Logik LOG32lw782

[budm]

Re: Logik LOG32lw782

What do you use for the meter ground point when you are making all these voltage readings? It sounds like you are using the metal chassis as the ground ref. point.

[joehezzer]

Re: Logik LOG32lw782

What do you use for the meter ground point when you are making all these voltage readings? It sounds like you are using the metal chassis as the ground ref. point.

grounding on the chassis when test the outputs of the boards, although the caps have a + and -.

[budm]

Re: Logik LOG32lw782

But you are measuring the DC voltage on the primary side (hot side of the circuit), using the chassis as he ground ref?
For example on post 43 you indicate 120V on the main filter cap.

"the voltage jumped around a bit so i earthed to the chassis, saying that i will resolder that connection. I got 120v, the cap is rated at 450v. All the tracks look good on the back as i checked and re soldered pretty much all of the board as there was a couple of dodgy joint"

[joehezzer]

Re: Logik LOG32lw782

Aah yes you are right I did ground to chassis when I did the big cap. My apologies

[budm]

Re: Logik LOG32lw782

When you work in the primary side of the circuit, you need to use the negative leg of that 450V cap as the ground ref for your meter. Chassis ground is the Cold side ground ref point.
So take the reading right at the two legs of that main filter cap when TV is OFF and when TV is ON.

[joehezzer]

Re: Logik LOG32lw782

When you work in the primary side of the circuit, you need to use the negative leg of that 450V cap as the ground ref for your meter. Chassis ground is the Cold side ground ref point.
So take the reading right at the two legs of that main filter cap when TV is OFF and when TV is ON.

Right I am with you cheers

[budm]

Re: Logik LOG32lw782

So what DC voltage do you get on the main filter cap? We need to know if the PFC Voltage booster is working or not first.

[joehezzer]

Re: Logik LOG32lw782

ok so i took main cap off and got 137uf on the tester then resoldered it back on to board and got 350 volts, so i believe the main cap is ok correct me if i am wrong i have re edited this post thanks to Tom66 cheers matey

[tom66]

Re: Logik LOG32lw782

Uh, the PFC voltage shouldn't be 450V... it should be closer to 390V, nominally 392V, on these sets.

[joehezzer]

Re: Logik LOG32lw782

HI tom sorry matey rechecked it was 350 volt not 450 sorry my fault lol will re edit my other post to stop any confusion lol

[tom66]

Re: Logik LOG32lw782

350V is too low. What are symptoms - 24V measuring too low? This is a common fault on this PSU. I don't know how to fix it, I've always just swapped them, maybe one day I will try but in general I regard them as difficult to fix PSUs.

[joehezzer]

Re: Logik LOG32lw782

350V is too low. What are symptoms - 24V measuring too low? This is a common fault on this PSU. I don't know how to fix it, I've always just swapped them, maybe one day I will try but in general I regard them as difficult to fix PSUs.

the symptoms i have is the set just has no power no standby light, so bought a second hand supposedly working psu still nothing, thats the problem with second hand boards you just take the risk. have replaced a few boards, this is the first one that has not worked

[joehezzer]

Re: Logik LOG32lw782

just tried another cap wich i believe to be working got the same reading

[tom66]

Re: Logik LOG32lw782

Do you have any 5V or 3.3V standby output? Only buy boards where seller accepts return if board is faulty.

[joehezzer]

Re: Logik LOG32lw782

Do you have any 5V or 3.3V standby output? Only buy boards where seller accepts return if board is faulty.

will just check

[joehezzer]

Re: Logik LOG32lw782

pl803 pin the white one in the pics i have 3.3v marked in red

[multimeter]

Re: Logik LOG32lw782

is there a 5v stb pin?,that will have to be there ,this will supply voltage and give you power to the front led standby light,even if nothing else is working,if it isnt ,we need to find out why...,your 3.3v will maybee be for inverter on signal.

[joehezzer]

Re: Logik LOG32lw782

is there a 5v stb pin?,that will have to be there ,this will supply voltage and give you power to the front led standby light,even if nothing else is working,if it isnt ,we need to find out why...,your 3.3v will maybee be for inverter on signal.

just looking at schematic of psu think its the right one, pin 6 on pl803 standby

[multimeter]

Re: Logik LOG32lw782

120!! is that a typo? should be min of 230*1.41 so around 325 vDC

i normally like to test the mains input voltage at source rather than take the standard 230v-240v,the 17th edition wiring regs for uk,for test and measurement (2391),has been standard-tised to 230v and not 240v,it can mislead you on the filter cap measurement,ive seen voltages around 245v-250v in some areas in domestic propertys around the uk

230v * 1.44 = 331.2 v at the filter cap (power on)

240v* 1.44 = 345.6 v at the filter cap (power on)

so i like to measure the voltage,then times by 1.44 to give ,what should be on that filter cap.

these psu's are a pain in the ass.

[multimeter]

Re: Logik LOG32lw782

pin 12 +5v

pin 10,11 +3.3v

pin 1,2,3 +5v

are you seeing any voltage on those?