hisense HLS106T69PZ missing lcd/on/off voltage

[attainteddragon]

all voltages are present from ps except the lcd on/off voltage, connection xp812, 10th pin down.
when starting from the touch pad, the voltage goes from 22mv to 61mv.
at this point all other voltages are stable and present, but the backlights are not present and with a torch, no image is on the screen.
i can jump the ps with resistors and the backlights work fine.
this must be a common fault, as i have 3 or 4 of them here, all in the same state.
thanks for any guidance.

[newtothis]

Re: hisense HLS106T69PZ missing lcd/on/off voltage

Mainboard.

PSU provides 5v Standby.. Main sends >2.5v to PSU when power button is triggered.. PSU receives >2.5v at ON/OFF pin and starts all other voltages.

So Main isn't sending ON/OFF signal.

[attainteddragon]

Re: hisense HLS106T69PZ missing lcd/on/off voltage

that was my thought, but as always, i would love to track the problem down.
i was trying to trace the signal, but main boards are a pain.

[Jay W]

Re: hisense HLS106T69PZ missing lcd/on/off voltage

I have the same exact issue with a Dynex(Hisense) main board. I have so far discovered that when the TV is first plugged in, the standby LED is lit. This made me think it was in full standby mode. Then I noticed that almost all of the components on the main board had voltage, like it thinks it is turned on. The power board connector shows that the 5,12, and 18 volt wires are energized. I dont have it right here but I believe PSU and STB are sitting at 0 volts, instead of having 3v when it would run normally.

On the power switch connector, without the power switch connected, it does not show the expected 3v, 3v, ground, 3v at the main board. Instead it shows lower voltages and the ground appears to have some voltage.

My current theory is that the strange voltages at the power switch connector are telling the processor to turn some things on when the TV is first plugged in, but not all, and the backlight and LCD are not up while the rest of the TV is powered on. Plus it is not really in standby mode like it should be.

And even though most of the TV is powered up, the CPU is confused and thinks it is not really in standby, so pushing the button does not get it out of standby. I will start tracing down the low voltages at the power switch connector to see if I can tell where that is originating. I have a similar working Hisense board that allows me to compare voltages.

So far I have changed the EEPROM and several of the main board electrolytic surface mount capacitors, but not all of them. Nothing yet has gotten it to work as I just discovered the odd voltages after changing some things.

[attainteddragon]

Re: hisense HLS106T69PZ missing lcd/on/off voltage

Have you tried to jump your power supply on to see if your psu is putting out the correct voltages and that your inverter is working properly.

I have recently discovered that hisense have an office not too far from me, and i will be contacting them shortly to see if they can shed some light on this issue, or offer a repair for it.

[CapLeaker]

Re: hisense HLS106T69PZ missing lcd/on/off voltage

Try taking the on / off pin out and jump the PSON pin on the PSU through a 1k ohm resistor to STBY voltage. Why taking the pin off? because you don't want do back feed voltage and maybe fry more. Now you control on / off, not the main board.

[attainteddragon]

Re: hisense HLS106T69PZ missing lcd/on/off voltage

I did think about trying something like that, but i wasn't sure if i could get away with it.
I can remove the ps on pin from the loom to protect the main board.

I'll put it back on the bench tomorrow and have another look over it.
Thanks capLeaker.

[attainteddragon]

Re: hisense HLS106T69PZ missing lcd/on/off voltage

Well, here is the update.
With the ps pin removed from main board loom and fed back to stby,
the back lights come on, but there is no display information. No signal, volume control, channel change etc. So I'm assuming that the ps on voltage also has other signaling paths on the main board.

on a good note, i dragged out another one of these sets and it is currently working, so i can get some running voltages to help assist a little.

Whatever is failing must be just out of the sets tolerances as this set had the identical fault when i last looked at it.

[CapLeaker]

Re: hisense HLS106T69PZ missing lcd/on/off voltage

Ok. To check the main board out, look with an oscilloscope at the LVDS, while flicking the menu on off all the time. You should see a signal change. Look at the T-Con board for blown fuses etc.

[attainteddragon]

Re: hisense HLS106T69PZ missing lcd/on/off voltage

This is my first time using a scope, so I'm taking my time to try and get things right.

With the on signal jumped, there is voltage on the lvds, but no data.
I also scoped the working set, and the data for the tv, having no signal, is clearly visable.

I then put the working main board into the faulty set to make sure there were no issues with the tcon and panel, and they are all good.