DLP Lamp Ballast diode replacement

Discussion in 'Technical Repair' started by wayneh, Aug 12, 2013.

  1. wayneh

    Thread Starter Expert

    Sep 9, 2010
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    I need guidance on replacing the diodes on the ballast board for a mercury lamp.

    I'm helping a friend fix her Toshiba DLP TV model 62HM84. The bulb was bad (I could see a melted area inside it) and we replaced it, but it still doesn't start up. You can hear a spark noise as it tries to start the arc.

    These Toshiba models are notorious for failure of the lamp's ballast board, so I intend to remove it next and take a look. These boards were made by Rubycon, Toshiba PN 23122468 ballast. I cannot find a schematic. The TV's service manual has the other schematics, but not for the ballast board. The best photo I can find is attached.
    Ballast 2.jpg
    The 2 large diodes in the rubbery sleeves D2 and D3, and the R3 1kΩ resistor in front of them fail so often that you can even buy a "repair kit" on e-bay containing these. But he wants $30 for <$5 worth of parts. I refuse.

    Best I can tell from other folks reporting successful repair, the diodes are Sanken "damper" diodes FMV-G2GS.
    Screen Shot 2013-08-12 at 2.07.56 PM.png
    I'm just wondering if there's anything I should know about these, what their role is, and anything to look for if I need to source them from another manufacturer.
     
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  2. wayneh

    Thread Starter Expert

    Sep 9, 2010
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    To be more specific, it looks like I can get this diode locally. It looks good to me but it has a voltage rating of 1500V versus the original 1700V. I have no way to tell if that matters but it seems unlikely to me that the rating should be that critical?
     
  3. wayneh

    Thread Starter Expert

    Sep 9, 2010
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    I seem to be talking to myself, but here's another question.

    The R3 1kΩ resistor; it commonly fails to open. To me that sounds like a fuse.

    My normal inclination would be to replace it with one with a higher wattage rating. But if it saved some other part of the circuit by acting as a fuse, that would be a dumb choice. The next failure could be much worse.

    Thoughts?
     
  4. wayneh

    Thread Starter Expert

    Sep 9, 2010
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    Great news for this project: (not that anyone but me seems to care ;))

    Tonight I removed the ballast board from the TV and found that indeed the 1k R3 resistor failed to open and 1 of the two diodes D2 and D3 are toast (30Ω in either direction, IIRC).

    Gotta love the internet. I would have never even looked at these components if others had not done the heavy lifting before I got here.

    Still looking for a good damper diode. Recommendations?
     
    Last edited: Aug 15, 2013
  5. wayneh

    Thread Starter Expert

    Sep 9, 2010
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    Well, I've gone ahead and ordered the 1500v, 10A rated damper diode to replace the original 1700v, 6A rated one. I'm a little nervous about the lower voltage rating but hoping/assuming it won't matter, and that the higher amperage rating may help with longevity.

    Digi-Key had both the diodes and the Sil-Pad tubes that goes over each one.

    Fingers crossed.
     
  6. apprenticemart2

    Member

    May 7, 2013
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  7. Metalmann

    Active Member

    Dec 8, 2012
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    This thread makes me wonder about my latest repair job. Replacing the lamp on our DLP, Samsung.

    I've replaced 2 lamps within 5 years, but now I noticed it takes a lot longer to come up to full brightness. Could it be this ballast?? Or this diode?:confused:
     
  8. wayneh

    Thread Starter Expert

    Sep 9, 2010
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    Yes, I know these obsolete parts are still available, and I even found them as low as $3 each before shipping. Very tempting.

    I went with Digi-Key because they were the only place that I could find the Sil-Pad tubes that surround the diodes, and they also had the "modern" Fairchild damper diodes. And they ship inexpensively.

    I figure the diodes should work for a while at the least. It the set fails again soon, I'll have a good idea why.
     
  9. wayneh

    Thread Starter Expert

    Sep 9, 2010
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    From my limited learning about these things, you can be pretty sure it's either the bulb or the ballast.
     
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  10. wayneh

    Thread Starter Expert

    Sep 9, 2010
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    Woohoo! (Dancing a victory dance.)
    The parts arrived today from Digi-Key and after a bit of soldering, my friend's TV is fixed! She thinks I'm a freakin' genius.

    That may be true, but in this case all I needed was to be able to read. It was bad news, good news. Bad: Her TV failed by a well known and documented flaw. Good: The experience of those who went before made the repair fairly easy. Thank you internet.
     
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  11. Sensacell

    Well-Known Member

    Jun 19, 2012
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    In my experience, "after market", i.e. affordable replacement projector lamps are crap, lasting a minuscule fraction of the original factory lamp hours.
     
  12. LDC3

    Active Member

    Apr 27, 2013
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    It could be just the temperature.

    One winter, I was in a room with the temperature about 60 ºF. I turned on the lights and noticed that they were only half as bright as the day before. In about 15 minute, they were as bright as before. The reason is that the mercury in the fluorescent tubes needed to heat up and evaporate for the light to be at full brightness.

    You see the same warm up needed for sodium and mercury street lamps.
     
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  13. mrjhua

    New Member

    Oct 24, 2013
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    Hey WayneH!
    Love your post but I got a question do you still remember what the part number on the R3 and D2 and D3?

    A link would be great, I got the same problem my ballist went out on me.\
    Thanks
     
  14. wayneh

    Thread Starter Expert

    Sep 9, 2010
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    Sorry I missed your post until just now. Not sure how I missed it. :(

    I ordered the FFPF10F150STU-ND diodes from DigiKey, $1.20USD each. D2 and D3 are identical. I also ordered the thermal sleeves (BER156-ND THERM PAD TO-220 TUBE 11X25MM) there.

    I already had some 1K resistors and I just used one from my stock. I think it was 1/4 watt rated. The original resistor on the board was tiny, so the power rating was not much of an issue.

    The TV is still working fine after >2 months.
     
  15. dakotakid

    New Member

    Nov 21, 2013
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    Thanks for posting this info. I've had the ballast out of my Toshiba DLP for about a year and finally just got around to wanting to repair it. There is info about the repair on the net but seldom are the parts listed so thanks for providing that info. This was a big help and I guess I'll go ahead and try this repair before I just scrap the TV altogether.
     
  16. wayneh

    Thread Starter Expert

    Sep 9, 2010
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    Go for it! I was encouraged by finding very good take-apart videos and pictures. This proves it's a common problem. It was not as difficult to tear down as I might have thought otherwise.

    Once you get the board out, it'll be easy to check the components before you invest in new parts. Good luck!
     
  17. gmzombie

    New Member

    Dec 15, 2013
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    so ive dived into this same issue with my toshiba 62hm94 set but it seems to me that my dioades d2 and d3 are fine but i have d5 and d6 that are showing out along with the resistor. do you happen to know what i should use for that diode as they both say 46b on them with a purple line instead of a white line?
     
  18. wayneh

    Thread Starter Expert

    Sep 9, 2010
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    Sorry, I have no idea. I never found a schematic for this board so it comes down to reading numbers off components. Perhaps if you could post a good picture. Also, take a look with a good light and a magnifying glass. Sometimes it's much easier to read details that way.
     
  19. gmzombie

    New Member

    Dec 15, 2013
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    here is the pic i could take. it has one diode back in its spot. they are both the same diode and the diode itself just reads 46b 46b on it. its d5 and d6 that both read open on my meter and of course the resistor at r3
     
  20. Jonathanri

    New Member

    Dec 26, 2013
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    I have found a site http://www.replacementvparts.com that I bought the same ballast and it worked perfectly for only $30.00 plug in and play

    I have noticed that they also do have a bunch of other DLP parts. The prices are all very low

    Just thought this might help someone out there
     
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