Toshiba TV29C90 problem; Image fades to black...

[Arnold stewart]

Inspect the horizontal output transformer. It may have developped a
pinhole and is arcing to something close by. You may also try
resoldering all the transformer pins.

Dave Walker-Sharpe wrote:

Hi,

I have a Hitachi TV and sometimes, in certain weather it seems, the
picture will flicker around the edges briefly, then the screen will go
black, and the TV will drop out to standby. There is a kind of
electrical crackling noise from the back of the set whilst this is
going on. The TV always recovers, and comes back up as normal, but
may well die again 7 or 8 times before stabilising properly.

Does anyone have any ideas how I might fix this?

It was suggested to me that the HV supply transformer may be arcing,
and that a silicone spray was available to remedy the situation but I
haven't been able to track down this product, or really get to grips
with the problem itself.

Many thanks,
Dave

 

[Mike Berger]

The third wire is usually for a tachometer so you can read the fan
speed.

Leo Tick wrote:

On a cpu fan with three wires what is the protocol and
the signal in the sence wire. The question is asked
obviously because the fan does not spin but the fan part is ok
applying 12 v directly does get it to spin. Does the sence
line tell the mobo to turn on the 12v or what . If this is
the case what do I send down the sencs line to see if the
failure is in the MOBO.
Thanks

 

[Stefan Huebner]

I found (2) 1n47 diodes next to the original bad diodes. One of them
is shorted and the other appears open. Our local electronics store
has unfortunately closed down after 50 years of service and I would
rather not have to special order these diodes.

Hi,
as already said: 1N47xx zeners, the last two figures would indicate
the voltage, so you obviously need to find a way to find out the
original voltage. Does one really measure open (also in forward
direction) ? Then the voltage to something would probably have gone
way too high, bad if was the supply to the controller or some othe
chip you cannot buy. I have seen zeners in microwaves going short
quite often, they are run at maximum power dissipation even in stand
by.

 

[Jerry Greenberg]

First of all, if you have an LCD screen, there is no HV as like in a
CRT monitor, and there is no Horiz and vertical scans as such.

The DC voltages are checked with a DVM, and the waveforms (signals)
are checked with an oscilliscope. There are other test and
calibration equipments involved for doing adjustments. For particular
models there is the requirement of specialized test jigs, and etc. The
cost of the proper setup would far exceed purchasing new monitors,
computers, and appliances for life!

To service TV sets and monitors, it is best to have the proper
training and setups of the proper tools and instruments to do the job.

And, in all of these devices there are dangerous voltages. There are
safety conserns and procedures with all types of electronic equipment.

As for you to service your monitor, you will require the exact service
manual, not a similar one, and you will also require the aboved
mentionables. There are many things that are left out in service
manuals, because they assume that an experienced and qualified person
is working on the unit. They will not give the common basics that the
techs get during their traing and the gaining of experience.

I would suggest that for the few dollars, you give your set out for a
proper estimate, and then you would be able to make an intelligent
decision to have it serviced. There are very conserned safety issues
when working on any electrical appliances.

Jerry Greenberg
http://www.zoom-one.com

--


E-Star <unix_core@linuxmail.org> wrote in message news:<210820031246244471%unix_core@linuxmail.org>...

My monitor has no picture

Looking at a service manual for a similar monitor and this is what it
says. The front lcd is green so we know that all of the following are
active: Horizontal Sync, Vertical Sync, Video

It says to proceed by:
Check G2 voltage, high voltage, R, G, B cathode voltage.

I'm kinda hesitant to start because of the high voltage. Can someone
help me out and tell me how to proceed? If necessary I can point you
to the service manual I have.

Thank you

 

[Don ßailey]

"Stefan Huebner" <mail.stefan.huebner@gmx.de> wrote in message
news:3f44eac2.28408156@news.t-online.de...

I found (2) 1n47 diodes next to the original bad diodes. One of them
is shorted and the other appears open. Our local electronics store
has unfortunately closed down after 50 years of service and I would
rather not have to special order these diodes.

Hi,
as already said: 1N47xx zeners, the last two figures would indicate
the voltage, so you obviously need to find a way to find out the
original voltage. Does one really measure open (also in forward
direction) ?

Yes. They are both connected at one end and face in opposite directions
and the other one has shorted.

Then the voltage to something would probably have gone

way too high, bad if was the supply to the controller or some othe
chip you cannot buy.

uuuuughhgh.

db




I have seen zeners in microwaves going short

quite often, they are run at maximum power dissipation even in stand
by.

 

[E-Star]

Thanks, but you were little help.


In article <460a833b.0308211303.2dc5d13a@posting.google.com>, Jerry
Greenberg <jerryg50@hotmail.com> wrote:

First of all, if you have an LCD screen, there is no HV as like in a
CRT monitor, and there is no Horiz and vertical scans as such.

The DC voltages are checked with a DVM, and the waveforms (signals)
are checked with an oscilliscope. There are other test and
calibration equipments involved for doing adjustments. For particular
models there is the requirement of specialized test jigs, and etc. The
cost of the proper setup would far exceed purchasing new monitors,
computers, and appliances for life!

To service TV sets and monitors, it is best to have the proper
training and setups of the proper tools and instruments to do the job.

And, in all of these devices there are dangerous voltages. There are
safety conserns and procedures with all types of electronic equipment.

As for you to service your monitor, you will require the exact service
manual, not a similar one, and you will also require the aboved
mentionables. There are many things that are left out in service
manuals, because they assume that an experienced and qualified person
is working on the unit. They will not give the common basics that the
techs get during their traing and the gaining of experience.

I would suggest that for the few dollars, you give your set out for a
proper estimate, and then you would be able to make an intelligent
decision to have it serviced. There are very conserned safety issues
when working on any electrical appliances.

Jerry Greenberg
http://www.zoom-one.com

--


E-Star <unix_core@linuxmail.org> wrote in message
news:<210820031246244471%unix_core@linuxmail.org>...
My monitor has no picture

Looking at a service manual for a similar monitor and this is what it
says. The front lcd is green so we know that all of the following are
active: Horizontal Sync, Vertical Sync, Video

It says to proceed by:
Check G2 voltage, high voltage, R, G, B cathode voltage.

I'm kinda hesitant to start because of the high voltage. Can someone
help me out and tell me how to proceed? If necessary I can point you
to the service manual I have.

Thank you

 

[Sam Goldwasser]

E-Star <unix_core@linuxmail.org> writes:

Thanks, but you were little help.

What exactly wasn't helpful?

Jerry stated the facts. And it does sound like you don't have the
experience to go inside a CRT monitor safely. There are deadly voltages
inside. Sorry.

You said: "The LCD was green". What LCD? Is this a flat panel monitor
or a CRT monitor? If it's an LCD, there is no high voltage, G2, or
RGB cathodes, but it's also probably not a repair job even for a
pro without the specific documentation and spare parts for that model.

Assuming it's a CRT monitor, you will need a multimeter to measure the
cathode voltages, and a high voltage probe to measure G2 and the high
voltage.

However, if you have green on the screen, the G2 and HV are OK.

You might have a failed green drive circuit, a CRT H-K short in the
green gun, a missing power supply, or something further back in the
video chain.

--- sam | Sci.Electronics.Repair FAQ Home Page: 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 Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: The email address in this message header may no longer work. To
contact me, please use the Feedback Form at repairfaq.org. Thanks.

In article <460a833b.0308211303.2dc5d13a@posting.google.com>, Jerry
Greenberg <jerryg50@hotmail.com> wrote:

First of all, if you have an LCD screen, there is no HV as like in a
CRT monitor, and there is no Horiz and vertical scans as such.

The DC voltages are checked with a DVM, and the waveforms (signals)
are checked with an oscilliscope. There are other test and
calibration equipments involved for doing adjustments. For particular
models there is the requirement of specialized test jigs, and etc. The
cost of the proper setup would far exceed purchasing new monitors,
computers, and appliances for life!

To service TV sets and monitors, it is best to have the proper
training and setups of the proper tools and instruments to do the job.

And, in all of these devices there are dangerous voltages. There are
safety conserns and procedures with all types of electronic equipment.

As for you to service your monitor, you will require the exact service
manual, not a similar one, and you will also require the aboved
mentionables. There are many things that are left out in service
manuals, because they assume that an experienced and qualified person
is working on the unit. They will not give the common basics that the
techs get during their traing and the gaining of experience.

I would suggest that for the few dollars, you give your set out for a
proper estimate, and then you would be able to make an intelligent
decision to have it serviced. There are very conserned safety issues
when working on any electrical appliances.

Jerry Greenberg
http://www.zoom-one.com

--


E-Star <unix_core@linuxmail.org> wrote in message
news:<210820031246244471%unix_core@linuxmail.org>...
My monitor has no picture

Looking at a service manual for a similar monitor and this is what it
says. The front lcd is green so we know that all of the following are
active: Horizontal Sync, Vertical Sync, Video

It says to proceed by:
Check G2 voltage, high voltage, R, G, B cathode voltage.

I'm kinda hesitant to start because of the high voltage. Can someone
help me out and tell me how to proceed? If necessary I can point you
to the service manual I have.

Thank you

 

[David]

There is no vertical hold adjustment at all, even in service menu.
Time to have the failure fixed, which probably will mean calling on an
experienced technician that can properly troubleshoot and repair the
failure.

David

Michael Spencer <msa@naples.net> wrote in message
news:fad01f1.0308211445.f082837@posting.google.com...

Hi,

remember when you could stick an insulated screw driver in the back of
a TV to adjust the vertical hold ?

My Proscan 37 needs this adjustment but I don't have a clue if any of
the openings in the back of the set are what I am looking for, or if I
need to address the service menu with the remote (don't know the
keystrokes, anyway) or what.

It's actually just a vertical roll on a set that is a few years old.
There has to be a simple way to fix this?

Anyone?

Michael Spencer

 

[Mick G]

The value of most of the larger caps is 470mfd with a voltage rating of
6volt
the smaller ones are for coupling and are 47mfd and 22mfd at 12volt (47mfd
should do for all)

"JW" <nospam@dev.nul> wrote in message
news:gt3kjvkhc07u5dhggal53bv80qltn0g9m4@4ax.com...

On Sun, 10 Aug 2003 19:12:14 +1000 Lionel <nop@alt.net> wrote in Message
id: <bh52fk$hfr$2@pita.alt.net>:

Given that it's an electrolytic, it's probably just for power filtering.
You can check by using an ohmmeter to see if '-' goes to ground (eg; the
mounting bracket) & '+' goes to the 5V or 12V power rail.

Or 3.3V and 1.5V on the AGP bus, which would be the case with any GEforce4
card.

 

[Mark D. Zacharias]

The RAM i.c. on these is a known problem: They require resoldering to fix
intermittent / no audio problems. The solder pads at this chip are fragile -
the slightest shearing motion while soldering can damage them.

Mark Z.


"Jiri Kuukasjärvi" <Jiri.kuukasjarvi@XXpp.inet.fi> wrote in message
news:rbd1b.1544$Cf4.667@read3.inet.fi...

Hi!

I have this malfunctioning Onkyo TX-DS575 home theater amplifier.
There´s a problem with the DD processor board (quite large PCB,
connected to the display pcb)

As I connect signal to the amp, audio comes out ok. That´s if the
processor board isn´t connected. If it´s connected, audio volume is very
low even if I turn the master volume to the max. If I use the coaxial
inputs.. No sound at all.

The 3.3V regulator (NEC 29M33) seems to be ok.

I already called the local service that has parts for this model.
New board costs 74eur.

So, any ideas on what might be wrong on the board or elsewhere in the
amp? Do you have schematics for machine?

TIA!

- Jiri K.

 

[DaveC]

On Thu, 21 Aug 2003 14:05:11 -0700, Leo Tick wrote
(in message <dua1b.39$R5.2294@typhoon.nyu.edu&gt:

Thats what I am doing now. My problen IS why doesent the fan turn (now since
at one time it did) when plugged in to the 3-pin. If the signal in the
sence wire tells the MOBO what the speed it is turning at then the MOBO
must be getting some temp info so that it can adjust the voltage to
the fan. But I dont believe my MOBO has that circuitry as chips which do
that are not there. Hence my question and confusion

Fan drive circuit is burnt out.
--
Dave C.
dave-usenet3016@mailblocks.com

 

[Dave D]

"Michael Spencer" <msa@naples.net> wrote in message
news:fad01f1.0308211445.f082837@posting.google.com...

Hi,

remember when you could stick an insulated screw driver in the back of
a TV to adjust the vertical hold ?

My Proscan 37 needs this adjustment but I don't have a clue if any of
the openings in the back of the set are what I am looking for, or if I
need to address the service menu with the remote (don't know the
keystrokes, anyway) or what.

It's actually just a vertical roll on a set that is a few years old.
There has to be a simple way to fix this?

Anyone?

Michael Spencer

Televisions have progressed a long way since old vertical oscillators which
required tweaking every so often. Vertical roll these days is indicative of
a fault, and your set must be repaired. This is a relatively simple repair
usually, and shouldn't cost too much. The culprit is likely ageing caps or
dry joints, any experienced tech should be able to sort it out for you.

Dave

 

[Dave D]

"Sam Goldwasser" <sam@saul.cis.upenn.edu> wrote in message
news:6wn0e2ocdv.fsf@saul.cis.upenn.edu...

E-Star <unix_core@linuxmail.org> writes:

Thanks, but you were little help.

What exactly wasn't helpful?

Jerry stated the facts. And it does sound like you don't have the
experience to go inside a CRT monitor safely. There are deadly voltages
inside. Sorry.

You said: "The LCD was green". What LCD? Is this a flat panel monitor
or a CRT monitor?

I think it's one of those CRT monitors with a little LCD for displaying
status info like the old Iiyamas. I'm not sure why he was rude to Jerry
though.

Dave

 

[Andy Cuffe]

techforce wrote:

I can get you one, but its sorta Steep. I sent you an Email about it, not
sure if you got it ?

"Robert McPherson" <rm502@bellsouth.net> wrote in message
news:1fe013f5.0308210914.5bfe420a@posting.google.com...
Original # 95-4170. Anyone have a new or good used transformer for
sale or know of a source for one? Thanks!

What's it go to? I have a quite a few Zenith junk boards that probably
have good flybacks.
--
Andy Cuffe
baltimora@psu.edu

 

[Jerry Greenberg]

It sounds like you may (not likely) have a different uPC in this set,
but this would be an unusual part to change for your problem
description. Or they may have changed something in the service setup
(more likely) for the feature type.

Many parts of the setup software is very difficult for a tech who is
not properly trained or very experienced with this type of model
series.

When changing anything that has to do with the firmware or uPC, if
this is what he did, it is very important he used the exact origional
type, and not put in something similiar. When working in the uPC area,
the setup may have to be redone. This requires the proper test
facilities, and knowledge base for the model type.

This is why I tell people that they should normaly send their sets to
the factory authorised service rep, if they are not sure about the
standard service shop. These sets are very difficult to service and
setup, and many of the problems are a challange for the most
experienced techs.

What the tech will need is the exact origional service manual for this
series of set, and go through the setups for the options, and make
sure that they are set right. Any components changed that deal with
the firmware in the set must be verified to be correct.

As for changing parts in the video path, this usualy has nothing to do
with the pin or scan problems, unless you also had video problems as
well. Since I did not diagnose the set, it would not be right for me
to comment on any part of the required service performed. I would only
be able to comment on probabilities of circumstances.

Jerry Greenberg
http://www.zoom-one.com

--


Vince <guarna@enteract.com> wrote in message news:<Xns93DEA61A02368vguarnaairlogicnet@155.229.126.70>...

I had a Sony KV-32XBR45 (32" XBR) television that developed video problems
(it was jittering and pulsating between hourglass and pincushion) and I
recently had it fixed. Now that I have it back, I noticed that several
features are missing such as (1) side-by-side picture (alternative to
PIP...PIP still works tho), (2) Freeze picture doesn't function, (3) PIP
has 2 size settings instead of 3, (4) The "Display" button on the remote
just cycles between showing time/station and not showing time/station. It
used to also cycle through showing closed caption and turning External Data
Service on.(5)...lots of other little things.

The repair shop indicated power supply problem and also damaged video
drivers. Seemed reasonable. But, given the missing features, it sure seems
to me there's in new logic board in the TV. So, my first question, is there
video circuitry along with logic circuitry on one board in this TV? (In
other words, is it reasonable that the logic board would have to be swapped
to fix a video problem?)

My second question is, does anyone recognize the feature differences? My
repair shops appears to just have ordered a replacement board from some
non-Sony source (who claims they shipped him the right parts). I'm trying
to help the repair shop identify exactly which board they did get instead
of what they should have gotten.

Or....is this really the right board and somehow has old software flashed
into it (or maybe even has a configuration setting set wrong that can be
easily corrected)?

Would appreciate any help anyone could offer.

Regards.

Vince
guarna@enteract.com

 

[geo73]

Maybe the fan function is
controlled through the BIOS setup.
Some motherboards have this
option at the -power- setup
always on/when needed etc.
If so the board might need
to reach some temperature to
enable the fan.

 

[Ricardo Matos Abreu]

I'd bet on Q107 and its surrounding parts, since they're responsigle for
bias. Also check FR101 and all those low voltage resistors.

Ricardo

"Wdyorchid" <wdyorchid@aol.com> wrote in message
news:20030822041804.10910.00000511@mb-m14.aol.com...

Take a look at this schematic. The green line is faulty line measuring 28V
which should be 1V. Assuming that replacing four transistors in these
general
areas would solve it, but it didn't. What can I be missing?

Details: Q111, Q109, Q129C, and Q129A replace same time. Measurements were
taken and still the same as before. (Thinking Q111, Q109 drives the output
transistors (Q129A, Q129C, replacing them would solve something) All the
transistors were checked with a diode tester but didn't paid attention to
comparing them before installing them. What is the correct way to test
them
with a diode checker? (I'd been using a logic pulser before but lost it.)
Receiver is a Dolby pro logic RX-V480.

http://autotails.tripod.com/zoom.htm

 

[Mark D. Zacharias]

It does sound like the counter belt. Must be a hall sensor or some such run
off the same belt.

Mark Z.


"Adam Vaughn" <adamant316@aol.com> wrote in message
news:20030821224841.06260.00000201@mb-m19.aol.com...

Hello everyone. I recently acquired my first Betamax VTR, a Sony SLO-323
industrial-type unit. For the first couple of days I owned it, it worked
like a
charm (wouldn't play most of the tapes I could find due to it being
single-speed only, but looked nice when recording to it from other
sources).
Unfortunately, it has developed a strange problem which is somehow related
to
the tape counter (which is a bit misaligned in the front window, but
otherwise
appears fine). Whenever the counter is about to roll-over to the next
group of
100s (i.e. from 099 to 100, or 999 to 000), the counter will stop
mid-rotation,
and the tape itself will stop a few seconds later. This only occurs during
recording or playback, and does not seem to affect rewind or fast-forward
operations. Manually resetting the counter during this allows the set to
continue to run, but is inconvenient. I have attempted to locate whatever
belt
operates the counter, but this deck is very cramped. What is the likely
cause
of this problem, and how could I possibly fix it? Might lubrication of
something be the fix? Also, I am unable to get the deck to record from the
VHF
input; is this normal? TIA.
-Adam

Adam Vaughn
Collector of old computers, video game systems, radios and other
electronic
equipment...
Visit my page at
http://www.angelfire.com/ma2/AdamVon/index.html

 

[chuck]

Are you saying on your webpage that both the left and right channels
have the same offset? If so I would look at the -44 v source for the
problem. If not Q105, Q107, and R113 would be prime suspects. Also,
if you didn't use exact replacement parts, I would check the lead
orientation very carefully. This amp is designed to shutdown entirely
if there is any amp problems. It should shut down in 2 to 3 seconds.
Chuck




On 22 Aug 2003 08:18:04 GMT, wdyorchid@aol.com (Wdyorchid) wrote:

Take a look at this schematic. The green line is faulty line measuring 28V
which should be 1V. Assuming that replacing four transistors in these general
areas would solve it, but it didn't. What can I be missing?

Details: Q111, Q109, Q129C, and Q129A replace same time. Measurements were
taken and still the same as before. (Thinking Q111, Q109 drives the output
transistors (Q129A, Q129C, replacing them would solve something) All the
transistors were checked with a diode tester but didn't paid attention to
comparing them before installing them. What is the correct way to test them
with a diode checker? (I'd been using a logic pulser before but lost it.)
Receiver is a Dolby pro logic RX-V480.

http://autotails.tripod.com/zoom.htm

 

[Jerry G.]

Your monitor most likely has a lot of dried up caps. You can use an ESR
meter to test them, or replace all the caps. This is common with these
models when they get old.

Considering the age of the monitor, and the low cost these days, I would
replace the monitor rather than spend the time and money on it.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
==============================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
Instruments http://www.zoom-one.com/glgtech.htm
==============================================
"Technical" <dpbarry@freenetname.co.uk> wrote in message
newstlbkv8evmd48r0evegssk1v0b49lcm5ra@4ax.com...
Hi all..

Any ideas where to start looking for the fault on the above monitor.
Power seems to be geting to the system okay but the power light just
flicker on then disappears.

Also, on the same type of monitors, if they are left switched on but
not used for a period of time, they are intermittent at coming back
on. Switching them completely off at the power socket for a few hours
and then switching them on again seems to bring them back to life but
on some, they need a good 'slap' at the back. You can hear the
initial HT sound then a second later what sounds like a relay
switching and the picture comes up.

Whats the relay sound?

Declan