Toshiba TV29C90 problem; Image fades to black...

[Mike S.]

In article <EqCdnZYSPdiogpbZRVn-ug@is.co.za>,
Bert <lijbertv_at_xsinet_dot_co_dot_za> wrote:

----- Original Message -----
From: "Gerard Bok" <bok118@zonnet.nl
Newsgroups: sci.electronics.repair
Sent: Sunday, March 05, 2006 1:44 PM
Subject: Re: Alkaline charging followup


On Sat, 4 Mar 2006 21:50:42 +0200, "Bert"
lijbertv_at_xsinet_dot_co_dot_za> wrote:

December around the 21st last year I did have a question on charging a
rechargeable alkaline AA battery.
Using those 2 in my wireless optical mouse.
Normal battery did last 1 month
Alkaline battery did last 5 month,
Alkaline recharge battery 2.5 month, empty reading is 1 volt.
Started charging both batteries on 1.68 volt, the charging current was
110
mA per battery.
Charging current after 10 hour is 95 mA for both batteries, constant
voltage
1.689 volt.
Hope this will help someone sometime.

And the number of spontaneous exploding charging cells is still
zero, I guess ?

--
Kind regards,
Gerard Bok

No exploding cells, do check every hour or so that the voltage on the
battery stays below 1.7 volt and the battery is still cool to touch.
Remember it is a rechargeable AA alkaline cell.
Greetings
Bert.

Seems like a lot of babysitting effort just to recharge a battery. Are you
doing this as an intellectual exercise, or do you really plan to keep this
going? This is why the commercial chargers used for RAM cells are controlled
by dedicated circuitry. The batteries are pulse-charged, and the duty cycle is
controlled by the voltage of each individual cell as read in between charging
pulses. As the voltage of the cell approaches 1.65V, which is the defined
terminal voltage for a RAM cell, the duty cycle of the charging pulses
approaches zero. Trying to replicate this, over several hours, by manual
checking against a constant-voltage source sure seems like a lot of work.

 

[tvguy]

Jeff Hacklerwrote:
dkuhajda@locl.net wrote:
Absolutely, unplug it to reset the system control. With all the
different manifestations of the Gemstar circuit in an RCA, many odd
problems are easily fixed with a simple unplugging to reset any
software glitches.

Beyond that troubleshooting by a qualified technician will be
required.

WHAT A PIECE OF *** WHO THE *** WOULD BUILT A TV THAT NEEDS TO BE

UNPLUGGED AND PLUGGED BACK IN TO WORK[/QUOTE]

RCA has had this feature for a few years now since the gemstar
module had came out. All this feature does is resets the memory. If
there is no problem with the set, it will return the picture back to
normal. If there is a problem the picture will stay out.

 

[tvguy]

Arfa Dailywrote:
"tvguy" <no@spam.invalid> wrote in message
news:1A6Of.198994$H54.155366@fe03.news.easynews.com...
It don`t sound like a bad inverter if it is running good when
plugged
directly to the wall outlet. If it only does this when plugged into
the powersupply of the computer then this would be a problem of the
computers powersupply. Did you try to plug it into another computer
to see if you still have the same problem ? I would suggest to try
this first and see what happens.


Maybe I read it wrong, but I don't think that this is what the guy
was

saying. I read it as he was always using the external power unit, that
came
with the LCD monitor, and if he left it plugged in the wall, ie with
power
always available to this power supply, but with the monitor turned
off, when
he came to switch the monitor on, it came on ok. If, however, he
plugged in
to any power source that was turned off for periods of time eg his
UPS, or
unplugged from the wall for any length of time, then when he came to
put
power back on the PSU, and then tried immediately to switch on the
monitor,
he got the buzzing, spitting failure to start up, which is typical of
a
defective switching PSU, with bad electrolytics. Perhaps the OP can
confirm
??

If this is actually the case, then all the stuff about Windows and
rebooting
etc is probably a red herring. It just relates to the length of time
all
this takes, which gives the power supply time to struggle to a
startup.

Arfa[/QUOTE]

If that was what he was stating. I may have read his post wrong to
what he was trying to say. Then I would have to say yes that he has
something wrong with the external powersupply.

 

[budgie]

On 5 Mar 2006 16:54:52 -0800, imapeppertoo@excite.com wrote:

All,

Thanks for all the posts. As usual, the wealth of information on this
forum is stunning. As suggested, I dug deeper into the caps and found
some issues. I replaced them as suggested and now have all the
inverters operational hot or cold.

I'm sure all readers would benefit from knowing what those issues were.

 

[Jeff Hackler]

tvguy wrote:

Jeff Hacklerwrote:
bigdaddy wrote:
I have this TV and for few months it has started given me problem.
When I switch it on I get a horizontal line with sound. If I lift
or
press the corner of the circuit board a little bit, the full
picture
with sound appears. The picture is more stable when I lift the
corner
at the scart side rather than pressing it. If I leave it at that,
the
picture remains but unstable. Even walking on the carpet makes it
unstable.

I took out the Tuner and I did not find any dry or crack solder
joints
even with 3.5 X Loop. I have examined the board under the light
with
the same magnification and re soldered many joints which I thought
suspicious. Still the symptom persist.

I would like to know if anyone knows a specific cause and cure of
it.
Thanks.

THERE WAS AN ISSUE LIKE THIS WITH RCA TVS SOME TIME AGO. THERE WAS A
SWITCH THAT SAID NORMAL/SERVICE AND WHEN YOU SWITCHED IT TO SERVICE
YOU
GOT A HORIZONTAL LINE. THEN THOSE MORONS WOULD CALL A SERVICE SHOP
BECAUSE THEY HAD THOUGHT THEY BROKE THEIR T.V.

I would like to tell this moron Jeff Hackler that there is no service
switch in side this tv set.
[/QUOTE]
DON'T HAVE TO. YOUR MOM ALREADY TOLD ME WHILE SHE SNORTED COCAINE OFF
MY DICK.

 

[Arfa Daily]

"Ryan Underwood" <nemesis@icequake.net> wrote in message
news:na6dnQkNwIo4PJbZ4p2dnA@fidnet.com...

Hi,
I just acquired a Lab-Volt model 189 bench supply, 1966 vintage. It has a
passthrough AC output, a variac output, and a variable DC output.
Unfortunately, the variable outputs do not work (0 voltage independent of
knob setting). The pass through output does work though.

The fuse is a screw-in type, black thumb screw reads "Fuse" and when it
pulls
out, there is a loose metal cylinder around the end of the fuse. I have
no
idea how to test this type of fuse or even what it is called.

Anyone have pointers where to get started on this thing? The construction
appears to be nothing more than a bunch of transformers and a knob. I'm
not
familiar with these variable type supplies.

Thanks.

The fuse is easily enough tested using a simple ohm meter, or by

substitution, but to be honest, if you do not have sufficient knowledge to
be able to troubleshoot a simple power supply of this vintage, I really
would not recommend that you start poking around inside, as there are
dangerous voltages present in any mains power supply. Sorry to be so
negative about this, but I'm only thinking of your safety ...

Arfa

 

[davie_snert]

ibbotsnm Wrote:

Hi Richard

I have obtained the repair manual from a company here in the UK and
have recently tried to re-align the trays.
Firstly the manual although helpful in listing the various parts etc.it
loses a lot in the translation from Japanese to English. I think you
are absolutely correct in your assumption that the trays are arranged.
It is probably necessary to fully dismantle the CD assembly from the
rest of the unit first before any realistic repairs can be carried out.
I have a copy of those instructions if you require one. My problem
was that the initial snarl up was because of one of the two spring
mechanisms that elevate the disc in the drive position had itself
miss-aligned due to a small part of the plastic breaking. This I
repaired and after quite some time I managed to understand the
'Carousel' action of the mechanism. By rotating the small bevel gear
(the white one that drops loose when the unit is disasembled) 5
complete turns the first tray (Tray 2) is made to traverse from the
rear to the front of the unit. Place tray 1 into the rear of the unit
and turn the gear a further 5 turns and it should travel from the rear
to the front as did the first tray, at the same time the first tray is
elevated up to the top front position. the tray will need a little
assistance during this operation since it normally works the other way
up and relies on gravity to lift (drop) the tray into position. a
similar operation is followed by tray 3 so allowing tray 2 to take over
the drive position. I also found that the gears didn't rotate fully five
times the second time but jammed causing the whole mechanism to foul up.
I managed to cure this by disassembling the whole gear mechanism and
turning the 'black gears' to a slightly different position from where I
was then able to rotate the whole mechanism freely. Although it
appeared to work when operated by hand, once I had reassembled the
whole unit it refused to operate fully under power. Thats where I
stand at the moment. No longer jamming but not yet fully aligned. I
will crack the problem yet.!!!

Let me know how you do. I will copy the written procedure if you
require it.


regards Norman Ibbotson

Hi Norman

I have the Denon UD M50. Not having the cd changer problem, but am
having a laser problem - it skips for no apparent reason. Have tried
various CDs, cleaned them all thoroughly, but it still happens. Just
wondered if the repair manual would help. Do you have a link where I
could get a copy of the repair manual? Thanks!!

Dave Marshall


--
davie_snert

 

Hopefully this is the right group for this question. I have no
intention of doing this repair myself--rather, I would take it in for
service.

I have a Sharp 32N-5350. I've had it for about 5-6 years with no
problems.

Today, while watching, the TV quite suddenly shut itself off. It was
exactly as if I had turned it off using the remote.

Clicking the remote to turn it back on did nothing (no response at
all). I unplugged the TV from the outlet and tried a different outlet.
When I tried to turn it on again, it made a clicking noise, exactly as
if it was going to turn on, and then made a sound that I think was
degaussing, and then clicked again and did nothing.

I had to leave, and when I came back 15 minutes later, I tried again
and the same thing happened, except this time I heard about a second of
audio before it clicked off.

I was planning on getting a new TV within the next six months anyway,
so it's no huge tragedy. However, if this sounds like an inexpensive
problem to repair, the TV would still be useful to me.

So:

1. Any other troubleshooting steps I could try to help diagnose the
problem?
2. Does it sound like a serious problem?

I see from ads online that I could get a brand new tube TV for under
$200, so I guess it would have to be REALLY inexpensive to warrant
repair.

Any thoughts or insight would be greatly appreciated.


Phil

 

[Mark]

Hi. The tape cassete will not move onto the reels. I've checked the belts,
gears but no visible damage. If I move the gearing by hand, it works , could
it be electronic? Any help would be appreciated. Mark.

 

[427Cobraman]

Have both a DE845 and DE945 and also have the service manual. Neither
unit will power on. The 845 had chattering power and I found bad solder
joints in the display board. After repairing those, the unit ran for
about a minute and a half then shut down...never to restart. All fuses
are good, and the standby power circuit seems to be working fine. When
pushing power button nothing happens (front panel or remote). So, I'm
assuming there is a problem with the standby circuit. According to the
schematic, the main power x-former is off until the the standby relay
is switched on, so ruling out that area. Is there a built-in protect
that prevents unit from coming out of standby? I took voltage readings
earlier but will recheck them one I get home and post them. BUT, if
memory serves, I had 5vdc out from some terminals and 10-13V on the
collector of Q901 which supposedly powers the relay (RY901). I'm
looking for guidance on how to approach this problem. I'm proficient
with O-scope, DVOM, ESR meter, and general electronic repair. Just
never messed with audio receiver/amps before. Thanks,

Alex

 

[Luddite]

indago <elindago@earthlink.net> wrote:

I have an Amphenol Millivolt Commander Model 870, about 30 years old. It is
a sensitive, FET unit that uses batteries. Most of the batteries are
general AA 1.5 volt batteries (8), but 2 of the batteries are Duracell
Mercury 1.4 volt batteries (Duracell ZM9). I suppose that these batteries
are a reference voltage. Mercury batteries are no longer in use, so I used
two 1.5 volt batteries in their place.

When I turn the on and select battery test, the meter does not move. It is
supposed to move to above the Battery OK mark. Also, when I select the
positive DC, the meter pegs negative, and when I select the negative DC, the
meter pegs positive. The batteries are all new batteries, so there is not a
problem with dead batteries.

Anyone ever worked with one of these meters and can give me some insight
into the problem with it?

Polarity of mercury cells is reversed as I recall,turn the one pair
around if the holder will accept it.

 

[Arfa Daily]

"427Cobraman" <quartermiler1320@yahoo.com> wrote in message
news:1141724037.005753.43770@p10g2000cwp.googlegroups.com...

Have both a DE845 and DE945 and also have the service manual. Neither
unit will power on. The 845 had chattering power and I found bad solder
joints in the display board. After repairing those, the unit ran for
about a minute and a half then shut down...never to restart. All fuses
are good, and the standby power circuit seems to be working fine. When
pushing power button nothing happens (front panel or remote). So, I'm
assuming there is a problem with the standby circuit. According to the
schematic, the main power x-former is off until the the standby relay
is switched on, so ruling out that area. Is there a built-in protect
that prevents unit from coming out of standby? I took voltage readings
earlier but will recheck them one I get home and post them. BUT, if
memory serves, I had 5vdc out from some terminals and 10-13V on the
collector of Q901 which supposedly powers the relay (RY901). I'm
looking for guidance on how to approach this problem. I'm proficient
with O-scope, DVOM, ESR meter, and general electronic repair. Just
never messed with audio receiver/amps before. Thanks,

Alex

Very first thing is to make sure that no front panel buttons are being

accidentally pushed by slightly wrong assembly of the front panel. Make sure
that all buttons move, and click.

Assuming that there is no attempt by the main power relay to close, when you
try to turn it on, you can try forcing it, by temporarily shorting the
collector to the emitter on the relay driver transistor. DO NOT have any
speakers connected to it at this time. If unit then appears to come up ok,
check all of its display and operation functions. If anything here seems not
to be working correctly, chances are it's a system control problem, possibly
related to the work you already did on the front pcb. If all is still
looking good, check across ALL speaker outputs for DC. If there is any, then
check power supplies to output stages carefully. Some of these big amps
monitor the power supplies, and if anything is wrong, block operation,
although that's only a potential issue if the main power relay does close
momentarily. If everything is still looking ok, you can give it some input,
and see if the outputs look normal on all channels, on a 'scope. If this
looks good, you can risk some speakers, and then carefully recheck all
functions. If there are any noted problems, they should give you a clue as
to where to look. If it all appears to be working ok, then the only
circuitry that you then need to concentrate on, is the relay drive, back to
the system control micro, but check the circuit around the system control
micro carefully, for any pins that may have a power up blocking function.
With the standby supply present, and the system control idling, you should
be able to verify that there are no incorrect inputs to the micro.

Arfa

 

[Mark D. Zacharias]

Arfa Daily wrote:

"427Cobraman" <quartermiler1320@yahoo.com> wrote in message
news:1141724037.005753.43770@p10g2000cwp.googlegroups.com...
Have both a DE845 and DE945 and also have the service manual. Neither
unit will power on. The 845 had chattering power and I found
bad solder joints in the display board. After repairing those, the
unit ran for about a minute and a half then shut down...never to
restart. All fuses are good, and the standby power circuit seems to
be working fine. When pushing power button nothing happens (front
panel or remote). So, I'm assuming there is a problem with the
standby circuit. According to the schematic, the main power
x-former is off until the the standby relay is switched on, so
ruling out that area. Is there a built-in protect that prevents
unit from coming out of standby? I took voltage readings earlier
but will recheck them one I get home and post them. BUT, if memory
serves, I had 5vdc out from some terminals and 10-13V on the
collector of Q901 which supposedly powers the relay (RY901). I'm
looking for guidance on how to approach this problem. I'm
proficient with O-scope, DVOM, ESR meter, and general electronic
repair. Just never messed with audio receiver/amps before. Thanks, Alex

Very first thing is to make sure that no front panel buttons are being
accidentally pushed by slightly wrong assembly of the front panel.
Make sure that all buttons move, and click.

Assuming that there is no attempt by the main power relay to close,
when you try to turn it on, you can try forcing it, by temporarily
shorting the collector to the emitter on the relay driver transistor.
DO NOT have any speakers connected to it at this time. If unit then
appears to come up ok, check all of its display and operation
functions. If anything here seems not to be working correctly,
chances are it's a system control problem, possibly related to the
work you already did on the front pcb. If all is still looking good,
check across ALL speaker outputs for DC. If there is any, then check
power supplies to output stages carefully. Some of these big amps
monitor the power supplies, and if anything is wrong, block
operation, although that's only a potential issue if the main power
relay does close momentarily. If everything is still looking ok, you
can give it some input, and see if the outputs look normal on all
channels, on a 'scope. If this looks good, you can risk some
speakers, and then carefully recheck all functions. If there are any
noted problems, they should give you a clue as to where to look. If
it all appears to be working ok, then the only circuitry that you
then need to concentrate on, is the relay drive, back to the system
control micro, but check the circuit around the system control micro
carefully, for any pins that may have a power up blocking function.
With the standby supply present, and the system control idling, you
should be able to verify that there are no incorrect inputs to the
micro.
Arfa

Could just be the micro isn't getting any power. A regulator might have
died, a crystal might be intermittent, and I'm thinking there were a couple
1 ohm power supply resistors that would go bad on these. I'll check.

Mark Z.

 

[Arfa Daily]

"George" <Nospam@no.net> wrote in message
news:skoq02hej1m1962n4rg9isdrjlbtskt6og@4ax.com...

I am looking to build a power supply for a LCD flat panel monitor.
Thanks

Such power supplies are available dirt cheap, ready built. I wouldn't even
consider building one. Had to renew the one on an HP LCD monitor here,
recently. Just got a generic 12v 4amp switch mode psu from one of my normal
component suppliers.

Arfa

 

[Sam Goldwasser]

"3T39" <rubbishrat@hotmail.com> writes:

Hello, George!
You wrote on Tue, 07 Mar 2006 08:44:39 GMT:

G> I am looking to build a power supply for a LCD flat panel monitor.
G> Thanks

An old PC PSU can be utilised for this, with the benefit of good regulation.
If you use a modern ATX unit short out pin 14 to ground to get it to start
up. Yellow is +12V

With best regards, 3T39. E-mail: rubbishrat@hotmail.com

You may need to provide a load on the +5 or other output for it to run
stable. This was always required of older AT supplies, don't know how
many ATX supplies require it.

--- sam | Sci.Electronics.Repair FAQ: 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 Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

 

[Damir]

On Tue, 07 Mar 2006 00:46:00 GMT, "Patt" <pattj@shaw.ca> wrote:

I have a Hoover vacuum, Legacy 740, model #U4537910. I have to replace the
cord. What is the easiest way to get at the motor to make this repair?
Patt

From the right,maybe?

 

[jumper]

Hello all,
I have a Sharp Hi8 ViewCam VL-4000 camcorder. The pinch roller has
fallen off. I managed to get it back in place but it does come off
after a while.
How do I get it fixed in place? The camcorder functions ok and image
quality is as normal as long the pinch roller is in place..
Can anyone give me advice?

Thanks,

 

[subseb]

I fixed the CD player. As it turns out my suspicions were correct
about the PSU. When A cd sarted up or the motor sled screw, and laser
diode were powered up the LED would dim ever so slightly, this was
really hard to notice becuase of the nature of LED's behaviour versus
voltage. This indicated thre might be a PSU fault.
I checked the voltage of all the voltage regulator IC's on the circuit
board against the manufacturers IC parts minumim and maximum vallues.
These were 5V dropper type voltage regulators, and there specified
minimum output value was 4.83V. I registered 4.6V minimun when a cd
was trying to be read, so there was obviously a problem here. I
checked all the connections, they apperaed to be okay, no black marks
or obvious component degredation. So I resoldered all the critical
components in the PSU stages, i.e. transformer connections, diodes,
power resistors and smoothing capacitors. I noticed when I powered
the unit on that the LED was brighter and the operation of the
transport and general cd loading was faster, and more importantly the
unit actually played the cd!!

I expect the reason of fauilure was a simple mechanical fault, one of
the solder joints in the PSU section was dry or cracked, possibly
from excess vibration, being moved around the country so much.

This fix took me some time, to remove everything and these Rotel CD
players are a bugger to work on, there are so many screws to get
through. Anyway the AC supply probably wasn't being fully rectified
so the supply current was halfed. In effect the voltage regulators
were working but there was not enough current supply to keep the
voltage stable hence it dipping, this efected the tracking to the
extent that the cd player would mostly give up trying to read a cd.

 

[James Sweet]

Ian Stirling wrote:

adam8ants@yahoo.com wrote:

I have a SONY plasma TV. It's developed a problem - a thin horizontal
black line that goes from one end of the screen to the other (about 4"
from the top of the screen). I've also noticed that several other
people have reported the same problem. I've even seen folks selling
their plasma TVs on ebay with this same problem.

The bad news is that I am told by service technicians that the problem
is a bad display driver board, which is part of the display panel.
Cost to repair: $2,000.

My gut tells me it's a bad chip somewhere. I shouldn't have to replace
the entire display. Correction - I shouldn't have to throw a $4,000 tv
in the garbage after three years.


It is not inherently impossible to fix.
I'd estimate you could probably set up a station to try to fix it for
well under 10 million dollars.

If you could find an identical panel with a broken glass it might
technically be possible to transfer the driver from one panel to the
other, but with the ones I've seen there would be absolutely no way in
hell of doing this at home. It really is a shame, I don't understand why
they bond them rather than just using some sort of connector.

 

[**THE-RFI-EMI-GUY**]

Nope should be OK. Another problem could be if the B&O requires the
speakers to be floating without reference to ground. Your quad convertor
or external speakers may be shorting the output to ground.

Cartrivision1 wrote:

I checked and it seems that my particular Bang & Olufsen stereo uses 4
ohm speakers:

Power output RMS DIN: 2 x 40 W / 4 ohms
Harmonic distortion: <0,1%
Intermodulation: <0,3%
Frequency range + / - 1,5 Db: 20 - 30000 Hz

Could this be the root of my problem?



thanks,
CTV

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"Š

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P