[TechAssist] Re: Hitachi 46UX13K very intermittent
- From: Hermantvr@xxxxxxxxxxxxx
- To: techassist@xxxxxxxxxxxxx
- Date: Wed, 29 May 2002 11:29:54 EDT
Always resolder the horizontal drive transformer. I have had intermitten
starts in this unit because of c917 in the primary side of the main power
supply, however esr all the electrolitics on the primary side of the power
supply, also there is a voltage regulator on the signal board that always has
bad solder. Usually causes no or intermitten audio. DO not remember the IC #
, however it is a 3 pin IC that loods like a transistor and the bad solder
should be VERY noticable.
Tommy Herman
Herman TV
Taylorsville NC 28681
In a message dated 5/29/02 11:13:27 AM Eastern Daylight Time,
wwood_38478@xxxxxxxxx writes:
>
> > The customer has brought this set in 5 times for
> > a
> > "dead set" condition.
> > The first 4 times I played it for weeks and found
> > no problem other than a slight short vertical at
> > the top, which corrected itself quickly.
> > A few weeks ago he said that the set was not
> > working again, and would I come and check it
> > there.
> > I agreed, and found that it had sound but no
> > picture and apparently no high voltage.
> > Using the old NE2 neon bulb trick, I could detect
> > High voltage around Q777, but not around the
> > flyback.
> > No ammount of beating, twisting, or pushing would
> > restore operation however.
> > The set is now back in the shop and It WORKS.
> > No, there is nothing wrong with the customers
> > voltage, checked that while the set wasn't
> > playing.
> > I have pulled the sweep/power supply/convergence
> > board out anyway, expecting to at least find some
> > bad solder.
> > The only bad solder I can see, even with high
> > magnification, is on pins 11 and 12 of the blue
> > convergence amp. yet, the convergence is ok.
> > Quite frankly I don't have a clue about what to
> > do
> > to make this set play reliably, other than to
> > resolder the ihvt, etc.
> > I don't think the driver transformer is at fault
> > as
> > hv was detected at the hor. output transistor.
> > Would the slight, temporary, vertical short scan
> > be
> > a factor???
> > Convergence IC???
> > Does anyone have any suggestions??????
> > Thanks
>
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