[TechAssist] Re: How does the TV know?FIXED
- From: Paul <dntwntv@xxxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Wed, 21 May 2003 11:06:15 -0700 (PDT)
Hi Phil I don't know if you read the original post on the fix for my problem.
If you didn't it was the 22mfd@50v cap C871 that Phil Hull knew about and
replied to the orignal problem post. Even though my problem with this set was
just the opposite, I also, have heard of and even experienced other sets that
would not turn on if used with isolated transformers. One more thing to keeps
us guessing. Paul
Philip Bader <tjanphyl@xxxxxxxxxxxxxxx> wrote:
BTW I read in a past tech article (can't remember where)that techs were
having troubles running larger screen TVs (32",35< etc) thru their
isolation transformers, as the heavier loads were loading them down.Some
of these sets simply would shut down at turn on or not power on at all.I
assume there was a "on" current rush that may have caused a sag in the
transformer's secondary voltage that the SMPS detected as a problem and
triggered it's safety circuitry.(like an air conditioner's compressor
dropping out with a power sag in the home from a storm)These 1:1
isolation transformers do have a wattage rating, and cannot adjust for a
wide range of loads.Just a thought.
Phil Bader
George wrote:
>
> Paul,
>
> Do you know if the 1/4 w 20k ohm resistors might be warming up, Check them
> before and after warm up for value change. Try freeze spray after warm up to
> see if it reverts back to no start on direct AC line. Also Check or try
> replacing that transistor. Just some speculation on my part.
>
> George
> Afana Electronics
> Moreno Valley, CA
>
> ----- Original Message -----
> From: "Paul"
> To:
> Sent: Tuesday, May 20, 2003 6:45 PM
> Subject: [TechAssist] Re: How does the TV know?FIXED
>
> > Yes Kevin that is the sequence. Ist power up in a/m, if on (line a/c),
> will try but wont turn on. Switch to Isolation will turn right on. If let
> run for a min.or two,then switch back to line a/c, will turn on and off as
> normal all the rest of the day. The circuit is one that I have not seen
> befor that I can remember. It has a pnp transistor with base and emitter in
> parallel with the 115v line separated by 1/4w resistor on ea. leg. 115v on
> b&e. collector goes to the pos. side of the 22mfd cap and a zener diode
> through a 20k 1/4w resistor. The zener is a 1v. Phil Hull noted that .01
> leakage could cause no start. I am not sure but it looks like a form of 115
> reg.maybe. Incidently I checked the capacitance of the bad cap to satisfy
> your curiosity. it measured 3.4 mfd. Time to go home. Later, Paul
> >
> > Kevin wrote:
> > So let me get this straight. If the set was plugged into the isolation
> > transformer first thing in the morning, the set would come on. But if
> > the set was plugged into the wall first thing in the morning, it would
> > not come on. Correct? If so, this is very puzzling. I do know that
> > caps that are toast will work off and on, and will work if an AC voltage
> > "warms" up the cap and gets it going again, like in a vertical circuit
> > with a black line at the top. What function was the 22uF cap
> > performing? This might be a clue to look into.
> >
> > By the way, I also own a Dick Smith esr meter, and it is the best $70 I
> > ever spent. I had my Sencore first, but it is not very easy to use to
> > test caps in circuit. I do use it to test inductors and to ring
> > flybacks etc. But the tool I use the most is my ESR meter. I like to
> > test the value of the cap when the ESR is so high because it reminds me
> > of the days not so long ago when I only had a capacitance meter that
> > checked value only. Many times I would take a cap out of circuit, check
> > its value and put it back in. Little did I know that the ESR value is
> > also very important. But I had no way to test it until I got my Sencore
> > and my ESR meter.
> >
> > Kevin Wilks
> > Kevin's TV & Video Repair
> > Penticton BC Canada
> > kevintv@xxxxxxx
> >
> >
> > -----Original Message-----
> > From: techassist-bounce@xxxxxxxxxxxxx
> > [mailto:techassist-bounce@xxxxxxxxxxxxx] On Behalf Of Paul
> > Sent: Tuesday, May 20, 2003 3:14 PM
> > To: techassist@xxxxxxxxxxxxx
> > Subject: [TechAssist] Re: How does the TV know?FIXED
> >
> > Yes Kevin I do have Dick Smith meter and yes it was above 99. No I did
> > not check the capcitance,and it was a 22mfd not a 220mfd. Not that it
> > matters in particular for the purposes of this discussion. If it is that
> > bad I don't normally check it any further. I think of more importance to
> > me anyhow,is why the set would turn on when plugged into isolation but
> > would not turn on when plugged in the wall outlet? Why did the circuit
> > that that cap was in, work in isolation but not line a/c?and why would
> > it work when switched in a couple of minutes to line and continue to
> > work all day.? Paul
> >
> > Kevin wrote:
> > So you mean the esr value was above 99 ohms (if you have the Dick Smith
> > ESR metre). If the esr was above 99, then of course there would be no
> > reading. It would read like it wasn't connected to anything. I have a
> > sencore that can read up to 999 ohms for esr and even some caps have an
> > esr above that value. Did you measure the capacitance of the 220uF cap?
> > Just curious.
> >
> > Kevin Wilks
> > Kevin's TV & Video Repair
> > Penticton BC Canada
> > kevintv@xxxxxxx
> >
> >
> > -----Original Message-----
> > From: techassist-bounce@xxxxxxxxxxxxx
> > [mailto:techassist-bounce@xxxxxxxxxxxxx] On Behalf Of Paul
> > Sent: Tuesday, May 20, 2003 1:02 PM
> > To: techassist@xxxxxxxxxxxxx
> > Subject: [TechAssist] Re: How does the TV know?FIXED
> >
> > There was no reading. Readings on my esr meter of" 00" would indicate a
> > short. I don,t recall ever seeing a reading of "0" on my meter. To cear
> > up the confusion there was no esr, nothing on the readout but the
> > indicator for power. Paul
> >
> > Kevin wrote:
> > That is unusual. An esr of "0" indicates a good capacitor. What was
> > the value?
> >
> > Kevin Wilks
> > Kevin's TV & Video Repair
> > Penticton BC Canada
> > kevintv@xxxxxxx
> >
> >
> > -----Original Message-----
> > From: techassist-bounce@xxxxxxxxxxxxx
> > [mailto:techassist-bounce@xxxxxxxxxxxxx] On Behalf Of Paul
> > Sent: Tuesday, May 20, 2003 12:01 PM
> > To: techassist@xxxxxxxxxxxxx
> > Subject: [TechAssist] Re: How does the TV know?FIXED
> >
> > Sorry Kevin, esr was" 0" , out of circuit. Paul
> >
> > Kevin wrote:
> > "0" esr or value?
> >
> > Kevin Wilks
> > Kevin's TV & Video Repair
> > Penticton BC Canada
> > kevintv@xxxxxxx
> >
> >
> > -----Original Message-----
> > From: techassist-bounce@xxxxxxxxxxxxx
> > [mailto:techassist-bounce@xxxxxxxxxxxxx] On Behalf Of Paul
> > Sent: Tuesday, May 20, 2003 10:36 AM
> > To: techassist@xxxxxxxxxxxxx
> > Cc: phil245@xxxxxxxxxxxxx
> > Subject: [TechAssist] Re: How does the TV know?FIXED
> >
> > Hi Phil, You nailed it, C871 22@ 50V fixed it.I was sure I had checked
> > esr on all the caps on the pwr sply bd.Naturally I missed that one.It
> > read 0. It came on this morning after being unplugged over night.
> > Thanks again for putting an end to this nightmare. I am still however at
> > a loss to know why the isolated a/c supply would made a difference?
> > Everything else being equal.Just curious.Someone mentioned regulation in
> > the isolated was better as a possible reason. Paul
> >
> > "Phillip R. Hull"
> > wrote:
> > I would replace C 871 22@ 50V Also D870 is very critical and I have
> > found dead units when this diode Zeners at .1 v high (04AZ36X) Part#
> > A7118305 Check the line voltage with Iso transformer and without. Its
> > probably different.
> > Phillip R Hull STET
> > phil245@xxxxxxxxxxxxx
> > FAX 517--569-3075
> > ----- Original Message -----
> > From: "Paul"
> > To:
> > Sent: Monday, May 19, 2003 3:25 PM
> > Subject: [TechAssist] How does the TV know?
> >
> >
> > > I posted this problem last week for a Toshiba CX3586A that I am
> > working
> > on. This set will not turn on if left unplugged over night unless it is
> > plugged into an isolated power supply. I have measured both and they are
> > both 119V. I thought the problem was a 470@160V in the 115V supply. I
> > replaced it, checked (turn on) several times, put the back on,left it
> > unplugged over the week end. Tried it this morning no start. Plugged
> > into
> > the isolated pwr came right on. If left in the isolated pwr sply for a
> > few
> > min.,it then will work in the wall a/c. What is the difference? ac is
> > ac,right? Paul
> > >
> > > Paul ,B
> > Central TV&Video
> > Grover Beach Ca.
> > >
> > >
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> > Paul ,B
> > Central TV&Video
> > Grover Beach Ca.
> >
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> > Paul ,B
> > Central TV&Video
> > Grover Beach Ca.
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> > Paul ,B
> > Central TV&Video
> > Grover Beach Ca.
> >
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> > Paul ,B
> > Central TV&Video
> > Grover Beach Ca.
> >
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> Central TV&Video
> Grover Beach Ca.
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--
Philip Bader
Jan Phyl TV Inc. (estab. 1976)
3420 Recker Hwy. Winter Haven, Fl. 33880
Fax (863) 299-8821
email: tjanphyl@xxxxxxxxxxxxxxx
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