Oevia 252fhd-t11 DPS-408AP B power supply

[mcross]

I have a Olevia 252fhd-t11 that the power supply is only putting out 12v to the inverters, should be 24v, there is no 24v coming from the ps anywhere. I put in pic;s with the top removed from the heatsink on the dc side. Tv has sound but no backlight, was working sometime and not others. PS is a Delta DPS-408AP B
Any ideas
Mike

[retiredcaps]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

The main board controls VBL (backlight) and probably VLAMP (???). I'm guessing VBL should be HI (> 3V). VLAMP might also need to be HI in order for the backlights to come on.

[tom66]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

Try checking the voltage across the large 390uF 450V capacitor. I don't think I've ever seen an LCD power supply with such a large capacitor, assuming it's using PFC (more than likely.)

[mcross]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

The vbl is 2.3v, nothing on the vl, the big cap is 398v
must be in the vl ?
Mike

[tom66]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

398V is good, but on the 24V pins, you only have 12V? Can you see what they measure with the inverters unplugged?

[mcross]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

Tom66,
with them unpluged I still get 12v
By the way the vlamp is not used as there is no connector going to it
Mike

[multimeter]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

are you getting stable and correct voltage PS-ON ?,this will come from main board to PSU

[mcross]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

I am glad you asked, did not check before, only getting 2.2v on ps-on and 5v sectionis only reading 2.4v

[multimeter]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

sounds like a problem on main board,not fully turning the psu on,can you put a resistor between PS-ON and STB PIN?,to see if the power supply voltages comes up?this would be with the main board disconnected

[tom66]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

Can you unscrew the large heatshield covering the left hand side of the board?
https://www.badcaps.net/forum/attach...7&d=1369856268
then show us what lies within. Don't run the PSU for longer than 30 seconds at a time with that shield off.

[multimeter]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

can we have a good quality pic of the main board also?

[tom66]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

2.2V on PSON should be fine.

[mcross]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

Tom that one i an not as it is soldered and has ic's or regulators atached,
I put the resistor on and checked , it is still the same voltage, heres the pic of the main also

[multimeter]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

id have thought a PS-ON voltage should be around the 3v mark,hmm!

do you have an ESR meter to check those output caps?if these are bad,this will cause the voltage drop also

[tom66]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

Personally I would be considering the poly-cap which couples the transformer drive or a bad TL431/optocoupler. Without getting that shield off, mighty difficult to test things.

[mcross]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

Yes i have a ESR meter, will check the caps, I can remove the sheld, but then there is no sink for the ic, and ground?

[tom66]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

Perhaps you can get a picture from the sides so we can peak under the shield and get an idea of how it is laid out?

[mcross]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

heres pic, ESR was good,

[mcross]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

Ok , I got another PS that was working in a tv. It gives the same readings as the old one. I am now looking else wher for the problem. I have uploaded a pic of the complete set up. I think the t-con may have a part in it . There is a ribbon cable going from the t-con to the master inverter. also the Vlamp has no wire going to it, just the vbl, it goes to the master inverter.
Mike

[mcross]

Re: Oevia 252fhd-t11 DPS-408AP B power supply

Tom, and multimeter, Ifound a problem, My meter is bad, got a new and the voltages are good, now going to rethink it all as I beleave the main board is the problem. please look at the pic';s in the above post and let me know your thoughts
Mike