Toshiba TV29C90 problem; Image fades to black...

[Wild_Bill]

It's been a long time since I dealt with CRT horiz output
sections/transistors, and the latter ones were in VGA monitors.

In the Repair FAQ there are safety, testing and troubleshooting procedures
for horiz section faults, including the lightbulb in series with the HOT B+
setup, IIRC.

The HOTs (transistors) are fairly rugged semis, but operating at 15+kHZ and
high peak/fast risetime conduction cycles.

FWIW section..

A few conditions wrt HOT failures that I can recall at the moment include
bad/cold/broken solder connections, loss of horiz drive and drifting
values/faults in the tuning capacitors (the small value 1 and 2kV caps).

Small low voltage/battery powered testers aren't very reliable, IMO, for
testing/evaluating HOTs, since reliable leakage testing at higher voltages
than most small testers are capable of, should be performed to determine the
junction's performance compared to the datasheet published specs.

The above point being that one rarely knows for sure if they're receiving
genuine exact replacement parts nowadays, and testing before installation is
likely the best way to find out if the part are bogus.

My recommendations (and many other archived repair recommendations) for Sony
TVs and monitors, is to research the failure and buy all the recommended
repair parts from a Sony authorized distributor, especially for PSU and H,V
sweep faults.

--
Cheers,
WB
..............


"Sylvia Else" <sylvia@not.here.invalid> wrote in message
news:8u5dluFctkU1@mid.individual.net...

On 13/03/2011 4:29 PM, Sylvia Else wrote:

I've bitten the bullet, and bought a new television.

Still, I'm puzzled by the failure in the old one. The transistor has
clearly failed, as far as I can see. Removing the small inductor mentioned
above stops the clicking noise, which is consistent with there no longer
being a short across the SMPS.

I'd have expected the set to now turn on and produce sound. But it
doesn't.

The SMPS uses a quasi-resonant circuit, and disconnecting the inductor has
a side effect of removing the feedback for the SMPS. But on my, admittedly
limited, understanding of such circuits, it should still work.

Sylvia.

 

[Phil Allison]

"Wild_Bull"

FWIW section..

A few conditions wrt HOT failures that I can recall at the moment include
bad/cold/broken solder connections, loss of horiz drive and drifting
values/faults in the tuning capacitors (the small value 1 and 2kV caps).

** Not to forget arcing inside the CRT or the horizontal transformer.

Small low voltage/battery powered testers aren't very reliable, IMO, for
testing/evaluating HOTs,

** 99 % of them cannot do any test on them at all.

since reliable leakage testing at higher voltages than most small testers
are capable of, should be performed to determine the junction's
performance compared to the datasheet published specs.

** Pure gobbledegook.

The above point being that one rarely knows for sure if they're receiving
genuine exact replacement parts nowadays,

** Instead of what - fakes ??

and testing before installation is likely the best way to find out if the
part are bogus.

** Absolute bullshit.

No simple test will reveal a device that is merely sub-standard or of a
similar but cheaper type to the original.

The only way is to deal with reliable suppliers ONLY.

My recommendations (and many other archived repair recommendations) for
Sony TVs and monitors, is to research the failure and buy all the
recommended repair parts from a Sony authorized distributor, especially
for PSU and H,V sweep faults.

** Wear a belt and braces too - do you ??



..... Phil

 

[Sylvia Else]

On 14/03/2011 7:51 PM, Phil Allison wrote:

"Wild_Bull"

FWIW section..

A few conditions wrt HOT failures that I can recall at the moment include
bad/cold/broken solder connections, loss of horiz drive and drifting
values/faults in the tuning capacitors (the small value 1 and 2kV caps).


** Not to forget arcing inside the CRT

In a vacuum?

or the horizontal transformer.

Sylvia.

 

[Phil Allison]

"Stupider than Anyone Else.

** Not to forget arcing inside the CRT

In a vacuum?

http://en.wikipedia.org/wiki/Vacuum_arc


** One of the most common causes of HOT failures.

Dumbass.



..... Phil

 

[Wild_Bill]

Arcing, shorts and HV leakage can all take place within a CRT.
I've seen several CRTs that had HV leakage to the Focus element (didn't
damage the HOT though).. there may be some examples in the Repair FAQ of
this type of fault and other CRT faults.

--
Cheers,
WB
..............


"Sylvia Else" <sylvia@not.here.invalid> wrote in message
news:8u6b4pFhe5U1@mid.individual.net...

In a vacuum?

or the horizontal transformer.

Sylvia.

 

[Clifford Heath]

On 03/14/11 17:44, Phil Allison wrote:

** You need a " Power Transistor Tester" - published as a full construction

Thanks.

I would post the schem on ABSE, but like so many others I no longer have
access to the site.

You mean you have no access to ABSE? Spend $US3.95 at www.teranews.com and
get free lifetime access to all the binary groups, limited to 50MB/day.

Clifford Heath.

 

[Phil Allison]

"Clifford Heath"
Phil Allison wrote:

** You need a " Power Transistor Tester" - published as a full
construction

Thanks.

I would post the schem on ABSE, but like so many others I no longer have
access to the site.

You mean you have no access to ABSE? Spend $US3.95 at www.teranews.com and
get free lifetime access to all the binary groups, limited to 50MB/day.

** Not worth a hoot to me for posting schems or pics unless everyone has the
same.



...... Phil

 

[Stroonz]

On Mar 13, 1:11 am, "Phil Allison" <phi...@tpg.com.au> wrote:

There is an inbuilt resistor from B to E in nearly all HOTs of 20 ohms or
less.

******Bollocks.

Most horiz output internal resistors are between 25 and 50 ohms.
Besides, 20 ohms isn't 5.7ohms. In circuit, E to B reads an ohm or
under as the secondary of the horiz driver transformer is directly
across it.. Out of circuit, a reading of 5.7 ohms E to B is a bad
transistor. It's not common in horizontal outputs, but an E to B
short does happen.


On Mar 13, 1:11 am, "Phil Allison" <phi...@tpg.com.au> wrote:

** Probably normal.

**** More likely a stupid answer.

A common problem in Sonys is a bad solder connection on the secondary
of the horiz driver transformer, so instead of reading under an ohm,
the cold solder causes a reading of several ohms up to the internal
resistor value. Simply resoldering the horiz driver will restore
proper reading if the output is otherwise OK.


Twit.

Hey, this is fun!!!!!

 

[Phil Allison]

"Stroonz is a Shithead "

"Phil Allison"

There is an inbuilt resistor from B to E in nearly all HOTs of 20 ohms or
less.

******Bollocks.

Most horiz output internal resistors are between 25 and 50 ohms.

** I have seen them with 20 ohms and less.

You need to get out more.

Besides, 20 ohms isn't 5.7ohms.

** The OP corrected her error in the next post - which you have not
bothered to even read.

The 5.7 ohms was measured from C to B.

No clue was given about the use of in or out of circuit testing.

In circuit, E to B reads an ohm or
under as the secondary of the horiz driver transformer is directly
across it..

** Not all HOT drive circuits are like that.

** Probably normal.

**** More likely a stupid answer.

** Why don't you go and get fucked ?


....... Phil

 

[b]

Sony tvs are notorious for being picky about spares. I dislike them
for that reason, as they usually get repair estimates rejected due to
cost grounds.And that's assuming spares availability...

I recently dumped a 25" CRT set (FE2 chassis I think) - shorted
horizontal output stage. Common fault with the chassis - the
transformer fails, killing the line o/p transistor and damages the
micro. Unless you replace the lot in one go, with genuine sony bits,
you're back to square one... plus the uPc is NLA and an awkward smd
type. Set was BER, a shame considering it was barely 8 years old.
-B

 

[Phil Allison]

"Stroonz is a SHITHEAD "

Most horiz output internal resistors are between 25 and 50 ohms.

** I have seen them with 20 ohms and less.

You need to get out more.

Besides, 20 ohms isn't 5.7ohms.

** The OP corrected her error in the next post - which like a total
shithead you have not bothered to even read.

The 5.7 ohms was actually measured from C to B.

And the bitch gave no clue about the use of in or out of circuit testing.

In circuit, E to B reads an ohm or
under as the secondary of the horiz driver transformer is directly
across it..

** Not all HOT drive circuits are like that.

Many have a low value R in series with the base with a diode across it.


** Why don't you go fuck a dead donkey ?



....... Phil

 

[Phil Allison]

"Stroonz is a PSYCHOTIC SHITHEAD "

Most horiz output internal resistors are between 25 and 50 ohms.

** I have seen them with 20 ohms and less.

You need to get out of that asylum more.

Besides, 20 ohms isn't 5.7ohms.

** The OP corrected her error in the next post - which like a total
shithead you have not bothered to even read.

The 5.7 ohms was actually measured from C to B.

And the mad bitch gave no clue about the use of in or out of circuit
testing.

In circuit, E to B reads an ohm or
under as the secondary of the horiz driver transformer is directly
across it..

** Not all HOT drive circuits are like that.

Many have a low value R in series with the base with a diode across it.

The original exchange was:

" > The horizontal deflection output transistor measures 5.7 omhs from

emitter to base in either direction.

** Probably normal. "

See - no reference is made to any particular set in my remark .


** Why don't you go fuck two dead donkeys ?



....... Phil

 

[Stroonz]

On Mar 14, 8:01 pm, "Phil Allison" <phi...@tpg.com.au> wrote:

** I have seen them with 20 ohms and less.

******** Yes, but those are called shorted.



On Mar 14, 8:01 pm, "Phil Allison" <phi...@tpg.com.au> wrote:

** Not all HOT drive circuits are like that.

******** She didn't ask about all HOT drive circuits, she asked about
HERS.

** Why don't you go and get fucked ?

......  Phil

Now is that nice?

 

[Phil Allison]

"Stroonz is a LYING PSYCHOPATH "

You said a 5.7 ohm reading was "probably normal" for her Sony.

** Wrong.

The original exchange was:

" > The horizontal deflection output transistor measures 5.7 omhs from
emitter to base in either direction.

** Probably normal. "

See - no reference is made to any particular set in my remark .

** Why don't you go fuck two dead donkeys ?

 

[kreed]

On Mar 15, 11:38 am, "Phil Allison" <phi...@tpg.com.au> wrote:

"Stroonz is a SHITHEAD  "



Most horiz output internal resistors are between 25 and 50 ohms.

** I have seen them with 20 ohms and less.

    You need to get out more.

Besides, 20 ohms isn't 5.7ohms.

** The OP corrected her error in the next post  -  which like a total
shithead you have not bothered to even read.

 The 5.7 ohms was actually measured from C to B.

 And the bitch gave no clue about the use of in or out of circuit testing.

In circuit, E to B reads an ohm or
under as the secondary of the horiz driver transformer is directly
across it..

** Not all HOT drive circuits are like that.

 Many have a low value R in series with the base with a diode across it..

** Why don't you go fuck a dead donkey ?

Im very annoyed now, I was sipping coffee when I read that, and some
got sprayed from laughing

......  Phil

 

[Stroonz]

On Mar 14, 9:38 pm, "Phil Allison" <phi...@tpg.com.au>blathered:

** The OP corrected her error in the next post  -  which like a total
shithead you have not bothered to even read.

******* Doesn't matter if she corrected it or not. You were INCORRECT
when you believed a 5.7 ohm E to B reading was normal in HER SONY.

On Mar 14, 9:38 pm, "Phil Allison" <phi...@tpg.com.au>blathered:
** I have seen them with 20 ohms and less.

Yes, and they were shorted. OTOH, if you can cite a transistor that
was actually used as a horiz output that has an emitter-base resistor
of less than 20 ohms, I'll happily concede.

On Mar 14, 9:38 pm, "Phil Allison" <phi...@tpg.com.au> droned:

 The 5.7 ohms was actually measured from C to B.

******** Read above ^


On Mar 14, 9:38 pm, "Phil Allison" <phi...@tpg.com.au> wrote:

 And the bitch gave no clue about the use of in or out of circuit testing.

******** We don't know if she's a bitch or not. She might be quiet
pleasant.....


On Mar 14, 9:38 pm, "Phil Allison" <phi...@tpg.com.au> wrote:

** Not all HOT drive circuits are like that.

No one said all HOT drive circuits are like that. But again, she
wasn't interested in every conceivable version of the drive circuit,
she was interested in HER Sony. Her Sony doesn't have a "low value
resistor in series with the base". If you don't know what you're
talking about or can't offer correct specific information, you really
should pipe down, or at least qualify your opinions as just that.


On Mar 14, 9:38 pm, "Phil Allison" <phi...@tpg.com.au> wrote:

** Why don't you go fuck a dead donkey ?

......  Phil

Common Phil, where does one find a dead donkey, even if one was so
inclined to be intimate with it. You may not be the smartest guy on
the web, but you are a riot!!!

 

[Stroonz]

On Mar 14, 9:58 pm, Stroonz <str00...@aol.com> wrote:

Oh, and the quiet above is a typo: reverse the "e" and "t"

 

[Stroonz]

On Mar 14, 10:08 pm, "Phil Allison" <phi...@tpg.com.au> wrote:

** The OP corrected her error in the next post  -  which like a total
shithead you have not bothered to even read.

****** Yes, the OP did correct her error, something you refuse to
do. You said a 5.7 ohm reading was "probably normal" for her Sony.
You were wrong and can't admit it. Nice character flaw Phil.

The original exchange was:

" > The horizontal deflection output transistor measures 5.7 omhs from
  >  emitter to base in either direction.

** Probably normal.  "

See -  no reference is made to any particular set in my remark .

It's hard to explain this to someone who is unfamiliar with Sonys, but
I'll try again: If everything in her Sony is normal, the E to B
resistance reading will be under an ohm in circuit. If the secondary
of the horiz drive trans in her Sony is open or the connection is bad,
it will read the internal emitter to base resistor directly, if the
transistor is so equipped. (some Sonys of this era use no e to be
resistor). If the transistor is measured out of circuit, it will read
approx 35 ohms e to b if it's not shorted. Under NO CIRCUMSTANCES
will this TV show 5.7 ohms across the e to b junction. Such a reading
is ABNORMAL. Perhaps you left the "ab" out of your reply.

And I know you'll requote her correcting her reading, but it doesn't
change the fact that you believed and proclaimed as fact that an E to
B reading of 5.7 ohms in HER SONY was normal.

** Why don't you go fuck two dead donkeys ?

......  Phil

You know, vile, classless folk take all the fun out of a debate.

Enjoy your last word Phil......

 

[Sylvia Else]

On 15/03/2011 10:33 AM, b wrote:

Sony tvs are notorious for being picky about spares. I dislike them
for that reason, as they usually get repair estimates rejected due to
cost grounds.And that's assuming spares availability...

I recently dumped a 25" CRT set (FE2 chassis I think) - shorted
horizontal output stage. Common fault with the chassis - the
transformer fails, killing the line o/p transistor and damages the
micro. Unless you replace the lot in one go, with genuine sony bits,
you're back to square one... plus the uPc is NLA and an awkward smd
type. Set was BER, a shame considering it was barely 8 years old.
-B

That's the kind of scenario that's deterred me from replacing the
transistor. Your comment about the damage to the microprocessor is
particularly relevant given my inability to persuade the set to produce
sound with the transistor removed, or even to enter/leave standby mode.

Sylvia.

 

[kreed]

On Mar 15, 2:42 pm, Sylvia Else <syl...@not.here.invalid> wrote:

On 15/03/2011 10:33 AM, b wrote:

Sony tvs are notorious for being picky about spares. I dislike them
for that reason, as they usually get repair estimates rejected due to
cost grounds.And that's assuming spares availability...

  I recently dumped a 25" CRT set (FE2 chassis I think) - shorted
horizontal output stage. Common fault with the chassis - the
transformer fails, killing the line o/p transistor and damages the
micro. Unless you replace the lot in one go, with genuine sony bits,
you're back to square one... plus the uPc is NLA and an awkward smd
type. Set was BER, a shame considering it was barely 8 years old.
-B

That's the kind of scenario that's deterred me from replacing the
transistor. Your comment about the damage to the microprocessor is
particularly relevant given my inability to persuade the set to produce
sound with the transistor removed, or even to enter/leave standby mode.

Sylvia.

Not familiar with the set so I don't know exactly - but functions
related to sound may
be powered from a rail generated from the EHT transformer.

Even if not, it is possible that it may be muted or disabled by the
CPU if the EHT circuit isn't working correctly.
Many other functions may be shut off for safety also.

In the past I have found that the majority of sets/monitors (note -
have not worked on many newer than the 1990's)
will work once the H out transistor is replaced, however this isn't
always the case. The tuning caps (usually across the transistor) can
fail or lose capacitance causing the voltage to go through the roof
(they often look normal),
yokes can burn out (Samsung, usually inside on the H section where you
can't see it without removing from tube, usually from corrosion), the
EHT transformer can short internally, or can develop an arc through
the plastic casing to chassis.

Arcing from out of the housing on some transformers that contains the
focus and screen pots. I have seen often

Some of these arcs can be particularly bad, in fact some seem to
manage to burn their way through silicon sealant and continue the arc
as before. (note -too close to the frame to allow a decent thickness)

In some cases, the only way I could stop this was to remove the
aluminium frame from around the transformer, and cut away a section of
it near the where the arc was so as to give the transformer nothing to
arc to. It also allowed more clearance for a thicker coat of silcone
sealant to prevent future problems.



I am leaving out things like dry joints and obviously damaged
components as I assume most people on this group would look for these
before posting.