Toshiba Blu-Ray Player - No Power

[caphair]

All the voltages are present even standby but there is no standby light and unit doesn't respond to any keys.

Ps_on has 1.4v and does not change when power button pressed. I've tried grounding that pin and still nothing happens.

Mainboard issue?

[ohmmy]

Re: Toshiba Blu-Ray Player - No Power

Does sound like a main board issue. Maybe someone else can be of more help

[budm]

Re: Toshiba Blu-Ray Player - No Power

So what voltages do have on the connector of the power supply (5V, 12V, 5VSTBY) as shown by the labeling on the board? Since the PS_ON signal does not toggle which will point to problem on the main board.

[goontron]

Re: Toshiba Blu-Ray Player - No Power

So what voltages do have on the connector of the power supply (5V, 12V, 5VSTBY) as shown by the labeling on the board? Since the PS_ON signal does not toggle which will point to problem on the main board.

he pulled the PSon on to ground, if the PSU was good wouldn't it have powered on?

[budm]

Re: Toshiba Blu-Ray Player - No Power

Since ps_on is sent from the main board to turn on the switched 5V and the switched 12V, if PS_ON is stuck high then he should see the switched 5V and switched 12V, he indicated all the voltages are present but did not say if they are correct voltage, and if he ground the PS_ON then the switched 5V and the switched 12V should go away. Most power supply uses active high, but he can find out by seeing if the switched 5V and switched 12V change state.

[caphair]

Re: Toshiba Blu-Ray Player - No Power

So what voltages do have on the connector of the power supply (5V, 12V, 5VSTBY) as shown by the labeling on the board? Since the PS_ON signal does not toggle which will point to problem on the main board.

12.45v
5.20v (vcc)
5.20v (vcc)
5.14v (standby)
1.4v (ps_on)
3.30v (open/close) - eject this goes down to 1.20v when pressed but disc tray does not react.

Would the main board issue be the microprocessor? It feels pretty hot to the touch for such a small board and chip.

[caphair]

Re: Toshiba Blu-Ray Player - No Power

Since ps_on is sent from the main board to turn on the switched 5V and the switched 12V, if PS_ON is stuck high then he should see the switched 5V and switched 12V, he indicated all the voltages are present but did not say if they are correct voltage, and if he ground the PS_ON then the switched 5V and the switched 12V should go away. Most power supply uses active high, but he can find out by seeing if the switched 5V and switched 12V change state.

When I grounded ps_on I did not remeasure voltages but with the mainboard disconnected I don't get all the voltages at the output pins

[budm]

Re: Toshiba Blu-Ray Player - No Power

so it looks like the PS_ON is stuck high (that is why all the outputs are present), it should toggle HI/LO when power switch is toggle.
"Would the main board issue be the microprocessor? It feels pretty hot to the touch for such a small board and chip."That is the possibility right now you are having main board problem. The IC should not be too hot to touch.
"When I grounded ps_on I did not remeasure voltages but with the mainboard disconnected I don't get all the voltages at the output pins" That is normal since the power supply is no longer receiving the PS_ON to turn on the switched 5V, 12V; only 5VSTBY will be present.

[caphair]

Re: Toshiba Blu-Ray Player - No Power

So it essentially can't be repaired without replacing the entire board?

If the ps_on is stuck high, shouldn't the unit just constantly be on and working? Lol

I tried spraying the chip with freeze spray to see if any changes occur and it didn't.

[mmartell]

Re: Toshiba Blu-Ray Player - No Power

Not if it's more than just the pson signal. Sounds like there is no processing of any kind going on.

[stj]

Re: Toshiba Blu-Ray Player - No Power

find the reset circuit on the mainboard.
dont ask, find a schematic or learn what it is.

start at the cpu's reset pin
*and make sure the oscillator/crystal is running.

[caphair]

Re: Toshiba Blu-Ray Player - No Power

find the reset circuit on the mainboard.
dont ask, find a schematic or learn what it is.

start at the cpu's reset pin
*and make sure the oscillator/crystal is running.

Is this different than unplugging the unit and holding down the power button for 30 seconds?

I can't find a schematic anywherefor this. Only a user's manual. Is there something I can try without one?

[stj]

Re: Toshiba Blu-Ray Player - No Power

get a datasheet for the cpu.

[caphair]

Re: Toshiba Blu-Ray Player - No Power

I couldn't find one for it. I searched "Mediatek MT8551"

[budm]

Re: Toshiba Blu-Ray Player - No Power

This Philips uses the same MT8551, see SCH for pinout.

[caphair]

Re: Toshiba Blu-Ray Player - No Power

This Philips uses the same MT8551, see SCH for pinout.

Thanks a lot! Looks very similar. So I found the reset pin, how do I actually do that? Ground it?

[stj]

Re: Toshiba Blu-Ray Player - No Power

meter or scope it to see what it does when you connect the power.
what it *should* do is go to ground for a fraction of a second, then go to the main voltage - that i assume is 3.3v

if it stays grounded then you need to find out why,
if not, you can connect it to ground for a second to see if he cpu starts.

and check the clock crystal / oscillator.

[caphair]

Re: Toshiba Blu-Ray Player - No Power

Ok so I thought I found the reset pin but in fact there are two spots on underside of the main board labeled test1 and test2 which I misread as "reset1 reset2"

That schematic doesn't give a detailed look at what pin exactly is reset on the cpu

[stj]

Re: Toshiba Blu-Ray Player - No Power

well i took a quick look, it does have the reset circuit together with a 5v to 3.3v regulator that's related.
i dont know how similar yours is though.
did you check any crystals or oscillators?

[caphair]

Re: Toshiba Blu-Ray Player - No Power

I found a similar circuit like that 5v to 3.3v its labeled 3.3v and has a white border to distinguish the components within it.

I did try grounding one end of a resistor that had 3.3v on it in that circuit similar to the schematic but nothing happened. No change.

I don't have an oscilloscope to test the crystal unfortunately