Mitsubishi DLP

[severach]

Re: Mitsubishi DLP

Why not have the ladies make them for you?

[PlainBill]

Re: Mitsubishi DLP

OK, I've had a chance to check out the Mitsubishi and have a LITTLE more information. When it is turned on there is the very audible (clear across the room) of something spinning up. Within 5 seconds the sound is inaudible (to my ears). I assume this is the color wheel. If I stand next to the set with the sound muted I can hear a low pitched rumbling sound, much like I would expect from a fan. This is not audible at normal viewing distances.

After the picture goes 'wonkey' I can hear the rumbling sound at normal viewing distances IF the audio had been muted. I was expecting something much higher pitched. At this time I have not made an attempt to trace the sound to a specific assembly.

Wizard, does this description match what you would expect from a bad color wheel? And do you have a part number and source of a replacement?

Thanks,

PlainBill

[i4004]

Re: Mitsubishi DLP

toasty, great confusion humor there!
<wink>

if i picked up the pieces right, wheel slows down(because of bearing problem) and the phase (between Digital Micromirror Device and wheel) is lost, ergo you get luma channel in..hehm..some color...

http://electronics.howstuffworks.com/dlp2.htm

that motor should be some sort of servo system, so i guess wheel is now vibrating and that offsets/confuses that feedback mechanism..to think speed is ok, while it really is not....
(i don't see how can this issue be anything else than that wheel, because it alone produces the colors in such a system. DMD on it's own is just a b/w image...)

but how long can the DMD itself last?
i mean it's essentially a mechanical device...
good lord!!!

heh, i like the idea about recording sounds on pc...i used something similalr myself when i was curios about how long is my fridge working/staying off...
not because i'm deaf(though my dad surely is) but i can't really wait those on/off cycles...

[PlainBill]

Re: Mitsubishi DLP

I haven't dug through that part of the schematics, but it would seem there must be a sync signal from the color wheel to the DMD controller. I can see several causes for the problem. The problem could be the wheel was not running at the proper speed, the sync signal was not generated at the proper time, the sync signal was lost on the way to the controller, the controller was defective are just a few of the possible causes.

What had me baffled was the lack of any error indicator. To me it would be obvious that the controller should be programmed to report a loss of sync signal or motor speed out of range. The only thing that made sense was a sync signal out of phase. But what do I know? The first TV I worked on had a black and white picture and over a dozen tubes.

PlainBill

[Toasty]

Re: Mitsubishi DLP

>>was the lack of any error indicator<<
Funny that. I thought so too, but with no exposure to those sets, I couldn't say.

You'd think that was the case. I mean, we've had servo motors and PWM controlled motors since the first portable tape players came out. Why wouldn't this advanced (light bulb and spinning color wheel, are you kidding me??) TV set have an error message that the wheel speed is wrong, etc.

>>The first TV I worked on had a black and white picture and over a dozen tubes.<<
Philco 19" *ahem* *cough* "portable". BWAHAHAHAHAA!!!

Yeah. Made out of STEEL boys & girls!

I still have the spare fusible resistors for it...

[Wizard]

Re: Mitsubishi DLP

Samsung and RCA will report error if color wheel doesn't spin up correctly.

Cheers, Wizard

[i4004]

Re: Mitsubishi DLP

>What had me baffled was the lack of any error indicator.

me too, for first 20sec..then i went "error indicator for whom?"
as not everybody will be willing to attempt to repair it...

those who do repair will probably know even without indicator...

[PlainBill]

Re: Mitsubishi DLP

>What had me baffled was the lack of any error indicator.

me too, for first 20sec..then i went "error indicator for whom?"
as not everybody will be willing to attempt to repair it...

those who do repair will probably know even without indicator...

Well.... Maybe. Perhaps you have noticed not all TV techs are created equal? A message would make the fault obvious. And since it could all be done in firmware....

PlainBill

[i4004]

Re: Mitsubishi DLP

true, but it can't be repaired thru firmware...
<wink>

it would be usefull, but i think their line of reasoning(why they didn't put that in) was the one i mentioned above

one more thought: can it be that you didn't access the service mode of that device?
perhaps it does include indication, but just in that mode...

[PlainBill]

Re: Mitsubishi DLP

true, but it can't be repaired thru firmware...
<wink>

it would be usefull, but i think their line of reasoning(why they didn't put that in) was the one i mentioned above

one more thought: can it be that you didn't access the service mode of that device?
perhaps it does include indication, but just in that mode...

Good question. I HAVE accessed the service mode. Most of the information is pretty mundane - hours of operation, hours on present lamp, etc. I never examined all the screens in detail. The only service functions possible are centering the picture and saving the light engine parameters - looks like I may get to try that one soon.

PlainBill

[PlainBill]

Re: Mitsubishi DLP

I've got about 4 electronics projects in the works at the moment, and several real life issues that are taking my time, so progress is slow. I'd decided to check out the source of the noise (it's getting worse) and ship my light engine in for rebuilding if that seemed to be the problem. It would take an extra two weeks, but would save $300. Well, this is getting seriously weird.

I pulled the back off the set and verified both the DMD fan and the fan in the vent duct were free to spin. I couldn't actually touch the ballast fan even by pulling the lamp. After blocking the lamp switch and turning it on I got the expected good picture. But get this, the source of the low pitched noise is the fan in the vent duct!!! I heard a high pitched whine from the area of the DMD fan, but when the DMD fan is stopped by the 'finger on the hub' (never on the blades) trick, the whine went away. And with the back off the set, it is behaving much better.

About the only idea I have left is to stick a thermocouple into the back of the set and monitor the temperature when it fails. I know of a few tricks I can do to cool the light engine / lamp area without changing the temperature of the main electronics and power supply area. Can this be a pure thermal problem?

PlainBill

[tmwalsh]

Re: Mitsubishi DLP

Quote:Can this be a pure thermal problem?

Why not? Your first post noted that it occurred in the warmth of the afternoon, only after operation for a while. My expectation is that it is reaching a temperature equilibrium that is raised by an increased room temperature. The bearings on the color wheel motor may be 'permanently lubricated', but their idea of permanence is when you come in to buy a new one, or a new set. If you can disassemble it, why not take the motor apart, clean the bearings, and re-lube them? If the lube is failing, or marginal, an increase in temperature can make the motor drift to the point where the phase locked loop or whatever they are using cannot compensate with increased volts/amps.
In addition, it is possible that the cooling fan motors have a lubrication problem or a dust buildup problem on the blades or in the ductwork. I cleaned my son-in-laws computer one time, as he was ignorant of the necessity. There was a plastic duct from the rear that fed a fan mounted on the CPU. It was literally full of critter hair of one sort or another. Dunno if it caused permanent damage, but it was not observable without disassembly.
Of course, take all this with an alka-seltzer, as a grain of salt might raise your bloodpressure...
tom

[PlainBill]

Re: Mitsubishi DLP

Quote:Can this be a pure thermal problem?

Why not? Your first post noted that it occurred in the warmth of the afternoon, only after operation for a while. My expectation is that it is reaching a temperature equilibrium that is raised by an increased room temperature. The bearings on the color wheel motor may be 'permanently lubricated', but their idea of permanence is when you come in to buy a new one, or a new set. If you can disassemble it, why not take the motor apart, clean the bearings, and re-lube them? If the lube is failing, or marginal, an increase in temperature can make the motor drift to the point where the phase locked loop or whatever they are using cannot compensate with increased volts/amps.
In addition, it is possible that the cooling fan motors have a lubrication problem or a dust buildup problem on the blades or in the ductwork. I cleaned my son-in-laws computer one time, as he was ignorant of the necessity. There was a plastic duct from the rear that fed a fan mounted on the CPU. It was literally full of critter hair of one sort or another. Dunno if it caused permanent damage, but it was not observable without disassembly.
Of course, take all this with an alka-seltzer, as a grain of salt might raise your bloodpressure...
tom

All fans have been checked and are dirt free (with the possible exception of the ballast fan). My mechanical skills are adequate at a macro level; I'm reluctant to try anything on the color wheel. I'm quite good at taking clocks apart; getting them back together - not so good.

I'm coming to the conclusion that it is NOT the color wheel itself, but either the circuitry controlling the color wheel speed or something processing the sync signal. I'm sure I'm over-thinking the problem. I did a few simple experiments and am getting further from a decision all the time. Here's a quick summary:

Back on, room temperature about 73°F, color good for about 1 hr.
Back on, room temperature about 77°F, color good for about 1/2 hr.
Back off, room temperature about 77°F, color good for > 8 hrs *
Tried using a 120mm case fan
Back on, fan positioned to blow air through back grill onto light engine, color good for > 8 hrs * (12V fan running at 7 volts - very low speed)
Back on, fan positioned to blow air through right side grill onto power supply and control boards (fan at full speed) color good for 1/2 hr.
Back on, fan positioned to suck air from left side of TV (the lamp fan exhausts air through the left side; this was assisting that flow plus ventilating the chassis) Color good for 1 hr at slow fan speed; > 6 hrs * at full fan speed. * indicates the test was terminated without the color going bad.

I don't want to use the 120 mm fan blowing onto the light engine, this could have the effect of blowing dust into the mirrors. A smaller fan can be positioned so it cools the electronics of the light engine. Or I could use a smaller (80mm) fan to assist chassis ventilation. Or use a faster fan in the exhaust duct.

Or I could just sent the light engine in to be rebuilt, specifying that it fails when the internal temperature reaches 85°F.

PlainBill

[Nama]

Re: Mitsubishi DLP

What did you end up doing Bill?. Is your TV working?... I'm about to buy a faulty 52" Mitsubishi DPL TV WD52525 for cheap. Although it may not be a cheap fix for me. I will still learn something.

[PlainBill]

Re: Mitsubishi DLP

What did you end up doing Bill?. Is your TV working?... I'm about to buy a faulty 52" Mitsubishi DPL TV WD52525 for cheap. Although it may not be a cheap fix for me. I will still learn something.

I've made progress, but the final resolution is still pending. I've established it appears to be heat related, but haven't eliminated all possibilities. I put an 80mm case fan on the grill just behind the light engine. The set will operate all day, even when the room temperature hits 80°, with this fan running on as little as 5 VDC.

As is the case for many people in these days, money is tight; I don't want to spend $300 only to have TSM tell me the problem was the ballast fan, or they didn't find any problem, thanks for the money. Plus it hasn't escaped my attention that the noisy fan in the vent duct is probably moving less air than it should.

My current plan - when I find time - is to pull the light engine and make sure the ballast fan is operating smoothly. A replacement for the duct fan is available for about $20, that's also a 'must do'. I've also thought of a duct for the DM fan so it pulls room air rather than chassis air (a simple cardboard collar would do that). And I want to measure the temperature near the light engine so I can establish a temperature at which it fails.

If I recall correctly, the WD-52525 is notorious for having bad caps on the DM module in the electronics chassis. This is demonstrated by a blinking light.

PlainBill

[PlainBill]

Re: Mitsubishi DLP

OK, here is the final update on this problem. Replacing the fan in the exhaust duct didn't help. The enhanced cooling from the 80mm fan helped for a while, but over the summer of 2009 it became obvious the problem was getting worse. Initially the TV was performing perfectly with the extra fan powered at 5V. Then it became necessary to up the voltage (and fan speed) to maintain proper operation. By the end of the summer even with the fan running at full speed the TV would lose color lock within an hour.

About this time I found a used, but guaranteed light engine on eBay for $200. I ordered it and installed it. Unfortunately the seller had done a poor job of packing it and the mounting plate was bent and the lens assembly was twisted. After some discussion I swapped the lens from 'my' light engine to the 'new' one and tried it. The replacement light engine has been functioning perfectly for more than a year now. No additional cooling fans have been necessary.

My conclusion is there was a problem with the electronics board in the light engine. Something (possibly a capacitor) was changing in value and the synchronization pulses from the color wheel were not being handled properly. Unfortunately, I never investigated that area. I had foolishly assumed that a major part of the electronics would be UNDER the light engine, rather than virtually everything being on the back side.

PlainBill

[Evil Lurker]

Re: Mitsubishi DLP

I just aquired one of these sets today for the price of a couple gallons of gas... seems as though I have gotten myself hooked up with the local Sears installer who frequently hauls a bunch of TVs to the dump on a regular basis and well basically he was happy for me to haul it off for no other reason than to get it out of his store. Looks like I'm going to be in for a ride with this one... and a fairly hefty repair bill if it needs new bulbs and/or light engine. But I figure if I can get it up and going for $300 it ain't too bad for a 65" set.

Will post pics as soon as I get some lithium batteries for my digital camera and get time to tear into it.

[Evil Lurker]

Re: Mitsubishi DLP

OK I have had some time to tinker with the set. So far it powers on OK, and I have access to all the basic menus via the front panel controls. Picture looks good but maybe a bit dim. So far its not throwing any error codes.

But, here is the problem... henever I plug in an HDMI device, the TV recognizes it but will not display a picture.Tried it on both ports. I can go into the antenna channels and it displays the "ant races" on the analog chanels, havent hooked it up to get a signal on the digital ones yet. Any ideas what might be causing the no picture on the HDMI problem?

[PlainBill]

Re: Mitsubishi DLP

OK I have had some time to tinker with the set. So far it powers on OK, and I have access to all the basic menus via the front panel controls. Picture looks good but maybe a bit dim. So far its not throwing any error codes.

But, here is the problem... henever I plug in an HDMI device, the TV recognizes it but will not display a picture.Tried it on both ports. I can go into the antenna channels and it displays the "ant races" on the analog chanels, havent hooked it up to get a signal on the digital ones yet. Any ideas what might be causing the no picture on the HDMI problem?

The HDMI processing is handled by two ICs on the DM board. The tuners and the analog inputs are processed on the signal board and passed to the DM board. One possibility is the TV is not handling HDCP handshaking of an HDMI signal.

One way to handle this is to hook up various signal sources and analyze what does and does not work. Finding a used DM board should not be difficult.

PlainBill