Toshiba TV29C90 problem; Image fades to black...

Jeff wrote:
My Sony mini-DV accidently dropped into water at the weekend. The
camcorder was in bags for 5 minutes in the lake. Monday, I asked the
technician to see whether they can repair it. They said it is not
worth to repair for a water damage normally. So, I asked them some
procedures try to save my camcorder by myself. I have once repaired
some TVs, radios, oscilloscopes and other lab instruments. On monday,
I disassembled my cam. Tuesday, I rinsed all the pcb boards with
alcohol(99.9% pure), drier and put a layer of engine oil to prevent
oxidization.
Click to expand...
That's it. I can't bear to read any farther. Next you probably soaked it
in kerosene, gasoline, xylene, nitric acid, hydrochloric acid, sulfuric
acid, bleach, lye, acetone, maggot urine and koala dung, and wrapped the
boards in aluminum foil to prevent cosmic rays from entering.

ENGINE OIL??!

Did you remember to coat the lenses with JB Weld to protect the coatings?

--
"Here, Outlook Express, run this program." "Okay, stranger."
 
dmills@spamblock.demon.co.uk writes:

In sci.electronics.design Tom Del Rosso <tdnews01@att.net.invalid> wrote:
N. Thornton wrote:

Bad neutral connection in the panel, causing the voltage to swing up?
The UK isnt wired like that, so we dont get that problem.

We have center tapped transformers, where the center tap is grounded at
the source. What do you have? Since you use 220-240V I would guess you
don't need a center tap and neither line is grounded.

Usaually delta-star transformers with the neutral point grounded at the
transformer. 230V from any of the 3 phases to neutral, 400V between
phases.
Click to expand...
I think I've forgotten the few ee/ece courses that I'd taken many
years ago, but from what I remember, I don't get the voltage between
any two phases equal to 400V. I did
the math like follows:

The phase diff between any two phases is 120 degress. So we can draw
a circle and three radii at 120 degrees to each other. The length of
the radii is 230 V. The voltage between any two phases is the length
of the line joining the tips of those two radii. By this math, you
get the length to be equal to 2 * 230/sin(60) = 531.16 V!!

What's wrong here?

-- pankaj
 
On Wednesday, 10 Sep 2003 09:34:32 -500, "Asimov"
<Asimov@-removethis-bbs.juxtaposition.dynip.com> wrote:

"Jason D." bravely wrote to "All" (10 Sep 03 03:48:33)
--- on the heady topic of "Big battle with WEIRD vertical deflection problem in =
PTK195 chassis."

If there are spikes in the output ramp then it would seem like a supply
filter electro problem to me. Have you checked what the supply noise
looks like on the scope? If not then the pump up might be off value.
Click to expand...
In RCA's PTK195 (based on CTC195) projector still under warrenty:

Came in with blown vertical IC and crispy 26V supply resistor changed
both and saw noisy waveforms.

Changed pump cap, no difference, finally found the 1.5 ohm 2W is open.
This resistor is connected to .22nF 100V to ground from the output of
TDA8172 vertical IC. Changed both cap and resistor. Got perfect
vertical waveforms. Now I have a cooked vertical IC after a minute.
Now I know why: one of yoke is bad.

RCA using this vertical IC TDA9302 and TDA8172 very rarely blow so if
you see one with blown one, be suspicious because this is when
something is killing that vertical IC. A half-dried pump cap doesn't
faze vertical IC, customer complaint with squished top pix got that
fixed instead. Usually often is tuner & micro grounds if the pump cap
isn't the problem.

Back to this damned projector, how can I tell which yoke is guilty?

Cheers,

Wizard
 
These statement indicate to me that you will destroy your camcorder beyond
ANY hope of repair.
 
I will clean the contamination on the commutator. I will grease all
moving tray parts. I could never come up with the commutator idea
myself. I*ll let you know how it goes. Thanks.

Repeat of original post:
My DVD does not power up when pressing power button. A tiny standby
light can be seen. But after opening up the unit, I*ve located
an orange blown fuse similar to a resistor on the power supply board.
It*s labeled P115. This fuse is stamped with *750*
on it. I*m not sure what 750 stand for but after replacing this
with an identical replacement (750) it works fine but blows after
pressing *disk skip* button. Soon I got an idea and
replace it with a 43-Ohm resistor and the unit powers up and works
till today.

But here*s the catch. The 43-Ohm resistor heats up too hot to
the touch when the CD tray is opening or closing. The display will
dim when pressing disk skip far to many times. To reset the dimming
light I have to unplug it from the wall. I fear it may burn the chip
that controls the motor one-day. What is the best approach to solve
this problem?

Sorry for the ’ on the message, if any know how to solve it
please let me know.

Sounds like a motor is shorted. Sony's replace the entire pickup ass'y
complete with motors. A bit pricey, but it should fix your problem.

If it's a simple permanent magnet motor, the short may be due to
a buildup of contamination on the commutator. This can sometimes
be easily removed. Just putting a Band-Aid on the problem by increasing
drive means it will come back, probably quite quickly. Additional damage
may be the result if the driver can't handle it.

See the CD repair guide for info on motors.
http://www.repairfaq.org/sam/cdfaq.htm#cdmot

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: The email address in this message header may no longer work. To
contact me, please use the Feedback Form at repairfaq.org. Thanks.



Mark Z.


"Koji San" <apple26pie@yahoo.com> wrote in message
news:fa1ef2c1.0309110412.1ee28e1c@posting.google.com...
My DVD does not power up when pressing power button. A tiny standby
light can be seen. But after opening up the unit, I’ve located
an orange blown fuse similar to a resistor on the power supply board.
It’s labeled P115. This fuse is stamped with “750”
on it. I’m not sure what 750 stand for but after replacing this
with an identical replacement (750) it works fine but blows after
pressing ‘disk skip’ button. Soon I got an idea and
replace it with a 43-Ohm resistor and the unit powers up and works
till today.

But here’s the catch. The 43-Ohm resistor heats up too hot to
the touch when the CD tray is opening or closing. The display will
dim when pressing disk skip far to many times. To reset the dimming
light I have to unplug it from the wall. I fear it may burn the chip
that controls the motor one-day. What is the best approach to solve
this problem?
Koiji
Click to expand...
 
Yes, the drive IC is hot when the tray sometimes refuses to eject
completely. I will take your advice and let you know how it turns out.
Thanks.

Try a lower value resistor. 2.2 ohms to maybe 4.7 ohms. You might be able to
get away with this indefinitely. Problem is, there'll also be a drive IC
getting hot from the short.

Mark Z.


"Koji San" <apple26pie@yahoo.com> wrote in message
news:fa1ef2c1.0309110412.1ee28e1c@posting.google.com...
My DVD does not power up when pressing power button. A tiny standby
light can be seen. But after opening up the unit, I’ve located
an orange blown fuse similar to a resistor on the power supply board.
It’s labeled P115. This fuse is stamped with “750”
on it. I’m not sure what 750 stand for but after replacing this
with an identical replacement (750) it works fine but blows after
pressing ‘disk skip’ button. Soon I got an idea and
replace it with a 43-Ohm resistor and the unit powers up and works
till today.

But here’s the catch. The 43-Ohm resistor heats up too hot to
the touch when the CD tray is opening or closing. The display will
dim when pressing disk skip far to many times. To reset the dimming
light I have to unplug it from the wall. I fear it may burn the chip
that controls the motor one-day. What is the best approach to solve
this problem?
Koiji
Click to expand...
 
One question: Will it be helpful to put a heat sink on the hot IC
motor driver if I can*t solve the dirty motor problem?
Koiji

Try a lower value resistor. 2.2 ohms to maybe 4.7 ohms. You might be able to
get away with this indefinitely. Problem is, there'll also be a drive IC
getting hot from the short.

Mark Z.


"Koji San" <apple26pie@yahoo.com> wrote in message
news:fa1ef2c1.0309110412.1ee28e1c@posting.google.com...
My DVD does not power up when pressing power button. A tiny standby
light can be seen. But after opening up the unit, I’ve located
an orange blown fuse similar to a resistor on the power supply board.
It’s labeled P115. This fuse is stamped with “750”
on it. I’m not sure what 750 stand for but after replacing this
with an identical replacement (750) it works fine but blows after
pressing ‘disk skip’ button. Soon I got an idea and
replace it with a 43-Ohm resistor and the unit powers up and works
till today.

But here’s the catch. The 43-Ohm resistor heats up too hot to
the touch when the CD tray is opening or closing. The display will
dim when pressing disk skip far to many times. To reset the dimming
light I have to unplug it from the wall. I fear it may burn the chip
that controls the motor one-day. What is the best approach to solve
this problem?
Koiji
Click to expand...
 
"RJ" (joanrex@sbcglobal.net) writes:
These statement indicate to me that you will destroy your camcorder beyond
ANY hope of repair.


I thought he'd already done that.
Click to expand...

Michael
 
Hi!

About the only thing I wouldn't have done was to put motor oil on the
circuit boards, but maybe desperate times call for desperate measures?

If you're absolutely certain that everything has dried out (including all
the mechanical pieces) and can safely give the optics and mechanical parts
related to the optics a good cleaning up and relube where needed, I see no
reason why it isn't worth the try to see if you can save your camcorder
yourself. Even with no display, it might still be perfectly serviceable for
some things.

Don't use a good tape for your initial test and run it hard after you've
cleaned up the mess and put things back together. See what happens. Water
damage is far from the worst that could have happened to your camcorder, so
a miraculous recovery of basic functions may not be too much to ask.

William
 
I don't know about that particular turntable, but most of the ones I've worked on, the rubber record mat can be removed, and there is an opening in the table for installing the belt. Just take the platter off and put the belt around the hub, put platter back on and rotate it until the opening is by the motor shaft. Then take a small flat blade screwdriver and insert between the belt and platter hub and strech it over the motor shaft.
Virgil
"Violent Zen" <violentzen@yahoo.dieyouspammingfuck.com> wrote in message news:5c48b.8366$PE6.564@newsread3.news.pas.earthlink.net...
I just bought a Yamaha YP-B2 turntable from a guy for 15 bucks. The problem
is that the belt is completely off. I have no idea how it is supposed to be
placed. Any idea where I can find this information? Also, what would be a
good resource for stylus and cartridge replacement for this model? Thanks.

Scott
Click to expand...
 
On 10 Sep 2003 21:09:48 -0700, freelait2000@yahoo.com (Jeff) wrote:

I disassembled my cam. Tuesday, I rinsed all the pcb boards with
alcohol(99.9% pure), drier and put a layer of engine oil to prevent
oxidization.
Click to expand...
Groan. If the board or components were not completely dry, the engine
oil just sealed in the moisture. I'm not sure where you got that
great idea, but lubrication should be done AFTER you get it work, and
only in place designated in the sacred books of Sony.

99.9% pure alcohol is also somewhat of a waste because the stuff is
hydroscopic and almost immediately degenerates to about 90.0%
(depending upon humidity). Might as well use the drug store 90%
ispropyl alcohol (not the 70%).

The tape was still in the deck, I didn't energize the
loading motor because I didn't know the polarity of it. Today
(Wednsday) I ask the technician to eject the tape.
Click to expand...
OK. That means you didnt' apply power and hopefully were swift enough
to eject the tape without power. You don't wanna apply power while
it's still wet.

Unfortunately, some
not-shining-speck on the drum cannot be removed. I know this is result
of some chemical reactions. My question is the drum, include other
mechnics, cannot work anymore?
Click to expand...
Having the drum nice and shinny is a good thing. A blemish or two
will not bother operation very much. If the blemish is coarse, rough,
pitted, or abrasive in any way, then it will abraid the tape and
eventually cause tape failure. Find a magnifying glass (or
microscope) and inspect for roughness.

Suggestion: Get some cheap 90% alcohol to remove the engine oil. If
you slopped oil all over everything, dunk the whole mess in alcohol.
Hit it with an air hose to remove the accumulated water. Make sure
the air hose has a filter and a dryer so that you don't spray rusty
water into the camcorder. When you think you have removed all the
surface water, you probably haven't. Bake the camcorder at about 150F
in an oven or just place it in a warm place (above a large monitor).
Stay away from the hair dryers and microwave ovens. Let it bake for
at least a day. Then shove in the battery and see what happens.

I've dealt with various electronic devices over the years and have
often been amazed at how long it take for some circuit boards to dry
out. The combination of close spaced traces, hydroscopic circuit
boards, high impedances, and SMD components that trap water, causes
the drying time to increase considerably.

Good luck and welcome to "Learn by Destroying".


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice http://www.LearnByDestroying.com
# jeffl@comix.santa-cruz.ca.us
# 831.421.6491 digital_pager jeffl@cruzio.com AE6KS
 
Here’s the result. Two 12-Ohm resistors combined to make 6-Ohm.
I guess they are 1 watt. They are working perfectly, no more heating
up. A heat sink is put on the drive IC but don’t know if
it’s going to last. Thanks again for your help.

Try a lower value resistor. 2.2 ohms to maybe 4.7 ohms. You might be able to
get away with this indefinitely. Problem is, there'll also be a drive IC
getting hot from the short.

Mark Z.


"Koji San" <apple26pie@yahoo.com> wrote in message
news:fa1ef2c1.0309110412.1ee28e1c@posting.google.com...
My DVD does not power up when pressing power button. A tiny standby
light can be seen. But after opening up the unit, I’ve located
an orange blown fuse similar to a resistor on the power supply board.
It’s labeled P115. This fuse is stamped with “750”
on it. I’m not sure what 750 stand for but after replacing this
with an identical replacement (750) it works fine but blows after
pressing ‘disk skip’ button. Soon I got an idea and
replace it with a 43-Ohm resistor and the unit powers up and works
till today.

But here’s the catch. The 43-Ohm resistor heats up too hot to
the touch when the CD tray is opening or closing. The display will
dim when pressing disk skip far to many times. To reset the dimming
light I have to unplug it from the wall. I fear it may burn the chip
that controls the motor one-day. What is the best approach to solve
this problem?
Koiji
Click to expand...
 
Subject: A couple of Zenith tips was: Rewinding pc coil for 9-1270
Zenith boards ?? anyone know inductance? 9-1
From: "Dave Moore" novalves@nospamdatasync.com
Click to expand...

Thanks again for the pointers John. The set is up and running just fine
thanks to your *fudgin* advice ;-)

=^^=DM
Click to expand...
'Velcome....
Your CRT size story reminded me of what I went through the first time I tried
the generic flyback. This was also a dual focus setup as yours was, and I
pulled just the chassis because the CRT in this model Zenith is an RCA with the
sealed yoke (and I have a test jig setup for all RCAs). On the test jig (20"),
the TV ran fine with the new flyback and horiz output for a couple of days. We
delivered it back, and it started normally back in the original cabinet, but
would shutdown on bright scenes, where it never did on the test jig. That's
where the fudgin' come in!

John
 
The RCA / GE Thompson company will supply the schematics (service
manual), if it has been published for distribution. We handle a number
of RCA parts sales for clients.


A few suggestions:

Your problem is probably in the power supply and or the scan stages,
especially the horizontal output section. The inverter devices, any
power output devices, plus a number of support components are most
likely damaged. This can be a difficult repair. After replacing any
parts, you must make sure that you did not miss any others that are
damaged, or the new parts will fail upon re-connecting the power back
up.

After replacing all the suspect parts, you would be best off to test the
set with a variac that has an amp meter with it. After replacing the
suspect parts, temporarily disconnect the degaussing coil, and turn the
variac power up very slowly and watch the amp meter. If it goes higher
than about 1 amp, and there is no raster on the set, then there may be
other faults.

Once the set is working, monitor the temperature of the components in
the supply, in case anything is overheating.

Switching power supplies are difficult even for the most experienced
technicians to service. Caution must be taken for safety concerns when
working in TV equipment.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
==============================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
Instruments http://www.zoom-one.com/glgtech.htm
==============================================
"budnlori" <lbnorris@megsinet.net> wrote in message
news:da31fe06.0309120341.79b7933b@posting.google.com...
Need some help from you techies out there.

Where can I find some schematics on this unit ? I checked on the
web and Sams, cannot find anything. Unit is about 1 year old.

My son somehow plugged the AC/DC plug in wrong and smoked the unit. I
assume the problem lies on the combo board on the right side. Yes
the fuse is good, there's some type of board mounted perpendicular
on this combo board with some darkness on it.

Thanx in Advance.
 
Check for high ESR caps in the power supply, and scan output circuits.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
==============================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
Instruments http://www.zoom-one.com/glgtech.htm
==============================================
"Clouseau" <lt_clouseau@o2.pl> wrote in message
news:29b93c53.0309120101.42990ce1@posting.google.com...
I have a TV Grundig. When I start it it's OK but after few seconds,
the screen becomes black except some kind of Z moving vertically in
the middle of it.
Thanks,
Clouseau
 
In article <fhj2mvo43rco8itjiv8q9hniatli0cji00@4ax.com>,
jeffl@comix.santa-cruz.ca.us says...
| Bake the camcorder at about 150F
| in an oven or just place it in a warm place (above a large monitor).
| Stay away from the hair dryers and microwave ovens.
|

I agree with all you have said, apart from not using an hair dryer,
why?

I often use water as a last resort for cleaning up equipment and use an
hair dryer to dry them out. The air flow tend to blow moisture out from
under IC's, and the heat output can be quite gentle. I have never had a
problem after using an hairdryer.

Certainly a microwave oven should NEVER be used. Any electronics placed
in a microwave oven will be instantly, and quite dramatically,
destroyed.


--
Regards,
Harry (M1BYT)...

Remove the 'NOSPAM' in my email address to reply.

Free Amateur Radio Courses:-
http://www.ukradioamateur.org
 
On Fri, 12 Sep 2003 12:38:24 GMT, Tim Schwartz
<toschwartz@worldnet.att.net> wrote:

Hello all,

I've got a Thorens TD-180 turntable with a runaway speed condition.
Usually, this is caused by the lamp that shines on the photo cell going
bad, but not here. There are pulses coming out of the photo cell, and
the lamp works.

I've tried contacting both the US distributor to order a shop manual,
and I've e-mailed Thorens in Switzerland to no avail, and its been
months. Does anyone have a schematic that I could get a photocopy of?
Any other suggestions would be welcomed too.

Regards,
Tim Schwartz
Bristol Electronics
Click to expand...

Tim The dip ic goes bad on these fairly often which can cause this
symptom. Can't remember the no. at the moment but it is a common
part. Chuck
 
If the belt is stretched, you may need to get a new one from Yamaha.
I believe this is the model that no generic belt would fit. The
Needle Doctor would be a good source of cartridges. This is a pretty
decent table and there are a wide variety of cartridges that work well
with it. Chuck.

On Thu, 11 Sep 2003 19:39:45 GMT, "Violent Zen"
<violentzen@yahoo.dieyouspammingfuck.com> wrote:

I just bought a Yamaha YP-B2 turntable from a guy for 15 bucks. The problem
is that the belt is completely off. I have no idea how it is supposed to be
placed. Any idea where I can find this information? Also, what would be a
good resource for stylus and cartridge replacement for this model? Thanks.

Scott
Click to expand...
 
I agree with all you have said, apart from not using an hair dryer,
why?
Click to expand...
Because they usually prove ineffective with highly dense SMD circuit boards,
such as those found in Mini-DV camcorders. The spacing between the parts and
the board are going to be very tight, so there are places where you will never
get enough airflow to blow water out of an undesirable place. Baking the
boards with sensible levels of sustained heat will speed up evaporation and
help to ensure a more thorough drying, which is especially important with
highly dense and miniaturised circuits. A problem from a single drop of water
is magnified the smaller, denser, and more complex the circuit becomes. -
Reinhart
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top