Hitachi Power LED flashing

[mick4555]

HITACHI 32HB26T61U Smart TV

When plugged in the power LED flashes 8 times and then nothing so I presume thats an error code but I cannot find anything on the internet about it so I am hoping that somebody on here can help.
Board No,s
17MB211S
IPS62



Thank You

[nomoresonys]

Maybe start with testing the voltages at the connector on the powerboard with the cables all hooked up, it's the connector that the cable from powerboard to mainboard hooks into, most times there's a legend/map nearby that gives the expected voltages, you measure them with your mutimeter, set meter to 20 vdc then report them, put neg probe on chassis metal ground, pos probe on pin of connector, measure in standby take note, leave probes where they are then power on tv and again take note of voltages, report them here, example pin 1-ps-on-0 volts standby-power on-3.3 volts. Try to post some clear straight on pictures of each board and one of the whole back to see how they are connected if possible.

[mick4555]

Hi
I have tried to look into things a bit further and actually manage to get a universal remote to switch it on and of but still no go. I have found now that the Standby led flashes 12 time when you pwer it of before standby.
The voltages bet the powerboard and mainboard I have tried to show on the diagram in the pins image.
Also I found that the voltage to the backlight led seems to be at about 0.5 while in standby and the goes upto about 5v and slowly dropping off when powered on.

[dick_barton]

Check the standby voltage (pin 3) changes when you turn on the TV out of standby

There should be 24V between the two legs of C55 to power the backlight booster circuitry.

[mick4555]

hi
Checked pin 3 it goes from 3.26v in standby to 0.06v power on

Voltage across c55 is 42v standby and 62v power on

Looks like the diagram of pins is upside down pin 1 is at the bottom

Thanks
Mick

[dick_barton]

If this is you schematic then C55 capacitor is on the 24V supply and the cap is rated at 35V so it cannot have 62V at power on

[mick4555]

Hi

I have rechecked the capacitor with leads connected to both the leads of the capacitor marked in the picture with 3 meters and it shows 42v on standby and 62 power on.
The capacitor is stuck down so cant read the rating on it but it sounds like major problems


Thanks
Mick

[mick4555]

Hi

I have just checked the voltages on either side of Diodes D23 D24 D25 and its showing 26v-28v ac on one side and 62v dc 0n the other of each one

[nomoresonys]

Recheck those diodes, WITH TV UNPLUGGED from power, meter in diode mode, check then reverse probes, should have a reading in one direction and none when probes reversed, if any read strange, take it out of circuit and recheck, keep in mind other components in the circuit could make the diode read differently, if any one seems different than the other then maybe check it out of circuit, maybe check all the diodes just for good measure and the resistors.

[yokoono]

If the left LED flashes, goes out and stays off you have defective LEDs in the backlight. If the left LED flashes non-stop you have software problems.
At 62V the backlight had to turn on. Conclusion: defective backlight.

[mick4555]

Hi sorry it sound like there is some confusion arising. The led that is flashing is the standby led on the front panel. The 62v reading is at the c55 capacitor I have now managed to unstick it from the board and it is only rated 50v. I have checked the big diodes on the top off the board and they all seem ok.
The outlet for the backlight led only shows about 7v which drops off to nothing very quick.

[mick4555]

sorry got it wrong after checking again the 62v does get to the led backlight connector I was checking the wrong side (red wire) then the return goes to
an ic MP3398A but they are not turning on so looks like backlight issue.

Thanks

[dick_barton]

What is the voltage on Pin 2 of the IC (EN input)

What dc voltage do you have on either end of D6 (or D10). Have you checked them out using your meter in diode mode

[dick_barton]

There are only 2 sets of led strips each with 11 leds so if in series would be 22 leds at say 3.2V each = 70.4V
I think you have an open circuit led(s) or open circuit in the connections to or between the two strips.

https://tinyurl.com/y6rgjodr

[mick4555]

hi
It shows 62-63v on both ends of D6 yes I tried the diodes in diode mode and they seem ok. The IC is on the back of the board so not very easy to get at.
Looks like I will be trying to dismantle the display tomorrow not the best job going.

Thanks Mick

[dick_barton]

I would hold fire on dismantling the panel for the moment because I am a little confused. Although the schematic is not the same as your power supply it appears to be similar.

I would have expected D6 to have 24V on the one side of it and the boosted led voltage on the other side and not for both sides to read the same.

If anyone else could offer their opinion it would be helpfull.

[dick_barton]

What is the voltage rating of the capacitor marked in blue circle?

[dick_barton]

Originally Posted by dick_barton

What is the voltage rating of the capacitor marked in blue circle?

Would help if I included the photo

[mick4555]

Hi

the capacitor circled in blue is rated at 100v
the capacitor with the red mark on is rated at 50v

Unfortunately I have just powered it up to see if I can make out any sign of life on the display and with a light shining on it and the input list was just about visible with the light in the right place but I have also noticed that the panel is broken so no go. I am not sure how long the people that brought it to me had been carrying it in there car.

Thanks for your help
Mick

[dick_barton]

That's a pity.