[TechAssist] Re: FIXED Magnavox XS2552 C102, chassis 25P613-00AA, blows HOT immediately, need to know value of B+

  • From: "Damon" <damon101@xxxxxxxxxxxxxx>
  • To: <techassist@xxxxxxxxxxxxx>
  • Date: Fri, 21 May 2004 19:23:18 -0500

Heyyyy.....now that makes sense!!!  Increased frequency may fit with my
theory which I copied here:

OK Kevin, after looking over your post and thinking about "Why would this
bad timing cap cause the HOT to short immediately after  turning the set
off?" I realized one thing that's missing when you turn it off......the
horiz drive pulse.

Now the one thing I was having problems with was "Why didn't the damper
diode absorb the negative portion of the retrace pulse....which normally
kills the HOT???

Now imagine if you will (I said that before..didn't I?) increased frequency
, and a diode damper whose trr (turn on switching time) is slow enough to
not be able to turn on due to the higher frequency......and the transistor's
horiz drive signal helped to dissipate that when it was running and wasn't
present only during turn-off.....Huh?? Huh?? Whaddya think? I wonder if this
TV could run for hours and only dies when turned off....if so I think we
have a winner here....

Damon Brunger
Telrad Electronic Services
Ft Wayne, IN 46815

----- Original Message -----
From: "Phil Bader" <tjanphyl@xxxxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Friday, May 21, 2004 3:47 PM
Subject: [TechAssist] Re: FIXED Magnavox XS2552 C102, chassis 25P613-00AA,
blows HOT immediately, need to know value of B+


| The H. output/fly circuit is a tuned L/C circuit. The "L" being for one, =
|
| the inductance of the fly windings. The "C" being tuning caps mainly.
| There must be resonance by a specific balance between the two, with=20
| resonance being the horiz. scan freq, 15750Hz. In some PC monitors that=20
| ran different horiz. scan freqs (15750hz, 35KHz,etc) they used relays,=20
| or later, switching FET's to switch in and out timing caps so  the L/C=20
| resonance would be maintained throughout the range of  H.  frequencies.  =
|
| By adding, or taking away tuning caps this was accomplished.
| In standard TV where one refresh rate is used, it's constant. A cap=20
| decreasing in value is like putting a smaller cap in, and detunes the=20
| circuit.
| Much like in RF power tranmitters with a "Pi" network coupling the final =
|
| RF output to the transmission/antenna system,this mis-match causes "SWR" =
|
| or standing waves, which can damage the final outputs. (in this case, HOT=
| )
| Thats how I understand it. Time to go home!
| Whew.
| Phil Bader
|
| Peter oliver wrote:
|
| >The way I understand it is that as the timing capacitor decreses in valu=
| e=20
| >the Frequency of the horz pulse increses (inverse relationship to the ou=
| tput=20
| >voltage). And since the Voltage developed in a Flyback circuit is partia=
| ly=20
| >developed by the timing of the circuit a higher frequncy devleoped by a =
| open=20
| >timing cap, yoke or coil anomomoly results in a higher operating voltage=
| =20
| >when that voltage exceeds the breakdown of another components a failure =
|
| >occurs. If I rember right that cap is directly off the collector of the =
| HOT=20
| >had one about a month ago that chared itself (had also caused a HOT fail=
| ure=20
| >the first time but the HOT I used was overrated enough to hold it). But =
|
| >being in that location it might also possibly help dispate some of the=20
| >inital pulse, I guess another way to describe the theory of operation as=
| =20
| >pretty much like a back EMF phenomina.
| >
| >Peter Oliver
| >Tucson Radio TV
| >
| >From: Kevin <kevintv@xxxxxxx>
| >Reply-To: techassist@xxxxxxxxxxxxx
| >To: techassist@xxxxxxxxxxxxx
| >Subject: [TechAssist] Re: FIXED Magnavox XS2552 C102, chassis 25P613-00A=
| A,=20
| >blows HOT immediately, need to know value of B+
| >Date: Fri, 21 May 2004 12:29:58 -0700
| >
| >Nobody knows the answer, I guess.
| >
| >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 becyn
| >Sent: Friday, May 21, 2004 10:31 AM
| >To: techassist@xxxxxxxxxxxxx
| >Subject: [TechAssist] Re: FIXED Magnavox XS2552 C102, chassis
| >25P613-00AA, blows HOT immediately, need to know value of B+
| >
| >As Al said, I think you need to do some study on the theory of
| >operation. It
| >will help tremendously in you troubleshooting efforts.
| >
| >I have a saying that I use here; "You can't efficiently fix something
| >unless
| >you know how it works". Serendipity goes just so far...
| >
| >Jim McVey
| >McVey Alltronix
| >327 Broadway
| >Newburgh Ny 12550
| >ph: 845 561 8383
| >fx: 845 561 9017
| >Consumer electronics &
| >computer service.
| >Factory authorized for
| >over twenty brands.
| >----- Original Message -----
| >From: "Kevin" <kevintv@xxxxxxx>
| >To: <techassist@xxxxxxxxxxxxx>
| >Sent: Thursday, May 20, 2004 10:58 PM
| >Subject: [TechAssist] Re: FIXED Magnavox XS2552 C102, chassis
| >25P613-00AA,
| >blows HOT immediately, need to know value of B+
| >
| >
| > > So the timing cap keeps the flyback primary pulse within the specs of=
|
| > > the HOT?  I have also had a bad connection on the timing cap and all
| > > that happened was the picture was affected.  Does whether the HOT is
| > > shorted or not depend on the design of the circuit?
| > >
| > > 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 becyn
| > > Sent: Thursday, May 20, 2004 3:34 PM
| > > To: techassist@xxxxxxxxxxxxx
| > > Subject: [TechAssist] Re: FIXED Magnavox XS2552 C102, chassis
| > > 25P613-00AA, blows HOT immediately, need to know value of B+
| > >
| > > It will send the flyback primary pulse over the C-E 0r C-B ratings of=
|
| > > the
| > > H-out.(not to mention the timing skew)
| > >
| > > Jim McVey
| > > McVey Alltronix
| > > 327 Broadway
| > > Newburgh Ny 12550
| > > ph: 845 561 8383
| > > fx: 845 561 9017
| > > Consumer electronics &
| > > computer service.
| > > Factory authorized for
| > > over twenty brands.
| > > ----- Original Message -----
| > > From: "Kevin" <kevintv@xxxxxxx>
| > > To: <techassist@xxxxxxxxxxxxx>
| > > Sent: Thursday, May 20, 2004 5:47 PM
| > > Subject: [TechAssist] Re: FIXED Magnavox XS2552 C102, chassis
| > > 25P613-00AA,
| > > blows HOT immediately, need to know value of B+
| > >
| > >
| > > > Timing capacitor, C505 9.1 nF @ 1600 volts, was open (measured 20
| >pF).
| > > > I used C5149 for the HOT.  Thanks for all the replies.
| > > >
| > > > Why would this bad timing cap cause the HOT to short immediately
| >after
| > > > turning the set off?  Thanks.
| > > >
| > > > 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
| > > gulftech@xxxxxxxx
| > > > Sent: Thursday, May 20, 2004 6:23 AM
| > > > To: techassist@xxxxxxxxxxxxx
| > > > Subject: [TechAssist] Re: Magnavox XS2552 C102, chassis 25P613-00AA=
| ,
| > > > blows HOT immediately, need to know value of B+
| > > >
| > > > Kevin,
| > > >
| > > > First, I don't like NTE or SK replacements, especially for HOT's.
| > > Next,
| > > > it is always best to start with the original.  If you don't have th=
| e
| > > > original, cross it to a generic with equal or better specs.  If you=
|
| > > > cross
| > > > it to an NTE and then try to use a generic that also crosses to the=
|
| > > same
| > > > NTE is not reliable.  The D1849 is a 7A, 120 wt, w/ damper.  The
| >NTE,
| > > is
| > > > lower gain and lower power rating (70 wt).  If you must use an NTE,=
|
| > > try
| > > > an NTE2318.
| > > >
| > > > Still, I am concerned about the HOT shorting immediately.  Check fo=
| r
| > > > open
| > > > safely caps in the horizontal deflection.  Often, you can see them
| > > > cracked and a little carbon burn on them.  This would cause you hig=
| h
| > > > voltage to run way high and take out the HOT.
| > > >
| > > > HTH,
| > > >
| > > >
| > > > Ken Smith
| > > > Gulf Technical Services
| > > > 3034 Gulf Breeze Parkway
| > > > Gulf Breeze, FL  32563
| > > > 850-934-8324 (Voice) 850-932-0819 (Fax)
| > > >
| > > >
| > > > On Wed, 19 May 2004 16:20:01 -0700 Kevin <kevintv@xxxxxxx> writes:
| > > > > I used a D1849 which crosses to an NTE 2353.  I don't have the
| >exact
| > > > > Phillips replacement.  I have done this before many times before
| > > > > with no
| > > > > call backs.  Even if the D1849 wasn't exactly the same as the
| > > > > Phillips
| > > > > part, it should be good enough for test purposes.  It should not
| > > > > fail in
| > > > > 1 second.  What, in your estimation, is the best generic sub for
| >NTE
| > > > > 2353?
| > > > >
| > > > > 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
| > > > > gulftech@xxxxxxxx
| > > > > Sent: Wednesday, May 19, 2004 3:05 PM
| > > > > To: techassist@xxxxxxxxxxxxx
| > > > > Subject: [TechAssist] Re: Magnavox XS2552 C102, chassis
| >25P613-00AA,
| > > > > blows HOT immediately, need to know value of B+
| > > > >
| > > > > Kevin,
| > > > >
| > > > > Quit using those darn NTE outputs and buy a good stock of real
| > > > > transistors.  You end up beating yourself to death because of a
| >bad
| > > > > sub
| > > > > and think it's something else.  Costs you time, money, and
| >patience.
| > > > >
| > > > >
| > > > > Ken Smith
| > > > > Gulf Technical Services
| > > > > 3034 Gulf Breeze Parkway
| > > > > Gulf Breeze, FL  32563
| > > > > 850-934-8324 (Voice) 850-932-0819 (Fax)
| > > > >
| > > > >
| > > > > On Wed, 19 May 2004 12:49:10 -0700 Kevin <kevintv@xxxxxxx> writes=
| :
| > > > > > I measured the B+ before I installed the HOT by putting a 110
| >ohm,
| > > > > 30
| > > > > > watt resistor from collector to ground.  The B+ measured 127
| > > > > volts,
| > > > > > and
| > > > > > the STR30130 was ouputting 130.2 volts.  Thinking everything wa=
| s
| > > > > > good, I
| > > > > > installed the new HOT (Q502 NTE 2353) and turned the set on.
| >The
| > > > > HV
| > > > > > came up but 'sounded funny', so I quickly turned the TV off and=
|
| > > > > > discovered a totally black fuse and shorted HOT.  My flyback
| >rings
| > > > > > good.
| > > > > > Could it still be a bad flyback?
| > > > > >
| > > > > > Kevin Wilks
| > > > > > Kevin's TV & Video Repair
| > > > > > Penticton BC Canada
| > > > > > kevintv@xxxxxxx
| > > > > >
| > > > > >
| > > > > >
| > > > > >
| > > > > >
| > > > >
| > > >
| > > >
| > > >
| > > >
| > >
| >------------------------------------------------------------------------=
|
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| > >
| > >
| > >
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|
| --=20
|
| 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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