Magnavox tv problem,

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dacflyer
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Magnavox tv problem,

Post by dacflyer » Sat Apr 14, 2007 12:59 pm

hi all, i got a magenetbox t vee here
model # 27TS52 C103
chassis 27X602 - 00BB

if i rember right Edd helped me with it before back in 04'
Edd's suggestions fixed it,

anyway the set is dead now, was watching it and it just turned off, i thought the H.O.T. or something in the power supply went belly up,
i have checked all the obvious things, B+ , regulator , H.O.T etc.
but all check out all ok,, the signals from front buttons go into the micon controller,,but nothing comes out.. i have my 5volts stand by etc..but i cannot figgure out what else is wrong,, i need tips or a schematic if anyone has it,, its obviously not any of the common problems typically found ..
someone help me out,, its a good tv, i'd hate to throw it out..

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Janitor Tzap
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Re: Magnavox tv problem,

Post by Janitor Tzap » Sat Apr 14, 2007 3:58 pm

dacflyer wrote:hi all, i got a magenetbox t vee here
model # 27TS52 C103
chassis 27X602 - 00BB

if i rember right Edd helped me with it before back in 04'
Edd's suggestions fixed it,

anyway the set is dead now, was watching it and it just turned off, i thought the H.O.T. or something in the power supply went belly up,
i have checked all the obvious things, B+ , regulator , H.O.T etc.
but all check out all ok,, the signals from front buttons go into the micon controller,,but nothing comes out.. i have my 5volts stand by etc..but i cannot figgure out what else is wrong,, i need tips or a schematic if anyone has it,, its obviously not any of the common problems typically found ..
someone help me out,, its a good tv, i'd hate to throw it out..
Hmm....

Sounds like the X-ray shut down circuit is being triggered.

I had a Toshiba 27" that was like that.
I found a shorted transistor in the X-ray circuit was the cause.

Sorry.....
I can't help you on the schematic.:sad:
But have you tried looking it up in the SAMS PHOTOFACTS?


Signed: Janitor Tzap

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Post by dacflyer » Sat Apr 14, 2007 7:13 pm

its not even attempting to fire up...so its not even able to trigger the
x-ray protect circuit

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shillyard
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Tv trouble shooting.

Post by shillyard » Sat Apr 14, 2007 9:03 pm

Did you check the high voltage section ? A problem there will look like a smps problem.
If its not worth repairing its not worth buying.

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Post by dacflyer » Sun Apr 15, 2007 2:00 pm

i already said it wasn't the Hv section (B+ etc )

and its not a smps..its a STR type regulated PS.. and its working..

Edd time for you to step in here...lol

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Post by positronicle » Sun Apr 15, 2007 4:18 pm

--Edited by Positronicle--

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Post by Janitor Tzap » Sun Apr 15, 2007 4:40 pm

dacflyer wrote:i already said it wasn't the Hv section (B+ etc )

and its not a smps..its a STR type regulated PS.. and its working..

Edd time for you to step in here...lol
Hmm....

I did a Google on your Chassis.
Found that their are a few people who are seeing the same problem.
But no one with a good answer.

Well.....
Break out your ESR Meter and start going through the Electrolytics in the SMP.
And check around the Horizontal Drive Circuit.

I've been seeing a Repair kit that Mat-Electronics is currently selling for the
Philips 25" & 27" Sets.
CAT#61-280
Horizontal Driver Repair Kit for Philips L01.1U
It replaces the:
BU4508DX
BC547
BC557
47Mfd/50V
220Mfd/35V

Hmm....
These sets use multiple signals from different parts of the set.
One of which is a Power Good Signal that comes from the secondary windings of the Flyback, going to the standby power regulator circuit.
If you loose that signal. The set won't startup.

I'd start there next if you can't find anything in the SMP.

Good Hunting!


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Post by dacflyer » Mon Apr 16, 2007 11:12 am

i looked there in that area.. still nothing...
nothing seems to be out of the ordinary... this one is driving me nuts.. O_o

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Post by Edd » Mon Apr 16, 2007 12:05 pm

.

Now really ? ....2004...don't remember that far back for specifics, but apparently trouble is of a different nature for you should have your old "footprints" of that repair to zero in on.

Two immediate points of analysis come to mind:

1.....

Fire up the set and wait long enough to see if the pic kine comes on and then advance the kine drive pot on the flyback enough to see if failure mode is due to there being no vert deflection...with its white line and,if so, proceed to locating the resistor/fuse on the flyback winding that is supplying power to the vert ckt and check its rect and filtering and finally feeding the Vert out I.c.. If that res (R445 ?? 1 ohm 1/2) was open and the VERT output is one of the LARGER units , vice the smaller, old common LA7836 series, it is certainly suspect of having been the culprit. Along with hi ESR electros in that PS or that sets vert ckt's ancillary components. Parts should be in the 4xx numbering series on that sets vert ckt.

2.....

If the power supply is suspect. run an evaluation by completely pulling the HOT xstr and tacking in a 500 -1K 10 W ww res
from the collector/emitter lands. That should then let the power supply alone be started and the checking of its different voltage outputs be made.
If it doesn't come up, be sure all of the power supplys electrolytics pass ESR testing.

THEN ...if having an operative power supply...then the Hoz out section would be suspect...reinstall the HOT and confirm that there is no problem with the HOZ driver connections being open from current zapping.


Checked out LRC resources downstairs, but Sams didn't show coverage for that model ???? Hows about a date of manufacture from the units rear label.


73's de Edd
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Post by dacflyer » Mon Apr 16, 2007 2:55 pm

Fire up the set and wait long enough to see if the pic kine comes on and then advance the kine drive pot on the flyback enough to see if failure mode is due to there being no vert deflection...with its white line and,if so, proceed to locating the resistor/fuse on the flyback winding that is supplying power to the vert ckt and check its rect and filtering and finally feeding the Vert out I.c.. If that res (R445 ?? 1 ohm 1/2) was open and the VERT output is one of the LARGER units , vice the smaller, old common LA7836 series, it is certainly suspect of having been the culprit. Along with hi ESR electros in that PS or that sets vert ckt's ancillary components. Parts should be in the 4xx numbering series on that sets vert ckt.

set does not fire up...so theres no secondarys from the flyback at this time..

2.....

If the power supply is suspect. run an evaluation by completely pulling the HOT xstr and tacking in a 500 -1K 10 W ww res
from the collector/emitter lands. That should then let the power supply alone be started and the checking of its different voltage outputs be made.

all i get is the 130 volts from the STR30130 regulator,and the 5 volts stand by, when i press the power button the B+ comes up,but if i press the power button again, it will not turn off.but eitherway i have my B+,just cannot get the HORZ signal to fire up the secondarys.

If it doesn't come up, be sure all of the power supplys electrolytics pass ESR testing.
checked the usual suspects already.

THEN ...if having an operative power supply...then the Hoz out section would be suspect...reinstall the HOT and confirm that there is no problem with the HOZ driver connections being open from current zapping.
HOZ circuit checks out ok, just no drive on the base..i am starting to suspect the jungle ic., because theres no signal to the HORZ drive transformer

Checked out LRC resources downstairs, but Sams didn't show coverage for that model ???? Hows about a date of manufacture from the units rear label.

JUNE 1996

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Edd
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Post by Edd » Tue Apr 17, 2007 12:02 pm

.

Seek and ye shall find......

http://www.servomagazine.com/forum/view ... t=magnavox

BEEEEEGIN QUOTATIONATATABLE MARKEE-MARKEES:

"i did find that C432 was open but it didn't check bad while in circuit.. i removed it.ESR was at the bottom of the scale
i replaced it. with a known good one from the junk pile..
is this cap known for getting hot ? very warm to the touch.. its operating with in its rated limits
and cap checker says it in good shape..

FINNNEEEE QUOTATIONATATABLE MARKEE-MARKEES:

Since the unit is not working, you can not do the old fingertip /temp evaluation test.

With your further sequencing of the statement "Do this thang be supposed to get waaaaaaaarm"...just after your having acquired it from the "junk pile"...now....within its 3 years of operation to date...it also being used in a stresssed and critical application. There is a like possibility of it now being "hammered down" with the strong, fast rise time, high current recuring spiked pulses that it has been handling in the interim.

Hint...its replacement with a tandem pair of 105 degree temp units to make up the like capacitance value will result in a 400% improved reliability factor.


Finally if that was not it, I still can't zero in on its schematic , but might find its brother / ckt equivalent if I knew what that chassis' was using for its frontal IF-VIDEO_CHROMA chip --- Jungle-gym chip--- H.O.Xstr.--plus hz driver xstr--- VERTICAL Eye See---( which I think... might actually be that smaller LA78xx series), and finally, it is using the somewhat reliable STR30130 linear chip..... as compared to a more taxing SM design of chip.

73's de Edd
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:grin: :razz: :grin:



Wellll.. I guess that it is okay to be ignorant in some areas, but some people that I have met, just downright abuse the privilege.


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dacflyer
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Post by dacflyer » Tue Apr 17, 2007 3:42 pm

Hmmmm grovel grovel....just what does this cap do anyway ? (C432)
haven't suspected it, but i'll check it..if thats the culprit, i'm gonna be kicking myself..
i'll let you know later this evening......

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Post by dacflyer » Wed Apr 18, 2007 6:10 pm

Edd >> i checked that C432 cap..its as good as new according to my capanalizer 88A .. (4-20-07)

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Post by dacflyer » Fri Apr 20, 2007 10:57 am

bump up.....

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Edd
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Post by Edd » Fri Apr 20, 2007 1:09 pm

your time to bumpitty bump up...with:

...can't zero in on its schematic , but might find its brother / ckt equivalent if I knew what that chassis' was using for its frontal IF-VIDEO_CHROMA chip --- Jungle-gym chip--- H.O.Xstr.--plus hz driver xstr--- VERTICAL Eye See---( which I think... might actually be that smaller LA78xx series), and finally, it is using the somewhat reliable STR30130 linear chip..... as compared to a more taxing SM design of chip.

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