Toshiba TV29C90 problem; Image fades to black...

[Arfa Daily]

"EADGBE" <hwbosshoss@comcast.net> wrote in message
news:4ca08117-23b7-48de-b7ef-733200c162d0@x41g2000hsb.googlegroups.com...

Good News!

This headphone amplifier has been REPAIRED and is now working
perfectly.

Here's what happened:

I have been taking parallel measurements between the "good" and "bad"
channels since the beginning.

I took voltage measurements, resistance measurements, tested ALL
capacitors, and tested ALL transistors.

But someone in my original thread (I can't remember who offhand --
sorry) did mention checking the circuit board traces.

"No need," I thought. "The circuit board and all solder joints look
fine to me."

But in a fit of desperation, I nonetheless decided to whip out a
tester I hadn't used yet: my magnifying glass.

That's when I found it -- a *microscopic* crack in the trace between
the emitter of Q208 and its adjoining 3.3 ohm resistor. The crack was
so incredibly tiny that I easily overlooked it--repeatedly.

I took one of my jumper leads and clipped one end of it to Q208's
emitter and the other end of it to the 3.3 ohm resistor.

I then took voltage measurements. EVERYTHING WAS NOW ON SPEC:

Q205's collector now measures +7.09V, and Q206 now has the following
measurements:
B: +6.51V
C: +7.08V
E: +5.84V

I was able to bridge the crack with a well-placed solder trail, and
the headphone amp now sounds great.

A BIG "THANK YOU" TO EVERYONE WHO HELPED ME OUT! I OWE YOU BIG TIME.

Well done on finding the problem - a deserved result. However, can I make
one suggestion ? Don't rely on just solder to bridge the crack, as it *will*
cause trouble again. The crack causes the solder to form a crystalline
'wall' above it, inside the joint, as it resolidifies. Any cracks, however
tiny, *must* be bridged by at least one strand from some hookup wire. If you
can get a good joint to a solder point either side of the crack, then do
that. If that is not practical, scrape back the solder resist on the
tracking either side of the crack, and then bury your strand of wire in the
solder bridge. As I know that you do these repairs to further your
knowledge, that is a professional 'reliable repair' tip that you should add
to your knowledge base.

Arfa

 

[James Sweet]

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:m%vPj.8664$GE1.6295@nlpi061.nbdc.sbc.com...

Sam Goldwasser wrote:
orange <orange47@gmail.com> writes:

I bought this ancient laptop (Toshiba T2000SX) on flea market.
It uses two batteries (second one is for BIOS):
-pa8725u (14.4V 2.2AH NiMH) shows 0,45VDC
-XZ0072P09 (6V NiCad) shows 0VDC

They are dead, but I'd like to just try to recharge them. Of course
there is no
original AC power supply. So, can I use standard
AC/DC converter (1000mA max)? Or maybe the 9V NiMh recharger?
Should I just connect + to + , set voltage to 12VDC and let it charge
for a while?

There is power connector on side of laptop, it says 18VDC.
It has 4 pins but I don't have pinout..
if I obtain it, can I try it with 12V ATX PSU?

It's nearly 100 percent certain that the battery is dead for good.
Even "zapping" is rarely successful on these batteries. And something
that probably hasn't been charged in 10 or 15 years is even more
hopeless.

You have nothing to lose by trying to charge it but don't expect
miracles.

It would be worth trying to run the laptop on a DC power supply matching
the battery voltage with sufficient current. However, even if you had
the
AC adapter, it probably wouldn't run the laptop without a good battery.


There often is hope: If 12 NiMH AA-cells would fit into the same space as
the 14.4V battery that would yield the same of even higher capacity than
the original. Should cost less than $25 when on sale. Most have 2.3Ah,
some are claimed even higher.

NiCd are harder but places like Batteries Plus should be able to help. Of
course there comes a point where one has to think about how much money it
is worth sinking into such an old machine.

--
Regards, Joerg

Or if you don't need the battery, just look on ebay for a compatible power
supply and use the laptop plugged into the wall.

 

[James Sweet]

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:m%vPj.8664$GE1.6295@nlpi061.nbdc.sbc.com...

Sam Goldwasser wrote:
orange <orange47@gmail.com> writes:

I bought this ancient laptop (Toshiba T2000SX) on flea market.
It uses two batteries (second one is for BIOS):
-pa8725u (14.4V 2.2AH NiMH) shows 0,45VDC
-XZ0072P09 (6V NiCad) shows 0VDC

They are dead, but I'd like to just try to recharge them. Of course
there is no
original AC power supply. So, can I use standard
AC/DC converter (1000mA max)? Or maybe the 9V NiMh recharger?
Should I just connect + to + , set voltage to 12VDC and let it charge
for a while?

There is power connector on side of laptop, it says 18VDC.
It has 4 pins but I don't have pinout..
if I obtain it, can I try it with 12V ATX PSU?

It's nearly 100 percent certain that the battery is dead for good.
Even "zapping" is rarely successful on these batteries. And something
that probably hasn't been charged in 10 or 15 years is even more
hopeless.

You have nothing to lose by trying to charge it but don't expect
miracles.

It would be worth trying to run the laptop on a DC power supply matching
the battery voltage with sufficient current. However, even if you had
the
AC adapter, it probably wouldn't run the laptop without a good battery.


There often is hope: If 12 NiMH AA-cells would fit into the same space as
the 14.4V battery that would yield the same of even higher capacity than
the original. Should cost less than $25 when on sale. Most have 2.3Ah,
some are claimed even higher.

NiCd are harder but places like Batteries Plus should be able to help. Of
course there comes a point where one has to think about how much money it
is worth sinking into such an old machine.

--
Regards, Joerg

Or if you don't need the battery, just look on ebay for a compatible power
supply and use the laptop plugged into the wall.

 

[GAGI-9A6AAG]

"EADGBE" <hwbosshoss@comcast.net> wrote in message

This headphone amplifier has been REPAIRED and is now working
perfectly.

good4u )

i was folow developing of case you got....i am hobbist to and from my
experience i can tell that malfunctions caused by "cold solder" are most
dificult problems to solve...especiali when there is some random states of
working and it doesnt working...and again...and again...but you cant see it
where does it happening...

even tracking signals is sometimes waste of time...even method of searching
cold solder in dark room (so you can see the sparking place)...seems
sometimes is pure luck that matters! )

Greethings from Croatia...
Gagi

 

[JANA]

The value you wrote, 4.7 uF 25 Volt / Non Polarized, is a common
capacitor. Many of the electronics parts dealers can have this type of
capacitor.

If you want to be fancy, you can take 2 of 10 uF / 25 Volt capacitors in
series. Put them back to back with the two negative leads joined, so
that you are left with the positive leads. In theory this will work, but
in practice with some circuit designs, this approach is not a very good
solution.

--

JANA
_____


<Mr.Frank263@gmail.com> wrote in message
news:58868fa4-24b3-4d8d-9a2a-818aedee6c36@c58g2000hsc.googlegroups.com...
with which type and value to replace the below capacitor, I tried my
best to find a new one but could not
4.7uf 25v non-polarized electrolytic capacitor of handy t.v., two
and a half inch, made in Taiwan

 

[James Sweet]

i was folow developing of case you got....i am hobbist to and from my
experience i can tell that malfunctions caused by "cold solder" are most
dificult problems to solve...especiali when there is some random states of
working and it doesnt working...and again...and again...but you cant see
it where does it happening...

They're one of the most common faults as well, many times more extensive
failures start out as cold solder joints. Often prodding or flexing the
board will make them more obvious.

 

[GAGI-9A6AAG]

"James Sweet" <jamessweet@hotmail.com> wrote in message

They're one of the most common faults as well, many times more extensive
failures start out as cold solder joints. Often prodding or flexing the
board will make them more obvious.

indeed....first and nice example are PC monitors....their PCB is mostly
always in malfunction cause of some cold solder (except when is about HV,
horizontal transistor..etc...)

 

[Arfa Daily]

"GAGI-9A6AAG" <gagi@hi.htnet.hr> wrote in message
news:fumjqt$r1k$1@sunce.iskon.hr...

"EADGBE" <hwbosshoss@comcast.net> wrote in message

This headphone amplifier has been REPAIRED and is now working
perfectly.


good4u )

i was folow developing of case you got....i am hobbist to and from my
experience i can tell that malfunctions caused by "cold solder" are most
dificult problems to solve...especiali when there is some random states of
working and it doesnt working...and again...and again...but you cant see
it where does it happening...

even tracking signals is sometimes waste of time...even method of
searching cold solder in dark room (so you can see the sparking
place)...seems sometimes is pure luck that matters! )

Greethings from Croatia...
Gagi

Interestingly, for the most part, I used to find the locating of bad joints,
one of the *easiest* things to do in fault-finding. As well as having sharp
eyes to spot obvious ones, use of the right techniques i.e. prodding,
flexing, heat, cold, and above all, having a good idea exactly *where* to
look, and at what *type* of component, would quickly reveal the source of
the problem.

Sadly, that has now gone 'out of the window' with modern soldering
materials. I have found many bad joints made in lead-free, that have shown
no external physical signs of being bad, such as cracked around, and have
gone good and bad completely at random, failing to respond to any of the
'normal' techniques for finding them. Add to this that my eyes are not as
good as they were 20 years ago (even 5 years ago...) and that *all*
lead-free joints *look* bad with their dull crystalline surface, and I would
have to agree that now, bad joints are likely to turn a job from a
one-coffee money spinner, to a pot-of-coffee frustrating money loser ...
:-(

Arfa

 

[GAGI-9A6AAG]

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message

Interestingly, for the most part, I used to find the locating of bad
joints, one of the *easiest* things to do in fault-finding. As well as
having sharp eyes to spot obvious ones, use of the right techniques i.e.
prodding, flexing, heat, cold, and above all, having a good idea exactly
*where* to look,

hehe, sure, when; as you said also; cold solder is obvious...
but when it isnt..then?!...its supposed that you know theory very well so
you can persume what it could be...

like; if RGB is losing red color; sure you wont look horizontal-transistor
then you will first look the cable or connector inside )


however; i agree that prodding and flexing PCB is most accurate technique of
finding cold solder....i use a wood stick or back of screw driver for
that...

for nosie sparks but not visible ones i am using "home made" and primitive
stetoscope....i put in ear one side of gum pipe and with other side i am
"scanning" for noise it bothers me...hehe, moving around electronic
components like trough mine field )

 

[GAGI-9A6AAG]

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message

Interestingly, for the most part, I used to find the locating of bad
joints, one of the *easiest* things to do in fault-finding. As well as
having sharp eyes to spot obvious ones, use of the right techniques i.e.
prodding, flexing, heat, cold, and above all, having a good idea exactly
*where* to look,

hehe, sure, when; as you said also; cold solder is obvious...
but when it isnt..then?!...its supposed that you know theory very well so
you can persume what it could be...

like; if RGB is losing red color; sure you wont look horizontal-transistor
then you will first look the cable or connector inside )


however; i agree that prodding and flexing PCB is most accurate technique of
finding cold solder....i use a wood stick or back of screw driver for
that...

for nosie sparks but not visible ones i am using "home made" and primitive
stetoscope....i put in ear one side of gum pipe and with other side i am
"scanning" for noise it bothers me...hehe, moving around electronic
components like trough mine field )

 

[William Sommerwerck]

Add to this that my eyes are not as
good as they were 20 years ago (even 5 years ago...) and that *all*
lead-free joints *look* bad with their dull crystalline surface, and I
would
have to agree that now, bad joints are likely to turn a job from a
one-coffee money spinner, to a pot-of-coffee frustrating money loser ...

What would happen if service technicians got together and agreed to refuse
to service equipment made with lead-free solder?

 

[William Sommerwerck]

Add to this that my eyes are not as
good as they were 20 years ago (even 5 years ago...) and that *all*
lead-free joints *look* bad with their dull crystalline surface, and I
would
have to agree that now, bad joints are likely to turn a job from a
one-coffee money spinner, to a pot-of-coffee frustrating money loser ...

What would happen if service technicians got together and agreed to refuse
to service equipment made with lead-free solder?

 

[Mark D. Zacharias]

<fdmor1967@gmail.com> wrote in message
news:7099e134-a266-4f93-8911-3426976e0a7b@b1g2000hsg.googlegroups.com...

Hi there,
recently I was given a vintage Hitachi D-E65 cassette deck that seems
to be in pretty good shape. However once powered up in I have found
that I cannot get the eject button to work on the deck - it simply
will not open, and I do not wish to force it. There isn't a tape
stuck or anything like that, but the door refuses to open. Any ideas
what may be causing this?
thank you!

Bad belts. The mech cannot rotate through to lift the pinch roller etc into
place, thus it's stuck. To release it, just rotate the flywheel through it's
full rotation until the head block falls back down. The flywheel must rotate
in the correct direction of tape travel, so do watch that. You might have to
tick a solenoid plunger in the middle of all this if the mech locks fully in
the PLAY position.

To fix it you'll absolutely need to replace the belts. Hitachi's were pretty
notorious for this problem.


Mark Z.

 

[Mark D. Zacharias]

<fdmor1967@gmail.com> wrote in message
news:7099e134-a266-4f93-8911-3426976e0a7b@b1g2000hsg.googlegroups.com...

Hi there,
recently I was given a vintage Hitachi D-E65 cassette deck that seems
to be in pretty good shape. However once powered up in I have found
that I cannot get the eject button to work on the deck - it simply
will not open, and I do not wish to force it. There isn't a tape
stuck or anything like that, but the door refuses to open. Any ideas
what may be causing this?
thank you!

Bad belts. The mech cannot rotate through to lift the pinch roller etc into
place, thus it's stuck. To release it, just rotate the flywheel through it's
full rotation until the head block falls back down. The flywheel must rotate
in the correct direction of tape travel, so do watch that. You might have to
tick a solenoid plunger in the middle of all this if the mech locks fully in
the PLAY position.

To fix it you'll absolutely need to replace the belts. Hitachi's were pretty
notorious for this problem.


Mark Z.

 

[Arfa Daily]

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:2L2dnY9G2JgRgZLVnZ2dnUVZ_tCrnZ2d@comcast.com...

Add to this that my eyes are not as
good as they were 20 years ago (even 5 years ago...) and that *all*
lead-free joints *look* bad with their dull crystalline surface, and I
would
have to agree that now, bad joints are likely to turn a job from a
one-coffee money spinner, to a pot-of-coffee frustrating money loser ...

What would happen if service technicians got together and agreed to refuse
to service equipment made with lead-free solder?


I think we'd all go tits-up William ... !!

Arfa

 

[Arfa Daily]

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:2L2dnY9G2JgRgZLVnZ2dnUVZ_tCrnZ2d@comcast.com...

Add to this that my eyes are not as
good as they were 20 years ago (even 5 years ago...) and that *all*
lead-free joints *look* bad with their dull crystalline surface, and I
would
have to agree that now, bad joints are likely to turn a job from a
one-coffee money spinner, to a pot-of-coffee frustrating money loser ...

What would happen if service technicians got together and agreed to refuse
to service equipment made with lead-free solder?


I think we'd all go tits-up William ... !!

Arfa

 

[ian field]

"jakdedert" <jakdedert@bellsouth.net> wrote in message
news:rg1Oj.47083$Er2.1997@bignews6.bellsouth.net...

Robert LaCasse wrote:
On Thu, 17 Apr 2008 22:13:13 -0700, Dennis Lee Bieber
wlfraed@ix.netcom.com> wrote:

|> On low-beam (55W I believe), at freeway cruise, my Aprilia only
|>manages 13.5-13.8; on high-beam (35W) it achieves 13.8-14.1 --
according
|>the trip computer voltage display.

That's an interesting observation.....

That's amazing, I mean the low-beam (55W), unlike the Aprilia, I
have the standard 2 halogens, and they draw 120watts so your system is
different.

Unless you have a HID lighting system....it's hard to beat the
battery drain from the mains....

My headlights (mains X2) don't come on till after the scooter is
started, so I'd have a very mission impossible problem to add there....I
suppose your mains work the same way....probably easier to change than a
Majesty400.

Thanx for the nfo.....

could you please delete sci.electronics.repair from this thread, as it
seems to be drifting away to a mostly 'motorcycle' issue rather than an
electronic one. I have no idea what an Aprilia is, nor any desire to
know.

Its a terrifying monster that preys on big girly wuss's.

Be afraid..............be very afraid!

 

[ian field]

"jakdedert" <jakdedert@bellsouth.net> wrote in message
news:rg1Oj.47083$Er2.1997@bignews6.bellsouth.net...

Robert LaCasse wrote:
On Thu, 17 Apr 2008 22:13:13 -0700, Dennis Lee Bieber
wlfraed@ix.netcom.com> wrote:

|> On low-beam (55W I believe), at freeway cruise, my Aprilia only
|>manages 13.5-13.8; on high-beam (35W) it achieves 13.8-14.1 --
according
|>the trip computer voltage display.

That's an interesting observation.....

That's amazing, I mean the low-beam (55W), unlike the Aprilia, I
have the standard 2 halogens, and they draw 120watts so your system is
different.

Unless you have a HID lighting system....it's hard to beat the
battery drain from the mains....

My headlights (mains X2) don't come on till after the scooter is
started, so I'd have a very mission impossible problem to add there....I
suppose your mains work the same way....probably easier to change than a
Majesty400.

Thanx for the nfo.....

could you please delete sci.electronics.repair from this thread, as it
seems to be drifting away to a mostly 'motorcycle' issue rather than an
electronic one. I have no idea what an Aprilia is, nor any desire to
know.

Its a terrifying monster that preys on big girly wuss's.

Be afraid..............be very afraid!

 

[James Sweet]

<tnom@mucks.net> wrote in message
news:ehmu041cmkkmrjomg3job3i79p9t0779kk@4ax.com...

I have a 10 year old 32" Magnavox that pincushions intermittently.

If you smack the housing it usually has an effect on the condition so
I suspect a connector or other hardware problem.

Before I actually tackle taking this 200 pound TV apart I thought I'd
ask for specific locations that may be suspect in the horizontal sweep
section of the TV. Any suggestions?

Cracked solder joint(s) in the pincussion circuit. Usually it sits somewhere
between the horizontal and the vertical sections.

 

[James Sweet]

<tnom@mucks.net> wrote in message
news:ehmu041cmkkmrjomg3job3i79p9t0779kk@4ax.com...

I have a 10 year old 32" Magnavox that pincushions intermittently.

If you smack the housing it usually has an effect on the condition so
I suspect a connector or other hardware problem.

Before I actually tackle taking this 200 pound TV apart I thought I'd
ask for specific locations that may be suspect in the horizontal sweep
section of the TV. Any suggestions?

Cracked solder joint(s) in the pincussion circuit. Usually it sits somewhere
between the horizontal and the vertical sections.