Hitachi 46ux7b dim picture

T

Ted Machcinski

Guest
I have a Hitachi TV that has a dim picture. It has gotten darker over
time.I suspect a bad cap. I have tested several on the monitor board
but so far everything checks out ok. The b+ voltage to the neck boards
is arount 208 volts, right around where it should be. There is also
about a inch bright shadow of the objects on screen. Any help would be
great. Thanks Ted
 
I would suggest getting the service manual and making sure that the bias
voltages to the CRT elements, and the screen voltage is in specs. Also check
the HV. If the service manual gives references to waveforms, such as the
video drive levels, and for blanking pulses, these should also be verified
with a scope to make sure they are in specs.

Don't rule out the CRT possibly going weak. But, it is important to check
all other aspects first.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"Ted Machcinski" <Tmachcinsk@aol.com> wrote in message
news:adca1444.0401130944.2b8110d6@posting.google.com...
I have a Hitachi TV that has a dim picture. It has gotten darker over
time.I suspect a bad cap. I have tested several on the monitor board
but so far everything checks out ok. The b+ voltage to the neck boards
is arount 208 volts, right around where it should be. There is also
about a inch bright shadow of the objects on screen. Any help would be
great. Thanks Ted
 
Bad surface mount caps in comb filter module. Also in PIP module if it has
it. Then look for a tube drive or related problem. The power supply in
that is also known for failing capacitors due to the old age.
David

"Jerry G." <jerryg50@hotmail.com> wrote in message
news:bu1usn$ijp$1@news.eusc.inter.net...
I would suggest getting the service manual and making sure that the bias
voltages to the CRT elements, and the screen voltage is in specs. Also
check
the HV. If the service manual gives references to waveforms, such as the
video drive levels, and for blanking pulses, these should also be verified
with a scope to make sure they are in specs.

Don't rule out the CRT possibly going weak. But, it is important to check
all other aspects first.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"Ted Machcinski" <Tmachcinsk@aol.com> wrote in message
news:adca1444.0401130944.2b8110d6@posting.google.com...
I have a Hitachi TV that has a dim picture. It has gotten darker over
time.I suspect a bad cap. I have tested several on the monitor board
but so far everything checks out ok. The b+ voltage to the neck boards
is arount 208 volts, right around where it should be. There is also
about a inch bright shadow of the objects on screen. Any help would be
great. Thanks Ted
Click to expand...
 
Thanks for all the help. Just found out pic in pic is nice and bright,
never used it so never noticed. That rules out power supply and
deflection board. Problem is in p in p board somewhere. Thanks Ted
 
Sorry the problem is not in the PIP module. It seems to be somewhere
between Video imput after it goes to the PIP input but before it gets
mixed back it with the PIP output. Thanks Ted
 
Again: COMB FILTER. 3 or 4 surface mount capacitors. Be very careful not
to damage the glass pack inside the can. Right in the middle of the signal
pcb. VERY common failure.

The PIP module still will need the capacitors ESR checked as they are
usually a failure waiting to happen.

David

"Ted Machcinski" <Tmachcinsk@aol.com> wrote in message
news:adca1444.0401151206.5bf15f29@posting.google.com...
Sorry the problem is not in the PIP module. It seems to be somewhere
between Video imput after it goes to the PIP input but before it gets
mixed back it with the PIP output. Thanks Ted
Click to expand...
 
Thanks everyone. Dave you got it C 201 on the comb filter
board.Picture looks great now. I have a few questions having never
worked with sm caps before. I have a + and - near one side of the cap
are these non polarized. Not having a SMC I replaced it with a non
polarized electrolitic. It is doing the job will this be ok or should
I get a SMC. Sure was though soildering with a normal iron. Thanks
again for the help Ted
 
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