"Leonard Caillouet" wrote in news:zg7Gg.19427$yO4.2699@dukeread02:
Leonard is right. Old Mitsubishi televisions have a gorgeous picture tube and last a long time, but after 10 years, the electrolytic caps go bad by the pound. You have to replace a lot of them, clean up all the crap on the board around where they leaked, repair the traces of foil where they corroded, and replace any parts that got wiped by the leakage, if there is any. But if you do all of that, the television will come out really nice and you will have a good TV. The only sets really worth this much trouble are the really big picture tube ones like 35" and larger (They made a super fantastic 40" CRT set.). A 27" set might not be worth this much trouble unless you are doing it as a hobby and have plenty of time to kill.
"Leonard Caillouet" wrote in news:pBaGg.19447$yO4.5222@dukeread02:
He is right, look for the bad caps. Buy an ESR meter and use it, it will be well worth the money. I think that MCM has a nice one, get the one with the analog meter on it, much better than those darned LED ones. I think that Tenma (Really cheap brand.) has one that is actually pretty good. The only thing that I don't like about it is that the analog meter is not well damped, the needle swings too freely if you ask me but this is a personal preference and does not really render the meter less worthy.
To use an ESR meter, unplug the set and then touch the meter leads across electrolytic caps. A large swing on the needle means that the cap is probably good. A small swing of the needle or no swing at all means that the cap is way dried out or open. Small value electrolytic capacitors (4.7uF or smaller) will give only a small swing on the needle anyway. Learn how to use the meter and what to expect by testing it on some new caps. Try a small one, 1uF, a larger one 10uF, and two larger ones 47uF and 100uF so that you will know what to expect of the meter.
This meter works in circuit with no power on the set. This test will not positivly indicate bad capacitors. A shorted capacitor or one with a very low resistance across it, say a coil or low value resistor, will show up the cap as being good. Remove cap from circuit to double check anything suspicious.
Oh, I found the cheap meter for you at MCM electonics, here is a link:
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It cost $125 and is actually quite good. Buy this meter, it is worth it. Just to show you, MCM has two other ESR meters prices at $549 and $769 so for the $125 that they want for this very much working ESR meter, you can see that it is well worth it and comes with an analog meter. What could be better? Go for it.
I don't want to buy ESR meter for one time repair. I used to work with electronics a lot but now I switched to software and don't touch this anymore. This was my kid's TV and it worked flawlessly for almost 15 years. I desided to give it a shot but don't know if it worth my time. Do you suggest not to mess with it any longer and get a new set? I can get 27" tube TV set for under $200
Oh, sorry. Well, the people in here gave you good advice. You will be changing a lot of electrolytic capacitors. The only practical way that I know of to locate them all is with an ESR meter. You could also try bridging the caps with a similarly sized electrolytic capacitor (Observe polarity) while the set is running to see if it improves the situation. This is an "Old Time Practice" that worked. It is not as easy as the ESR meter and if you have several bad caps, then this method may not work for you. If you have a meter that measures capacitance, you could take each capacitor out and measure it, replace any that are not up to par, and move on. Cleaning and repairing as you go.
No, this is not worth your time if you ask that question. By all means, buy the new set and be done with it. You have a 15 year old television and even if you get it fixed perfectly, and this will take many hours of your time, you will still have a 15 year old television that will not be worth $30 at a garage sale. If you spend 6 hours on it or more, how much money could you make in that time? Enough to buy a TV set? Then just buy it and be done with it. I was under the impression that you wanted to repair this set for something to do, as a hobby sort of thing. It is in no way worth repairing from an economic standpoint at all, period.
"ladybug" wrote in news:1156295997.387291.224160 @h48g2000cwc.googlegroups.com:
Why are you doing this? It is a 15 year old television and you already asked if it would be worth your time. Well, is it so far? Not being mean or a smart ass or anything, just trying to get you to step back a minute and see the forest for the trees. Best wishes and good luck.
As far as the correct part for a 1.2 Ohm current limiter, any 1/2 watt low value resistor will work fine, a 1-2.2 ohm will work fine. All it does is act as a fuse. It burns up if the chip overheats or burns out. Then you find out what made it burn out, like a shorted chip, replace it, and put in a new resistor. It is just a fuse.
OK, I have said this many times, but I will say it again. The mantra that you have to have an ESR meter to fix these sets is just WRONG. An ESR meter will identify some physically leaky caps, and it is very handy for most repairs, but you can get virtually all of the bad caps in these mitsubishis with inspection for electrolyte leakage. I have tested hundreds of these leaky caps and found that low capacitance and high DA are far more likely on the leaky ones than high ESR. You might miss other problems, but high esr caps that aren't leaky in these sets are not common. In this case, I would bet my next paycheck that you could fix it and never test ESR. We do test caps for ESR but it is almost never the diagnosis that gets the bad ones in these sets. You could use the techniques below and fix almost all of them with enough time and enough capacitors. A DMM and a good nose and eyes will get nearly all of them.
The ways to identify physically leaky caps are:
Visual inspection. If there is a spot on the board around the cap or dark goo on the legs it is leaky.
The smell test. Heat the leads and smell for bad tuna.
Listen for a sizzle when heating the solder.
Look at the solder side. If there is darkening of the trace or a powdery look to the solder that is less shiny than surrounding solder, it may be leaky. If the solder is harder to heat than surrounding joints, you likely have corrosion from electrolyte leakage.
All of the dark traces need to be scraped to bare copper and tinned. The board neds to be wahsed with a solvent like isopropanol or denatured alcohol to get off any remaining electrolyte.
When in doubt about a cap that is a black polar electrolytic in a mits of this vintage...change it.
Leonard
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Is there not value in a DIY project that keeps a product out of the landfill for a couple more years? Sure the crt is likely aging, but we fix these all the time and find that the crts are still looking very good. Did one a couple of weeks ago. Looked great, client was happy. He could have replaced it with a POS Philips set for tnot much more than the repair, but chose to fix it. A DIY on these should cost no more than about $25 and some time and patience. I do things myself all the time that a professional in some field would not bother with and spend more time than it might be worth, but there is the sense of satisfaction in completion of such a project.
I find ladybug's tenacity in this repair to be interesting and laudable.
Leonard
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I'll try to get it fixed just to keep it out of landfill for a while. I got something screwed up this time though. I needed to take a list of all the caps that I need to replace for ordering, and tried to free up main board as much as possible to see caps values. I unhooked tube control board and some connectors. After I made a list of caps I replaced burned 1.2 Ohm resistor with 2 Ohm that I pulled up from old VCR. After I put everything together I wanted to give it a try but it didn't come to live. I could hear power relay clicking when I pressed power button and there was high pitched sound from the fly. I noticed that there was no light in the end of picture tube. I took tube control board off again and there were tube pins 1 and 2 ? (2 left pins) bent together. I got them straighten up and re plug control board back but still nothing. From what I can say pin 1 is a ground and I shorted pin
2 to the ground when pin got bent inside of the socket. Don't know what could get damaged. There is no cathode light in the end of picture tube anymore.
When the caps went bad, the vertical ic probably shorted. You also will have to replace the resistor off the flyback derived power supply winding which opens when the ic shorts. I no longer do Mitsubishi warranty service so I don't have a manual. You'll need one or a pin out of the LA7838 to trace back the B+ line to the power supply diode and the open resistor attached to it. Chuck
I got new caps but TV seems to be completely dead now. I don't have power on the main high voltage transformer so tube gets nothing. No cathode light, no high voltage... I checked the fuses, no problems there.. I can hear power relay clicking when I press power button on the remote, so controls are good. Any ideas?
"ladybug" wrote in news:1156809810.350898.9610 @i3g2000cwc.googlegroups.com:
Gosh I tried like hell to get you away from this thing, Ladybug. After all the work you put into it, now this. (And it is STILL just an old 27" TV set!) ...sigh.
"Any ideas?" ...yeah, pitch the set and be done with it already. But I assume that is still not an option, yet?
Is horizontal output transistor shorted? This is a large, usually black transistor (Black plastic, maybe metal back on it, with three legs on it, attached to a large metal plate of some kind to dissipate the heat.) over near the flyback transformer. If you put an ohmmeter probe on the collector (Center leg) and the other probe on the emitter (leg on the left side) does it read a very high value of ohms or is it shorted (Very low ohms, usually
1 ohm or less.)?
If shorted then you have opened up something in the power supply circuit that feeds the B+ to the horizontal output circuit, could be a resistor or fuse (Some fuses look like small resistors, attached with wires to the board.) and the horizontal output transistor will have to be replaced. Could also have been caused when you put the CRT board back on with bent pins on the CRT. Now that they are straightened out, the set might work if you find out what happened to your B+ for the horizontal output circuit.
Seriously though, if the set is not fixed really soon with just a few last things to do, consider cutting your losses and running on this. How much more kicking can your heiny stand on this job?
"Leonard Caillouet" wrote in news:ElWGg.25988$yO4.7618@dukeread02:
Of course there is, when it is something that one can manage and is able to accomplish within reason.
Uh huh. And where is this, at "Emmet's Fix It Shop" over in Mayberry? Lemmie guess, the Sears catalog is still a big ticket item for bathroom reading too? It did not "look great" but may have been acceptable for the time being.
Agreed, but you have a clue and some obvious experience with television repair. You can tell by the questions that Ladybug is asking and the terms being used that this person has no television repair experience at all. You would recommend a 10+ year old Mitsubishi set with caps bad by the pound, along with bad solders and everything else that can go wrong with a 10 year old set to a beginner to cut his eye teeth on? Ladybug would have been better off with a Radio Shack 150 in One electronic project kit and I am not being cruel in saying that. At least then Ladybug could have accomplished something useful like a photosensing alarm for the front door and would have learned something along the way.
Here, this auction has ended, but the seller still has a 300 in One Electronic Project Lab Kit for $5.50.
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I am not "down on Ladybug" at all, I simply tried to temper Ladybug's enthusiasm with some of real life's harsh realities. Like the cost of a replacement set v.s. the hours that would be spent on trying to fix it and the fact that after all is said and done, Ladybug would be left with a 10+ year old television with a picture tube that is fading away, never to return to it's original brilliance and luster afterwards, possibly flaring wherever there is green in the picture, you get the idea, and nothing can be done about it other than to lower the contrast to a very dim picture, short of replacing the CRT, unless you want to start with a single winding around the flyback and the necessary resistors to try and boost the filament voltage of the set, a temporary measure at best.
Oh, make that 15, F-I-F-T-E-E-N years old! Here is what Ladybug had to say in an earlier post...
"Ladybug" wrote in news:1156299337.813287.261140@
74g2000cwt.googlegroups.com:
Sure it is worth Ladybug's time, as long as Ladybug is accustomed to earning twenty seven cents an hour. Yes. I suggested not to mess with it any longer and get a new set and that was pretty darned good advice. "Been there, done that" sort of thing.
So Leonard, how are you and Ladybug coming along on this DIY project anyway?
Thanks for you help, Ohmster. Actually I found myself liking to fix this old TV. Kids have smaller back up TV for now so there is no rush to get it fixed right away. I got a schematic from the local library and it proven to be a good reference. I figured out why power was lost. Firstly a diode D553 ES-1F appears to be bad and reads open in both directions. I temporary replaced it with a rectifying diode that holds
600v. I found that I have 23V output and other voltages untill pin 8 of LA7838 gets connected. Once I connect it all voltages from transformer dissapear, and cathode light goes off. I suspect that I need a new LA7838... Will try to get a replacement shortly.
Life is good here in Mayberry, and I think I know the difference between "looked great" and "acceptable for the time being."
Your condescending attitude toward DIYers doen't seem to be very helpful. You gave your opinion and it is sound for many people. Apparently Ladybug chose a different path than you thought wise. No need to be an ass about different perspectives and diferent values nor to assume that others don't know what they are talking about.
Leonard
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