Toshiba TV29C90 problem; Image fades to black...

[Jason D.]

On Fri, 28 Oct 2005 05:36:11 GMT, "William R. Walsh"
<newgroups1@nojunquemail.walshcomptech.com> wrote:

Hi!

Got one here that is a stumper:

Okay, forgive me if you've done this and if it sounds obvious:

Did you check the offending relay? Perhaps it has burned contacts or is
otherwise not functional.

William

If you're famillar with this ITC008, this relay is used for degaussing

only. This relay clacking is syptom of a problem.

Cheers, Wizard

 

[Asimov]

"Jason D." bravely wrote to "All" (28 Oct 05 02:12:02)
--- on the heady topic of "DOG: Intermittent Click click, clickclick! RCA
ITC008 (27F650TYX1)"

You didn't mention the audio output anywhere...
I have read of this behaviour in RCA's caused by the audio output.
If the relay is good then it's a shot in the dark...

A*s*i*m*o*v


JD> From: jpero@sympatico.ca (Jason D.)
JD> Xref: core-easynews sci.electronics.repair:346535

JD> Got one here that is a stumper:

JD> RCA 27F650TYX1, no pic or sometimes pic but goes out when relay
JD> intermittently clicks and heater dims and brightens, sometimes dims
JD> out and back on every time relay clicks. Let TV batter the relay with
JD> time, now no picture. Relay clicking is very erratic in pattern.

JD> Did voltages checks: 5V stable for the micro/jungle, 7V good, 22V
JD> good and never above specs, 126V never above but when it unloads
JD> becaue of horizontal drive cutting out voltage drops to appox 106V
JD> then relay clicks voltage comes back up and horizontal cuts in at all
JD> once.

JD> Did troubleshooting tips:

JD> Pulled crt board & vertical plug. Click click click still unaffected.
JD> Pulled BL001 plug to disable pincushion. Still clicking.
JD> Checked EHT (aka X-ray protect), never above 2.3V.
JD> Checked beam sense, within specs.
JD> Checked vertical & horizontal waveforms, all GOOD.
JD> Scoped the cathodes for emissions, kine bia sensing come up and get
JD> into operation when heaters is hot enough.
JD> Checked SMPS with scope, good there too.

JD> Flexed & smacked the chassis with no effect on that fault.

JD> Oh YES, did cut off both plugs and solder both ends of pincushion 3
JD> wires (two brown and one blue wires, wire order in correct positions),
JD> have done this modifications 20 times before with success.

JD> Sigh! Looks like either big IC (IV001?) is the blame or data bus
JD> "dirty". Seen this before?

JD> Cheers, Wizard

.... If all else fails, hurl it across the room a few times!

 

[carneyke]

I seem to remember the shaper being a high failure item. Either you get
one from Agilent (few hundred dollars, if available) or get a scrap
unit and hope it works.

 

[mark]

Change the A.C. filter capacitor that should cure usually in the 10's of
microfarids at 150V
"tempus fugit" <toccata@no.spam.ciaccess.com> wrote in message
news:630da$43622d80$d1d89eb3$21068@PRIMUS.CA...

Thanks for the suggestions guys. I'll try some of these things out.


"Asimov" <Asimov@-removethis-bbs.juxtaposition.dynip.com> wrote in message
news:MSGID_1=3a167=2f133.0_43612958@fidonet.org...
"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf> From: "tempus fugit" <toccata@no.spam.ciaccess.com
tf> Xref: core-easynews sci.electronics.repair:346437

tf> Hey all;

tf> I'm trying to repair an old tube portable record player. When it is
tf> on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and then
paint a mark for which was the quietest way. One way: lots of hum, the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline (or
sometimes a voltage doubler) and used a large value resistor bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub. Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

... Just a little force field zap.

 

[Mike Berger]

That sounds more like a selenium rectifier -- if it were bad
you'd smell it!

tempus fugit wrote:

There was also some small device which I assume was a transformer that hadd
100mA marked on it. It looked like a trasformer with cooling fins.

 

[Mike Berger]

Not anymore. You can't recover usable components from modern
electronics so there are no kids scrounging it.

The values of components used in tube circuits are usually
drastically different from what's commonly used in modern
digital circuits and won't have much appeal.

gb wrote:

In any event do NOT chuck to the garbage. Find a bright young mind (high
school) that is interested in electronics -- and needs his first "junk box
of components -- there is at least one in every neighborhood

 

[Leonard Caillouet]

I keep seeing this recommendation for changing the VDRs. While there may be
some value in changing them due to damage in the metal oxide from repeated
conduction events, when the HOT fails and takes out the power supply, the
VDRs are not likely to be a problem. VDRs are protection or dumping
devices. If they check open with a DMM they are not likely to be a problem
in the PS. They can be tested for clamping voltage, though if they are
failing, they fail by leaking rather than not clamping at near the rated
voltage. A handy way to test them is with the h-pulse drive on a sencore
tester and a scope.

It is more important to use the correct parts, ie higher rank 2sc4834 and to
verify the duty cycle of these. I use P rank versions, that we get very
inexpensively from ACME Enterprises in Orlando and match them. Virtually
all units that fail this way are fixed completely with just the HOT,
Q601,Q602, R607, and resoldering the components in the base circuit.

When the PS fails on its own or due to surge damage, it is important to
check all of the components in the primary, particularly the poly caps. Of
course, the VDRs are suspect in these cases. When the PS fails due to
loading such as a shorted HOT it is rare to see problems other than the
parts listd above.

Also, the 2SC4927 can be replaced with several other transistors that will
run cooler and may be more reliable. We have had success with the 2SD1881
but others will work as well.

Leonard

"Skype_man" <skype_man@lycos.co.uk> wrote in message
news:brednbR1H96j4fzenZ2dnUVZ_tKdnZ2d@rogers.com...

Typical failure: 2SC4927 shorted horizontal output, bad
connections @ the horizontal drive transformer, shorted
Q601, & 602 2SC4834 PWM switching regulators, open
.1 ohm fusible resistor R607, VDR 601 bad 1-807-288-11,
& "possibly" bad VDR 602, & 603, but these are usually ok.

Use Sony SP-Kit, & VDR 601. # 1-807-288-11, Sky.

 

[CJT]

mark wrote:

Change the A.C. filter capacitor that should cure usually in the 10's of
microfarids at 150V

If the voltage on it measures 150V, then a 250V cap might be a better
choice for a replacement.

"tempus fugit" <toccata@no.spam.ciaccess.com> wrote in message
news:630da$43622d80$d1d89eb3$21068@PRIMUS.CA...

Thanks for the suggestions guys. I'll try some of these things out.


"Asimov" <Asimov@-removethis-bbs.juxtaposition.dynip.com> wrote in message
news:MSGID_1=3a167=2f133.0_43612958@fidonet.org...
"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf> From: "tempus fugit" <toccata@no.spam.ciaccess.com
tf> Xref: core-easynews sci.electronics.repair:346437

tf> Hey all;

tf> I'm trying to repair an old tube portable record player. When it is
tf> on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and then
paint a mark for which was the quietest way. One way: lots of hum, the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline (or
sometimes a voltage doubler) and used a large value resistor bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub. Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

... Just a little force field zap.

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form che...@prodigy.net.

 

[James Sweet]

Mike Berger wrote:

Not anymore. You can't recover usable components from modern
electronics so there are no kids scrounging it.

Sure you can, I'm not a kid anymore but I still scrounge plenty of
usable components. The most useful stuff usually lies in power supplies
and CRT displays, lots of nice juicy power semiconductors and inductors,
lots of capacitors, diodes, fuse holders, connectors, etc. Digital
devices often have eeproms, various logic devices, LEDs, all sorts of
stuff. If anything there's more cool stuff to salvage than there was 20
years ago.

 

[GerryO]

Jumpster Jiver Wrote:

GerryO wrote:

Hi,

Picture and sound work great on our Sony Trinitron KV-27TW70, as long
as we use a vcr tuner routed through the rear of the set a/v inputs.
On occasion the tuner works properly, and when it doesn't there's
anywhere from a slightly shrunken picture to a white flat line in the
center.

Believe the tuner has been repaired/replaced once, after possible
damage by a power surge.

Any tuner repair suggestions? Re-solder some specific connections?

Thanks, Gerry


Sounds like two totally different problems.
A defective tuner can give you a snowy picture, total snow, or a blank
or blue screen.
A shrunken picture or flat line are caused by a problem with the
vertical deflection circuit.
If both problems seem to come and go at the same time or seem to
affect
each other then I would suspect a problem with a voltage that supplies
both the tuner and vertical section, or loose solder joints in the
related circuits.

So if power to both the tuner and the vertical section is occasionally
interrupted ONLY when the set's tuner is being used (as there's never a
picture or sound problem when using a vcr tuner that's connected to the
set's rear a/v inputs), does selecting VIDEO turn OFF power to the
set's tuner, which could have a short or loose connection?

Thanks, Gerry


--
GerryO

 

[Ken G.]

It would be far easier to get a cammera that uses AA batterys . I have
seen a few that take 2 AA and some that take 4 AA then get one or 2 of
those solar yard lights that take ordinary AA batterys and remove the
cells & battery holder & mount them in someting small and light and keep
some batterys charging in daylight

 

[Ken G.]

Not at the cost of new players .

 

[Alt Beer]

"bstanton@null.com" <B Stanton> wrote in message
news:lb62m1t57qasrqdrer78qisaq1hs1e02cr@4ax.com...

I've inherited my grandfather's shop, and there are boxes of
old components, from transistors in metal cans to rolls of
cotton insulated wire and capacitors that look like wax
sealed rolls of paper and foil. Little to none of it is
actually "new," it's mostly removed from older equipment.
There are also rectifiers that look like multiple square
pieces of metal separated by some rectifying material.

Is any of this worth anything? I'd like to junk anything
without value, but not if it's useful. Do people repair
older equipment with this stuff for "authenticity?" Not
many tubes in the collection. Comments are welcome.

Probably like gold dust to repairers and old radio
enthusiasts who like to keep equipment authentic at all cost.

 

[James Sweet]

Charon wrote:

I have an older crt projection big screen and I now have retrace lines
that appeared after turnning the set on a few times and hearing a arc
immediatly when turnning on. I waited too long to fix the arc and it
has affected something else.

The arcing was comming from the Red CRT from under the node and arcing
to the chassis, I have since fixed this but have been unable to track
down what is causing the retrace lines. The B+ voltage appears correct
but I do not have an oscilloscope to test ripple in any of the parts.
Any one know what the arcing may have effected ? The blanking circut or
perhaps from the flyback backwards ?

Are the retrace lines on all three CRTs?

 

[Shoreline Electronics]

This is a common scenario.

Careful! The main filter caps bite hard on these!

---------------------------------------------------------------
Text pasted from WinSTIPS 2.0
http://www.ServiceSoftware.com
---------------------------------------------------------------

HITACHI 50UX26B

Shuts Down Randomly. May Take 2 Hours Or 2 Minutes.

Jeff Stielau : 2/19/03 : Shoreline Electronics

After Pulling The Chassis &amp; Resolder All Heatsinked Parts &amp; Connectors (
None Looked Suspicious To Begin With) Problem Still Existed.
Replacing The Strm6511 (Ici1901) Fixed The Set. Change The 2 Small
Electrolytics Next To It For Good Measure.

---------------------------------------------------------------



--
==========================
Jeff Stielau
Shoreline Electronics Repair
344 East Main Street
Clinton,CT 06413
860-399-1861
860-664-3535 (fax)
jstielau@snet.net
========================

"oldskoolplaya806" &lt;oldskoolplaya806.23kror@diybanter.com&gt; wrote in message
newsldskoolplaya806.23kror@diybanter.com...

I too have the same model television. It seems this is the most common
problem for these units. On mine however, you can hear the tv click
when you press the power button. I have removed the back and the fuse
is still good. In fact the red indicator light (on the circuit board
inside tv) comes on when you turn the tv on. Neither the outside
indicator light or the screen however come on. Its as if the tv is
turning partially on, but not all the way. Any advice would be helpful.
I just dont see the reason to take it to a repair shop. I'd rather see
if I can get it fixed myself. And if anyone has the service manual for
it... I would appreciate that too. Thanks

Matt Walker (oldskoolplaya806@hotmail.com),
Lubbock TX


Bob Shuman Wrote:
Angela,

I have the same model manufactured at approximately the same time
frame. We
have not experienced the problem you describe, but I did have the main
power
on/off relay go bad so it had to be replaced. I only mention this
since it
was a pretty easy fix and if you can't find any cold solder joints on
the
main
power board you may want to check the resistance of the relay contacts
themselves (mine would stick closed after the set was turned off, but
I
could
imagine that they could just as easily become resistive and have the
potential to
fail in the manner you describe as well).

After dismissing cold solder and checking the other components Leonard
cited, I'd look at the relay. Hope you can get this fixed. We still
love
our set. If you need a schematic, let me know as I think I have the
service
manual somewhere.

Bob

"Angela D'Andrea" adandrea@austin.rr.com wrote in message
news:73a7a341.0311160728.26a6f322@posting.google.com...-
We have a Hitachi Ultravision Model 50UX26B projection TV that was
made in July 1996. Lately it has been shutting itself off at random
times. Hitting the power button on the remote usually turns it back
on again (you actually need to hit the power button twice; the first
time you hear the TV click and the second time it comes on).

Thanks for you help.

Angela D'Andrea
Austin, Texas-


--
oldskoolplaya806

 

[Arfa Daily]

"bigdaddy" &lt;NOspamMZBEG@notsoblueyonder.co.uk&gt; wrote in message
news:d63nv15pclqae7acmt295m5n84pc3jejoc@4ax.com...

Hi,

I need LiPoly Charger and Discharger Circuit for an armature DIY
enthusiast.

Try the following link

http://www.elektor-electronics.co.uk/Default.aspx?tabid=28&amp;year=2005&amp;month=4&amp;art=52740

Arfa

 

[dkuhajda@locl.net]

Do you realize you are replying to a post that is 2 years old?
I have no doubt the tv was either already patched or pitched by now.

 

[RDC]

dkuhajda@locl.net Wrote:

Do you realize you are replying to a post that is 2 years old?
I have no doubt the tv was either already patched or pitched by now.

Didn't even realize it, lol. Still, it's not to say that the info may
help someone else that searches the forums.


--
RDC

 

[Jerry G.]

Most likely something is pulling too much current, and thus causing the
power supply to go in to protection. Also, if the tube is getting weak,
the protection can turn the set off.

--

Jerry G.


&lt;fynnashba@yahoo.com&gt; wrote in message
news:1141507800.606656.321370@p10g2000cwp.googlegroups.com...

Please good pals,
l'm working on a JVC color Tv Pal system.
The problem is that on powering this set will work for just abt 10 to
15 seconds and will go off then the timer on light will show as if the
timer off has been set. the tube does not light up of course due to the
short duration but a test on the hi voltage (flyback) side shows
everything is working but... What might be the problem? I'm suspecting
the u-com. can that be?
I also gathered the set was left for the kids to watch when this
fault came about.
Any suggestion is welcome Thanks

 

[JR North]

The FF/RW during play is "Cue/Review" and is handled by speeding
up/reversing the spindle drive. FF/RW after stop requires the gearing to
shift on the deck. Since the tape loads and plays ok, Either the
transport gearing/belt or the mode switch is faulty or out of adjustment.
JR

VCR Gymnast wrote:

My Sony SVO-2100 S-VHS VCR (with the SVBK-10 RS232C interface) has an
interesting problem: all functions work except REW and FF. However, if
these buttons are pressed during PLAY, the reverse or forward speed of
the tape playing will increase as it should. The problem is that normal
REW and FF won't work. The machine tries, but the tape transport does
not move, so the VCR quits after 5 seconds or so. I'm not sure if this
has anything to do with the interface or if the machine might have
gotten stuck in some mode where regular REW and FF doesn't work, so any
ideas will be appreciated.

--
--------------------------------------------------------------
Home Page: http://www.seanet.com/~jasonrnorth