Sharp Aquos LC-32LE600E, No 12v as no PNL_POW

[foxyUK]

Can anyone help me diagnose this? Almost not worth bothering with, but it has 'sentimental value' for the owner. I'm no TV technician, but dabble a bit.
The TV has standby power but no reaction at all to switching on or reboot steps, No flashing lights or response to menu button. All voltages on the power board are correct apart from missing voltage on pin 12 of CN7003.
There is 13 v on U7053 but no 3v signal to switch it on. I don't really understand whether the 3v should come from U7401 in the standby control area, or (as suggested elsewhere) from the mainboard via pin 12.
Also don't understand why the mainboard schematic shows PNL-POW, PS-ON, VON and LAMP-ERR as all on the same line, even though voltages measured are different.
Thanks!

[Diah]

at sticky
you are talking om label and pins name with out photos and measurements... so how some one can think and help ?

[foxyUK]

at sticky
you are talking om label and pins name with out photos and measurements... so how some one can think and help ?

Thank-you, but measurements are all OK apart from the missing ones, which are zero. Photos won't help, but can provide links to the schematics if helpful? I suspect it ideally needs someone familiar with the model or Sharp range at least.

[Diah]

sorry--- i did distributed yours threats... good luck for trouble shooting on yours own way

[foxyUK]

sorry--- i did distributed yours threats... good luck for trouble shooting on yours own way

Hello Diah;
I don't know what y u mean by the above... guess it's a language thing.
Anyway, I'll give this issue one more shot. I'll attach photos of the boards and bits of schematic. To recap, the TV has standby power and red standby light, but no reaction to switching on. I thought it may be a power issue, but now thinking more likely mainboard, which is likely out of my depth for troubleshooting.
The attached schematic shows part of the psu board (the other half deals with detecting backlight LED shorts, so hopefully not relevant). CN7003 voltages 13v, 3.3v (AC Detect and PS_ON), and 5v Bus are all correct. PNL_PWR (3.3v) is missing, and in consequence 12v power is missing on CN7004. This signal voltage is generated by a monitor microprocessor IC2002 on the mainboard.
I isolated the 'low' line from IC2002 and via a pullup resistor applied the 'high' 3.3v to pin 12 (PNL_POW) of CN7003. This brought up the 12v power as anticipated but has not changed the no-boot of the TV at all. This suggests that other faults are being flagged to IC2002, preventing start??
Unfortunately, replacement used main boards seem to be unavailable, and in any event the listed prices are higher than a similar used TV.






Although the TV is a 600e, the manual only shows variations from the base model, 700e.

[Diah]

so when you feed PNL_POW with 3.3V you got the 12V which missing.. mean PSU are working, but you should have one pins on the PSU for error if it go high,,, the MB will not send PNL_POW on and backlight too

[lotas]

In this model, due to backlight errors (Lamp - error), the memory with errors in the eeprom is full and the TV is blocked. If you have a programmer, you can try to reprogram the eeprom 24C64 (I have a firmware dump).

[Diah]

In this model, due to backlight errors (Lamp - error), the memory with errors in the eeprom is full and the TV is blocked. If you have a programmer, you can try to reprogram the eeprom 24C64 (I have a firmware dump).

yes this correct,,, but if this lamp_error go to Zero / chassis , there will be reset of LED driver boards and IC 2002, but the problem now we don't know when he feed the PNL_POW with 3.3V to switch it on ... if the wire of it he slide it out from PSU or MB or remain in place.... this critical points

[lotas]

When power is applied, the processor reads the eeprom (which contains errors) and does not give a command to turn on until the memory with errors is cleared.

[Diah]

When power is applied, the processor reads the eeprom (which contains errors) and does not give a command to turn on until the memory with errors is cleared.

yes i know this lotas.... there are option in service menu to disable ERROR_ON and some one tum it off then dumped it ... but if there are error indeed why i don't go a head to discover it and repair it ?

[foxyUK]

yes this correct,,, but if this lamp_error go to Zero / chassis , there will be reset of LED driver boards and IC 2002, but the problem now we don't know when he feed the PNL_POW with 3.3V to switch it on ... if the wire of it he slide it out from PSU or MB or remain in place.... this critical points

Thank-you both for your inputs!!

The PNL-POW wire from the Main to PSU was cut before driving PNL-POW high at the PSU.

Pin 6 of LB, IC7054 is indeed high, 3.3v. (is that the EEPROM? I don't have a parts list for the psu) I don't have the gear/ability to reprogram. Is there mileage in forcing this low with a pull down?

[Diah]

Thank-you both for your inputs!!

The PNL-POW wire from the Main to PSU was cut before driving PNL-POW high at the PSU.

Pin 6 of LB, IC7054 is indeed high, 3.3v. (is that the EEPROM? I don't have a parts list for the psu) I don't have the gear/ability to reprogram. Is there mileage in forcing this low with a pull down?

so you have indeed the Lamp-error pin high !

[lotas]

LCD TELEVISION TECHNICAL BULLETIN

[Diah]

LCD TELEVISION TECHNICAL BULLETIN

THX lotas this what exactly what i mean for the dump you mentioned before

[foxyUK]

Unfortunately, that procedure has no effect. Probably unsurprising, as there has been no board change or firmware revision.