Toshiba TV29C90 problem; Image fades to black...

<anglomont@yahoo.com> wrote in message
news:d8a7152b-907f-4270-b9c2-68d46460c86b@34g2000hsh.googlegroups.com...
it will not turn on at all(nor talk/batt low diodes) even with
new battery...
Here is its schematic
http://www.geocities.com/anglomont/nb3908.jpg
resoldered batt and charge contacts, q15 and q101 seem ok, any other
suspect areas ?
tnx
Click to expand...
Volts at IC4 VDD pin 39 ? If no, pin 4 Q101? If yes to that, D16 o/c, C76
s/c or L3 o/c maybe ? If volts at pin 39 IC4, clock running on pins 18 and
19 (or 21 - 22 maybe)? L4 o/c ?

Arfa
 
<j_slobo@hotmail.com> wrote in message
news:ce59ac53-6740-4bf6-9f47-e99a7be219d4@s50g2000hsb.googlegroups.com...
Is there some way to detect a 3-5volt say khz clock using an ordinary
instrument(no osciloscope)
Click to expand...
A crystal earpiece, assuming voltages not more than 50 volt.
A much underestimated piece of diagnostic test gear.


--
General electronic repairs, most things repaired, other than TVs and PCs
http://www.divdev.fsnet.co.uk/repairs.htm

Diverse Devices, Southampton, England
 
<astroncer@yahoo.com> wrote in message
news:3271315f-dff3-40a0-91e2-11829f986ea0@i36g2000prf.googlegroups.com...
Hi, I had a loose power socket and superglued it and that lasted just
fine for a few months. Then it went out beyond
an ability to glue it again, but still have a occasional power
connection when moving it. I pulled out the motherboard and the solder
on the bottom side of the board where the socket connects, the solder
was burnt away and brittle.

I'm not much of a solderer, just have a cheap soldering iron with a
large tip. Is there a pretty much common method to repair this, I was
thinking of dropping a drop of solder where the solder failed instead
of finding somebody to repair it. Then putting the laptop back
together and see if it works and do a re-superglue of the offending
loose socket.

Thanks for any tips or suggestions. Tools needed, over my head in my
abilities?

It's a compaq presario 1692

Thanks
Click to expand...

Doesn't sound like you know how to solder at all.

Do a bit of Googling on soldering techniqes, you'll soon learn how to do it
properly, and practice on a bit of scrap PCB if you can find any - you need
to be quick and efficient to prevent damaging your motherboard further with
excessive and prolonged heating.

Your idea of dropping a drop of solder just will not work - the basis of
soldering is that you have to heat up both items to be soldered together to
a temperature sufficient to melt the solder. Solder will not bond to a
metal colder than its melting point, you will get what is called a dry
joint or cold solder joint. You will be able to just scrape the solder off
with your finger. You need to heat up both the component and the PCB solder
pad simultaneously with the iron, then apply solder and let it melt over the
entire joint area, then remove the iron and allow to cool.

If the solder pad is damaged, you may have to add some thin wire to effect a
good repair.

Good luck, and DO practice first, trust me on that one.




Gareth.
 
<astroncer@yahoo.com> wrote in message
news:3271315f-dff3-40a0-91e2-11829f986ea0@i36g2000prf.googlegroups.com...
Hi, I had a loose power socket and superglued it and that lasted just
fine for a few months. Then it went out beyond
an ability to glue it again, but still have a occasional power
connection when moving it. I pulled out the motherboard and the solder
on the bottom side of the board where the socket connects, the solder
was burnt away and brittle.

I'm not much of a solderer, just have a cheap soldering iron with a
large tip. Is there a pretty much common method to repair this, I was
thinking of dropping a drop of solder where the solder failed instead
of finding somebody to repair it. Then putting the laptop back
together and see if it works and do a re-superglue of the offending
loose socket.

Thanks for any tips or suggestions. Tools needed, over my head in my
abilities?

It's a compaq presario 1692

Thanks
Click to expand...

Doesn't sound like you know how to solder at all.

Do a bit of Googling on soldering techniqes, you'll soon learn how to do it
properly, and practice on a bit of scrap PCB if you can find any - you need
to be quick and efficient to prevent damaging your motherboard further with
excessive and prolonged heating.

Your idea of dropping a drop of solder just will not work - the basis of
soldering is that you have to heat up both items to be soldered together to
a temperature sufficient to melt the solder. Solder will not bond to a
metal colder than its melting point, you will get what is called a dry
joint or cold solder joint. You will be able to just scrape the solder off
with your finger. You need to heat up both the component and the PCB solder
pad simultaneously with the iron, then apply solder and let it melt over the
entire joint area, then remove the iron and allow to cool.

If the solder pad is damaged, you may have to add some thin wire to effect a
good repair.

Good luck, and DO practice first, trust me on that one.




Gareth.
 
<j_slobo@hotmail.com> wrote in message
news:ce59ac53-6740-4bf6-9f47-e99a7be219d4@s50g2000hsb.googlegroups.com...
Is there some way to detect a 3-5volt say khz clock using an ordinary
instrument(no osciloscope)
Click to expand...

With a multimeter that measures frequency.



Gareth.
 
<j_slobo@hotmail.com> wrote in message
news:ce59ac53-6740-4bf6-9f47-e99a7be219d4@s50g2000hsb.googlegroups.com...
Is there some way to detect a 3-5volt say khz clock using an ordinary
instrument(no osciloscope)
Click to expand...

With a multimeter that measures frequency.



Gareth.
 
astroncer@yahoo.com wrote in news:3271315f-dff3-40a0-91e2-11829f986ea0
@i36g2000prf.googlegroups.com:

Hi, I had a loose power socket and superglued it and that lasted just
fine for a few months. Then it went out beyond
an ability to glue it again, but still have a occasional power
connection when moving it. I pulled out the motherboard and the solder
on the bottom side of the board where the socket connects, the solder
was burnt away and brittle.

I'm not much of a solderer, just have a cheap soldering iron with a
large tip. Is there a pretty much common method to repair this, I was
thinking of dropping a drop of solder where the solder failed instead
of finding somebody to repair it. Then putting the laptop back
together and see if it works and do a re-superglue of the offending
loose socket.

Thanks for any tips or suggestions. Tools needed, over my head in my
abilities?
Click to expand...
Buy a soldering iron that is the right size at radio-shack.
Could be cheap, provided you practice, a lot, soldering on old PCB boards.


Fix your board yourself.

Use GOOD solder 63/37 NOT 60/40.

It's a compaq presario 1692

Thanks
Click to expand...




--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
 
astroncer@yahoo.com wrote in news:3271315f-dff3-40a0-91e2-11829f986ea0
@i36g2000prf.googlegroups.com:

Hi, I had a loose power socket and superglued it and that lasted just
fine for a few months. Then it went out beyond
an ability to glue it again, but still have a occasional power
connection when moving it. I pulled out the motherboard and the solder
on the bottom side of the board where the socket connects, the solder
was burnt away and brittle.

I'm not much of a solderer, just have a cheap soldering iron with a
large tip. Is there a pretty much common method to repair this, I was
thinking of dropping a drop of solder where the solder failed instead
of finding somebody to repair it. Then putting the laptop back
together and see if it works and do a re-superglue of the offending
loose socket.

Thanks for any tips or suggestions. Tools needed, over my head in my
abilities?
Click to expand...
Buy a soldering iron that is the right size at radio-shack.
Could be cheap, provided you practice, a lot, soldering on old PCB boards.


Fix your board yourself.

Use GOOD solder 63/37 NOT 60/40.

It's a compaq presario 1692

Thanks
Click to expand...




--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
 
On Sat, 14 Jun 2008 03:15:26 -0700 (PDT), "j_slobo@hotmail.com"
<j_slobo@hotmail.com> wrote:

Is there some way to detect a 3-5volt say khz clock using an ordinary
instrument(no osciloscope)
Click to expand...
You can use your computer's sound card. You can add a voltage
divider to insure the sound card Line input is getting less than about
3 Vpp, if you want to make sure you don't clip its input. (The input
can handle 5V without damage, but the wave will be clipped.) If you
want to avoid loading the clock output with the sound card input
(which can be in the 2K to 47K range), you can use big resistors for
the divider. Don't worry about dividing it down too low... the sound
card has 16 bits of resolution, so you'll be able to see
sub-millivolts easily.

SHAMELESS PLUG: You can try my Daqarta software for free.
It has calibration options so you can use it as a real scope (as well
as spectrum analyzer, frequency counter, voltmeter, sound level meter,
signal generator, etc, etc). If you decide not to buy (US$29.00)
after the trial expires, the inputs stop working but the signal
generator keeps working FREE forever, along with file analysis, etc.

I'll be glad to answer any questions.

Best regards,


Bob Masta

DAQARTA v4.00
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
FREE Signal Generator
Science with your sound card!
 
On Sat, 14 Jun 2008 03:15:26 -0700 (PDT), "j_slobo@hotmail.com"
<j_slobo@hotmail.com> wrote:

Is there some way to detect a 3-5volt say khz clock using an ordinary
instrument(no osciloscope)
Click to expand...
You can use your computer's sound card. You can add a voltage
divider to insure the sound card Line input is getting less than about
3 Vpp, if you want to make sure you don't clip its input. (The input
can handle 5V without damage, but the wave will be clipped.) If you
want to avoid loading the clock output with the sound card input
(which can be in the 2K to 47K range), you can use big resistors for
the divider. Don't worry about dividing it down too low... the sound
card has 16 bits of resolution, so you'll be able to see
sub-millivolts easily.

SHAMELESS PLUG: You can try my Daqarta software for free.
It has calibration options so you can use it as a real scope (as well
as spectrum analyzer, frequency counter, voltmeter, sound level meter,
signal generator, etc, etc). If you decide not to buy (US$29.00)
after the trial expires, the inputs stop working but the signal
generator keeps working FREE forever, along with file analysis, etc.

I'll be glad to answer any questions.

Best regards,


Bob Masta

DAQARTA v4.00
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
FREE Signal Generator
Science with your sound card!
 
"j_slobo@hotmail.com" <j_slobo@hotmail.com> wrote in news:ce59ac53-6740-
4bf6-9f47-e99a7be219d4@s50g2000hsb.googlegroups.com:

Is there some way to detect a 3-5volt say khz clock using an ordinary
instrument(no osciloscope)
Click to expand...
With a few ICs and LEDs you can build a logic probe with pulse detection.

http://www.eng.cam.ac.uk/DesignOffice/mdp/electric_web/Exper/EXP_7.html
has several interesting circuits, easy to build.

and for a 'delux' device
http://members.cox.net/berniekm/super.html





--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
 
Might I point out that an oscilloscope _is_ an "ordinary instrument"? At
least, in my sense of the word "ordinary" -- it's ordinarily found in any
electronics shop.

I work at Microsoft Hardware, and there has been a total switchover to
multi-color LCD 'scopes. The cheaper ones are not _horribly_ expensive.
 
Might I point out that an oscilloscope _is_ an "ordinary instrument"? At
least, in my sense of the word "ordinary" -- it's ordinarily found in any
electronics shop.

I work at Microsoft Hardware, and there has been a total switchover to
multi-color LCD 'scopes. The cheaper ones are not _horribly_ expensive.
 
stratus46@yahoo.com wrote in news:0f0e8190-5002-4df7-a522-d77de45c1a20
@v1g2000pra.googlegroups.com:

On Jun 14, 3:34 am, bz <bz+...@ch100-5.chem.lsu.edu> wrote:
snip

Buy a soldering iron that is the right size at radio-shack.
Could be cheap, provided you practice, a lot, soldering on old PCB
boards.

Fix your board yourself.

Use GOOD solder 63/37 NOT 60/40.

60/40 is _bad_ solder ?
Click to expand...
Yes. It passes through the 'plastic' stage during cooling. Do NOT jiggle or
you get a cold solder joint.
It melts at a higher temperature. Harder to get melted and get good solder
flow.

63/37 is _that_ much better?

Yes. Get a eutectic solder. [melts at the minimum temp for an alloy of
those metals].

Or did you mean
40/60 which _is_ bad solder ?
Click to expand...
50/50 is worse than 60/40 and 40/60 is even worse.
[bad and good in relation to electronics usage. If you are a plumber, 50/50
might be better for your work.]
If you're patient with eBay, you can get a Metcal in parts for <$100.
Bought 6 so far for at work. After using a Metcal you won't want to
use a Radio Shack soldering tusk.
Click to expand...
A GOOD, temperature controlled, soldering iron is, OF COURSE, better than a
cheap iron.




--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
 
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:g30a4s$ptc$1@registered.motzarella.org...
j_slobo@hotmail.com> wrote in message
news:ce59ac53-6740-4bf6-9f47-e99a7be219d4@s50g2000hsb.googlegroups.com...
Is there some way to detect a 3-5volt say khz clock using an ordinary
instrument(no osciloscope)

A crystal earpiece, assuming voltages not more than 50 volt.
A much underestimated piece of diagnostic test gear.


--
General electronic repairs, most things repaired, other than TVs and PCs
http://www.divdev.fsnet.co.uk/repairs.htm

Diverse Devices, Southampton, England
Click to expand...

What a fascinating collection of notes you've kept on repairs you've carried
out and published on your web site!

Thank you for that,

Chris
 
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:g30a4s$ptc$1@registered.motzarella.org...
j_slobo@hotmail.com> wrote in message
news:ce59ac53-6740-4bf6-9f47-e99a7be219d4@s50g2000hsb.googlegroups.com...
Is there some way to detect a 3-5volt say khz clock using an ordinary
instrument(no osciloscope)

A crystal earpiece, assuming voltages not more than 50 volt.
A much underestimated piece of diagnostic test gear.


--
General electronic repairs, most things repaired, other than TVs and PCs
http://www.divdev.fsnet.co.uk/repairs.htm

Diverse Devices, Southampton, England
Click to expand...

What a fascinating collection of notes you've kept on repairs you've carried
out and published on your web site!

Thank you for that,

Chris
 
jakdedert <jakdedert@bellsouth.net> wrote in news:ipT4k.4859$3F5.2098
@bignews2.bellsouth.net:

jakdedert wrote:
jakdedert wrote:
Bought from the 'E' place for cheap. Reported symptom: video comes on
and fades out. Figured it was high ESR smps caps.

Actual symptom: backlight comes on, image consist of random horizontal
lines, which eventually--after some intermittent vertical
scrolling--settle into a very nice image. Takes like two minutes to
warm up. Shutting the monitor down for some unknown time starts the
process all over again. Continuous viewing yields a stable image with
good resolution, brightness and linearity. Shutting down for short
periods is not problematic.

There is only one HV (100 @ 400v) cap in the ps. ESR is .46, which I
assume is within tolerance. Other caps in the ps also seem fine.

This presents so like a classic cap issue (needs to warm up), that I'm
going to next pull the video board and check caps there...possibly get
some freeze spray and see if I can duplicate symptoms that way.

Reality check: any problem with the above procedure, or experience
with this particular monitor? Any suggestions as to where to go if
the above doesn't produce a dx and fix?

Thanks as always,

jak

So far, no luck. ESRd all caps on video board. All good. Bad news is
that monitor rarely straightens up anymore. I got it to display
correctly only once this evening, so no chance of trying to reproduce
symptom via freezing components. Power supply voltages appear nominal
and clean. No effect from flexing components. Reseated all cables on
the video board.....

It looks like the horizonal rows are not being addressed, as the current
display is a series of fine vertical lines of whatever color is
predominant in that area of the display. Still some strange horizontal
scrolling effects when first powered, but they only last a few
seconds...two or three horizontal bars scroll down the screen, then
disappear.


Any help here? Is this toast [beyond my ability to fix...]? My scope
(20 mHz) is not fast enough to look at the video timing....

jak

Has this one gotten everyone as stumped as it has me?

After three days of occasional attention, the symptoms still present as
before. I occasionally see the beginnings of a legible image, with bits
of recognizable video scrolling down the screen. Usually these break
back up into a screen full of vertical lines again; but occasionally
I'll get an 'almost' image first.

Some help, even if it's just commiseration, would be appreciated. So
far, not a single reply.....
Click to expand...
You have my sympathy. What makes you think that the video signals should
be much higher than 20 MHz?




--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
 
jakdedert <jakdedert@bellsouth.net> wrote in news:ipT4k.4859$3F5.2098
@bignews2.bellsouth.net:

jakdedert wrote:
jakdedert wrote:
Bought from the 'E' place for cheap. Reported symptom: video comes on
and fades out. Figured it was high ESR smps caps.

Actual symptom: backlight comes on, image consist of random horizontal
lines, which eventually--after some intermittent vertical
scrolling--settle into a very nice image. Takes like two minutes to
warm up. Shutting the monitor down for some unknown time starts the
process all over again. Continuous viewing yields a stable image with
good resolution, brightness and linearity. Shutting down for short
periods is not problematic.

There is only one HV (100 @ 400v) cap in the ps. ESR is .46, which I
assume is within tolerance. Other caps in the ps also seem fine.

This presents so like a classic cap issue (needs to warm up), that I'm
going to next pull the video board and check caps there...possibly get
some freeze spray and see if I can duplicate symptoms that way.

Reality check: any problem with the above procedure, or experience
with this particular monitor? Any suggestions as to where to go if
the above doesn't produce a dx and fix?

Thanks as always,

jak

So far, no luck. ESRd all caps on video board. All good. Bad news is
that monitor rarely straightens up anymore. I got it to display
correctly only once this evening, so no chance of trying to reproduce
symptom via freezing components. Power supply voltages appear nominal
and clean. No effect from flexing components. Reseated all cables on
the video board.....

It looks like the horizonal rows are not being addressed, as the current
display is a series of fine vertical lines of whatever color is
predominant in that area of the display. Still some strange horizontal
scrolling effects when first powered, but they only last a few
seconds...two or three horizontal bars scroll down the screen, then
disappear.


Any help here? Is this toast [beyond my ability to fix...]? My scope
(20 mHz) is not fast enough to look at the video timing....

jak

Has this one gotten everyone as stumped as it has me?

After three days of occasional attention, the symptoms still present as
before. I occasionally see the beginnings of a legible image, with bits
of recognizable video scrolling down the screen. Usually these break
back up into a screen full of vertical lines again; but occasionally
I'll get an 'almost' image first.

Some help, even if it's just commiseration, would be appreciated. So
far, not a single reply.....
Click to expand...
You have my sympathy. What makes you think that the video signals should
be much higher than 20 MHz?




--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
 
"hr(bob) hofmann@att.net" <hrhofmann@att.net> wrote in message
news:261906b6-51f5-4e5a-b368-c0c68deb13f2@26g2000hsk.googlegroups.com...
On Jun 14, 12:30 pm, bz <bz+...@ch100-5.chem.lsu.edu> wrote:
stratu...@yahoo.com wrote in news:0f0e8190-5002-4df7-a522-d77de45c1a20
@v1g2000pra.googlegroups.com:

On Jun 14, 3:34 am, bz <bz+...@ch100-5.chem.lsu.edu> wrote:
snip

Buy a soldering iron that is the right size at radio-shack.
Could be cheap, provided you practice, a lot, soldering on old PCB
boards.

Fix your board yourself.

Use GOOD solder 63/37 NOT 60/40.
60/40 is _bad_ solder ?

Yes. It passes through the 'plastic' stage during cooling. Do NOT jiggle
or
you get a cold solder joint.
It melts at a higher temperature. Harder to get melted and get good solder
flow.

63/37 is _that_ much better?

Yes. Get a eutectic solder. [melts at the minimum temp for an alloy of
those metals].

Or did you mean

40/60 which _is_ bad solder ?

50/50 is worse than 60/40 and 40/60 is even worse.
[bad and good in relation to electronics usage. If you are a plumber,
50/50
might be better for your work.]



If you're patient with eBay, you can get a Metcal in parts for <$100.
Bought 6 so far for at work. After using a Metcal you won't want to
use a Radio Shack soldering tusk.

A GOOD, temperature controlled, soldering iron is, OF COURSE, better than
a
cheap iron.

--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+...@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
Click to expand...
Once you do solder it successfully, I would use a glob of epoxy to
help hold things together, not just depend on the glue to hold on by
itself. Good solder bonds can eventually break if they are under a
constant strain, the epoxy just might help lengthen your repair.

Bob Hofmann



I use my hot melt glue gun a lot. They are cheap and the main advantages
are that you can always peel away the glue if you need to, and it remains
flexible to absorb shocks and allows things to bend rather than snap. Epoxy
is pretty much permanent.



Gareth.
 
Let me know what the problem appears to be, and I will pass it along to the
designers.

"Franc Zabkar" <fzabkar@iinternode.on.net> wrote in message
news:l8j8541t3dhhqji6hu5fbh5i95j6tkqinq@4ax.com...
On Sat, 14 Jun 2008 07:02:27 -0700, "William Sommerwerck"
grizzledgeezer@comcast.net> put finger to keyboard and composed:

I work at Microsoft Hardware ...

That's handy to know. I have a wireless MS keyboard which I believe
has a design bug in its firmware. I wonder how one would go about
reporting something like that, or at least talking to a real human
being who understands the problem.
Click to expand...
 
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