Samsung Projection CRT HCN4226WX/XAA Will Not Turn On

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Old 02-09-09, 01:22 AM
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Samsung Projection CRT HCN4226WX/XAA Will Not Turn On

I acquired this TV from a friend. He said that the TV was on, then it just shut off (Super Bowl Sunday, poor guy). There was no pop or noise or anything. It was just like someone shut it off. When I attempt to turn it on, nothing happens. There are no LED's or noises.

I opened up the case, and the fuse looks fine. Nothing looks to be charred or disconnected.

When I plug in the TV (after it's been unplugged for a while) I can hear a very quiet sound, it sounds kind of like something is beginning to charge up or something. It reminds me of a camera flash charging up. It will last for maybe three or four seconds, then it goes totally quiet. If I unplug then plug it back in within a minute or so, I hear nothing.

I have a multimeter and know more about electronics than many people do, but I don't know a whole lot about transistors or diodes. I have a friend who said he would help me with soldering if it needed it. I'm a quick learner though, and I am great with following directions if someone would go step-by-step with me.

I haven't a chance to do any type of diagnostic on it, other than looking around back there with the back panel off. I did check the fuse and it is fine. Where would you suggest I start?

Thanks in advance for your help. I'm looking forward to enjoying my new TV with my family.
 
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Old 02-09-09, 05:54 AM
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You can save yourself a lot of time and trouble by replacing the power supply sweep module. Part # AA94-08574A costs around $150.00 . Not bad for a free tv.
Do a google search and might find a rebuilt one for even less.
 
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Old 02-09-09, 04:43 PM
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Craftsman_50 -
Thanks so much for the quick reply and the part number to get it up and running again. While replacing the whole board would be infinitely quicker and easier, I am looking at this TV as kind of a learning experience. Another part of it too, is I'm trying to do this without putting out any more money than I have to (attempting to keep my wife happier). The TV wasn't free, but was pretty cheap. I might replace the board though, if the whole "learning experience" thing doesn't work out.
For some time now, I have wanted to learn more about circuits, transistors, capacitors, and other electronics. This would be a great opportunity for me to learn how to do some of this stuff.
Which transistors and capacitors would it be worthwhile for me to check out, or have a history of failing? I have a sneaking suspicion that the problem lies somewhere between (or including) the large capacitors (The barrel shaped ones about three inches tall and an inch thick. Also, do they need to be removed before being checked?) and the H.O.T. I believe the barrel shaped ones are at least starting to build up a charge, judging by having my head close to the board when it is plugged in, and where I can hear a click before I can't hear any more noise. It also sounds like it may be somewhere around the voltage regulators before the H.O.T., somewhere in there anyhow. Would jumping the power button make any sense here? Part of me thinks not, since I am not getting any LED's or lights up there, and nothing happens at all when I press the power button.
Thanks again, and any more help anyone can give me would be greatly appreciated.
 
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Old 02-09-09, 05:17 PM
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If its a scream sort of sound,then that indicates thats there is a short or close to it on the secondary side of the ac power transformer.First thing to check is the HOT to see if the middle leg is shorted to one of the other legs.Outside legs normaly show shorted together when in circuit.If its not you will need to check the voltage on the middle leg.Should be around 130 volts dc from leg to groung.Post back and let me know.
 
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Old 02-10-09, 11:54 PM
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Does that mean I can check it while it is still on the board? Or do I need to remove it? Do I check it from the bottom of the board, or is there access to the contacts on top?
Thanks again for your help.
 
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Old 02-11-09, 04:43 AM
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Yes you check it in circuit.If its not shorted you need to plug the set in and monitor the voltage on it.You can check it from top or bottom,which ever you feel more save doing.
 
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Old 02-11-09, 11:08 PM
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I checked the HOT like you suggested. The middle leg is not shorting to either of the outer legs. I then plugged in the TV and checked the middle leg to ground, and got no reading at all on the multimeter. What would you suggest next?
Also, just to reiterate I am getting nothing from the power button at all. No LED's around it and no response when pressing it in. Could it be that the power button is bad?
Thanks again for your help.
 
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Old 02-12-09, 05:10 AM
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OK , that means the problem is going to be in the ac power supply circuits. Check the voltage on the power switch. One side should have + 5 volts dc to grd. Post back.
 
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Old 02-12-09, 10:01 AM
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Do I need to remove the screen to get to the power button, or is there an easy way to pop the button out? Or can I reach through the back of the TV to get to it?
 
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Old 02-12-09, 05:16 PM
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You could follow the cable to where it plugs into the circuit board and then just check to see if at least one of the wires has 5 volts.We are just checking to see if we have "standby power ".It's the part of the power supply that is always on to allow the remote and power button to start up the set.
 
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Old 02-12-09, 10:55 PM
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I am getting 2.32 volts to the power button instead of 5. Just for fun, I pressed in the power button while testing, and it dropped down to zero while the button was pressed in. I don't know if that's relevant, but I thought I would let you know.
 
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Old 02-13-09, 11:42 PM
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When I tested the HOT, I'm pretty sure it was the correct transistor. I thought it would be good to double check though. In the pic the arrow points to what I believe to be the HOT. Am I right?
Pictures by timblin - Photobucket
Thanks
 
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Old 02-14-09, 04:44 AM
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That appears to be the right one.To make things easier go to this site and download the service manual for your set.... eServiceInfo.com ....
 
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Old 02-14-09, 01:57 PM
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OK, have the service manual. Thanks.
What should I check next?
 
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Old 02-14-09, 02:35 PM
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Go to page 8-1 , 8-2 .That give you an idea of what volts your going to be checking.Now go to page 10-7.At the top find ICS802 Your going to find that part on the chasis and check to see if it has 5 volts dc on the out side.If it has power then find T801S on page 10-7.On the right side of it you will see fuses marked by an " ! " in a triangle.Find those fuses on the chasis and check if any are open.

Hang in there finding the parts in the diagram and on the board can get agravating. Beer 4U2
 
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Old 02-16-09, 05:41 PM
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I checked everything you told me to. It all checks out as good (the voltage on ICS802 was a little above five). Thanks so much for your help. What should I check next??
 
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Old 02-20-09, 04:51 PM
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Craftsman,

Do you have any other ideas?
Thanks so much for your help so far.

Jerry
 
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Old 02-21-09, 05:15 AM
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Well the stanby power supply is working.With no fuses blown on the secondary of the main transformer,thats moves us to think the primary is not starting up to provie power to the rest of the set.

Start by testing the resistors that are marked like R838 .Those are used as fuses too.Then if those check ok , I would replace both IC821 and IC831S . One IC kick starts the power and the other keeps it going.
 
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