Hi all
I got hitachi tv that wont turn on when i press power buton all it does is makes relay clicking noise but wont turn on.

I diasembled tv and on power unit found 2 diods burned

Can any one tell me is diod can cause it please?

Thanks

 

I have removed diods from board mesuared with multimeter and i have 470v on
Negative to negative and positive to positive
And reads 0 other way round is that ok 470v?

Thanks

 

Replace them with similar ones,and check the other side of PCB to see if traces are damaged.

 

Hello,

It looks like the diodes have been very hot, but are not burned (the PCB is discolored).
Check the large capacitors for bulging or leakage.

Does the meter have a diode test function?
This should read OL (or an other value for open lead) in one direction and about 0.5 to 1 (the voltage for the test current) in the other direction.

Bertus

 

To me it seems that traces are damaged since it looks like the discolored part is following a trace.

 

Its shows ol in one and 471 in other direction

Traces are fine

What can couse this problem where i need to start looking

Thanks

 

Check the caps like bertus said they generally are cause of problem in PSU.

 

All caps looks like new
It have fan on supply when i turn tv on fan spins just for split sec then click noise and off again

Thanks

 

The click noise is from the relay shutting down the TV.Since you cant get the error code you will probably have to take it to a repair shop or order a new PSU which is like 60€,check the fuse.
For how long did you have the TV?

 

Hello,

It looks like the powersupply goes into protection.
There must be an overload somewhere.

Bertus

 

How do i check it or where to start checking?

Thanks

 

Try some stuff from this webpage.
But still I wouldn't be messing with 90V unless I'm a professional repairman.

http://www.justanswer.com/tv-repair/6ev5e-hitachi-42pma400e-turn-no-picture-no-sound.html

 

Checked to that link

Got 5v to pin 6
And pin 1 &10 gnd 6 i got no voltage at all

What else can i check?
Thanks

 

Got tv on some how !!!

I gonna do some deep investigation to power supply

Thanks all

 

Tell us what did you do in case someone has the same problem.

 

Gone true pdf u send me

All was linking to power supply

Then i just gently moved all parts just in case of cold solder

Then pluged cable in boom fan did not gon off
Looked at the screen boom picture

Now testing in case it go funny again

At least i know here power unit cause it

Thanks

 

Hi all
I got hitachi tv that wont turn on when i press power buton all it does is makes relay clicking noise but wont turn on.

I diasembled tv and on power unit found 2 diods burned

Can any one tell me is diod can cause it please?

Thanks

Discolouration of the PCB is not as uncommon as it should be!

A DMM set to the diode test range should be used to check each diode out of circuit.

Its more likely that something on the load side of things is shorted and activating the PSU overcurrent shutdown.

A relay clicking could be the delay circuit for degauss in a CRT TV - the only thing I can think of a relay for in a LCD TV is possibly inrush surge limiting, either way it probably doesn't indicate much about the fault.

 

Its shows ol in one and 471 in other direction

Traces are fine

What can couse this problem where i need to start looking

Thanks

If those readings are from an analogue meter Ohms range, the 471 is pretty much meaningless.

Most DMMs have a diode check range that gives the forward volt drop of a diode - the reading gives some clue to what type of diode it is.

For leakage; you need to reverse the test leads and switch to the highest resistance range - normally any leakage indicates a faulty diode, but Shottky barrier diodes show some leakage as normal - recheck the forward voltage, a SB diode should read possibly as low as 0.2V.