Sony KDL 32L4000 Troubleshooting

[budm]

Re: Sony KDL 32L4000 Troubleshooting

I need to look at the schematic and see if I can force it off.

[budm]

Re: Sony KDL 32L4000 Troubleshooting

OK, remove resistor R219 (12K Ohms, page 2 of the power supply schematic I provided), this should stop switched Transistor Q202 (that provides VAUX2) from coming on so relay RL1 should not come on any more when you power up the board WITHOUT Grounding PS-ON pin.
If the relay still comes on then it is either bad Q202 or D208.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

I disconnected R219 from the circuit and removed ground from PS_ON. Relay continues to click. So it seems Q202 and/or D208 are bad. Is there a way to test them out in circuit? What should the next step be?

[budm]

Re: Sony KDL 32L4000 Troubleshooting

Do the resistance test in both direction on D208.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

0 ohms both directions, so it seems to be blown.

[budm]

Re: Sony KDL 32L4000 Troubleshooting

That Diode is connected in parallel with Emitter/Collector of Q202 (see schematic), so it can be shorted out diode or shorted transistor, so remove the diode sine it only has two legs and see if the diode will show shorted off the board or not, also check the resistance on the two empty pads after the diode is removed to see what you get.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

Will do, but I need to get a better soldering iron. The one I used to remove the resistor worked poorly, no hot enough and I don't think it will work well enough on smd.

In the meantime, can we discuss the Samsung Plasma I mentioned?

[vinceroger69]

Re: Sony KDL 32L4000 Troubleshooting

add a bit of fresh solder first as should help with removal

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

Thanks Vince,

I had cleaned and re-tinned the tip, but it still took a while to get the resistor off. I am thinking the solder may be lead free and my 30W iron isn't getting hot enough to efficiently heat the joint. I was able to heat up the solder and suck most of it off, but some still remained and the wick tape did a poor job of removing it.

I have ordered some fresh solder and wick tape and will try again when that arrives, in the meantime I am looking to secure a better iron as well. I also only have a conical tip on my iron and suspect that isn't sufficient either.

In the meantime, I have a Samsung PN42C450 B1DXZA where the red standby LED lights, but will not power on. When plugged in it will do a double click within a sec and then a couple seconds later you get a quieter single click. This sequence happens twice.

When you hit the power button this click sequence repeats, PS_ON has 3.25 V at stand by and drops to .06 V then rises to 3.25 between the two click series and then again after the second series. This process can be repeated a few time before the "standby" voltage stays at .06. My understanding is that this TV, like the Sony, has a high standby voltage and energizes when PS_ON is pulled low. If so, then it is trying to energize and fails; it tries twice then stops. Then after multiple attempts the system shuts down and will not try further without pulling the plug to reset. Does this seem correct?

Attached are photos of the TV and boards as well as voltage readings. I only have 3.25 V PS_ON and STD 5.21 V. Since no other voltages are generated I am also assuming that the power board is bad. Does this seem correct?

Also where I can look for the schematics for this TV?

The Problem Trace photo is more of a questions. The traces are dark in spots under around the CM 820-2 area of the board. Does this indicate a problem?

[vinceroger69]

Re: Sony KDL 32L4000 Troubleshooting

best move the samsung tv help request to another thread and keep this one just for the sony tvs i cant find a free schematic for the samsung only paid for ones

[budm]

Re: Sony KDL 32L4000 Troubleshooting

BTW, I do not wok on Plasma TV's, never study it.

[vinceroger69]

Re: Sony KDL 32L4000 Troubleshooting

BTW, I do not wok on Plasma TV's, never study it.

I dont either budm, although had to repair my panasonic plasma twice but all info was on this forum so no fault finding needed from myself.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

Thanks Vince and Bud,

Is there a way to move a message on the forum to start another thread or do I have to just Repeat the post in a new thread?

[vinceroger69]

Re: Sony KDL 32L4000 Troubleshooting

i would just start a new thread for the samsung plasma tv hopefully someone with more experience will be able too help

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

I have never worked with SMDs before but it is my understanding that what I want to do is either use hot air to liquefy the solder and pull up the device or to use solder wick to remove the solder so I can remove the device. I do not have an air station so I am looking to desolder it with an iron.

My concern is that my iron is an inexpensive pencil type at 30-35 Watts with a standard conical tip. I have read that temp. may actually be too high (no idea what it is) and that the tip may not provide proper contact to efficiently remove the device.

I don't want to burn out the diode while removing it as that will defeat the purpose. What are thoughts? Should I just try with what I have or should I look for better tools and if so what factors should I consider?

[vinceroger69]

Re: Sony KDL 32L4000 Troubleshooting

add some fresh solder first too both sides of the diode then try and heating both sides quickly moving between both sides of diode, it then should lift straight up off the board once melted enough, you can then test the diode. if the diode has markings like a line/white mark make a note of how its fitted for when you replace it.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

I moved the Samsung Plasma info to
https://www.badcaps.net/forum/showthread.php?t=71449
but haven't received any responses. Did I list this in the wrong place?

[vinceroger69]

Re: Sony KDL 32L4000 Troubleshooting

I moved the Samsung Plasma info to
https://www.badcaps.net/forum/showthread.php?t=71449
but haven't received any responses. Did I list this in the wrong place?

its in the right place its just not many of us work on plasmas so cant really offer much help only advice on what we would check ourselves if fault finding maybe see if samsung do a plasma training manual as some good fault finding tips in them.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

I did read over the plasma material, but it seemed to assume that the power board was working for the most part and was hoping someone with Plasma experience could give me a their thoughts based on what I was seeing.

Why are plasma so different from LCD? Seems like there is much commonality.

[Eaglecrest]

Re: Sony KDL 32L4000 Troubleshooting

OK, I had some equipment issues, but finally got to remove the diode with a bit of a struggle. I am sure less refined technique account for most or all and I think i burnt a little divit into the board, but i got it off and the pads show 0 ohms across them. Q202 also shows about 3 ohms across emitter and collector and about 2k ohms from base to collector and emitter.

The diode shows no reading on diode setting in one direction and .555 V in the other. My understanding is that the transistor is shorted and the diode is good and the shorted transistor caused the shorted reading for the diode. Is this correct?