[TechAssist] Re: Mitsubishi VS4507R weird vertical problem
- From: "Damon" <DAMON101@xxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Sat, 18 May 2002 08:38:51 -0500
Believe it or not, if that Zener D4001 (i think) is off by 0.2 volts it will
cause your problem, also found out it applies to Magnavox sets too. Used a
variable power supply to replace zener voltages on one Tv and I got
shrinkage, then vert bounce/full picture, then non linearity in the center
or 2/3 up from the bottom, etc while adjusting the voltage from 9-11 volts.
This zener can/will cause various symptoms, so if you're at your wits end,
just replace the diode.
Damon Brunger
damon101@xxxxxxxxxxxxxx
Telrad Electronic Services
Ft Wayne, IN 46815
----- Original Message -----
From: "Jorge Camboni" <geo@xxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Friday, May 17, 2002 7:46 PM
Subject: [TechAssist] Re: Mitsubishi VS4507R weird vertical problem
>
> Thank you Damon, I' ll find a way to re-check the voltages, but the zeners
> are not shorted nor leaky,
> the picture is very close to the right size while it lasts..... just lacks
> a lil from the top and
> that narrow stripe there, looks like an open bypass cap.... but there
ain't
> any left
> Will check again and tell you
> Thanks
> Jorge GY Electronics, Dallas
>
>
> At 08:51 a.m. 17/05/02 -0500, DAMON101@xxxxxxxxxxxxxx wrote:
> >
> >First re-estimate it so you get paid for this nightmare unit.
> >2nd check your +28 V at pin 8, and the same at pin 11, I think (vert pump
> >up).
> >Next, you MUST HAVE 10 or 11 volts at pin 1, if not there is a zener
diode
> >real close to the pin that will cause vert collapse, stretching in the
> >middle....even if it's off by 0.2 volts!!
> >Since you checked the caps I assume you also checked the Vert B+ off the
> >IHVT.
> >
> >Damon Brunger
> >damon101@xxxxxxxxxxxxxx
> >Telrad Electronic Services
> >Ft Wayne, IN 46815
> >----- Original Message -----
> >From: "Jorge Camboni" <geo@xxxxxxxxxxxxx>
> >To: <techassist@xxxxxxxxxxxxx>
> >Sent: Friday, May 17, 2002 3:37 AM
> >Subject: [TechAssist] Mitsubishi VS4507R weird vertical problem
> >
> >
> >>
> >>
> >> 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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