[TechAssist] Re: Mitsubishi VS4507R weird vertical problem
- From: "rick schram" <gmc1937@xxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Fri, 17 May 2002 23:26:55 +0000
>From: Jorge Camboni <geo@xxxxxxxxxxxxx>
>Reply-To: techassist@xxxxxxxxxxxxx
>To: techassist@xxxxxxxxxxxxx
>Subject: [TechAssist] Mitsubishi VS4507R weird vertical problem
>Date: Fri, 17 May 2002 03:37:26 -0500
>
>
>
>Hi fellows, need your help on a Mitsubishi rear projection set, VS4507R
>model, it has a very weird vertical problem:
>a couple of inches wide very dark horizontal stripe, almost at the top,
>crossed by a few white, retrace-like
>lines, and that pattern is SUPERIMPOSED to the picture, which can be seen
>faintly in the background.
>also the vertical amplitude decreased just a little (top).After a few
>minutes, the
>vertical amplitude decreases some more inches, and power goes off.This is a
>very technician unfriendly set,
>had to work with it at the customer's house, I managed to get the boards
>out and change all the
>bad and suspicious caps in the vertical section, (found a couple almost
>dry) and one dead
>cap in the power supply, checked all around the jungle IC, did a thorough
>resoldering and cleaning
>on the boards. All this job was not the most technical approach, but it is
>what you have
>to do first at the customer's place, and it was almost impossible to make
>serious measurements
>folded onto myself on the floor and struggling with a fierce cable-web :o))
>I hoped for the best and failed....
>Found NO TIPS on this model. Service manual is out of question (gave them a
>ridicously low estimate,
>hoping for usual LA7838 tale.. ), and to make a sad story worst, I can not
>bring this one
>to the workshop. SO...ANY HELP WILL BE SO MUCH APPRECIATED!!!!
>
>tnx in advance Jorge Camboni GY Electronics, Dallas (for so many years
>cx8bbh)
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check both zeners in vert circuit also check connections on the coil that
stands upright near the la7838 ic.also there is a cap that is 47 mf that
will give you a washed out with retrace lines.unfortunatly i dont have the
sche in font of me right now.but the cap is located on th left edge of the
defl board looking from the back its about midway down all most right on the
edge you will see the crap leaking out and or the leads will be
corroded.also unfortunatly you fell into the trap by just asuming it was
going to be one of those routine vert jobs never be afaid to charge for your
knowledge . the cap is not under a can but is near a ic.i always replace
thetwo zeners and caps and there is also a cap on thepower supply board c920
100 mf at 100v that controls the b+ to the vert ic.i will admit these sets
were not the best but ohhhh i have made fair amout of money off of them and
i fix most all of them in the home.i now charge 150 to 200 $ for this repair
and havent been refused yet.if i recall right it has a board mouted on the
back that is in the way with a mile of cable on it.
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