[tvservice] Re: FW: Re: New Post--Fuse keeps blowing; Dead TV
- From: "Robert W. Abel" <RWAbel@xxxxxxxxxx>
- To: <tvservice@xxxxxxxxxxxxx>
- Date: Tue, 27 Apr 2004 09:45:04 -0400
Anyone know how I go about getting removed from this list? Thanks!
----- Original Message -----
From: "graytv" <graytv@xxxxxxx>
To: <tvservice@xxxxxxxxxxxxx>
Sent: Tuesday, April 27, 2004 9:15 AM
Subject: [tvservice] Re: FW: Re: New Post--Fuse keeps blowing; Dead TV
> Shorted collector to ground is wrong.
>
> Horizontal output transistors in circuit should normally read, with black
> (-) to ground:
> Emitter to ground short- possibly a coil or very low ohm resistor between
> emitter and ground, but generally emitter is ground.
> Base to ground short - reading through horizontal driver transformer
> windings to ground.
> Collector to ground no short - should be very high ohms to infinity,
> depending on design, however the inintial reading may be skewed by
> capacitors charging up, hold the probes in place for 10 seconds.
>
> Out of circuit the only low ohm reading should be from base to emitter.
> Collector to base and collector to emitter should be high ohms.
>
> If after you removed the transistor, there was still a reading from the
> collector pad to ground, then there is a short somewhere along the B+
line.
> Colud be the flyback, timing caps, filtering caps, rectifiers, or in some
> cases (Panasonics especially), there could be a zener diode to ground off
> the B+
>
> You mentioned ohming the transistor. Don't you have a diode checker
setting
> on your multimeter to properly check a transistor junction?. Also, a
flyback
> (or any coil for that matter), cannot be checked by simply ohming the
> winding. You need to have an inductor tester to ring the flyback. Even
then
> this is not an infallible test for flybacks, as they can fail in ways that
> cannot be tested without specialized, expensive equipment.
>
> When you disabled the B+, did you check to see if the voltages were there?
> This set, along with most other newer sets, run in an always on standby
> state for many of the power supply voltages, waiting for the
microprocessor
> to put the set into the run mode. At the very least you shoud have a
standby
> 5v, and with this set you should also have B+.
>
> hth, Russ Gray, A+, Pres.
> Gray's Electronics Inc.
> 201-C Commonwealth Blvd.
> Port Orange FL USA 32127
> 386-322-0904 voice
> 386-322-3809 fax
> graytv@xxxxxxx email
>
> ----- Original Message -----
> From: "Mike Selnick" <selnick@xxxxxxxxxxx>
> To: <tvservice@xxxxxxxxxxxxx>
> Sent: Monday, April 26, 2004 8:21 PM
> Subject: [tvservice] FW: Re: New Post--Fuse keeps blowing; Dead TV
>
>
> >
> > Further to my message below, I checked all the pin-to-pin readings on
the
> > flyback xformer and one checked out ok. Bad horiz output tranistor?
See
> > readings below.
> >
> > ----Original Message Follows----
> > From: "Mike Selnick" <selnick@xxxxxxxxxxx>
> > Reply-To: tvservice@xxxxxxxxxxxxx
> > To: tvservice@xxxxxxxxxxxxx
> > Subject: [tvservice] Re: New Post--Fuse keeps blowing; Dead TV
> > Date: Mon, 26 Apr 2004 19:56:35 -0400
> >
> > Looked like a nice call at first. I disabled B+, gave it a new fuse,
> > plugged into 120vac, and the fuse did not blow. The horizontal output
> > transistor emitter and collector outer leads both seemed to be shorted
to
> > ground on the ohmmeter. After I removed the transistor, I did some
> ohmmeter
> > checks on it: Emitter to collector reads 7k ohms, emitter to base reads
> 5k
> > ohms, and base to collector reads infinity. (Reverse ohmmeter polarity
> > gives infinity for the same three readings.)
> >
> > Do you still think it's a bad transistor or that other faults are
> grounding
> > the emitter and collector?
> >
> > ----Original Message Follows----
> > From: "graytv" <graytv@xxxxxxx>
> > Reply-To: tvservice@xxxxxxxxxxxxx
> > To: <tvservice@xxxxxxxxxxxxx>
> > Subject: [tvservice] Re: New Post--Fuse keeps blowing; Dead TV
> > Date: Mon, 26 Apr 2004 10:06:25 -0400
> >
> > First thing I would do is disable the B+ to the flyback and sacrifice
> > another fuse.
> >
> > If it doesn't blow then check the horizontal output transistor for a
> short.
> > If it's ok then you might have a bac flyback.
> >
> > If the fuse still blows, then check the secondaries for shorts.
> >
> > BTW, a good check to see if the primary side is ok, after disconnecting
> the
> > B+, is to check pin 1 of U4101 for -40v to hot ground. If that is good
> then
> > the regulator circuit is almost certainly (never say never), working
> > properly.
> >
> > hth, Russ Gray, A+, Pres.
> > Gray's Electronics Inc.
> > 201-C Commonwealth Blvd.
> > Port Orange FL USA 32127
> > 386-322-0904 voice
> > 386-322-3809 fax
> > graytv@xxxxxxx email
> >
> >
> > ----- Original Message -----
> > From: "Mike Selnick" <selnick@xxxxxxxxxxx>
> > To: <tvservice@xxxxxxxxxxxxx>
> > Sent: Saturday, April 24, 2004 5:25 PM
> > Subject: [tvservice] Re: New Post--Fuse keeps blowing; Dead TV
> >
> >
> > > Thanks, Russ. Hello List members. My first time aboard. It's been
> > decades since I did TV repair work.
> > >
> > > I'm working on a 31-inch RCA GE 31GT659, Code 45104, Chassis CTC
186/7
> > > bought from Sears in Feb. 1996. Set is completely dead. Fuse f4001
> is
> > > open.
> > >
> > > I replaced the 5A. fuse and 2.3-ohm 15-watt power resister r4001 and
> > plugged the power cord into 120VAC power. Even *before* I had a chance
to
> > turn
> > the set ON, the Fuse immediately opened and f4001 resister was very hot
to
> > the touch. A good on-line troubleshooter recommended (for similar model
> RCA
> > GE set) that ic U4101 (STK730-010) is probably shorted and should be
> > replaced.
> > > I did quick ohmmeter checks of all the diodes and resistors in the
> > power
> > supply and they look ok.
> > >
> > > Question: What jumps out as the most likely faulty component to
> replace
> > and how would you test it beforehand? ( B+ filter? Degauss relay
k4201
> or
> > thermistor rt4201, Switch Mode xformer T4101, Hybrid Switch Mode Reg
U4101
> > ic, Closed caption filterQ3302?)
> > >
> > >
> > > ----Original Message Follows----
> > > From: "Hoyt's TV" <hoytstv@xxxxxxxxxxx>
> > > Reply-To: tvservice@xxxxxxxxxxxxx
> > > To: <tvservice@xxxxxxxxxxxxx>
> > > Subject: [tvservice] Re: New Post
> > > Date: Sat, 24 Apr 2004 09:36:29 -0400
> > >
> > > I think you have the honor of making the first post, Mike.
> > > I signed up for the list on March 21st and yours is the first I've
> seen
> > from
> > > it.
> > >
> > > Russ Hoyt
> > > Hoyt's TV
> > > Exeter, NH
> >
> > _________________________________________________________________
> > Test your 'Travel Quotient' and get the chance to win your dream trip!
> > http://travel.msn.com
> >
> > _________________________________________________________________
> > Test your 'Travel Quotient' and get the chance to win your dream trip!
> > http://travel.msn.com
> >
> >
>
>
>
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