Mitsubishi cs-2710ra vertical problem
in [Repair]
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From: Leonard Caillouet on 23 Aug 2006 06:39 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: 1. Visual inspection. If there is a spot on the board around the cap or dark goo on the legs it is leaky. 2. The smell test. Heat the leads and smell for bad tuna. 3. Listen for a sizzle when heating the solder. 4. 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 "Ohmster" <notareal(a)emailaddress.com> wrote in message news:Xns9828399BFFFAMyBigKitty(a)216.77.188.18... > "ladybug" <natayz(a)gmail.com> wrote in news:1156299337.813287.261140@ > 74g2000cwt.googlegroups.com: > >> 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. > > -- > ~Ohmster -------------------------------------------------------------------------------- I am using the free version of SPAMfighter for private users. It has removed 2273 spam emails to date. Paying users do not have this message in their emails. Try SPAMfighter for free now!
From: ladybug on 23 Aug 2006 10:13 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.
From: Chuck on 23 Aug 2006 13:24 On 21 Aug 2006 16:43:19 -0700, "ladybug" <natayz(a)gmail.com> wrote: >I replaced 5 leaky caps that I found but it didn't change anything. I >suspect that vertical output IC went kaput. After all it died suddenly >without gradual picture srinking. Is it LA7838 chip? Is there a way to >test it with multimeter? What is a good place to get a replacement? 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
From: Homer J Simpson on 23 Aug 2006 14:24 "Ohmster" <notareal(a)emailaddress.com> wrote in message news:Xns9827DD52CB590MyBigKitty(a)216.77.188.18... > "Leonard Caillouet" <nospam(a)noway.com> wrote in > news:pBaGg.19447$yO4.5222(a)dukeread02: > >> You can get it from Mitsubishi, but it will likely be a waste of $$$. >> It will not tell you how to fix the set. >> >> Leonard > > 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. http://members.ozemail.com.au/~bobpar/esrmeter.htm http://www.flippers.com/esrktmtr.html
From: ladybug on 28 Aug 2006 20:03
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? |