[TechAssist] Re: Mitsubishi VS4507R weird vertical problem
- From: Jorge Camboni <geo@xxxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Fri, 17 May 2002 19:31:28 -0500
Thanks Rick, that is what I really wanted, a guide to remind me of what I
might have skipped..
You remember that board in the back with its mile of cable :o)) verry well,
that
crap GOT ON MY NERVES :o) and I did not measure the zener voltages, (I had
to make all
measurements with the set off, taking the boards apart)
just made sure that they were not shorted or leaky. I did measure all the
caps in the power supply and
changed a dry one, I might have skipped that 47mf cap if is not very close
to the vert IC
Will check C920, it may be halfway and check fairly well ESR wise.
Thanks again, will email you the happy end :o))
Jorge GY Electronics, Dallas
At 11:26 p.m. 17/05/02 +0000, "rick schram" <gmc1937@xxxxxxxxxxx> wrote:
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>>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
>>
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>>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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