Samsung Spn4235 No video or sound

[lilmonk3]

Hello all and thank you for allowing me to join your great group.. I was given this TV in hopes that I could fix it and give it to the local VFW. When I push the power button I get the red power light blinks 5 times .. I get no sound except for the click of it trying to power on and no video.. So I broke it open to take a look and the first thing that jumped out at me was the 450v 330uf x2and 200v 1200uf x2 looked puffy.. One of the 450v poly caps was totally popped up and after removing the poly cap I can see a split in the cap.. The other 3 still have the poly caps intact.. I will be honest with ya all that this is my first adventure into fixing a plasma..So my question to you fine folks is, do you think there is much of a chance of fixing this thing by replacing those 4 HIGH VOLTAGE Caps and will I kill myself doing it . I have tried unhook the left board and power up and that made no difference and also did the same with the right board... Same ol' same ol'. The power board is a B4k-50 Rev1.2
Any insight on this would be greatly appreciated ....

[tom66]

Re: Samsung Spn4235 No video or sound

If you take the plastic disc off the top of the cap, does it appear bulged? It is common for the disc to bulge without the cap actually having failed.

I believe a common failure on these was capacitors but it was two small ones by the standby transformer.

Do you have a digital multimeter?

[lilmonk3]

Re: Samsung Spn4235 No video or sound

Yes I have a meter , and can follow directions... I am not an expert with a meter and circut boards, but am willing to learn and listen
Ok I popped the poly caps off all these caps. The 2 black ones(450v) look to be split a bit on the top and the brown (200v) are not split or bulged. I forgot to say earlier, that I did already order all these caps from digi because I knew someone that was placing an order, so I jumped in with him...

[lilmonk3]

Re: Samsung Spn4235 No video or sound

The meter I have is this one.. Most likely not as good as most of you have, but it is all I have

[tom66]

Re: Samsung Spn4235 No video or sound

Ah yeah, definitely bulged.

That meter is fine and looks like it is autoranging which considerably simplifies testing some things.

A few things to check.

Do you get stable 5V standby? (There should be a pin or two marked 5Vstby, 5Vst...) Check the voltage with the black probe in a spare screw hole on the back of the frame.

Are all the fuses on the power supply good? I have seen plasma TVs with a separate fuse for the high voltage PFC bus. Check all fuses you can see.

After you replace the caps, more testing can be done.

[lilmonk3]

Re: Samsung Spn4235 No video or sound

Yes I replaced all the 250v t8ah with some 250v 8a fuses I had from an old stereo that would blow fuses all the time.. Ok I am getting ready to show my lack of experience with this kind of stuff . I have the board removed from the chassis and sitting on a work bench.. Do I need to reinstall it ? Do I need to have it hooked up to 110? And to be real honest, I am not sure which setting to use on my meter.. I warned ya that I am not a guru I really like my life and dont want it to end by a TV sending me to meet my maker LOL.. Oh and I am a woman but not a blonde

[TechShui]

Re: Samsung Spn4235 No video or sound

LOL, what a coincedence.

I just started working a SPN 4235 today. It has a picture with a thin black line AND there's no audio. (not even with HDMI, RCA etc.)

I opened it up about an hour ago and lo and behold, the two 450V 330uf caps are puffy.

Hmm, I'm surprised the TV can still turn on. Assuming those were even the problem would be premature. The first thing I thought of was X-buffer, because of the black line.

That's also the same multimeter I'm using --Innova 3320.

I have the board removed from the chassis and sitting on a work bench.. Do I need to reinstall it ? Do I need to have it hooked up to 110? And to be real honest, I am not sure which setting to use on my meter..

Yes. Reinstalled.

And yes, hooked up to 110v. But don't turn the TV on just yet.

Set your meter to DCV (red).
Use any screw for ground with the black probe.
Then with the red probe check the pink plug going to the signal board.

Start on the left (blue wire) I think 5Vsb is the second wire.

Because of the giant heatsink in the way on the powerboard side. I would reccomend checking it on the signal board side, where there's more room. Unplug first it if you have to, (with the TV off).

There's also 5Vsb on the Y-sustain and Z-sustain. (left and right sides of the TV, they have heatsinks covered in black, and rows of 16 capacitors.)

[lilmonk3]

Re: Samsung Spn4235 No video or sound

Ok I will try to work on it tomorrow.. Have a puking kiddo tonight Grrr

[retiredcaps]

Re: Samsung Spn4235 No video or sound

Do not touch any of the heatsinks when TV is plugged into the wall or when it is turned on. Some of those heatsinks could be live and carry 200V DC or more.

In addition, it may take several minutes or more for the largest capacitors on the power board to discharge (i.e. go down to 0V).

[Vizor]

Re: Samsung Spn4235 No video or sound

Actually have this same TV brought it home turned it on Blue screen, no signal to anything took it apart cleaned it all up and now it will not come back on lol green light just blinks.

[lilmonk3]

Re: Samsung Spn4235 No video or sound

I have seen reference to the green light on the back panel.. But on my set, I am not getting that.. Heck I dont even know where it is suppose to be LOL

[lilmonk3]

Re: Samsung Spn4235 No video or sound

Ok I really need your input ... My 450v caps should be here today.. Will it be safe to desolder the old ones after I have let the tv set without power. If so how long should I let it set. If not, what should I do to make it safe... I think have a 20w/8ohm ceramic resistor that I could make a decharging tool out of.. But not sure it that would be big enough to do the job

[tom66]

Re: Samsung Spn4235 No video or sound

Ok I really need your input ... My 450v caps should be here today.. Will it be safe to desolder the old ones after I have let the tv set without power. If so how long should I let it set. If not, what should I do to make it safe... I think have a 20w/8ohm ceramic resistor that I could make a decharging tool out of.. But not sure it that would be big enough to do the job

You can check them with a multimeter set on the 500, 600 or 1000V range. They will most likely discharge within 30 seconds of being unplugged; modern power supplies have bleeder resistors which discharge them reasonably quickly, and the design of the power supply often means it tries to use as much energy from the cap as possible (to minimise its size to reduce the cost of the power supply.) If they aren't discharged you can short them out with a screwdriver. This would normally be bad for the caps, but you are replacing them anyway!

[lilmonk3]

Re: Samsung Spn4235 No video or sound

Ok all glass fuses are new and I am getting 5.05 V on the 5v stb

Ah yeah, definitely bulged.

That meter is fine and looks like it is autoranging which considerably simplifies testing some things.

A few things to check.

Do you get stable 5V standby? (There should be a pin or two marked 5Vstby, 5Vst...) Check the voltage with the black probe in a spare screw hole on the back of the frame.

Are all the fuses on the power supply good? I have seen plasma TVs with a separate fuse for the high voltage PFC bus. Check all fuses you can see.

After you replace the caps, more testing can be done.

[lilmonk3]

Re: Samsung Spn4235 No video or sound

Caps have arrived? So do I need to do anymore testing before I tear this apart to replace these caps?

[selldoor]

Re: Samsung Spn4235 No video or sound

Go for it! you cant test much more until you have a steady power supply.
Take care when de- soldering not to pull too hard if the solder is not quite melted, or you will pull the copper trace off the board. If you have any soldermop you can get some of the solder off first. If the solder on the board is hard to melt it will be without lead, sometimes adding a bit of new solder helps it to flow. Also heating the area to be de soldered with a hair dryer can help.

[lilmonk3]

Re: Samsung Spn4235 No video or sound

Go for it! you cant test much more until you have a steady power supply.
Take care when de- soldering not to pull too hard if the solder is not quite melted, or you will pull the copper trace off the board. If you have any soldermop you can get some of the solder off first. If the solder on the board is hard to melt it will be without lead, sometimes adding a bit of new solder helps it to flow. Also heating the area to be de soldered with a hair dryer can help.

I have few options for desoldering .. I have a all in one desoldering iron with the pump.. I also a 60w solder iron and desolder braid and hand held solder sucker... So one way another I will git r done If something tragic happens while I am doing this, have a beer in my memory LOL

[selldoor]

Re: Samsung Spn4235 No video or sound

If you hit it with ALL those at once something tragic could happen!! or the caps might
surrender and walk off the board.

[lilmonk3]

Re: Samsung Spn4235 No video or sound

LOL... I wont use all of them at once

[lilmonk3]

Re: Samsung Spn4235 No video or sound

Well all caps replaced smoothly.. BUT SAME OL PROBLEM.. Any have any other ideas?