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heatsink is arcing

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Rothwell

New Member
my toshiba dlp tv all of a sudden started making a buzzing noise when i start it up. the sound will work when i turn it on, but the lamp wont turn on, a hard knock in the back of the tv will get it working 90% of the time, i figure that should indicate a bad connection, right? i opened up the back of the tv and turned it on, i noticed a white-blue light coming from the lamp power supply, i figured this is probably an arc, although i couldn't see it directly because this part is burried from view in the back of the t.v. I called up customer support, and given the discription of the problem, they suggested that it was a problem with the lamp power supply, but replacing it would cost $60, so i figure i should try to fix what i have before i go spending that money. the only thing i can think of is that the heat sink is arcing, does anyone have any ideas what might be wrong? here is the part that i'm talking about TOSHIBA 46HM94 Projection - Lamp Ballast / Driver D4434M-01 Plasma LCD DLP Television Service Parts
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Well heatsinks don't arc - it's just a piece of metal. However, something else may be arcing to the heatsink, and it 'may' be possible to identify and replace that.

But $60 sounds a cheap enough repair anyway, a remarkably cheap price for a PSU.
 

Chippie

Member
But $60 sounds a cheap enough repair anyway, a remarkably cheap price for a PSU.
Do you have acess to a soldering iron? What other test equipment?

Nigel's answer is probably your best bet...especially if you have little electronics experience....
 

sheldonstv

New Member
the problem you may have is a dry joint around either the driver side of yr lamp invertor or one of the plated thro gnd connections on the pcb somewhere an easy fault to spot after you have removed the invertor board from the set.....if left you will destroy the mosfets on the board and probbably the lamp as well-if you arent sure of doing the job eitha get a replacement invertor or have someone repair the board for you
 

Rothwell

New Member
i managed to get a view of the part while it was hooked up to the tv so i could see exactly what was happening.
the spark is jumping between the capacitor and the resistor.. i dont know if just replacing one of those components would fix my problem, or if it's a problem much bigger than that with the voltage. better yet, it would be nice if there was some kind of insulating paint or something else that would work in a very tight space to keep the electricity from jumping. the only equipment i have is a soldering iron and a multimeter
 
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smanches

New Member
If it's jumping that gap, then either the insulation on the cap or resistor is cracked wide open, or something is causing too high of a voltage to be generated.
 
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sheldonstv

New Member
now this is where you need to take a close look at the capacitor to see if there isnt a crack in it(not an unusual failure...),also have a look at the pcb and see if where the arcing has occurred if the board has been marked or became conductive(you may find a dry on the solder side of the board which has been arcing for some time...or there may be some other failure which will need someone with a bit more experience of how the invertor works to repair the board for you....if you get it wrong you will cause some very expensive damage
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Just one point! - is the lamp faulty?, I seem to recall hearing recently that a duff lamp can cause the EHT to rise excessively and cause it toi arc over.

I've only ever seen one DLP set, that was faulty and we scrapped it - it's pretty well failed obselete technology.
 

Hero999

Banned
That's true a lamp failing can even cause the inverter to fail, if it's insulation isn't up to handling the open circuit voltage, it will arc over which will destroy it causing a permant short circuit.
 

Rothwell

New Member
i dont think it's the lamp's fault, this problem has been happening with the past 2 lamps, and we're not going to spend 300 dollars on another lamp. once this lamp is done with, so is the tv, it's given us too many problems. i'll be sure to never buy a dlp tv again.

so i tried putting this stuff called carona dope on the components that it was arcing from. it stopped the arcing, but not the problem. so this probably means that it is a bad capacitor?
 
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sheldonstv

New Member
thing to check is wether the lamp is seating in its connector ok-a hi resistance connection there will cause problems there may be a problem with the invertor regulation wise if the lamp isnt seating in the connector properly but most failures ive had were due to lamp failure-going sc then oc which usually destroys fets on the panel-easily fixed but its up to the customer wether they like the set enough to either have the pcb repaired or replaced(for reliability)and or replacement lamp....its up to you as the owner of the set as to wether you want to pay for a repair-you wont cure the fault in the way you are trying to do....
 

Bill217

New Member
I also have the same problem. found d-3 on ballast bd to be open and a small hole in the resistors side. Replaced the resistor but still not work. Does anyone know where i can get a schematic for this circuit? I would like to repair this myself
 

Rothwell

New Member
yeah.. my resistor also had a hole in it... i also replaced it. didn't fix the problem. which makes me think it's probably the capacitor, but i dont know what the 3 numbers mean. it says 102k 2kv 48 ... you can see in the picture.
 

Chippie

Member
i dont know what the 3 numbers mean. it says 102k 2kv 48 ... you can see in the picture.
The capacitor has a value of 0.001mfd or 1000pf and is a 2kv rated component...It's a high voltage cap and needs replacing like for like...


The 102 is the clue...its a standard designation for values...Have a read on Google for component values..
 

tcmtech

Banned
Most Helpful Member
I have fixed loads of welders and plasma cutters and a few CFL driver boards that had arc over problems on circuit boards.
Its an easy fix too. Just take a utility knife/exacto knife or a dremmel with a small burr cutter on it and cut out all of the bad board where the arc happened. Then make sure your electrical solder connections are good then just fill it all in with RTV silicon.
I have repaired many $1000+ circuit boards with about 10 minutes of work and a few squirts of silicone.

Many of the circuit boards on home electronics are not sealed and after a while they get dust build up and the higher voltages track over and then burn a carbon track into the board.
To prevent further problems I usually coat and seal the whole board in clear coat spray paint as well. Then they are reasonably dust and moisture proof.
 
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