Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

[sordids999]

Hello

tv will not power up
upon testing the power supply i found 3 diodes i tested in circuit with giving readings both ways,so i thought they was blown but once removed they are fine SB5B5 5amp with readings of 290 are the readings low ? and could this still be the fault ?

thanks

[tom66]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

If they read different forward to backwards they're probably OK.

[tw2005]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

I don't know if this is just uncanny but the DIGIHOME post that's popped up has a variant of this PSU that I would say is very close and there's a lot of talk about those 3 diodes and one being faulty, replacing these and working again.

check it out. same diodes too

Edit: I think I misread your info, thought you said low readings but out of cct ok, so probably a waste of time now but maybe there's some other helpful info in there.

[sordids999]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

ok ill check that post out but i cant get a reading on voltages for U37 regulator its fluctuating or could the diode be doing this ?

[tw2005]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

ok ill check that post out but i cant get a reading on voltages for U37 regulator its fluctuating or could the diode be doing this ?

I think I jumped the gun, don't know. just saw the vestel PSU part number 1 below yours and thought it had the answer but thinking I'm just confusing things.

[tom66]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

ok ill check that post out but i cant get a reading on voltages for U37 regulator its fluctuating or could the diode be doing this ?

Did you check the diodes before jumping onto the main board?
If you suspect the power board to be bad (shorted diodes or otherwise) maybe try checking the power board output voltages.
Schematic:

[sordids999]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

sorry tom still going through the power supply even the voltages are fluctuating on the Psu so ill check all the diodes first

[sordids999]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

tested diodes i cant any shorted

[tom66]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

tested diodes i cant any shorted

Just to make sure. A good diode reads one value one way (150-700mV) and reads open (O.L. or single "1") another way. That's what you're getting?

[sordids999]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

correct tom
if i disconnect the main board from the power supply voltages are steady on the psu but with main connected voltages are fluctuating on mainboard and psu

[tom66]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

Ok, try checking voltage on pin 3 of CN3 (power board connector) marked ST_BY in schematic.

[sordids999]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

i have no legend CN3 thats blank my psu has CN4 which is pin 3 also but with mainboard connected i have 0.29 volts but fluctuating but with mainboard disconnected i have 0.00 volts

[sordids999]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

diode values as in attached picture diode HER307 have different readings compared to the one diode next to the SB5BS diodes not sure if that matters though ?

[tom66]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

They are different types of diodes, so it is fine.

[sordids999]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

thanks tom so due to not having any voltage from the ST_BY do you suspect its the Psu at fault ?

[tom66]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

STBY is a signal from the main board to the power board. So it could be a main board thought. I'm not sure until I've had a good look at the power board schematics. Will have a look later.

[sordids999]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

with the main board disconnected i have :
pin 1 24 volts=23 volts steady
pin 9 +5v_STBY =5 volts steady
pin 10 12 volts=11.7 volts steady

no other voltages on the rest of the pins

[tom66]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

Ok, do those go away with main board connected?

[sordids999]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

no tom with the main board connected pins 1,9,10 voltages just fluctuate

[tom66]

Re: Finlux 50F8090S-T STANDBY FLASHING WONT TURN ON

And the STBY pin is fluctuating?
It looks like the main board is causing problems.
You can try flashing it with new firmware, if you can get hold of a copy of it.
Otherwise, it is time to get a new main board, unfortunately.