Samsung HL-R4667W DLP Ballast?

[madhatter]

Hello,

I am currently working on a Samsung HL-R4667W DLP TV. The lamp is new, and will work intermittently. It appears that this TV will try to strike the lamp 3 times before timing out and giving the 3 light error message. If I keep trying, eventually the lamp will light. When it tries to strike the lamp, I can hear a rapid clicking, and when I look into the vents in the rear of the set, I can see arcing/sparking on one of the components on the ballast board. I have removed the ballast and the component where the arching/sparking is happening appears to be a "Surge Arrestor" manufactured by EPCOS. This looks similar, but the colors are different: hxxp://cpc.farnell.com/1/1/5108-230v-dc-surge-arrestor-a81-a230x-epcos.html This component looks like a really big diode, but white and no bias. It is labeled FS1 on the PCB. There are no signs of cold solder points or burning. I will try re-heating both pads on this component, but should I consider replacing it, or are other factors causing this problem? Any help is greatly appreciated.

 

[Resqueline]

I'm not familiar with these specific tv's but I have some general lcd considerations.
FS1 is an overvoltage gas discharge tube and tolerates an almost unlimited number of arcs. It seems to be striking (instead of the tubes?) but it need not be faulty.
Check out the wiring to the lamps for continuity. Also, check out any small-value capacitors often placed in series with the outputs. I've seen smd types go bad there.
Re-heating those seems to restore them. Nothing's certain here, but if you can post a good close-up of the ballast it could be helpful.

 

[madhatter]

Thank you very much for the quick reply. I have successfully tested for continuity on the lamp wiring to L5 and L8 (I assume those are test points, as the physical wiring goes into a brown potted casing. There are 4 smd components on the reverse of the board, but I am not up to speed on the identification of them. The soldering looks good. I have taken some high quality photos of the board, maybe they will be helpful. I re-sized them to meet maximum file size, but I have full resolution (~3MB) if needed

 

[Resqueline]

Ah, I see it's not a flatscreen but a rear projection tv with an arc lamp.. And a smokers tv at that, messy stuff to work on..
L5 & 8 are so-called ferrite beads (small inductors for noise suppression) but happen to work nice as test points. I gather the potted thing is a transformer of some sorts.
The four diodes, the surge arrestor, & C9 work as an ignitor circuit, so FS1 should flash during ignition attempts. Check the diodes for being equal & C9 for capacitance.
I'm not sure if it's significant but check R11 for correct resistance while you're at it. Any weakness in any one of the parts out there will lead to a weak ignition pulse.
Here & here are some threads I found discussing several aspects of this problem with that kind of lamps, drivers, & tv's.

 

[madhatter]

Yes, you are absolutely right, it is a Rear Projection DLP from a bar -- lots of smoke. I have tested the diodes, r11,and c8 and c9 (there are 2 capacitors) The diodes all give me the same reading (OL when tested reversed, and 0.5 V when tested with correct polarity), and r11 is within tolerances (6.54 M-ohm). I am, however unsure about the caps. I am not familiar with these types of caps or the expected values. They both read :

630
µ 15

repeatedly on the sides. When tested in circuit I measure 153 nF / 165 nF (depending on the polarity, they seem not to have a bias)

And you are correct again, the potted thing appears to be a small transformer

 

[Resqueline]

That means 630V (DC) & 0.15µF so your measurements would indicate they're ok. If the transformer is bad the strike would be weak too. Can't tell how to test that though..
Have a look & see if the threads I found applies to you, or just Google the name of the ballast (label on the potted thing) for more results. You can hook a PC to that thing..
It seems there's to be a DC voltage (380V?) on the output of that supply but I'm not sure which conditions applies when testing. You don't want a strike when measuring..
But there seems to be other aspects to consider too with these beasts; rated lamp power, lamp strike voltage, lamp spark gap, safety switch, hour counter, etc..

 

[(*steve*)]

What's the resistance of gooey sticky, nicotine soaked tar?

I would be inclined to clean up the high voltage parts of the board as best I could. At the very least it would make it more pleasant to work on, but there's always the possibility that the buildup of tar has contributed to some leakage etc. that makes it harder to get the arc lit.

Arc lamp! How very 1880's! Sounds like steam punk to me

 

[madhatter]

Thank you for your suggestions. I actually have 2 sets to work with, so part swapping is an option. I do know that the lamp is good (tested in other set) and the safety switch is working (lamp will not try to strike with it open) I have not tried to measure the 380v input yet, I figured I had found the culprit when I saw the sparking. From what I have read, the rapid clicking sound indicated a bad ballast, but I thought I could repair it instead of replacing the whole board. I guess the next step would be to measure input voltage, and try swapping the ballast from the other tv.