Mitsu 55511 Power Faults

Given that it is a Mitz RPTV, a going over with a good ESR meter and checking any capacitors. It is also prudent to check the main power supply circuit for proper function. I would not be suprised if there is liquid coolant on the boards somewhere.

I picked up an DCR/ESR meter and starting going over the boards. I've gone through most of the caps on the two power supply boards and replaced a couple that were marginal but still nothing. I'll continue on with the signal board and the small PCBs attached to the power supply PCBs.

As far as coolant leak, at first I didn't see anything but as I was going over the boards with the ESR meter it appeared there was a greasy looking film on the center board (looks the low voltage DC supply with the audio amplifier). So does a good degreasing usually solve the power up problem is it is leaked coolant?

I've also done more DC voltage checks and on the signal board there is a connector labeled FL which has a +24V and Flash connection which go to the low voltage DC board and the high voltage boards. The +24V is reading 0V and the Flash is reading 1.35V. Does anyone know if these are normal readings when in a powerup state?

Thanks, burnin

If the 24v line is low you likely have a bad convergence output IC or a bad vertical output IC.

This series of sets is later than the ones that have lots of bad caps, and we have not seen coolant problems in these.

Le>>

Are the convergence and vertical output ICs powered when the set is first plugged in? I wouldn't expect that they are but I'll try looking into this. Just in case this is not the issue I'll post more specific details of the issue.

The set started exhibiting a problem where it would shut off as if it lost AC power and then power back up to a standby state. It also did this when in a standby mode, it would power off completely and then come back on and the power LED would blink until it completed its standby mode.

Eventually it started powering off and reseting rapidly so I unplugged the set and came back to it later to see what was up. At that point when I plug the set in the power LED just blinks continuously.

I do not have the schematics for this set and even though the set is only a couple years old its not worth paying for service as the screen has some burn issues. I've poked around checking voltages where they are labeled and I've ran an ESR meter through the boards and replaced any cap that was questionable but no luck.

I'm already looking at a few 1080p DLP sets to replace this box and not one of them is a Mitsubishi. After owning a cheap RCA RPTV for 7 years with no problems and only having this hi-def Mitsu for only a couple of years and experiencing easily burned CRTs and now a power on issue I will never buy a Mitsubishi set ever again.

If nobody has any further suggestions and I don't find the power on problem I'll likely just drag the box out in the backyard and torch it. :)

burn> If the 24v line is low you likely have a bad convergence output IC or a bad

No. The standby circuits are active, but the 24v supply is not until the set is powered on.

This sounds like a reset or standby supply problem. Likely a rather inexpensive IC. Could be lots of other problems. Real troubleshooting is needed.

Screen burn is an issue with ANY brand CRT based product that is used inappropriately. This is a fine set and these have had very few problems. If you have burn-in, you had the contrast too high without varying the use patterns for too long a period.

Mitsubishi has some of the best products available. If I were looking at DLP sets I would certainly give them a look.

Troubleshoot or call a good mits tech. Torch it if it makes you feel better.

Leonard

Thanks for the info Leonard, I'll go over it one more time to see if I can find anything. I suspect it will be something inexpensive but I also worry that if I call in a tech they'll just want to swap an entire board at which point the set probably wouldn't be worth the expense to me.

As far as Mitsubishi's quality it isn't fair for me to judge it based on a single set, but it is frustrating being on the wrong end of the statistical curve. They do have a nice 1080p DLP set, and I may even take a look, but as the saying goes once bitten twice shy.

Anyhow, thanks again.

burn>

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I said a "good" mits tech. Any that just routinely swap boards need to be passed over. Now, sometimes, boards are not field repairable. That would be the case with some of the digital boards. In those cases there is not much you can do but swap boards. A good tech starts with the intent of repair at the component level, usually. This is no different with Mits or any other manufacturer's products, but you want someone who repairs a lot of Mitsubishi to be sure that they will be efficient and effective.

If you have a catastrophic failure on a set this age, Mitsubishi might even provide some relief, but you will have to have a good diagnosis before they will even talk to you. I know of no company that has been as consumer oriented as they have. They do go beyond the norm to kepp cusotmers.

Leonard