Samsung LN32A300JID Whacked Voltages

[PlainBill]

Re: Samsung LN32A300JID Whacked Voltages

Thanks for the boost PlainBill....
This is what I have found so far, the 16-pin is a MC330167P found at http://pdf1.alldatasheet.com/datashe.../MC33067P.html
The V at Vcc is 15v with Vref showing 5V.
The 8-pin is a Q0165R which I believe is found at http://77.221.132.234/datasheet/FSQ0165R.pdf
There is not a FS is front of the number on the chip but this is all I could find that made any sense. The V at Vcc is 16.3V, Vfb = 800mv, Vsync = 1.7V, Vstr = 160V, and the drains are showing 163V.
On the back is a FAN7530 found at http://www.fairchildsemi.com/ds/FA/FAN7530.pdf
I'm scratching my head where to go on this one.
All readings were taken with the ground clip at the neg. leg of the big cap.
Also the correct readings for the transformer at the lower right corner is 162V at the 2 top right corner pins, 0V at the pin by designator LP801 and 0V on the 2 lower pins at the bottom edge.
Did notice something while probing around taking V readings on various components. The V on the DP802 diode (directly below + leg of big cap) is 162V on stripe side and 130V on the opposite side. DP804 (raised diode directly below big cap) is 162V on both sides. There are also a couple of more diodes on this board showing voltage on both sides. I thought diodes had voltage in one direction only or am I missing something....

As far as diode voltage is concerned, you are ignoring circuit topology. Diodes can be used for a number of purposes. In many applications they will have voltages present on both sides.

When measuring voltage, note that there is a heavy line (black on the bottom, white on the top) separating the Hot side from the Cold side. One very important thing to remember is that lethal voltages are present on the hot side. Also, always measure voltages on the hot side from the - lead of the big cap.

On the Cold side measure voltages from chassis ground or the ground pins on the connectors.

One point that has been giving me fits was identifying the voltage sense circuitry. On the picture of the top side of the board there is a mounting hole at bottom center. Just above that is a blob of white glue. GENTLY pry that off. There should be a three legged IC under that; what is the part number? And measuring from chassis ground, what are the voltages on the three pins?

Next questions. What is the line voltage in your area? What is the AC voltage across the power input pins? Also, what is the voltage across the large filter cap with the TV in standby, and with it powered on?

PlainBill

[Sam I Am]

Re: Samsung LN32A300JID Whacked Voltages

The three legged IC has KIA 431A 828 printed on it. The V is 4.3V on the right leg, 0V at the center, and 880mv on the left leg.
Line is 121V and there is 164V across the big cap regardless of the number of times I press the power button.

[PlainBill]

Re: Samsung LN32A300JID Whacked Voltages

The three legged IC has KIA 431A 828 printed on it. The V is 4.3V on the right leg, 0V at the center, and 880mv on the left leg.
Line is 121V and there is 164V across the big cap regardless of the number of times I press the power button.

The voltages don't make sense - which is good! Unfortunately, the area doesn't show up well in the picture due to glare. I'd like a picture of the upper left quarter of the back of the power supply - same orientation as the original. Only this time, without the glare.

The KIA431A is a voltage reference. There is another of these at the top of the picture in the top view. Again, what are the voltages on the pins of that one?

And back to the one at the bottom of the picture. The black component straddling the white line is an opto-isolator. What is the voltage across the two pins at the left?

I don't have a real good grasp of the voltage to expect across the large cap if the PFC circuit were operating properly. And I don't have a Samsung LN32A300JID - or any other TV - apart to compare it to. Hopefully someone older (or younger) and wiser can step in here with a little bit of help.

PlainBill

[Sam I Am]

Re: Samsung LN32A300JID Whacked Voltages

Ask and ye shall receive....
The other KIA431A is showing 2.4V at the top pin, 0V at the center, and 3.7V at the lower.
The opto-isolator is showing 4.3V on both left pins.
I have another Samsung 32" (LN-S3251D) that more or less powers up then immediately goes black. The red LED lights up on the front when plugged in, starts blinking when you cycle the power button, chimes, then goes to black screen.
I checked the big cap on that one and it shows 384V if that helps any.

[PlainBill]

Re: Samsung LN32A300JID Whacked Voltages

Ask and ye shall receive....
The other KIA431A is showing 2.4V at the top pin, 0V at the center, and 3.7V at the lower.
The opto-isolator is showing 4.3V on both left pins.
I have another Samsung 32" (LN-S3251D) that more or less powers up then immediately goes black. The red LED lights up on the front when plugged in, starts blinking when you cycle the power button, chimes, then goes to black screen.
I checked the big cap on that one and it shows 384V if that helps any.

Yes, it does. It tells me there is a problem with the PFC circuit. Hmm, where do we start? Maybe I'll stall. Nah, I've got things to do and I'm going to have to study the application note for the PFC controller. Oh, joy. Something new to learn today.

If you get bored waiting, go over to www.spearfishlaketales.com and start reading 'Rocinante' (it's the bottom story on the page). By the time they get the wings back onto Rocinante I'll be back with some ideas.

PlainBill

[PlainBill]

Re: Samsung LN32A300JID Whacked Voltages

Well, I've looked over the datasheet for the PFC controller. It looks to be fairly straight forward, BUT I would like a couple of pictures first. The first is easy - I need the upper right quarter of the back side of the power supply. The second is also easy if you understand what I am looking for. Many boards have some sort of orientation - or at least most labels are easiest to read if the board is oriented in a particular direction. This one is more so than most. And I find it much easier to correlate top side and bottom side pictures if the same points are at the top of each. SO in the interest of preserving the remaining shreds of my sanity, after taking that picture of the bottom side of the board would you flip it over left to right (or right to left), and take a picture of the top side, upper left quarter.

PlainBill

[Sam I Am]

Re: Samsung LN32A300JID Whacked Voltages

Like these.....

[PlainBill]

Re: Samsung LN32A300JID Whacked Voltages

Like these.....

Excellent. I'll have suggestions later today, Faraday willing.

PlainBill

[PlainBill]

Re: Samsung LN32A300JID Whacked Voltages

And away we go. The first point I will make is that potentially lethal voltages are present on this supply. I STRONGLY urge you to take precautions to prevent your getting a fatal shock. I will be using the designations on the power supply as much as possible to identify points I want tested. For these preliminary tests you can test the components in circuit.

First, with power off check DP802, DP804, and DP805 for shorts and check that they show conduction in only one direction on the diode range. Also check DP801 and DP806.

Next, check QP801S and lastly, what is the resistance of RP820?

The next test will be done with power on. Use the negative lead of CP815 (the large filter cap) as the ground point. Pin 1 of the FAN7530 (ICP801S) is at the upper right in the picture you took. What is the voltage on each pin of of ICP801S? If you have 0 volts at pin 8, try hitting the power button to take the set out of standby, or simply try having an assistant click the power button several times while you measure the voltage on each pin.

PlainBill

[Sam I Am]

Re: Samsung LN32A300JID Whacked Voltages

Okay.... here are some of the voltages and values you requested.
Axial diodes DP802, DP804, and DP805 check good with DVOM on diode check.
SM diodes (?) DP801 and DP806 show .025V and .0002V respectively with DVOM on diode check.
QP801S (power transistor) shows 570mV on one outer leg and 520mV on the other outer leg.
RP820 has a value of .18 ohms.
Now here is where I have some apprehension as I am unsure whether or not to power this board up with the ribbon cables disconnected. Furthermore, the power button cable connects to the mainboard. Then there's the question of the circuit board ground (jumper wire to chassis)? Will it be OK to leave the backlight ribbon cable disconnected?
Guidance please.

[PlainBill]

Re: Samsung LN32A300JID Whacked Voltages

Okay.... here are some of the voltages and values you requested.
Axial diodes DP802, DP804, and DP805 check good with DVOM on diode check.
SM diodes (?) DP801 and DP806 show .025V and .0002V respectively with DVOM on diode check.
QP801S (power transistor) shows 570mV on one outer leg and 520mV on the other outer leg.
RP820 has a value of .18 ohms.
Now here is where I have some apprehension as I am unsure whether or not to power this board up with the ribbon cables disconnected. Furthermore, the power button cable connects to the mainboard. Then there's the question of the circuit board ground (jumper wire to chassis)? Will it be OK to leave the backlight ribbon cable disconnected?
Guidance please.

Most of those values look good. I'm concerned about the readings on QP801S. That may have to be tested out of circuit. Well, maybe not. A D-S short would have blown the fuse.

As far as testing the voltages, I suggest hooking up all the cables except the inverter. If you can't hook up the ground wire directly, use a jumper wire to hook it to the chassis. And as I've indicated before, be careful.

PlainBill

[Sam I Am]

Re: Samsung LN32A300JID Whacked Voltages

The ICP801S readings are as follows:
Pin 1 = 0V, Pin 2 = .04V, Pin 3 = 0V, Pin 4 = 0V, Pin 5 = 500mV, Pin 6 = 0V, Pin 7 = 0V, and Pin 8 = 15.2V.

[PlainBill]

Re: Samsung LN32A300JID Whacked Voltages

The ICP801S readings are as follows:
Pin 1 = 0V, Pin 2 = .04V, Pin 3 = 0V, Pin 4 = 0V, Pin 5 = 500mV, Pin 6 = 0V, Pin 7 = 0V, and Pin 8 = 15.2V.

OK, let's see what that means

Pin 1 = Inv. Input. Should be about 2.5 volts

Pin 2 = Mot Input. Should be at 3 V

Pin 3 = Comp - diagram says 1-5 volt range

Pin 4 = CS - Current Sense 0V is right, the FET isn't being switched on.

Pin 5 = ZCD - Zero crossing detector Should be around 1.5 volts. This may be AC

Pin 6 = Gnd

Pin 7 = Out Should be a couple of volts on that, I would think.

Pin 8 = Vcc 15.2 volts is good.

OK, that's enough for tonight. I'm going to be busy tomorrow, but will look at it sometime. I'm wondering if there isn't circuit to disable the PFC when the set is in standby.

PlainBill

[Sam I Am]

Re: Samsung LN32A300JID Whacked Voltages

I'm wondering if there isn't circuit to disable the PFC when the set is in standby.
PlainBill

If there is..... please enlighten me at your earliest convenience.

[PlainBill]

Re: Samsung LN32A300JID Whacked Voltages

If there is..... please enlighten me at your earliest convenience.

Ahhh, crud!!! I knew there was something I was forgetting over the holiday.

Maybe I should keep a list....

PlainBill

[PlainBill]

Re: Samsung LN32A300JID Whacked Voltages

As closely as I can determine, Vcc to this IC is turned on at the same time as power to the SMPS controller. I'm having serious problems tracing the signal paths on the PFC. Pins 1 and 3 of ICP801S seem to be the key. Pin 1 should be roughly .0075 X the voltage across CP815. If pin 1 is below 2.5 volts, pin 3 should be in the 5V range.

At this point my best guess is the FAN7530 is bad. but I don't have a lot of confidence in that. The IC is available from Digikey for $1.86.

PlainBill

[Sam I Am]

Re: Samsung LN32A300JID Whacked Voltages

Man... I'm feeling like a
My visual inspection skills definitely need improvement.
Take a look at the first pic I posted at #27, the long slot to the immediate left of the identifier PC803S is where a substantial crack begins and cuts a diagonal line up to the center of RP812. It looks like 3 traces (twice through one) have been separated.
Hmmmm...... I've got a new Metcal tip I've been wanting to try out and this looks like a prime candidate for some trace repair.
I'll let you know how it goes.
Thank you for your assistance PlainBill.

[PlainBill]

Re: Samsung LN32A300JID Whacked Voltages

Man... I'm feeling like a
My visual inspection skills definitely need improvement.
Take a look at the first pic I posted at #27, the long slot to the immediate left of the identifier PC803S is where a substantial crack begins and cuts a diagonal line up to the center of RP812. It looks like 3 traces (twice through one) have been separated.
Hmmmm...... I've got a new Metcal tip I've been wanting to try out and this looks like a prime candidate for some trace repair.
I'll let you know how it goes.
Thank you for your assistance PlainBill.

Well, don't feel too bad about about your powers of observation - or the lack of them. I spent a fair amount of time looking over that area and never noticed the crack. When you pointed it out, I STILL spent a lot of time looking before I saw it. Reviewing some of the earlier pictures, the crack is quite visible in some of them.

PlainBill

[Sam I Am]

Re: Samsung LN32A300JID Whacked Voltages

Oh yeah... oh yeah... oh yeah...
The trace repair is a success and the set is fully functional.
Got to keep my eyes peeled for cracked boards from now on.