Sanyo DP50843 Won't power on.

[tvprobs]

Hello,

I have a Sanyo DP50483. TV won't power on, however i do get 5V standby. When i plug in the set it automatically gives PS_ON 3.1V and the LINE_OFF voltage drops. BL_ON and BL_DM never show signs of life. The voltages i get on the connections to the main board (Listed below) are all stable except PS_ON. The big miss i see in this system is that the 15V for the backlight never gets above 12.6V. Also the PS_ON is getting 3.1V, I don't know if that's enough to get the system to switch on the 15V backlight circuit (Or maybe i need the PS_ON to go low?). I tried connected a resistor from 5V standby to PS_on and got the same readings except closer to 5V on the PS_ON.

I've seen a lot of Main board issues with these models online, but i don't know my way around them when they aren't labeled clearly for test points. I I did try a new EEPROM ($15 figured why not?), but i see absolutely no difference in the voltages throughout the whole system (Including caps on the main board)


PS Connections are as follows (1st number M.B. Not Connected, Second number M.B. Connected)

PS_ON (0V,,, 2.9V-3.1V)
GND
5V STBY (5.1V,,, 5.1V)
5V MAIN (5.1V,,, 5.1V)
GND
12VA (0V,,, 12.6V)
12VA (0V,,, 12.6V)
GND
15V (0V,,, 12.6V)
GND
LINE_OFF (5V,,, 3.2V)
BL_DM (0V,,, 0.1V)
DL_ON (0V,,, 0)
NC (0V,,, 12.6V)

[CapLeaker]

Re: Sanyo DP50843 Won't power on.

Disconnect the BLon and Dim pin from the main board at the PSU. Take two 1k resistors and jump STBY voltage to BLon and DIM. See what happens if you turn the TV on.

[tvprobs]

Re: Sanyo DP50843 Won't power on.

Disconnect the BLon and Dim pin from the main board at the PSU. Take two 1k resistors and jump STBY voltage to BLon and DIM. See what happens if you turn the TV on.

The backlights do come on when those are jumpered. VCC and CNT pins have 5V and 4V respectively. No other pins are active on the inverter connections.

[CapLeaker]

Re: Sanyo DP50843 Won't power on.

so your main board isn't sending BLon nor the dim signals. These are getting generated on the main IC.

[tvprobs]

Re: Sanyo DP50843 Won't power on.

so your main board isn't sending BLon nor the dim signals. These are getting generated on the main IC.

So for my understanding. When those signals are generated properly from the main board it will allow the power supply to run the 15V line at 15V instead of 12.5V? This then activates the inverter side of the PSU and supplies the 24V for the driver of the back lights?

Please correct if i'm missing a step or a connection.

[CapLeaker]

Re: Sanyo DP50843 Won't power on.

No. It won't do that. If you have low 15V, I'd check the main filter capacitors on the PSU. I guess you have 2 problems to tackle.

[budm]

Re: Sanyo DP50843 Won't power on.

https://assets.shopjimmy.com/media/c...6wj-bottom.jpg
12.6V on pin 9 (15V) reading is correct because the 15V power supply section is not stuffed with parts for this PCB assembly version, it has jumpers installed for connecting the 12V power supply section to pin 9 (15V) and pin 14 (NC), that is why you are getting 12V on pin 9 (15V) and pin 14 (NC). You can see at the bottom side of the board and see how pin 9 (15V) 7 pin 14 (NC) are wired.
The blank PCB can be stuffed to make many PCB assemblies as needed for many TV models.
So right now the main board is keeping the BL-ON and Dim control lines LO.

[tvprobs]

Re: Sanyo DP50843 Won't power on.

https://assets.shopjimmy.com/media/c...6wj-bottom.jpg
12.6V on pin 9 (15V) reading is correct because the 15V power supply section is not stuffed with parts for this PCB assembly version, it has jumpers installed for connecting the 12V power supply section to pin 9 (15V) and pin 14 (NC), that is why you are getting 12V on pin 9 (15V) and pin 14 (NC). You can see at the bottom side of the board and see how pin 9 (15V) 7 pin 14 (NC) are wired.
The blank PCB can be stuffed to make many PCB assemblies as needed for many TV models.
So right now the main board is keeping the BL-ON and Dim control lines LO.

OK. that makes perfect sense. I saw that on the back, but i haven't had that actually be a correct reading in the past. That's what i needed to know. I'll play around with the main board for a while and see what i come up with. Trying to dig in to these a little more on my own.

[tvprobs]

Re: Sanyo DP50843 Won't power on.

Well after much fiddling around. I gave in and just bought a new main board. TV works perfectly now. Thanks to all who gave input.

[budm]

Re: Sanyo DP50843 Won't power on.

Thanks for the follow-up.