Toshiba TV29C90 problem; Image fades to black...

[RonKZ650]

I don't know if it's common or not, but I had one once with an intermittent
diode CR4106 near the regulator that would cause the regulated 130v supply to
drop to around 80v which is too low to start. Also had an open CR4109 causing
loss of the 5 and 12v supplys. Otherwise just the regular solder around the
flyback and driver transformer. Also if CR4704 off pin 8 of the flyback opens
up, the 130v regulated B+ will be too high, but this causes immediate shut
down, which isn't exactly your case.
Good luck.

 

[Peter Lord]

I had a similar problem on a NV HD680B - fault was two teeth stripped on the
loading arm gear only visible when the mech was out. The 680b is fitted with
a Z-Mech which I am currently attempting to buy a manual for. VCR gave
fault code F06 in my case.

I have a copy of the NV-HD650 schematic if you would like one.

Regards

Peter

"IanG" <iangilbert1@hotmail.com> wrote in message
news:b1a249af.0409231013.5d4c26e@posting.google.com...

I've just replaced a split loading motor drive bush on my Panasonic
NV-HD650 VCR (with K-mechanism). As far as I can see, there should be
no need to readjust the mechanism as I didn't disturb anything apart
from the motor, but on reassembly, there was a brief whirr of the
motor, then nothing. No fault codes and a when a video is pushed into
the slot, there is no attempt to pick it up.

I have decoded, I think, the phase diagram on the underside of the
case, and see that this refers to a tape in the loaded condition. My
problem is that I can hand wind the mechanism to the point where the
tape is in the lower position, but then it stops. At this point, the
metal pinion has reached the end of the rack and looks like it should
stop revolving when the main cam continues to turn. All looks OK so
far, but I cannot get the main cam to turn further and move the tape
loading arms. It looks like, if I could get it to wind a bit further,
that all the marks would be in alignment, so I am reluctant to start
dismantling further.

Does anyone know what might be stopping the mech at this point?

Thanks for any help

 

[NSM]

"Marc" <dbacks@attglobal.net> wrote in message
news:20e8027b.0410051259.68a478f3@posting.google.com...
| Sorry guys,
|
| about ten minutes after I posted, (see below) I located a photo of a
| similar new flyback transformer, and it appears that the "L" shaped
| metal rod previously mentioned was originally a sort of "U" shaped
| rod, (top to bottom) and that it is burnt into two separate pieces.
|
| I did not know that, and the flyback transformer is still soldered to
| the board, so it is a bit difficult to see.
|
| Now, here is my question: Is this burnt flyback transformer possibly
| or probably symptomatic of a larger problem?

It's usually the reason for failure. Replacing it is the first (and maybe
last) step to repairing the set.

N

 

[kony]

On 5 Oct 2004 13:02:34 -0700, larrymoencurly@my-deja.com
(larrymoencurly) wrote:

kony <spam@spam.com> wrote in message news:<mpq1m09c6eik4pdvj1e9773kcgdubtcq5k@4ax.com>...

Lights, LEDs, cable sheaths, etc, have little to nothing to
do with PSU quality, as a "power supply" rather than a case
ornament...

When dealing with unknown PSU, seek an online review.
Unknown generics made by same company, may wear quite a few
labels. Upon seeing the inside one can often note the
origin or at least assess certain components even from very
poor pictures, like size of transformer, inductors,
capacitors, and perhaps brand of fan. Ironically enough,
often the brand of fan is telling by itself, crap PSU almost
never use major fan manufacturer's products. One exception
there is that Sparkle used to use crap Yate Loon sleeve
bearing fans on their mid-grade OEM,

Do you know of any good PSU review sites, other than Tom's and
SilentPCReview? Almost everybody else's "full load" tests consists of
just connecting the PSU to a computer and running a game, but that
rarely applies more than 250-300W.

Unfortunately, no, the reviews I've seen do same, barely
loading a power supply then giving it 2 thumbs up! Most of
the reviews I've seen were not too good, mainly I prefer
those with hi-res pictures so we can see if there's been any
iimprovement or if they're still just slapping higher
wattage labels on same units.

While I don't claim the reviews are any good, there is a
large list here,
http://www.amdboard.com/psu.html

 

[Forza Azzurri]

I have the same problem only if I turn it on and off a few times
eventually it stays on. Any news on this from anybody.

Greatly appreciated

Jason wrote:

I have a 27" Sony KV-27S22. When I turn it on I get sound, but no
picture at all. The little red led beside the stanby/timer blinks
continuously. I really hate to throw this tv out, as it has a great
picture. Any suggestions as to what to check?

Thanks
Jason

--
'''
(0 0)
+----oOO----(_)----------+
| Preserving Azzurri |
| Calcio History |
| http://forzaazzurri.com|
+-----------------oOO----+
|__|__|
|| ||
ooO Ooo

 

[Jim Adney]

On Sun, 03 Oct 2004 14:24:03 -0500 John Fields
<jfields@austininstruments.com> wrote:

Separate windings as on two separate bobbins, each with the same width
and starting diameter and occupying a separate portion of the core.

Sure, you can do that, but you're changing the rules in the middle of
the game: You're giving yourself a larger winding window to work with.
(otherwise you would have slightly less than half as much length to
work with, so each winding would build up faster and taller. The extra
bobbin takes up some of your previous volume, so you come out behind.

Otherwise, separate bobbins is certainly a desirable thing to do, but
you have to allow extra space for it up front.

I could also suggest that I would just start with a longer core so
that I would need fewer layers, and that would save even more wire....

Folks who make transformers for a living know all that, and they
routinely hipot to 5kV winding-to-winding and winding-to-core, and
make stuff that can run at ungodly high temperatures, so I don't think
it's a big deal if it's planned for.

That's a MUCH easier problem than 300-500 AC volts between adjacent
turns.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[Jason D.]

On Tue, 5 Oct 2004 05:54:44 -0500, "Mark D. Zacharias"
<mzacharias@yis.us> wrote:

If it feeds the vertical circuit you could try a 1 ohm or a 2.2 ohm. The
rectifier needs to be a high-speed type.

Mark Z.

Yes, this mainly feeds power to vertical also one bit of other
circuit.

You have burned out vertical IC. Change LA7832, 100uF 35V capacitor
with one with 105C spec near that vertical IC, RGP10J diode and this
1.8 ohm resistor. The main reason for this blow up is that capacitor
dry up then vertical IC self-destructs.

The contact between heatsink and vertical IC needs a thin layer of
heatsink grease.

Cheers,

Wizard

"Philip Belleau" <philip.belleau@sympatico.ca> wrote in message
news:9ln8d.7059$HO1.370896@news20.bellglobal.com...
Hi,

Just like the subject says, does anyone either have a schematic or know
the
value of R541 (in series with D541, also blown but identifyable) for a JVC
27" TV model AV-27920?

Everything else seems in order.

Any help is appreciated and thanks in advance to those who reply.

Best Regards,

Philip

 

[James Sweet]

"larrymoencurly" <larrymoencurly@my-deja.com> wrote in message
news:755e968a.0410041257.1581ba4c@posting.google.com...

"James Sweet" <jamessweet@hotmail.com> wrote in message
news:<lu58d.2427$r3.597@trnddc05>...

Stuff just fails occasionally with no good explaination, could be
it was just a defective part that eventually quit.

I am eternally grateful for your answer, which not only completely
solved my problem with the USB port but will also magically turn the
rest of my life into bliss. So please give me your address so that I
can send you a $500 check, no, make that a blank check -- your advice
was that good.

Just what sort of answer did you expect? I seem to have misplaced my crystal
ball and I can't find my spell book either. How is anyone supposed to tell
you why a chip failed? It just happens.

 

[Mark D. Zacharias]

I'm going to digest this for a bit and will post back later.

Meanwhile, if you're posting through Google, they only add posts once or
twice a day.


Mark Z.


"ampapa" <vbtalent@yahoo.com> wrote in message
news:abe50b2b.0410051607.35bd9e50@posting.google.com...

Mark,

I spoke with my friend this afternonn and this was a refurb from the
factory his sister used to work for a Sony call center, but until
recently the receiver was working fine. He was having a on/off issue,
no lightning strike.

I mistyped earlier the 2 IC's that looked like they were replaced are
IC1205 and IC1501 as well as D1207 and D1206. I tested the diodes with
my DMM it has a diode test and they appear to be O.K. (tested one
direction then flipped leads). I'm not sure how to test the IC's?

I took some readings on the 2 IC's (IC1025 and IC1501) and was getting
.25v on leg 1 on both and 0v on the other legs. I also checked IC1206
and here is how it layed out, definitely out of wack...

8 - 1.6v
7 - 1.25v
6 - 6.76v
5 - 0
4 - .35
3 - 1.83
2 - 2.37
1 - 13.53

I wasn't sure what to test on IC1201 did you want me to look at the
reset pin 90 for 5v?

My biggest understanding issue is how do I determine the flow on the
schematic?

"This repair is going nowhere fast. It would be nice to have another
digital
board to sub."

My posts take forever to show up on the forum is there a way to speed
it up??? As far as another board I don't think I can find one? do you
know anyone selling them, cost, etc.


AJM,


"Mark D. Zacharias" <mzacharias@yis.us> wrote in message
news:<2sfdbjF1kqstmU1@uni-berlin.de>...
P.S.

If there's any history on this that I should know, now is definitely the
time to say. For example if there was a lightning strike involved.


Mark Z.




"Mark D. Zacharias" <mzacharias@yis.us> wrote in message
news:2se8frF1k5a04U1@uni-berlin.de...
I'd say that's close enough. You're going to have to see that the "5V"
line makes it to the microprocessor, and at this point you're going to
have to evaluate the reset line to the micro. Should toggle from ground
to
5V when you plug in the cord.

Mark Z.


"ampapa" <vbtalent@yahoo.com> wrote in message
news:abe50b2b.0410041424.bca6d5a@posting.google.com...
I've got 3 readings at the transistor Q1205, the center leg 13.53 and
the 2 other legs 6.79 and 6.21 respectively. I think this is wrong,
the schematic shows the "base" at 6.5v?



"Mark D. Zacharias" <mzacharias@yis.us> wrote in message
news:<2sbtf3F1irf6dU1@uni-berlin.de>...
Well, you need to check the standby voltages on the digital board.
Q1205
appears to be a 5 volt source.

Mark Z.


"ampapa" <vbtalent@yahoo.com> wrote in message
news:abe50b2b.0410031812.5ed4e95@posting.google.com...
The "standby transformer" is that T902 on the schematic?

I've got 13.5V on the header that leads to the "Digital" board.



"Mark D. Zacharias" <mzacharias@yis.us> wrote in message
news:<2sb6ulF1j87gbU1@uni-berlin.de>...
Measure from point 12V with respect to ground. I suspect your
standby
transformer is bad.

Mark Z.


"ampapa" <vbtalent@yahoo.com> wrote in message
news:abe50b2b.0410030317.608bb45f@posting.google.com...
No click when I push the power button and I do have my voltmeter
set
to A/C.

By looking at the schematic am I correct that the transformer
should
be seeing appx. 110v? or should I be looking for some other
voltage
being delivered to the transformer?

Also, in order for the A/C board to "enable" the turn-on relay
by
the
on/off switch then I should be seeing voltage coming back from
the
"Digital" board correct? I see the header that leads to the
"Digital"
board has 4 legs, GND, 12V, P_OFF and P.RY. Are these
designations
specific to the industry as to what they represent?


Thanks for the help,



"Mark D. Zacharias" <mzacharias@yis.us> wrote in message
news:<2s8l2qF1hj1gcU1@uni-berlin.de>...
If all the fuses are OK, then the power transformer probably
isn't
getting
voltage from the turn-on relay. Does it click when you press
the
Power
button? CNV902 gets no AC voltage to speak of til this relay
fires. (I
assume your voltmeter is set to measure AC voltage)

Mark Z.


"ampapa" <vbtalent@yahoo.com> wrote in message
news:abe50b2b.0410021015.2ce33916@posting.google.com...
Sorry if this is a double post.

Mark, are you saying there might be a fuse literaly
underneath a
circuit board and not necessarily hidden from view by a
circuit
board?
I checked about 5 or 6 fuses in this thing and all checked
fine.

My biggest problem is that when I read the schematic I can't
tell if
the transformer is supposed to be getting 110v from the A/C
board on
CNV902? If it is then I can trace it from there. That's my
real
dilema.

The schematic can be found here
(http://www.eserviceinfo.com/index.php?what=search2).

Thanks,


"Mark D. Zacharias" <mzacharias@yis.us> wrote in message
news:<2s7f2tF1ffucfU1@uni-berlin.de>...
These models often have fuses sort of hidden under a circuit
board
attached
to the transformer. If these fuses are blown you probably
have
a
blown
amp
channel. Sometimes just the output transistors for a given
channel
are
bad,
sometimes there are other small parts bad. Occasionally a
circuit
mod
is
required to lessen the bias at startup.

Mark Z.


"ampapa" <vbtalent@yahoo.com> wrote in message
news:abe50b2b.0410011801.4819cdbc@posting.google.com...
First off I'd like to say, "Hello." to the group. I hope I
can
gain
some knowledge from the group's collective input.

I have a Sony STR-DE635 stereo receiver that will not turn
on
and
I
would like to investigate into maybe seeing if I can
repair
it. I
found a set of schematics on this site which I believe
will
definitely
help.(http://www.eserviceinfo.com/index.php?what=search2)

I'm guessing but I think that the problem is related to
the
power
supply? On p.13 of this .PDF manual it has an A/C and D/C
schematic,
this receiver has a seperate board for each. I probed the
A/C
board
and found that it has voltage out to the "Digital" board
of a
little
over 12 volts but when I try to test the pins on CNV902 I
thought
I
should be getting appx. 110 A/C but only get appx. 2?
CNV902
is a
simple 2 wire connector leading directly to a transformer.

My common sense is telling me that why would I need a
transformaer
the size of Kansas for only 2 volts A/C? So, I'm guessing
this
might
have something to do with it? I could be in left field due
to
my
lack
of knowledge and inexperience, that's why I'm hoping you
guy's/girl's
can shed some light.

Thanks for any suggestions or hints you can provide.

 

[keith]

On Tue, 05 Oct 2004 03:47:13 +0000, NSM wrote:

"keith" <krw@att.bizzzz> wrote in message
newsan.2004.10.05.01.56.40.575135@att.bizzzz...

| So do engineers when they're bringing up a system where all
| of the tantallums were inserted backwards. You want to see fireworks!
| (well,it was 25 years ago - I've mostly recovered and the tinninus
| isn't so bad. <twitch&gt

I recall being told of a large TTL circuit board which was powered up with
reverse polarity. This was noticed due to the considerable amount of heat
being given off.

Everyone was mystified when the correctly rewired board worked OK. I guess
TTL is a little more tolerant than is generally believed.

TTL protection diodes are as strong as moose! Unless the chips got hot
enough to let the magic smoke out, they'll likely survive, though perhaps
somewhat injured.

--
Keith

 

[David Maynard]

keith wrote:

On Mon, 04 Oct 2004 22:33:31 -0500, David Maynard wrote:


keith wrote:


On Mon, 04 Oct 2004 03:21:58 +0000, daytripper wrote:



On Mon, 04 Oct 2004 01:50:54 GMT, "NSM" <nowrite@to.me> wrote:



"larrymoencurly" <larrymoencurly@my-deja.com> wrote in message
news:755e968a.0410031718.36d14f87@posting.google.com...
...
| National Semiconductor says that each USB port must have a 120uF or
| larger ....................................... But my USB card has
| only a 100uF aluminum capacitor and maybe a ceramic capacitor in
| parallel for this....

Close enough!

Except the tantalum cap would have much lower esl & esr figures than an
aluminum cap, making it more effective.

otoh, tantalums can have a brilliant failure mode ;-)


So do engineers when they're bringing up a system where all
of the tantallums were inserted backwards. You want to see fireworks!
(well,it was 25 years ago - I've mostly recovered and the tinninus
isn't so bad. <twitch&gt


LOL. Yeah, I'll bet.

You get a similar result plugging non keyed circuit boards into a vertical
card rack 180 degrees reversed.


A good reason to hang the mechanical designers by the short things. One
*should* have to go to great lengths to pluch dangerous things in
backwards. In this case they did just that. ...and even complained about
how hard it was!

Hehe. Well, with the one I mentioned it was an experimental prototype built
by the design engineer.

 

[NSM]

"Grace" <graceycheng@gmail.com> wrote in message
news:25c16729.0410052012.139f393@posting.google.com...
| I see... well thanks for all the information. i just didn't want to
| spend money on a new discman and it seemed like it would be a fun
| project to do.
|
| Thanks anyway. I opened it up again and it doesn't look like there
| were any corrosion but i'll give cleaning it a try anyway.
|
| I suppose any less expensive electronics wouldn't be worth getting
| fixed. I have an old T1-85 that's not working either. Oh well.

On some of those old TI's the buttons stopped working after a while and I've
never found a way to fix that.

N

 

[Rich.Andrews]

"NSM" <nowrite@to.me> wrote in news:sgI8d.14605$MV5.538@clgrps13:

"larrymoencurly" <larrymoencurly@my-deja.com> wrote in message
news:755e968a.0410041257.1581ba4c@posting.google.com...
| "James Sweet" <jamessweet@hotmail.com> wrote in message
news:<lu58d.2427$r3.597@trnddc05>...
|
| > Stuff just fails occasionally with no good explaination, could be
| > it was just a defective part that eventually quit.
|
| I am eternally grateful for your answer, which not only completely
| solved my problem with the USB port but will also magically turn the
| rest of my life into bliss. So please give me your address so that I
| can send you a $500 check, no, make that a blank check -- your advice
| was that good.

Assuming you are being sarcastic (it's not clear), I refer to this as a
CatRan question, i.e., "I was typing away on my computer and I was
holding the keyboard above my head and I was watching the screen through
my toes when all of a sudden the cat ran over my stomach and I noticed
the screen blinked twice. What causes that"?

N

Reminds me of the time an aquaintance went to lunch with me and a few of
the other engineers. He was in a rather "know it all" mood. I started
plying him with questions about how water softeners work, what causes
gravity, etc. He was doing good until I asked him, "Ever wake up on a
wednesday and think it was tuesday all day and then wake up the next day
and everything is ok again? What is that called?" He shut up after that.

r

--
Nothing beats the bandwidth of a station wagon filled with DLT tapes.

 

[CJT]

Rakesh wrote:

Hello All,

Whats the difference between an Oscilloscope and Logic Analyzer

Thanks
Rakesh

you go first

--
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.

 

[Rich.Andrews]

rakeshsv@gmail.com (Rakesh) wrote in
news:270b72.0410052048.51a38c0a@posting.google.com:

Hello All,

Whats the difference between an Oscilloscope and Logic Analyzer

Thanks
Rakesh

One is a graph of voltage vs time
The other is a graph of state vs time

r


--
Nothing beats the bandwidth of a station wagon filled with DLT tapes.

 

[Ned Konz]

CJT wrote:

Whats the difference between an Oscilloscope and Logic Analyzer

Nothing, for me. I have an Agilent 54621D "mixed signal oscilloscope" that
does both very well.

 

[Lionel]

Kibo informs me that keith <krw@att.bizzzz> stated that:

On Tue, 05 Oct 2004 03:47:13 +0000, NSM wrote:
"keith" <krw@att.bizzzz> wrote in message
newsan.2004.10.05.01.56.40.575135@att.bizzzz...

| So do engineers when they're bringing up a system where all
| of the tantallums were inserted backwards. You want to see fireworks!
| (well,it was 25 years ago - I've mostly recovered and the tinninus
| isn't so bad. <twitch&gt

<grin> They don't smell too good either.

I recall being told of a large TTL circuit board which was powered up with
reverse polarity. This was noticed due to the considerable amount of heat
being given off.

Everyone was mystified when the correctly rewired board worked OK. I guess
TTL is a little more tolerant than is generally believed.

TTL protection diodes are as strong as moose!

Well, the individual diodes aren't all that strong, but there's one on
every single I/O pin on every chip, so on a big PCB, the load will be
spread over a *lot* of diodes.

Unless the chips got hot
enough to let the magic smoke out, they'll likely survive, though perhaps
somewhat injured.

Yup. The best I've personally seen was the time I accidentally plugged a
2716 EPROM backwards into a programmer. It lit up like a xmas tree
through the UV window, but worked fine when I turned it around the right
way.

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

 

[Paul Helpfull]

if i max up the tv contrast and really lift the tv brightness then it isnt too bad

i'm guessing it has to be somethign on the vga side of the ps2



On Sat, 02 Oct 2004 07:57:32 GMT, Paul Helpfull <paul@helpfiull.com> wrote:

>any other ideas?

 

[Grumble]

Rich.Andrews wrote:

Reminds me of the time an aquaintance went to lunch with me and a
few of the other engineers. He was in a rather "know it all"
mood. I started plying him with questions about how water
softeners work, what causes gravity, etc. He was doing good
until I asked him, "Ever wake up on a wednesday and think it was
tuesday all day and then wake up the next day and everything is
ok again? What is that called?" He shut up after that.

Groundhog day?

 

[John Del]

Subject: GE TV model 27GT616, Ch. CTC 185AB3 intermittent
From: captainvideo462002@yahoo.com (Lenny)
Date: 10/5/04 1:55 AM

Does anyone know if there is any

history of these power symptoms associated with this chassis? Thanks,

Leaky smd caps in the micro reset circuit, causes low reset and micro lock up.
I've had a bunch do that.

John