Samsung Spn4235 No video or sound

[retiredcaps]

Re: Samsung Spn4235 No video or sound

Can anyone say whether high votage (450v) caps actually come in a Low-esr version?

The big filter cap doesn't work as hard. See

https://www.badcaps.net/forum/showthread.php?p=177869

[TechShui]

Re: Samsung Spn4235 No video or sound

Edit: Just saw your post retiredcaps, thanks for clearing that up.
Looks like they failed because of how close they are to that heatsink.

There is no screen flash .. Just the standby light blinks 5 times

Really? No backlight, not even in a dark room?

My backlight turns on, right around the 2nd of the 5 blinks.
The backlight/TV stays on too, until I hit power button, LOL

The fact that you have no backlight could indicate a Y-sustain problem.

Selldoor after reading one of your above post, I noticed that you said to test the voltage WITH the x and y disconnected.. The voltage that I listed above I think were taken with cables connected.. I have since retested with the y and x boards and the voltage on cn2 is the same, but cn1 reads zeros all the way across..

That's another difference between your TV and mine: With either (or both) of the sustain boards disconnected, I get the same readings (never "zeros all the way across").

My readings are fine. They match up with the markings on the boards. And they match the readings you took with everything connected.

What you call cn1 is cn801, the plug from the PS to the analogue board, right? That plug shouldn't even be affected by disconnecting a sustain. It makes no sense to me, but maybe someone has seen that problem before.

[selldoor]

Re: Samsung Spn4235 No video or sound

@lilmonk3 - Looks like voltage good - though nils are a query-did you hold the probe or could it have moved off ground - Desperate need for good photos.

[lilmonk3]

Re: Samsung Spn4235 No video or sound

No back light at all.. Just checked in a pitch black room.. Also when you took your readings, did you just only have the power plugged in, or did you hit the power button then test?

Edit: Just saw your post retiredcaps, thanks for clearing that up.
Looks like they failed because of how close they are to that heatsink.Really? No backlight, not even in a dark room?

My backlight turns on, right around the 2nd of the 5 blinks.
The backlight/TV stays on too, until I hit power button, LOL

The fact that you have no backlight could indicate a Y-sustain problem.That's another difference between your TV and mine: With either (or both) of the sustain boards disconnected, I get the same readings (never "zeros all the way across").

My readings are fine. They match up with the markings on the boards. And they match the readings you took with everything connected.

What you call cn1 is cn801, the plug from the PS to the analogue board, right? That plug shouldn't even be affected by disconnecting a sustain. It makes no sense to me, but maybe someone has seen that problem before.

[TechShui]

Re: Samsung Spn4235 No video or sound

Plugged in then turned the TV on before I measured.

But selldoor is right, if your black probe moved off ground, you would get 0.00V everywhere.

And good pictures would help ;-)

I still suspect Y-sustain and/or Y-buffers. Anyone else agree? :hmm:

[lilmonk3]

Re: Samsung Spn4235 No video or sound

Ok all.. I am working on getting some better pics but I will have to use my adroid.. Because my damn sis hasnt returned my canon rebel..I did do some more volt test.. The VS going to y and x board is VERY LOW.. 33v on both sides of power supply.. I will be placing an order later today for those 2 smaller caps that are circled in an earlier post.. Do you all think it could be those caps?

[TechShui]

Re: Samsung Spn4235 No video or sound

No I don't think those two caps are the problem.

Tom66 said he was just guessing, because some newer Samsung TV have a common problem with a pair of 10v 3300uf caps. (tom, if you're reading this please confirm).

Maybe something in the sustain boards is shorting VS? Did you test VS while it was plugged into the sustain boards? Try it both ways see if anything changes.

Maybe there's a Voltage Regulator somewhere on the power board that's gone bad. It'll be in the VS circuit. A service manual will have diagrams to help identify the circuit.

Here's another thing you could do:
Find the original fuses (hopefully you didn't throw them away) that you removed from this TV.

Test all 3 of them with your multimeter set to continuity.

If the fuses are good, you'll hear a beep. If one or more is bad, you won't hear anything. --means one of the original sustain fuses is blown.

You can also do this with the fuses that are in the TV now, just to make sure they're alright.

[lilmonk3]

Re: Samsung Spn4235 No video or sound

Techshui.. While waiting for some feedback, I pulled those 2 caps that are circled in the photo and one test fine and one is dead as dead can be .. I have tested the VS with both boards plugged and unplugged.. Same response.. I have tested all three fuses and they tested fine new and old ones..

[lilmonk3]

Re: Samsung Spn4235 No video or sound

The two caps I pulled were C39- 10v 2200 tested and got a reading..c41 50v 47 tested and got nothing.... Sis is suppose to return my camera tomorrow.. Ol Hyde

[TechShui]

Re: Samsung Spn4235 No video or sound

What did you use to test it?

[selldoor]

Re: Samsung Spn4235 No video or sound

"Ol Hyde" ????

Good - Im really hoping for some good pics.
As regard testing fuses - retiredcaps has said many many times:
"I don't recommend using continuity as a good way to reliably see if a fuse is good or not. A good fuse should measure less than 1.0 ohms.

Some multimeters will beep continuous if the resistance is less than 1800 ohms. No fuse is good when the multimeter beeps and the resistance reading is 1795 ohms."

[lilmonk3]

Re: Samsung Spn4235 No video or sound

Here are some pics

[selldoor]

Re: Samsung Spn4235 No video or sound

They are better but not super. In pic 2 I can see 3/4 black barrel fuses

Might be one bottom right just above the middle of the 3 yellow rectangles ( May not be a fuse but cant read it)

One Top left just to the left of the yellow rectangle

Two in the centre to the left of the yellow rectangle which is above the two greenwrapped transformers.

Golly - more or perhaps there the same ones?
Pic 3 top right near the copper coil where it says fuse ( always a good clue)

Middle bottom between the BIG cap and the heatsink.

Middle at the top of the heatsink and just to the left

There may be more - now you know what to look for.

Can we have pictures of the other boards


Ill be surprised if they dont all test good as your out voltages seem ok .

[vinceroger69]

Re: Samsung Spn4235 No video or sound

in the center by the yellow transformer to the left of the barrel fuse there are 2 capacitors there looks like one that maybe heat damaged just looks odd like its got hot and the outer covering of the cap has overheated and shrunk maybe worth testing the 2 caps just in case out of spec ie esr and uf

[TechShui]

Re: Samsung Spn4235 No video or sound

I was going to start my own thread, but I figured why not keep it all in here in case my findings help lilmonk.

So I've been testing my SPN4235 all afternoon. The weirdest thing happens when I probe certain pins of the PFC controller with the TV on.

Probing pin 1 of the PFC causes a buzzing sound to emanate from the upper right side of the power board.
(Maybe the big capacitor or the mosfet near it??)

Probing pin 7 causes buzzing from middle lane, where the two green transformers and one yellow are. I don't know which transformer is buzzing...
I didn't want put my ear too close to the LIVE heat sink

Probing Pin 8 causes buzzing from somewhere out West. Probably the tranformer near the two big 200v 1200uf caps. (or the caps themselves).

Probing Pin 15 causes a much louder buzzing from upper right sector again (Note that 15 is GND... what could this mean?)

Here are all the voltages for the PFC controller

Location IC1 (PFC ML4824) With the set OFF:

Pin 1 -IEAO = 0v
Pin 2 -IAC = 0.8v
Pin 3 -ISENSE = 0v
Pin 4 -VRMS = 0.8v
Pin 5 -SS = 0.2v
Pin 6 -VDC = 0v
Pin 7 -RAMP 1 = 0v
Pin 8 -RAMP 2 = 0.7v
Pin 9 -VEAO = 0v
Pin 10 -VFB = 0v
Pin 11 -VREF = 0v
Pin 12 -VCC = 0v
Pin 13 -PFC OUT = 0.2v
Pin 14 -PWM OUT = 0v
Pin 15 -GND = 0.8v
Pin 16 -DC ILIMIT = 0.2v

With the set turned ON:

Pin 1 -IEAO = 1.0~2.3v
Pin 2 -IAC = 0~0.8v
Pin 3 -ISENSE = 0~0.1v
Pin 4 -VRMS = 1.0~2.6v
Pin 5 -SS = 0.0~7.6v
Pin 6 -VDC = 0.1~4.2v
Pin 7 -RAMP 1 = 2.0~3.6v
Pin 8 -RAMP 2 = 0.1~1.8v
Pin 9 -VEAO = 0.1v
Pin 10 -VFB = 0.1v
Pin 11 -VREF = 1.8~2.6v
Pin 12 -VCC = 0.0v~7.1v
Pin 13 -PFC OUT = 0.0~12.2v
Pin 14 -PWM OUT = 0.0~7.2v
Pin 15 -GND = 0.1~3.6v
Pin 16 -DC ILIMIT = 0.0~2.6v

And here's a link to the ML4824 datasheet:

I've also attached the power board schematic that I got from ElektroTanya (no luck finding the entire TV manual).

There's fluctuation on almost all the pins of this IC, probably because it's turning on and off in a loop.

I also tested the two upper-right 450V 330uf caps (the same ones I replaced on Friday).
They are both 162V stable. And 384V with the set on.

Here are the bridge rectifiers:

BD1 Off / On

- = 0v / 0v
AC = 56v stable / 20~55v unstable
AC = 56v stable / 20~55v unstable
+ = 111v stable / 0~109v unstable

BD3

- = 0v / 0v
AC = 56v stable / 0~64v unstable
AC = 56v stable / 20~57v unstable
+ = 111v stable / 0~113v unstable

BD2

- = 0v / 0v
AC = 56v stable / 56v stable
AC = 56v stable / 56v stable
+ = 162v stable / 383v stable (matches the caps exactly)

The ones labeled BD1 and BD3 are attched to the long heatsink on the right side of the board. The BD3 is solo, by the standby transformer (bottom-right).

Is it normal for the + pin to be fluctuating like that?

[TechShui]

Re: Samsung Spn4235 No video or sound

UPDATE:

Just spent several more hours checking voltages, and I'm really mad at this TV right now. The TV seems to have a mind of it's own, it shows different readings at different parts of the day.

For example,
I retested all the components I tested earlier and they showed ALL STABLE. Like 13.1v on pin 13 (vcc) of the PFC... 18v on pin 8 of IC4 (amplifier).

And the two bridge rectifiers seemed pretty stable at 100~105.

I had to flip the board upside-down, while still leaving the mainboard connected. Used a piece of cardboard to shield the analog and digital boards.

I was measuring the PFC startup capacitor c250 which also showed stable 13.1v when I heard a relay click. And all of a sudden it shows 7.7v at c250!

I check the PFC, it's off, I check the big caps, they're at 162V. Oh, but the TV is still on! It was blinking green continuously. No error code, just continuous. I hit the power switch to turn it off, -nothing. Just keeps blinking.

While the TV is in this "green blinking mode", I check a few more things and notice the buzzing noise doesn't happen when I probe.

I have to unplug the TV to turn it off.

Turn it back on and the 5 red blinks are back! Fluctuation is back everywhere. PFC controller in a loop, amplifier in a loop. Capacitor c250 and c405 fluctuating. Probably others, but I didn't continue checking, because after 5 minutes the TV shuts off into standby.

Overheat? No, I touched the heatsinks and they're room temp, except for the one in the middle, that one's a bit hot (around 90 F).

A few questions:

1. Maybe cold solder joints are causing this erratic behovior? There's a lot of heavy stuff on this board.

2. Shouldn't all THREE bridge rectifiers have the SAME voltage? As per my last post, there's 384V at BD2, but 105V at BD1 and BD3.

3. What the hell does that green blinking mean? It hasn't happened again since. (it was about 2 hours ago when it did).

[selldoor]

Re: Samsung Spn4235 No video or sound

Whilst this might not help you I would suggest that you do not touch heatsinks while the tv is on. They can carry a voltage 60-70 v which can give you a nasty jolt. If that jolts you into touching the primary side - even bigger jolt - take care.

[lilmonk3]

Re: Samsung Spn4235 No video or sound

in the center by the yellow transformer to the left of the barrel fuse there are 2 capacitors there looks like one that maybe heat damaged just looks odd like its got hot and the outer covering of the cap has overheated and shrunk maybe worth testing the 2 caps just in case out of spec ie esr and uf

Good eye... Those do look odd.. I pulled them and you are correct, they test as zero nada zip... Caps on order.. In the meantime I am going to be working on a lifestyles wt322 that I got for Free that has 6 blown caps... I hope to have one of these damn things running by the weekend, so the guys at the VFW can watch a little baseball on a better TV than what they have now..

[lilmonk3]

Re: Samsung Spn4235 No video or sound

Techsui.. I was having the crazy readings myself. But its because the TV would shut off while I was testing.. No buzzing sounds here though

[vinceroger69]

Re: Samsung Spn4235 No video or sound

hopefully those caps maybe your issue then hope you have better luck with the new set you have picked up for free.