Toshiba TV29C90 problem; Image fades to black...

[Bob Urz]

Karl-Hugo Weesberg wrote:

Luke Skywalker has badly damaged it, but I think it CAN be repaired.

What do I need?

Perhaps you need a Master Vader.......

Bob


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[Norm Dresner]

"Chuck Harris" <cf-NO-SPAM-harris@erols.com> wrote in message
news:W-6dnRHW5N8LouPcRVn-oA@rcn.net...

Norm Dresner wrote:

Browsing through some papers, I just discovered that the "Signetics"
NE5534N Op Amp has an absolute maximum voltage spec of +-22V. I've got
a
bunch of them and it sounds like this should solve my problem. Well, I
might have to add some additional compensation to slow it down to
741-speed,
but I think that's the way to go.

Norm

The ST part is a grand total of $0.88 each. If you buy nothing else, then
that will be coupled with a $5 shipping charge... still not too bad for
the
real thing.

You're right -- there's nothing like the "real thing", unless there's
something better. One of the reasons that was given for not using a simple
3-terminal regulator here was that the OpAmp-based regulator would provide
much better regulation in general and better ripple rejection in particular.
If that's really true, then how could a better Op Amp hurt? I can't believe
that the designers of the circuit chose the 741 as the optimum device to use
over dozens of Op Amps that hadn't been designed yet.

BTW, I've also found out that the OP-27 has +-22V specs too and I've got
those as well. It's got lower noise and offset voltage, higher slew rate,
and wider bandwidth than the 741. Which of those do you think make it less
suitable?

Norm

 

[Lionel]

Kibo informs me that Sam Goldwasser <sam@saul.cis.upenn.edu> stated
that:

netspider4@lycos.com (Karl-Hugo Weesberg) writes:

Luke Skywalker has badly damaged it, but I think it CAN be repaired.

What do I need?

Give up. From what I recall, there wasn't much remaining.

Maybe if he bought a *really big* butterfly net to collect all the
pieces, & is *really good* at jigsaw puzzles...

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

 

[Gene the Skeptic]

Good suggestions, thanks.
Gene

 

[RonKZ650]

Is your 5v supply normal on pin 21? If it's low trace back to Q3901 5v
regulator and U4102 12v regulator to see if you've got correct voltage. Either
way, this is the area you need to be looking, the 12v output of U4102 goes to
Q3901 to make the 5v source, but also spits off to Q3102 then Q3101 then off to
your pin 2 reset through a few resistors ect, which should be at 5v normally.

I have been working on this set on and off for the past few weeks. I
kind of put it on the back burner for awhile though and just got back
to it. This was one that sometimes would not start up. John Del had
suggested checking the 5V reset voltage,(which would probably read
low), and then measuring the resistance on the reset pin of the UP
while heating nearby caps one by one with the soldering iron and
looking for a change. When the resistance dropped sharply that cap was
most likely the bad one.
I attached a couple of wires to pin 2, (reset), and ground measured
200K ohms. I plugged the set in and the voltage was 2.3 volts. The
high resistance suggested no loading or dead short so I tried turning
the set on and surprisingly it went on normally. I ran it for a few
minutes and shut it down and some time later it would not come back
on. I checked the voltage and resistance again and they were still
2.3V and around 200K resectivly.
I disconnected power and tried heating the caps while watching the ohm
meter and there was no change. I plugged the set back in and while
monitoring the 2.3 V I briefly cold sprayed the area of pin 2 on the
foil side of the board. The voltage abruptly dropped to zero and the
resistace dropped to 40K. I powered down and waited a few minutes and
the resistance eventually came back to 200K but when the set was
plugged back in the voltage remained at zero. Naturally the set will
not come on now. And now I have no voltage on pin 2 but still measure
200K.
I don't really know where the 2.3V went. So since there didn't appear
to be a short to ground on pin 2 I decided to try applying 5V to pin 2
and attempt turn on. The set came on, stayed on as long as 5V was
present and quit as soon as I removed the 5V.
I have no schematic and feel like I'll probably need one to chase this
further unless someone has some ideas. I'd really like to see this set
leave. Thanks for any help. Lenny Stein, Barlen Electronics.

 

[Chuck Harris]

Norm Dresner wrote:

You're right -- there's nothing like the "real thing", unless there's
something better. One of the reasons that was given for not using a simple
3-terminal regulator here was that the OpAmp-based regulator would provide
much better regulation in general and better ripple rejection in particular.
If that's really true, then how could a better Op Amp hurt? I can't believe
that the designers of the circuit chose the 741 as the optimum device to use
over dozens of Op Amps that hadn't been designed yet.

BTW, I've also found out that the OP-27 has +-22V specs too and I've got
those as well. It's got lower noise and offset voltage, higher slew rate,
and wider bandwidth than the 741. Which of those do you think make it less
suitable?

Norm

The higher slew rate and wider bandwidth will likely screw your circuit.
When the circuit was designed, and the board was layed out, it was done
with a 741. The things are very slow, and as such perfectly suited to
power supply use. With a faster opamp, you may find that your ciruit has
a tendency to oscillate, and to be bothered by powerline transients.

Or... it might work perfectly well. It is easy enough to try.

Do your circuit board a favor, and clip the pins off of the old IC flush with its
body, and remove them one at a time... it is always easier on the board
than solder wick, or those hand held vacuum thingies. I even do that with
my PACE desoldering station if I don't need to save the chip.

-Chuck Harris

 

[Mark D. Zacharias]

Unlike another reply here, don't replace the outputs unless they are
shorted, which they are not. Replace the STK350-230. Common problem. There
may be another issue with the protect circuit if it's not protecting when it
should.

Mark Z.


"Perion" <RazroRog@hotmail.com> wrote in message
news:SfKdnY7On_qak-jcRVn-qA@comcast.com...

If anyone is REAL bored maybe you could print this out, have a look at the
schematic at (pdf) at
http://mywebpages.comcast.net/dharp/files/str_se501/STR_DE515.pdf . It's
the
closest I can find to my str-se501 - the amplifier section is real close
to what
I have. See page 2 - at about G21. [All 5 of my ch. amps are like the top
three - I don't have IC601 or IC651]

Here's the deal:
1. It goes into protect mode - duh....

2. All the speaker relays for each channel are energized.

3. Center channel is reading full supply voltage (sum of B+ and B- vs.
just B+
or B- like all the other channels) on each of its output transistors from
collector to base! The other channels have near zero vdc on the base and
B+ or
B- from base to collector. Getting B+ to the base of Q553 and B- to the
base of
Q554). Also, output xistor resistances different than other four channels.

4. Removed both center ch transistors. Still goes into protect mode.
Traced
where opposite supply voltages on the bases back to STL350-230 center
channel
driver IC. The other 4 channels all read the same and have identical
static ckt.
resistances - they are driven from uPC2581 driver ICs. Probably explains
why
center ch. reading different resistances than other four.

5. Removed the STK350-230 center ch. driver IC. No more weird voltage
readings
at the output xistors' solder points. On the STK350-230 IC I was getting
B+ on
pin 6 (+VEOUT) to the base of the Q553 and B- on pin 5 (-VEOUT) to the
base of
the Q554 which seems crap to me - maybe I'm wrong. Anyway, it still goes
into
protect mode.

6. Can't find anything else that doesn't seem right on any of the
channels.

Question:
1. Any brilliant insights into this?
2. If it goes into protect mode, shouldn't at least one of the channel's
amp
over load detect transistors (like Q570) be turned on and inhibit that
amp's
associated speaker relay?
3. Down at R6 (the signals to the display board) it seems to get its
"protect
in" signal (24) from the "OC Offset DET" (overcurrent detector?) at D25.
It
looks to me like this monitors each channel's over load detectors so
again, if
in protect mode, shouldn't at least one channel's overload detector be
turned?
4. Do I have to do something special to reset protect mode other than
power down
and back up?

thanks,
Perion

 

[NSM]

"Bob" <balbert@access1.net> wrote in message
news:962dnQSdNrKgS-DcRVn-vw@hawaiian.net...
| Usually the case snaps together. Sometimes there is a screw under the
| little plastic where you'd slip in the telephone number. Also look under
| labels, which may be pasted on over a screw.

Or under rubber feet.

N

 

[OH YEAH]

"Marlboro" <ccon67@netscape.net> wrote in message
news:e3fd5378.0410260955.2623a5f1@posting.google.com...

easytoremember123@email.com (Wizard of Ozz) wrote in message
news:<fbcc7457.0410232240.7e6f903d@posting.google.com>...
I just bought a Samsung Syncmaster 793s 17" monitor. I'm using a very
old computer, with a very old video card, a SiS 6326 (Silicon
Integrated Systems) from 1997. I'm using Windows 98.

That's 1st problem


I installed the appropriate driver that came with the monitor CD.

I have read the entire FAQ at www.repairfaq.org and my problem didn't
come up.

up to a 2 % difference in linearity (I take this monitor to be on the
cheapo side). But I solved this problem by changing the Hz rate. And

That's 2nd problem

that's where my real problem comes in.

After reading the monitor CD manual to make sure I wasn't doint
something I would regret, I manually changed the refresh rate to 85 Hz
(always at 800*600). Perfect! Beautiful image. Except...

There are these evenly spaced vertical lines, just noticeable, across
the screen. Others might not complain about them. I'm a perfectionist

That's main problem

Ok, I'm confused....

Is this to say that THIS monitor is no good or just not for this particular
use? I have one just like it with the same problem. Mine is a secondary unit
and I have no use for it otherwise, but other than the faint vertical
streaks as mentioned by the OP in theirs, mine has an otherwise good
picture. Is it worth my while to sell it? IF this monitor is ok to use and
anyone CAN use it, let me know. I'll make you a decent deal.

TRM

 

[Graham]

No. Might as well try to power a lawn mower with an ice cream cone.

Might as well try and get Dolby 5.1 from a wax cylinder

 

[Charles Schuler]

"Grant" <grogers@lineone.net> wrote in message
news:1098712984.902953.21220@c13g2000cwb.googlegroups.com...

Hi all,

I have done some soldering on my gameboy advance and have created a dry
joint, I would like to know if is possible to test a solder joint using
a multimeter if so how and what make is recommended (I don't need
anything fancy).

A dry, grainy looking blob is not good. Add some good flux and reheat it
.... usually works fine.

 

[jakdedert]

Darren Harris wrote:

I need what will basically be a digital stopwatch. It will need to be
an accurate LCD timer/clock that can record a huge number of splits to
1/60th of a second, and since nothing like what I need is on the
market I'll obviously have to build one for myself, if this is
possible.

This may be a simple project, or a really complex one. But I was
hoping to get ideas on where/how to start.

Outisde of it's foot-print not being more than about 2 or 3 inches
wide, the following is what I'm after...

1) Two digital displays:
A) One for the main timer, which can be reset to zero at the press of
a button.
B) One that will show the latest split time, at the press of a button.

2) The ability to record/recall *at least* 256 splits.

Any advice on what parts and where to get them would be greatly
appreciated.

Thanks a lot.

Darren Harris
Staten Island, New York.

I think I'd look into whatever stopwatch programs are available for handheld
PDA's. There are some good deals out there for monochrome Palm OS devices.
(In fact, I'd unload one of mine to the right buyer.) It seems that I've
seen programs which might do what you desire. Certainly there are stopwatch
programs out there. Do a Google search....

Much easier to program a computer (PDA) to do the above, than to build a
dedicated hardware solution....

jak

 

[Art]

Also address the L14401 problem on the chassis before returning it for use.
"RonKZ650" <ronkz650@aol.comnospam> wrote in message
news:20041021163944.17257.00001801@mb-m25.aol.com...

Your horiz output is normal checking the way it does. My guess would be
the
flyback. I don't how how good your Fluke meter is, but on mine I can set
it for
AC volts and read off the collector of the horiz output. Should be aprox
300v
rms. If this voltage is there when the set is turned on, but no or low
high
voltage, the flyback is most likely bad. Also try unplugging the CRT board
and
the yoke, and see if HV returns. A shorted yoke or a CRT with no vacuum
can
cause this problem also.

 

[dkuhajda]

I can almost guarantee it is conductive glue under that capacitor in the
reset circuit.

David

 

[JURB6006]

Are the function buttons underneath ?

The newer style decks needed a really strong belt to eject. (except for type D)

If you just cleaned the belt, I would suggest replacing it before getting any
deeper. Sometimes the clicking is because of the same thing. If it's the deck
is what I think it is, the solenoid isn't the only thing moving things into the
play mode. Actually if it's autoreverse, the lack of tape movement will cause
the clicking, or actually it could be a failure of the reel sensor. IIRC they
used motor torque to engage and disengage the mech, the solenoid was mainly for
reverse.

Of course if this is the older type deck with the controls on the side I have
no idea.

JURB

 

[none]

On 26 Oct 2004 09:52:17 -0700, fynnashba@yahoo.com (kofi Mpengya)
wrote:

Please good pals,
A good friend of mine has this Epson Stylus Photo 825 printer
and would like to connect it to a standart TV ( as monitor prreview
for printing photographs). The printer has two ports; a USB and
another ten pin port which looks like an S-Video socket but the manual
that came with the printer does not say anything about this ten pin
port. Now my problem is how do I connect the printer to standard TV
from this port? because all the cable available seems to fit only DVD
player (5 pins)May I know the name of this ten pin cable / socket?and
where can I obtain some. Can I match it to the Audio-Video input of a
standard TV or is there any way I can hook it up to a stand alone
computer monitor. I know it can be connected to a PC thru" the USB
port but using a stand-alone monitor or a standard TV will be more
convinient.
I have consulted the Epson on-line customer section on the net but
no reply.
Thanks in advance.
Dan - Gh. W/A

There was a device made to do just that though I can't remember
offhand who made it or what it was called.
It was a hardware device that enabled you to view digital camera files
as well as jpgs on your tv screen.

 

[JURB6006]

Yup, now that's either a type B or C. The type B needs a good belt. Best if
it's bad and doesn't load the tape, cause sometimes it won't eject.

I've replaced quite a few of the cassette guides in these due to people using a
screwdriver to perform the "eject" function.

I'm going to be rooting around the boneyard today, if I run across these decks
I'll send you a picture.

I don't recall the size of that belt offhand, but it was very critical to have
a good one in there. I'll, however, have parts for this one in case that's not
the problem.

JURB

 

[arfster]

hey i have the same problem w/a sony KV XBR10, im not exactly sure what a
chassis is but would i be able to fix it myself? thanks...

 

[Elmer Bataitis]

"CGott" <curtgottler@yahoo.com> wrote in message
news:70fae150.0410271055.4efbc615@posting.google.com...

I have many old tubes, and was wondering where to look for what they
are worth. Is there any demand for them?

Do a websearch on each number.

You'll find lists of people selling that tube and the prices they want.It'll give you an idea if
anything is worth selling.

 

[Charles Schuler]

"CGott" <curtgottler@yahoo.com> wrote in message
news:70fae150.0410271055.4efbc615@posting.google.com...

I have many old tubes, and was wondering where to look for what they
are worth. Is there any demand for them?

Most old tubes are worth little to nothing. Transmitting tubes can be
sometimes sold at Ham radio flea markets. Same goes for tubes used in
antique radios.