[TechAssist] Re: SHARP TV 14A2-S - POWER FAILURE
- From: "VRM" <vrmsys@xxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Thu, 15 Nov 2001 16:55:59 -0000
Hello;
Thanks for the reply. Actually what I measure is 39Vdc instead of
207-230Vdc, that is a half wave rectified voltage from the LINE SOURCE (i.e.
220VAC).
The schematics (board wiring) gives a direct feed, that is 207-230Vdc
directly goes to collector of C4517, the emmiter of C4517 runs dircet and
should give out 17Vdc as an input to the STRF.
I will check for an OPEN or SHORTED resistor and update you ASAP. I will
also perform the ADVICE given and monitor the VOLTAGES as requested.
Thanks
----- Original Message -----
From: "Damon" <DAMON101@xxxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Thursday, November 15, 2001 1:28 AM
Subject: [TechAssist] Re: SHARP TV 14A2-S - POWER FAILURE
>
> Well, there's one thing I'm curious about. With the STRF ic in circuit do
> you get 3.9 volts or is it actually as you writ: 39 volts. If its 3.9 v
look
> for a series resistor before C4517 or between C4517 and your Strf as being
> higher in value. If you are actually getting 39 volts then you have
another
> resistor to ground that has opened or increased in value.
>
> The fact that you have to unplug the TV after it shuts down, points to the
> fact that you have activated the Hi voltage shutdown circuit. Can you
remove
> the horiz output and wire a 40 or 60 watt light from your B+ (130V??)
supply
> and monitor the power for a minute or two. Your regulation may be
activating
> the hi volt shutdown, so you need to start with a rock solid power supply.
> Damon Brunger
> damon101@xxxxxxxxxxxxxx
> Telrad Electronic Services
> Ft Wayne, IN 46815
> ----- Original Message -----
> From: "VRM" <vrmsys@xxxxxxxxxxxx>
> To: "Tech Assist" <techassist@xxxxxxxxxxxxx>
> Sent: Tuesday, November 13, 2001 4:09 AM
> Subject: [TechAssist] SHARP TV 14A2-S - POWER FAILURE
>
>
> > Hello;
> >
> > I will be pleased if anyone can help me solve this power failure problem
> on a SHARP TV model 14A2-S. This set was brought in with a blown STRF6653
> plus some zeners and resistors located in PS section. I replaced all of
them
> and the SET came on.
> >
> > I only made it stayed for the first time for between 2-4 minutes then
> powered OFF and left to do something else. The next time I attempted to
> power it it went into STANDY mode, so I used the remote to activate it,
BUT
> the POWER only stays on for 2seconds, then back into STANDBY mode. This
time
> the reote cannot be used again to power up, unless you switch OFF the
mains
> and try again.
> >
> > After analysing the schematics taking some readings around the STRF6653,
> it requires an input voltage of 17Vdc, but currently what is measured is
> around 12Vdc. There is a switching TRANSISTOR C4517 that should supply the
> 17Vdc to the STRF, from an input of 207-230Vdc. With the STRF in circuit,
> the input voltage of C4517 reduces to 39Vdc, when STRF is taken out of
> circuit, the input voltage ot C4517 is FULLY present.
> >
> > I then replaced the STRF and C4517 with new ones, thinking they be might
> FAULTY (degenerating), but the problem is still there.
> >
> > I am please welcoming ALL ADVICE and STEPS from all quarters in order to
> help solve this problem.
> >
> > Thanks to all in advance.
> >
> > Viktor
> >
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