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Discussion Starter #1
Greetings, I had a lot of fun repairing my old RCA 60" Convergence correction problem - thanks to this forum... Its been a while and that TV is still working as good as new!

Now to the new adventure... We purchased a Toshiba 72MX196 in 2006, while many others had trouble with their Toshiba DLP, ours did not have much problem until just before this Christmas!

The picture was getting a tiny bit dimmer so I ordered original (claimed by seller) lamp but sellers sent aftermarket, it work a bit but need a few restart to light up. I questioned the seller and they told us to return saying it was their supplier mistakes. I re-install original lamp, it work fine but this time it need a few re-start too to light up. A week later, it just refused to light up anymore. When turned on, I got solid Blue LED, then when it refuses to start, the Yellow LED (Lamp) flash 3 times every 3 seconds, pause a bit and did this for 5 times, a total of 15 flashes. The error codes in the manual does not show this sequence and calls to Toshiba C/S is almost useless, just said replace lamp.

I ordered original lamp (made by Phoenix) from Discount for $125, did the same "no light up re-start" thing so opened up the back cover, remove the light engine assembly (very carefully) to get a visual at the Ballast Driver (RUBYCON RPB-5468BA Toshiba P/N V71A00000100). This part is not available anywhere except some electronic company in Hong Kong.

I checked the usual resistor that burned out on other similar ballast but every thing seems at par. I re-flow some solder of heavier pins and re-install the ballast. plug in power and Yellow LED Blink a few more times before powering up. Hit power on remote, Blue LED came on, in a few seconds, I have dim picture for about 60 seconds and poof! no light. While the TV tried to restart, I went to the back of the TV (with cover still off) to look at what is going on - the lamp light up yellowish color, no too bright and start to brighten up to white light immediately, but within 5 seconds, the lamp shut off again. This tells me the lamp is getting power from the ballast driver but what is shutting it down? I by passed the overheat sensor with same result.

I read from the other forum all sort of things that others (with older DLP) are doing to fix the ballast driver and many are successful. At $4000, this is a very expensive TV but, today's 70" LCD can be had at $2000 so I don't thing I am going to sink much money into this TV.

It would be interesting though to find out what ticking... anyone with experience repair ballast driver place chime in... I took lots of photo on this repair and I will post it as soon as possible.

Cheers for the coming new year,
max:eek:lddude:
 

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Discussion Starter #3
Ballast is made by Rubicon, part number RPB-5468BA, so far in my search, its not available anywhere... I even went as far as a projection part supplier company in Guangzhou China that had a listing but no luck. I search high and low in the net, did not find any diagram or service manual either. I guess I will have to repair it at the component level. There's another board above the ballast that looks like a switching power supply for the ballast.

I re-installed the original Toshiba lamp yesterday, plug in power and picture show up! unfortunately, this lamo is 6 years old and nearing the end of its life so within 2 minutes, a loud pop (inside glass vessel broke) and lamp was gone.

My question here is, if the original lamp will function properly (while its alive), could it still be the ballast?
 

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Discussion Starter #5
So the other side of the argument would be, if the new lamp was able to strike up/light up, this means the ballast is providing the initial high voltage (probably in the range of 350 volt), then continue to brighten up into a whiter light, so this seems like the ballast had continue to supply the lower DC voltage to keep the lamp on, what would cause the lamp to shut off after 5~10 seconds? I can not blame color wheel or DMD because the picture and color is perfect...
The original Toshiba lamp indicated that it is rated from 38~100 Volts DC, which means Toshiba is still using DC to power the lamp, similar to their troublesome older model...
 

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Did you try authorized Toshiba parts suppliers like Encompass or Andrews? It is surprising that the ballast is not available.
 

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Discussion Starter #7 (Edited)
Encompass, yes & not available and they try to sell me the other board above the ballast as substitute.
I did not know about Andrew and search engine did not point to them. Many other forum suggested Conn in Florida, web site does not work - seems like that company is gone too... Yes its unbelievable when I contacted Rubycon, no one knows anything about their product, arguing that it is Toshiba product) until I sent them photos of Rubycon Label, then they said they need to refer me to their engineer in Japan.
Do you have link to Andrew's site?
Thanks, max

Edit: I got Andrew Electronics, correct?
part # search show nothing...
 

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Discussion Starter #10 (Edited)
Well $240 later with original Toshiba lamp (from Able Parts Burnaby), it still doing the same thing, during start up, the lamp strike up a light for few seconds, then started to brighten up, then a few more seconds later, it shut down for a minute and restart. I removed the large cap and resistors from ballast board and its power supply board to test the components but could not find anything wrong. Just wondering if I should start taking the whole light engine apart to see if I can find what is causing the shut down...

I just looked at Sharp LED, 70" (lower end) at US Costco, $1,850... wondering if I should even bother fixing, but on the other hand, I got a challenge on hand.
 

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What does it mean that you could not find anything wrong? How did you test the caps? Have you measured the output of the power supply?

You will likely gain little but trouble by dissassembly of the light engine for this problem. I would be monitoring the output of the power supplies and the signals from the DMD board to the ballast to determine where the problem might be.
 

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Discussion Starter #12
I had physically un-solder the caps and resistors from the circuit to test for leak and ohm values. I also have an old Heath Kit Cap tester that applied voltage to the cap while testing. All parts seems normal. I guess I could also just go buy some caps to replace them for the of it...

I did not measure the output of the ballast but just assuming that there should be enough voltage as the lamp definitely strike up an arc and then light up to almost full brightness, for up to 30 seconds at times.

And yes to DMD suggestion, because of the above situation, I am also suspecting some signal from DMD board shutting down the power to the ballast or, maybe something as simple as the color wheel not turning any more... I have not seen any picture of the screen as I had previously while the lamp is lighting up for that 30 seconds.

Back tracking a bit here, about a month before all this problem, I have 3 occasions where I had turned on the TV after a week off to find out its is not coming on right away, may take 2 more restart to get it going so there might be something going bad slowly since that time. It the same for my HD satellite receiver plugged to the same surge suppressor, where it started to get error occasionally that need to be unplug and re-plug and then one day it just refused to turn on.

As for checking the DMD signal, I have not got a clue on how to do this since I do not have service information, and its not likely that wife will allow more money into service manual. May be you can give me some pointer?

Thanks, max

By the way we are still enjoying that 60" RCA RPTV (Not HD but still great picture) I repaired back then :T
I have added a small fan hopefully to cool it enough to avoid coolant leak again.
 

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What parameters does your meter test on the caps?

There is a signal from the DMD to the ballast that indicates that the color wheel has locked on speed and the lamp can be lit. You need a schematic to know which lines to monitor.

There are suggestions for vendors for service manuals in the Service and Support stickies, some for a fee and some that are free.
 

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Discussion Starter #14
With an analog ohm meter, I set it at X10K, clip the red and black test lead one way, then the other way, meter will swing pass full and slowly discharge back to near zero, both times. Usually that tells me caps good but from good old day"s experience, a few caps will "leak" when voltage is applied so I also use the old HK cap tester, it has 2 leads that connect to the cap, and a Vacuum tube top round facing front with round green light in that, the bottom of the round green light opened up to triangular shape to show cap is good or stayed closed if cap is leaking. All 3 caps tested shows good.

Well the lamp had stayed on for up to 30 seconds or more at a time, wouldn't that tell me the color wheel has "Lock on speed"?
and, if that "is" the case, then something else is telling the ballast to shut down...:ponder:

I am going to spend sometime going back to the stickies as soon as I put my grandson to bed tonight. will keep you posted for sure... Cheers! max
 

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The ballast could be shutting down because of loss of signal from the DMD or because it is defective. If the lamp enable signal goes down first, before the lamp goes out, you have a problem in the DMD or system control. If the lamp enable signal continues after the lamp goes down, you likely have a PS or ballast or lamp issue.
 

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Discussion Starter #16
Thanks, that is what I have in mind and prepared to trace down, but due to plenty family matters (when one becomes grand parent and have to take care of parents in their 90's), I can only nip this project a little bit at a time. Watching TV is not priority so far and we do have 4 other smaller LCD at home. Wife:devil: suggest I just have to sit closer to gain that 72" experience! will keep you posted if any further ahead... cheers, max
 
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