line, and nothing on either +12V. As soon as the control board is connected, all of the supplies (+5V & both +12V) turn on and when I apply voltage to the BLON pin in this state, the backlight comes on.

I suspect the problem lies with the control board and I've tried a mild heat gunning. All of the regulators on the control board seem to be working properly (+5V, +3.3V, +1.18V).

What else can I check or do before replacing the control board?

Thanks

jts1957
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Jul 25, 2017, 3:20 AM

Post #2 of 4 (4376 views)
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Re: [frogcm] Toshiba 40L310U with potential control board issue [In reply to]	Can't Post

Prove that with all connected PWON toggles from one voltage state to another with each press of a power button.

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frogcm
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Jul 26, 2017, 11:24 AM

Post #3 of 4 (4335 views)
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Re: [jts1957] Toshiba 40L310U with potential control board issue [In reply to]	Can't Post

With everything connected, PWON stays at 3.28V regardless of what happens with the power button. The power button itself has 3.3V to it and shorts to ground whenever pressed. The remote causes no change to PWON either.

Without the control board connected, PWON is low and the 12V regulator is off, which I expect should be the state of the unit with the control board connected, before the power button is pressed. So, it seems to me that the control board is continuously pulling PWON high and otherwise misbehaving.

jts1957
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Jul 26, 2017, 5:41 PM

Post #4 of 4 (4333 views)
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Re: [frogcm] Toshiba 40L310U with potential control board issue [In reply to]	Can't Post

Since the Main board is no longer in control of P-ON (or BL-ON) it is therefore a likely candidate.

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Location: Far, Far Away

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