40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

[tieny]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

oops, made a mistake there, the 12.9V i wrote should say 26V to output.

[tom66]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

But no 12V coming into feedback? I expect both rails to be involved in the feedback.

[tieny]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

I have the 12.9V here, but i thought it was connected to ground?

Is that huge tracing on the pcb ground? Measuring that i also get 12.9V

[tom66]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

It's probably the 12V output plane. See if it has continuity to the positive terminal of the 12V caps, or output.

[tieny]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

Yep its connected to the 12V output.

[tom66]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

According to my calculations it should give 25.6V and 12.6V... which is still pretty high.

I put it into a little two-transistor power supply. At least the values are close enough so they're probably accurate, my power supply design is different any may regulate differently.

(W scale = volts for 12V)

This should be the correct category:
http://www.digikey.com/scripts/dksea...ity=0&PV174=23

Just select the right resistance value.

[tieny]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

So the original design is actually meant to output 25.6V and 12.6V?

I've read other stories of this TV with the same problem I have but no solid solution.

Could this be just be poor design? So even a small surge can cause the output to go only a little high and then go into protection mode..
I'll try replacing the resistors and see if it goes back down to 25.6V and if that solves the problem.

Nice program you have there, just wondering if I wanted to reduce the 25.6V down by one volt to around say 24.6V, what resistor values would I need?

[tom66]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

I'd say replacing that lower 12k with a 22k should do it.

I do not know if it is supposed to output that high, as this is a different power supply simulation.

The program is LTSpice, excellent freeware for stuff like this.

[tieny]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

I made the order on digikey, hopefully i got the right ones. They were about 8 cents each.

[tom66]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

I just hope that it is the issue at hand, but it's definitely pointing towards it... Very odd failure though; maybe Sony got some dodgy resistors?

[tieny]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

Well just replaced it and no luck again =(. I even tried the 22K resistor which dropped the voltage to 25.3V and 12.5V but same problem.

The error feed back diode on the inverter is still reading 3.6V

Theres one thing that I discovered on the power supply. The usual working voltage on the biggest capacitor is suppose to be 160V on standby correct?

I'm getting weird readings on that big capacitor. It'll go to 400V when I turn the TV on and it cycles through the problem, but once it goes back on standby the voltage will very slowly drop until it hits 170V (like about 5 minutes later).

I also noticed that once its on 170V during on standby, as soon as I unplug the power cord and replug it, that voltage will jump to 400V immediately and then slowly drop back down to 170V all during standby.

Is this unstable voltage on the primary side? I'll start looking around there.

[tom66]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

400V is normal, this TV has PFC. 170V in standby because PFC is turned off in standby mode. 25.3V is closer, may be good enough, still quite high though..

[tieny]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

But then its going to 400V when in standby? What is PFC?

ill try to find an 33K smd resistor and drop the 25.3V down another volt.

[tieny]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

is there a way or possible to disable the error feedback signal?

[tom66]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

What is the part# of the main chip on the inverter?

[tieny]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

Heres the part number:

SSI091ASN

[tom66]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

Hmm. I actually have an inverter here with that chip on, but it's going to be posted on Saturday as it's been sold.

No datasheets available. But I'll reverse engineer what I can from my board:

Pin 4 is grounded.
Pin 5 is error out.
Pin 6 may be Vcc. (Looks to come through a resistor from 24V, so chip probably has internal zener. Check voltage on this pin.)
Pin 7 is VREF. (Probably 1.2V, 2.5V or 5V.)
Pin 13 is grounded.
I think pin 20 is OLP (Open lamp protect. Should normally be low.)

So, try measuring OLP pin (#20) when it shuts down. Then force it low to see if a bulb gives problems. If it still cuts out, we need to look at the OVP for the input, or the Vcc.

[tieny]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

Looking from the picture of the chip, I count 24 pins. Top of the chip left to right, 1 - 12 and bottom of the chip, right to left is 13-24?

So 5th pin on the bottom of the chip from the left is pin 20?

[budm]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

You are using the new inverter board, correct?

[tom66]

Re: 40" Sony LCD KDL-40EX500 Seconds to black (6 blinks)

Those numberings appear correct; OLP is 4th from left on top of chip.