Toshiba TV29C90 problem; Image fades to black...

[Jeff Liebermann]

On Fri, 12 Sep 2003 14:03:08 +0100, Harry Bloomfield
<harry.m1bytNOSPAM@tiscali.co.uk> wrote:

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?

Try this test. Take a well used home hair dryer and use it to heat up
a piece of clean glass. Then, look at the glass under a magnifying
glass. You will find a layer of carbonized hair, dust, dirt, crud,
goo, and what not. I ruined a few pieces of optical electronics
before I realized what was happening. Granted, a new hair dryer is
quite suitable for the purpose, but the typical home hair dryer is
fairly dirty.

Getting the hot air into cavities (cans and shields) is a problem with
a hair dryer. For exposed circuit boards, I guess hot air is good
enough. However, for complex assemblies (camcorder), evenly applied
heat from an oven will penetrate the enclosed areas better and
accelerate evaporation.

Also, I have a few hot air guns that vaguely look like a hair dryer,
but at designed for paint removal, heat shrink tubing, and other high
temperature tasks. They are sufficiently different from the typical
home hair dryer that even a clueless idiot could make the distinction.
Unfortunately, I don't qualify, as I have grabbed the wrong one and
melted a few components. The hair dryer stays in the bathroom. The
shrink tube gun stays on the workbench.

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.

I have problems with water collecting under components. A hair dryer
will eventually remove the water by evaporation. I'm a bit more
brutal and prefer about 80psi clean air (dried and filtered) to blow
the water out from under parts and inside cans. The average hair
dryer just doesn't move enough air to do that.

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

I threw that in as the owner of the camcorder seems to be over his
abilities and I wanted to make sure that he wouldn't try it.
Motor oil?


--
Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
(831)421-6491 pgr (831)336-2558 home
http://www.LearnByDestroying.com AE6KS
jeffl@comix.santa-cruz.ca.us jeffl@cruzio.com

 

[Leonard G. Caillouet]

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Leonard G. Caillouet
Electronics World
Gainesville, FL

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[David]

Lots of protect circuit possibilities. Troubleshoot them one at a
time.
Do a Goole Groups Archive search at this newsgroup for "Toshiba
shutdown", "Toshiba RPTV", etc as many older Toshiba RPTV hints and
tips on the most common shutdown problems have been posted some time
ago (about 3 to 4 years ago).

Back when I had access to the shop where I worked hints and tips I
posted several tricks here.

David

"Fishhead" <none@not.com> wrote in message news:<bjsrgj01hdc@enews4.newsguy.com>...

Toshiba RPTV Dead. Power Light Blinks But Set Won'T Fully Power Up.The set
acts like its going to powerup, then clicks off.Replaced convergence amps
(Stk392-110). No help. I did find a possible open winding in T862.Any other
ideas??Thank for any help,Bradcasiasb@sbcglobal.net

 

[jakdedert]

"Michael Black" <et472@FreeNet.Carleton.CA> wrote in message
news:bjrbo2$19o$1@freenet9.carleton.ca...

"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.

Michael

I stopped even thinking about meaningful advice, when he said (in his OP)

that he put 'engine oil' on the boards after drying.....

jak

 

[Franc Zabkar]

On Thu, 11 Sep 2003 05:02:14 GMT, "RobertDubord"
<rdubord@globetrotter.qc.ca> put finger to keyboard and composed:

Can't find pinout for Toshiba 12 pin SIP vertical IC TA8432K in
White-Westinghouse TV model WTM-61904.

A datasheet is available from http://www.freetradezone.com.
Registration is free.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

 

[Malcolm Moore]

On 11 Sep 2003 19:38:34 -0400, Pankajkumar Chauhan <no_spam@dev.null>
wrote:

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

That should be 2*230*cos(30)= 398.37V
which simplifies to 230*sqrt3

Plot the 3 sine waves against time on the X axis. The 3 waveforms will
be 120 degrees apart.
The voltage between phases can then be easily visualised. When one
phase is at max +ve the other two will be -ve, but less than maximum.
While these are instantaneous values the same applies to the rms.
Your result above gives a figure greater than twice the phase voltage.

To use the phasor diagram you use in your post you don't just take the
distance between two radii, you add the inverted phasor of one to the
phasor of another and the resultant is the potential between them.

Regards
Malcolm.

 

[Ol' Duffer]

<snip>

This set came in with blown vertical IC and a very crispy 1 ohm 2W
resistor (snapped in two when I took it out) for 26V supply to the
vertical only. Fixed that up. Gee that's a FIRST for me to actually
have to replace that in RCA in my 1 and half years for a shop.

Well! This one really got me stumped, top most is bowed in,
non-linear lines and all shaking like mad while most of pix is
perfect. Got all my tools on that (scope, dmm and ESR meter)
All the 26V and 13V supplies are quiet and smooth, caps checks
good EXCEPT: on scope on output of vertical IC I see this like this:

1. Vertical foldover is usually caused by failed bootstrap capacitor.
2. These IC's need more drive than you might think. Input pulse
can look okay, but not be adequate if the preceding stage has
soft power supply.

 

[Jason D.]

On 13 Sep 2003 00:32:59 GMT, "Ol' Duffer" <dontsend@mespam.net> wrote:

Couple comments and a big update after this.

1. Vertical foldover is usually caused by failed bootstrap capacitor.

True, I have seen this so OFTEN in LA78xx IC series, usually running
with bad cap fries them but for some reason in RCA, this circuit
design is more tolerant of wimpy "bootstrap" but makes top drop down
cleanly appox 1" down. I called this pump up cap and customer
complaint got that fixed.

But what really get these TDA9302 & TDA8172 is bad solder connections
on IC itself (often seen this in philip sets).

2. These IC's need more drive than you might think. Input pulse
can look okay, but not be adequate if the preceding stage has
soft power supply.

Interesting, I'll check that against the schematics it has voltages
listed so will confirm.

Original repair I replaced: vertical IC & 26V supply resistor, now new
problem surfaced with this update.

Now to this UPDATE: Fixed that noisy waveform, the problem didn't go
away after I replaced that pump cap. There was open 1.5 ohm 2W
resistor that ties vertical IC output to the ground via a 0.22nF poly
cap. More like filtering than anything else. Made this looks like
bad pump but it is really noisy waveforms with lines and "foldover" at
top of screen.

Now I have new problem, Now fried that vertical IC after a minute.
Pix was PERFECT after that filter network was fixed. Burned out the
internal ramp circuit leaving retrace circuit intact and didn't burn
any of those fusible resistors.

When I have another good chassis with this type of RCA vertical
circuit, I'll beliefly uncouple that filtering network on that
vertical output and see what raw waveforms with good yoke looks like.

I do have RCA schematics for all chassis including old ctc169, 17x and
up on both cd and paper.

Cheers,

Wizard

 

[Mark D. Zacharias]

Yamaha no longer has belts for most of these older models. They sometimes
recommend an MCM replacement, which may or may not work right.

Mark Z.


"chuck" <chuck3565@deja.com> wrote in message
news:rmk3mv8719g86c84tiknfprbj27uqfh51v@4ax.com...

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

 

[Al Savage]

On Sat, 13 Sep 2003 14:24:31 UTC, "Lou" <loud1@netrax.net> wrote:

Anyone have a pinout for the adaptor cable so that I may construct so of
the newer adaptors for monitors? Anyone have adaptors for sale? Any
schematics? Any help appreciated.

ISTR that Sencore had the pinout at their website years ago.

--
Regards,
Al S.

 

[john]

So, you need to be an ASSHOLE about it ??

You're a REAL professional John, aren't you ?


ERIC



Now be nice Eric..

 

[Ian Stirling]

Loren Coe <loren@netnews.attbi.com> wrote:

In article <i8r8b.1056$4j3.501@bignews6.bellsouth.net>, jakdedert wrote:

"Michael Black" <et472@FreeNet.Carleton.CA> wrote in message
news:bjrbo2$19o$1@freenet9.carleton.ca...
"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.
Michael
I stopped even thinking about meaningful advice, when he said (in his OP)
that he put 'engine oil' on the boards after drying.....
jak

maybe this guy is a really bad troll? --Loren

Surely then he'd have dropped it into a stream, rather than a lake?
Or maybe he's got a really big bridge.
--
http://inquisitor.i.am/ | mailto:inquisitor@i.am | Ian Stirling.
---------------------------+-------------------------+--------------------------
If God hadn't intended us to eat animals,
He wouldn't have made them out of MEAT! - John Cleese

 

[Mark D. Zacharias]

Smaller caps near a heat source, yes. Others, probably not.

Dirty controls & switches, number one.
Solder connections, number two.

Other, more obscure sources of bad connections, number three. I worked on an
old Sansui integrated (sorry-don't remember the model number) on which the
B+ voltage for the outputs was lost intermittently due to bad physical
connections to the TO-3 devices.

A tech could probably fix it in pretty short order. A do-it-yourself-er,
well, maybe, maybe not.

Mark Z.


"Asimov" <Asimov@-removethis-bbs.juxtaposition.dynip.com> wrote in message
news:MSGID_1=3a167=2f133.0_3f637f7b@fidonet.org...

"Alisdair" bravely wrote to "All" (13 Sep 03 18:38:54)
--- on the heady topic of "Help needed fixing Sansui AU-101 amp"

Being an old amp and assuming it has been sitting unused for a long
while, I would highly suspect the most typical problem being marginal
aluminum can electrolytic capacitors. You have to ESR every electro in
the amp and change all that turn up bad. Only then you can go on to
diagnose other faults. Everyone here will offer the same advice.


Al> From: Alisdair <alisdair@tullo.dont_spam_me.me.uk

Al> hi,

Al> I've just got an old Sansui AU-101 amp, and it has a few problems:
Al> - there's no output on the right channel until it's been on a few
Al> minutes - both channels (but particularly the right) crackle when
Al> balance or volume are adjusted. Once the unit has warmed up the
Al> problem with the volume goes away.

Al> The sound quality is ok though once it's warmed up.

Al> I've done some searches and found suggestions for similar situations,
Al> like freezing transistors or replacing caps (largest first), any idea
Al> what to try first? I've done some electronics in the past so I'm not
Al> completely ignorant, never tried to recondition a hi-fi before
though.

Al> I'd appreciate any suggestions as to what to try, especially related
Al> to the AU-101 in particular.

Al> Thanks,

Al> Alisdair

... A fail-safe circuit will destroy others.

 

[Malcolm Moore]

Pankajkumar Chauhan <no_spam@dev.null> wrote in message news:<ty4isnyaoat.fsf@bertie.modck.cs.cmu.edu>...

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

That should be 2*230*cos(30)= 398.37V
which simplifies to 230*sqrt3

Plot the 3 sine waves against time on the X axis. The 3 waveforms will
be 120 degrees apart.
The voltage between phases can then be easily visualised. When one
phase is at max +ve the other two will be -ve, but less than maximum.
While these are instantaneous values the same applies to the rms.
Your result above gives a figure greater than twice the phase voltage.

To use the phasor diagram you use in your post you don't just take the
distance between two radii, you add the inverted phasor of one to the
phasor of another and the resultant is the potential between them.

Regards
Malcolm.

 

[Michael Black]

Ian Stirling (root@mauve.demon.co.uk) writes:

Loren Coe <loren@netnews.attbi.com> wrote:
In article <i8r8b.1056$4j3.501@bignews6.bellsouth.net>, jakdedert wrote:

"Michael Black" <et472@FreeNet.Carleton.CA> wrote in message
news:bjrbo2$19o$1@freenet9.carleton.ca...
"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.
Michael
I stopped even thinking about meaningful advice, when he said (in his OP)
that he put 'engine oil' on the boards after drying.....
jak

maybe this guy is a really bad troll? --Loren

Surely then he'd have dropped it into a stream, rather than a lake?
Or maybe he's got a really big bridge.

Now that is funny.

I didn't catch where you were going with the stream bit, until I read
the bridge bit.

"Who's crossing my bridge? You can't pass until you drop neat
electronic equipment over the side!"

Michael

 

[Asimov]

"Alisdair" bravely wrote to "All" (13 Sep 03 18:38:54)
--- on the heady topic of "Help needed fixing Sansui AU-101 amp"

Being an old amp and assuming it has been sitting unused for a long
while, I would highly suspect the most typical problem being marginal
aluminum can electrolytic capacitors. You have to ESR every electro in
the amp and change all that turn up bad. Only then you can go on to
diagnose other faults. Everyone here will offer the same advice.


Al> From: Alisdair <alisdair@tullo.dont_spam_me.me.uk>

Al> hi,

Al> I've just got an old Sansui AU-101 amp, and it has a few problems:
Al> - there's no output on the right channel until it's been on a few
Al> minutes - both channels (but particularly the right) crackle when
Al> balance or volume are adjusted. Once the unit has warmed up the
Al> problem with the volume goes away.

Al> The sound quality is ok though once it's warmed up.

Al> I've done some searches and found suggestions for similar situations,
Al> like freezing transistors or replacing caps (largest first), any idea
Al> what to try first? I've done some electronics in the past so I'm not
Al> completely ignorant, never tried to recondition a hi-fi before though.

Al> I'd appreciate any suggestions as to what to try, especially related
Al> to the AU-101 in particular.

Al> Thanks,

Al> Alisdair

.... A fail-safe circuit will destroy others.

 

[Alisdair]

Mark D. Zacharias wrote:

Smaller caps near a heat source, yes. Others, probably not.

Dirty controls & switches, number one.
Solder connections, number two.

Succinctly put, will do.

A tech could probably fix it in pretty short order. A do-it-yourself-er,
well, maybe, maybe not.

Well, I'll learn something, whichever way it goes. Thanks for the advice.

Alisdair

 

[JURB6006]

Answer Mr. Yanik's questions <u>and</u>:

Does it dual trace ? whether you can move the beams up and down or not.

Can you / did you swap the V and H plugins. If you do and get a vertical trace
instead of a horizontal one, you have 99.999999999999% cleared the mainframe.

If you have two V plugin spaces, make sure that nobody changed those settings
on the mainframe, this fooled me for a short time last month on the 7613 at
work. I thought I had a bad plugin, because I simply hadn't looked.

Anyway, if it turns out you need the Vplugin, there's always ebay, and we got a
place in Cleveland that deals in a bunch of old Tektronix stuff. It is not that
far, but it would be nice to have an idea of the specs. and what it is worth
working before getting serious.

JURB

 

[Jim Yanik]

dferree923@aol.com (DFerree923) wrote in
news:20030913140507.08239.00001143@mb-m14.aol.com:

Hi all,
I'm in need of some assistance with an older Tek 5403. I have the
manual for
the 5403 system, and have performed all of the calibration adjustments
on the PS board, and have adjusted the CRT. Everything is fine so far
(CRT is not a "sharp" as I think it should be, but still easily
readable).

The problem is that I cannot get this thing to work correctly. I
think the
problem may lie in one of the plug-ins. It has 5A48, and 5B42.
However, I have no way of testing/adjusting them (no manuals). The
5A48 "seems" to work, in that adjusting it changes the display (ch1,
ch2, etc..), but no vertical changes in the beam. My uncle said it
sounds like it may not be triggering correctly, but that was all he
could "guess" over the phone from Boston.

I figure I'd better let someone look at it. I got the scope for $20,
and
spent more than that for the manual. So far I've got $45 invested in
this scope, do you think it would be worth it to take it somewhere for
tests/repairs, since this is an older unit? If so, anyone know of a
good place around Indianapolis?

Many TIA,
Del

Well,you could invest in another vertical plug-in,or you could buy the
manual for the 5A48.
You weren't clear about your problem;are you not getting any vertical
deflection(Flat trace,moveable with position control),or not getting
vertical positioning (Signal displayed,proper gain/div,no positioning)?
Or both?

--
Jim Yanik,NRA member
jyanik@kua.net

 

[Jenny&Mike]

All this fuss, is this not a news group, where we can share news ? I am a
profressional in the communications industry and specialize in 3G mobiles
phones. I have tinkered with electronics all my life, so I came across a
transistor that has a few more tricks to it but it is the vertical section
where all the bits are blown, two caps and 2 transistors so go figure. lets
all help each other with all our experiances, then we all learn
Mike

"john" &lt;va3mmTAKEOUTTHIS@niagara.com&gt; wrote in message
news:newscache$rnw5lh$337$1@newsfeed.niagara.com...

So, you need to be an ASSHOLE about it ??

You're a REAL professional John, aren't you ?


ERIC



Now be nice Eric..