Greetings!

Sorry if this post is in the wrong forum, but I wanted to ask this pretty quick...

We have a classified section on our work intranet home page called the Trading Post.

The new issue comes out on Thursdays which would be today...

Long story short, there is an ad for a 52" Mitsubishi rear projection TV for $50!

I'm going to go look at it tonight, the guy says that it works great, but he's noticed that the picture
is getting dimmer... he states that the picture is still good, just not as bright as it used to be.

My question is what could be the problem that would cause a rear projection to start going dim?

I know that with a CRT, going dim usually means the tube is going bad...

Does this mean with a rear projection the guns are going bad?

Thanks!
Scott

How old is the set??

If you're lucky, it may just be dust buildup on the lenses and mirror.
If you're less lucky, it may be dust AND cigarette smoke buildup. :yuck:
If you're really unlucky, it may be that the guns are shot, at which point the set is probably not even worth the $50.

Bottom lline, good luck! :thmbsp:

Not sure how old the set is... he claims that the picture is still good and bright, just not as bright as it used to be... :scratch2:

I'll know more tonight... :yes:

Scott

If you can see the tops of the lenses on the tubes, dont touch them until you get it home. You might accidentally fix it in front of the owner! I've been amazed at how dirty the lenses can be, and still have a nice picture.

Greetings!

Sorry if this post is in the wrong forum, but I wanted to ask this pretty quick...

We have a classified section on our work intranet home page called the Trading Post.

The new issue comes out on Thursdays which would be today...

Long story short, there is an ad for a 52" Mitsubishi rear projection TV for $50!

I'm going to go look at it tonight, the guy says that it works great, but he's noticed that the picture
is getting dimmer... he states that the picture is still good, just not as bright as it used to be.

My question is what could be the problem that would cause a rear projection to start going dim?

I know that with a CRT, going dim usually means the tube is going bad...

Does this mean with a rear projection the guns are going bad?

Thanks!
Scott

If this is more than say, 7 years old or so, I would be VERY hesatint to buy it!!

But you will no doubt ask me "but I know people with projo's that are 10,15 even 20 years old, that still look as good as new, so this one should be ok right??

And my answer is-- I AGREE that a LOT of older projos can and often DO look very good, and they can last a long time-- 20+ years and still have near-perfect tubes. I own a 1994 model RCA projo, with hitachi tubes, and it looks BETTER than a lOT of newer sets!! this is NOT an exception to the rule, neither. Those old Hitachi-type sets(with tubes made by them) will last and last.. Maybe the splitter or fly might fail, or something a lot more minor, and in the Hitachi's, the STK's will no doubt need replaced, but the tubes will go on and on, unless someone watches them about 24/7. I would be willing to estimate that the sets with hitachi type tubes could get 35-50k hours on those tubes, (if they are good from the start), before the tubes become too weak to use. In the biz, those tubes are known as 'bulletproof"!!

Now, before you get thoroughly confused and say I am contradicting my own words, let me go on a bit. I said the projos with HITACHI tubes are good!! BUT... mitsibushi projos have VERY weak tubes that have TWO types of problems, that tend to start within FIVE years old and often SOONER!!
The FIRST problem that mits. projos often have is LEAKAGE from the coolant chambers on the front of the tubes. Modern (last 20 or so years) projo sets use a liquid that is placed between the screen of the projection crt and the lens assembly. The fluid is a lot like antifreeze, and it does 2 things. The first thing it does, (most obviously) is to cool the screen of the tube. the fluid conducts the heat from the phospor of the tube, and onto the chamber walls, which have heat-sink fins. This cools the phospor, and ,allows for a much brighter phospor to be used, allowing the kind of bright, vivid pictures most projos have produced since liquod cooled tubes were introduced in 1983 or so.

But the fluid does another function and that is to actively COUPLE the image from the crt face to the lens a LOT better that empty space would do. In this way, less light is wasted and more is used to produce the picture.

However, sometimes the seals on the coolant chambers of the tubes develop pinholes, and after the set warms up, it can leak out of the seal, and onto the circuit boards below. Mitsibushi sets in PARTICULAR suffer from this problem. The fluid is conductive and will RUIN the circuit boards!! Other brands do this too, and Samsung is currently seeing a lot of the same problem in their newer(2000-now) sets. But with Mits, after about 5 years or so, the circuit boards are NLA, meaning they are NOT available to replace them if you need to!! I know of several 1997-2002 mits. that have been junked because of this!!

Then too, there is the sad fact that mits tubes are not very good to begin with!! While an older Hitachi(1990-2000) will have about a 90% chance of having great tubes, the OPPOSITE is true of mits sets!! ibn fact, I cringe whenI am asked to repair a '90's mits, cause if I can get the original problem fixed, the tubes are probably shot(1983-93 or so), and if it is a newer one -1995-2000 or so) they may be leaking!! I recently saw a 1990 model 61" mits. in the trash in a nice cabinet with doors. I passed on it, as I figured the tubes were toast, as they nearly always are!! IN fact, i can think of only ONE brand of older projo with worse crt's than mits, that was NEC. After about 5 years, those tubes in them were GONE!!

So, the bottom line is "I wouldnt!!" Not an older MItsibushi!! projo!! An older RCA or Hitachi or Zenith from 1994-99 or so would be good, too, most likely, as would a toshiba, jvc or such from that time, but NOT a mits!!

Thanks for the reply Jack... it's good to hear from someone in the business! :yes:

I've been a tech myself some years back, but my area was professional audio, not TVs... :no:

I took a look at the set tonight and did notice it to be dimmer than most sets that I've seen.

It also looked like the blue gun was overdriven... the screen had a blue wash to it. There were
retrace lines as well.

The set is ten years old, and really in pretty good condition overall, but I think I will pass on the
set... it didn't feel right and with Jack's reply, that seemed to be the clincher!

Thanks!
Scott

Scott,

Probably a good decision on your part.Even if you could clean it up and get the set adjusted and calibrated properly(unless the CRTs are shot),you would probably not like the picture over time.When I did calibrations (ISF), I would cringe when I got jobs to do Mitsubishi's.I didn't like them.Just a personal observation.

If you're in the market for a large RP,especially CRT RPs,it seems that they are abundant in the used marketplace.People seem to be gravitating toward the flat screen,hang on the wall sets or digital RPs.

Those retrace lines were normal on older big screen sets.The larger the screen,the more visable and anoying the scan structure is.The newer HD sets have built in line doublers/scalers,taking the interlaced lines and converting them to a progressive line output.Pretty much eliminates them.

Not to make a negative post on this, but at least here in SoCal, there are Big Screen sets in practically every alley. Not worth a plugged nickel. That is, unless it's a fairly new one in nice shape. And even then, only $ a couple hundred. There was a 70" Mitsubishi VS-7017R in nice-looking shape at the church near me, and it sat beside the dumpster for a month in the rain. I noticed that finally it had been boosted into the dumpster this week. And it was in plain view of a busy highway for all that time, still there.

Typically I see Mitsubishi sets from the 90s being tossed, mainly for weak CRTs. I wouldn't get involved in any used bigscreen TV, unless I wanted it for personal use for some reason.

See CraigsList free items... Usually a few big screen TVs.

Charles

Thanks for the replies guys! :yes:

I talked it over with the wife last night and she said that if she had to give up her entertainment center (which is solid oak),
we would have to get a flat panel monitor that will go on the wall to gain back floor space.

She says that if I can wait till this fall after camping season's over, we'll start looking at large screen flat panels! :banana:

I guess I just got stars in my eyes when I saw 52" screen! :D

Scott

And like I said before, If you could find a mid-late '90's set from RCA, I think you would be pleased. The tubes will most likely look VERY good for a long time to come, and if the chassis says ctc-195(made from 1996-2002), it will have digital convergence and many other goodies. If you can get one with a ctc-169 chassis, it does not have full digital convergence, but will produce a great picture. These were made from 1990-about 1997(after which the 195 took over). BOTH of those RCA(or ge or proscan, as the go under all three names) chassis are made in what we call a "light box" where all of the "guts', INCLUDING the crt's and such, are made into a woooden box assembly, which weighs less than 75lb., and is removable from the cabinet, to make servicing them EASY!! The box is about the size of a trunk, and thus can be easily transoprted for service. in fact, that is how they are usually brought in for repair!! (the ctc-169 type Projo has ONE weakness-- that is the HV splitter, it goes out after about 5-15 yrs, but CAN be replaced by the owner, IF they have a bit of technical knowledge. The ctc-195 does not have that problem, but they lose the flyback easily, but it only costs about $40 or so, and can be repalced easily, too. They also get bad connections in the tuner area, those can also be repaired by a "leisure tech", if they are careful.

I would fancy to bet that you could find one of these sets rather cheaply, as they seem to be easy to find used. If you do decide to get a projo, and look for one of these, (made after 1993 or so, ) the picture should look VERY good, if it does not, or is dim,(along with the OSD) DO NOT get it!! AS I said, those tubes will deliver an outstanding picture for a very long time. I recently fixed one from 1997 or so, with a bad flyback, and it looked better than a lot of NEW sets!!


But-- do NOT buy an RCA or GE projo set made after 2002, as they now are making a cheap, all plastic piece of shit, that loses CRT's and flybacks on a VERY reguklar basis!! The tubes are NOT the "good ol' Hitachi ones, either-- they switched to a new, POS for them, too!!

BTW.Another weakness of the MItsubishi sets from the early 90s to mid 90s was electrolytic capacitor leakage.They actually leak out of the bottom of the capcitor usually on the negative lead.By the time the set develops a failure usually lots of them are leaking.I've changed 50 plus on big screen and 35" Mitsubishis and it's not uncommon to have to change 30+ on those as well as clean up corrosion and repair damaged circuit traces on those.BTW the 80's sets didn't suffer from this problem.I haven't seen leaking ones on 1996 and newer Misubishis but I had to change many high esr electrolytics on a 99 model last year.BTW my mom has a 1987 Mitsubishi that is still going strong.It came out of a beach condo in 2000 after the HV bleeder failed.So it wasn't played much until my mom started using it.It has been played 14 hrs a day or more for mearly 6 years now and the tubes are still going strong. The big tube 35" Mitsubishis seem to have much better tubes than the projos.I've seen many all the way back to 1987 with excellent pictures on them.I only saw one worn out 35" tube and it still had a good enough picture to bring $100 at an auction.I get used projo tvs all the time for nothing and sell them for $300 plus.I've had a lot of Magnavoxes where nothing was wrong except contaminated coolant fluid(big problem with Magnavox).The late 80s ones were problematic with high falure rates for the flybacks and having to replace the whole sweepboard to get it and another problem with the mid-late 90s ones is that now the high voltage divider blocks are starting to fail and they're NLA.Stay away from 2000-2001 Philips Magnavox.They put nearly all the small signal processing on a tiny board that is very high failure.Now the high voltage blocks mentioned from RCA for 169 chassis have become not available in OEM and the generic replacements are problematic.And mid-late 90s Zenith have a good picture but they are junk when it comes to reliability.Also they have poor high voltage regulation and the picture tends to bloom on bright scenes especially if the orginal flyback has been replaced.You can't get the exact one that was in there.All replacements are just that,not OEM.Sonys from the mid 90s had good pictures but the tubes are short lived.The worst ones are the 2002 models.If you see a 2002 Sony and it has solid color pin bases rather than clear and a 1.2 filament resistor near the flyback instead of a 1.8 ohm RUN as fast as you can.There was a bulletin and all the CRTs had to be replaced as well as the resistor mentined plus 2 tiny surface mounts.If the mods are done with clear color base tubes you're probably ok but the flybacks and HV dividers are high falure regardless.Sony has great picture quality but their reliabilty has gone to the dogs.

I would pass on it. In 20+ years of fixing these things, I have seen a ton of them that people got stuck with. "But it was such a good deal; the guy just gave it to me!" If he's practically giving it away, there is probably a reason. On a few occasions I have gone out to look at a set, only to find it is the same one I looked at somewhere else last month, and told the guy to trash it.

If it is getting dim, the tubes are probably getting weak. If it is just dirt on the mirror and lenses, it would probably be cloudy too.

I have also seen the "Capacitor guts all over the board" problem too. It could keep you busy for a long time changing caps and cleaning electrolyte off of the board.

Might also be bad surface mount electrolytic caps in the PIP module. I've rebuilt a bunch of those, and working on them will make you go cross-eyed. (if that is the problem, you'll probably have sync and color problems too)

Long story short: If it doesn't look near perfect, don't take a chance. You'll end up paying another $50 to dump it

:thumbsdn: