[Jim Howard]

haven't been on for a while. But I just picked up a samsung hl-t5075s, the old owner said capacitors. Well, they said it would go off and come back on, over and over. I don't know what to think but it is a 3d ready as well so I grabbed it up. Now I took off the back, turned it on, and only get the fans working, green light blinking for a while then it cycles off...and restarts the process for a couple time. then it just blinks all three front panel lights. I don't hear any clicking for the ballast, but a high pitched chirp in place of what I would expect to be a clicking...and No light. One comment, the inside was "full" of dust, I mean like a carpet of dust on the boards and all. I cleaned it out real good, and tried again....nothing.

So my big question is...what does the ballast actually "sound" like. And is this indicative of a bulb, or ballast or something else. Any ideas.
thanks all.
Jim

 

[lcaillo]

Some would call the ballast firing a chirp, some a buzz. There is usually a spark gap that you can see firing but on some later models there may not be. Switching power supplies can make a chirping or squealing sound when loaded by a short.

First guess would be a lamp.

 

[Jim Howard]

I will order a bulb on monday and see what happens. Will reply soon. oh, there doesn;t seem to be any comments about this tv model. is it just plain a goody? thanks for the fast reply.

 

[Jim Howard]

update: finances stopped bulb ordering until this past week....well no change. I did some checking online and thought about the ballast. mine does not make any noise, after all. Also, there is no flashing light thing indicating the ballast is charging the bulb. I found mention of the voltage. Where do I check the voltage? I cant find any images to show this point. I also wonder where I can find a ballast very cheap. (and I do mean cheap). Anyway, I see no swelled caps, so wondering what else I can check. We need(want) a tv. Any help/advice is very much appreciated.

 

[lcaillo]

Do you hear the color wheel spin up then lock to a steady speed? If it does not the ballast can't fire.

 

[Jim Howard]

the color wheel turns fine...speeds up and settles down. I removed the light, and watched the color wheel spin.

 

[Jim Howard]

I did read comments elswhere that we should check the voltage to the ballast (mentions a heavy 2 wire ??) I assume they don't mean the two wires going to the bulb. something about 230 volts if I rememeber. Wondering where that is to be checked.

 

[lcaillo]

NO! NOT the wires going to the lamp! Those have pulses that go to thousands of volts. You can check the voltage going to the balllast from the power supply which should be around 260-290 Vdc. You can check the control lines from the DMD board which have 3-5 volt dc or pulses. NEVER try to measure the output of a ballast!

 

[Jim Howard]

thankyou...saved my meter....I will check those wires sometime this week. Hopefully one of the 2 tvs I have will get fixed soon, cheaply. thanks

 

[Jim Howard]

OK, I checked teh voltage to the ballast and got 318 DC and a reading of 670 or so AC??? and there is no sign of the ballast even charging the bulb. No flash from the thing next to the transformer like I read about elswhere. maybe the ballast aint bad but the power to the ballast??? what is my next step? help...I need (wife wants) a tv. thanks

 

[Jim Howard]

sorry, you mentioned the control lines from the DMD board...what lines are you referring to?

 

[lcaillo]

In any DLP the color wheel has to spin up and servo lock before the DMD sends the lamp enable to the ballast. The control line from the DMD is usually a pulse labelled something like LE.

 

[Jim Howard]

so there will be a line literally labeled LE ? I will look this weekend. thanks

 

[lcaillo]

Usually something like that on the schematic or wiring diagram.

 

[Jim Howard]

ok, I am back after moving...Now I am hoping to attack the ballast board. Since I know the ballast is not doing its job, what and where would I start? Do I just check individual componenets on the board for issues? Can I do tht with the power off? especially concerning the transformer? Just don't have the money to buy another board right now. thanks for any help. I appreciate it.
Jim

 

[lcaillo]

It is very difficult to check a ballast. The parts that fail are not something that you are likely to be able to troubleshoot at the component level. The only practical way too test it is by replacement. Verify the signals to the ballast and the main supply and replace the lamp, then you will have to replace it to be sure.

 

[Jim Howard]

Well, I must say that is not what I wanted to hear...but...now I know. so I will wait till i get the money to get one from ebay or somewhere cheap. thanks. now if I could just figure out the lcd tv. You had mentioned something about a signal sent to the ballast. I havent checked that yet, been a while, so I will look for that and let you know. thanks again.

 

[lcaillo]

Get a service manual to identify the lines, but there is a lamp enable line that should change state when the color wheel servo locks. If that never happens, the ballast cannot fire.

 

[Jim Howard]

I just got the service manual so I am looking it over. Hope I can do this cheaply, like no budget. (yeah right)

 

[lcaillo]

Post what you find in your testing.