Toshiba TV29C90 problem; Image fades to black...

[Gareth Magennis]

"James Sweet" <jamessweet@hotmail.com> wrote in message
news:JVHSj.469$b%1.77@trndny04...

AC power adaptors are misnamed because they are mostly DC power
adaptors, i.e. they output DC. This means that the centre pin can be
either negative or positive, there is no fixed convention. Which means
that if you plug a positive pin power supply into a pedal which is meant
to have a negative pin power supply, you run the risk of burning out a
diode and possibly one of the 3 IC's and having to post on usenet for
help in trying to fix it.



They're not misnamed, they're called AC adapters because they adapt the AC
mains to whatever the equipment being powered requires, whether that be AC
or DC.

Well it's just a matter of opinion really. It doesn't make a lot of sense
to call them AC adaptors if there are no such adaptors running on DC, the AC
term is totally superfluous. It's like calling bicycles "Pedal Bicycles".

Anyway, in this context I was trying to make the point that it would be
better to think of Wall Warts as providing DC of either polarity, and to be
aware that occasionally you do get a Wall Wart that produces AC. I think
my terminology works a lot better.



Gareth.

 

[James Sweet]

"Wiebe Cazemier" <wiebe@halfgaar.net> wrote in message
news:60c46$481b8884$d4cc82be$20666@cache6.tilbu1.nb.home.nl...

On Friday 02 May 2008 18:46, Andy Cuffe wrote:

A CRT with two shorted guns is probably past hope. If you really want
to fix the monitor, start looking for a compatible replacement CRT.
Almost any 19" Trinitron monitor CRT should work.

Also when the guns only short intermittently? And, when it's warmed up,
the
problem is gone.

The problem with replacing the CRT, is that I'm almost completely sure
that the
image quality will be lower. When I bought this monitor, it required three
trips to the service desk to have it calibrated properly. Out of the box,
it
sucked. I've also seen other T766 models, which all sucked. If I am going
to
replace the CRT, I'm going to let an Eizo qualified repair company do it,
because they can do a better job of it. Problem is, Sony doesn't
manufacture
the tubes anymore, so it's possible it can't be repaired. And even if it
can,
as I said, quality will probably be lower than what I'm used to.

I would look for another monitor and get that calibrated if need be. CRT
monitors are cheap these days, plenty of really nice ones are getting
replaced by LCDs.

 

[David Farber]

"Sam Goldwasser" <sam@plus.seas.upenn.edu> wrote in message
news:6wskx17h6d.fsf@plus.seas.upenn.edu...

"Gareth Magennis" <sound.service@btconnect.com> writes:

"Sam Goldwasser" <sam@plus.seas.upenn.edu> wrote in message
news:6w3ap19b1v.fsf@plus.seas.upenn.edu...
This receiver seems to work fine in every respect except that the
volume
knob has to be turned up to a modest value before the speakers come
on.
This
will occur regardless of whether the speakers are actually enabled.

After that, it will usually run at any volume until power cycled

It has been sitting unused for about 10 years but don't know if this
was a problem back then.

Any common issues with this model?

Thanks.



Often this is down to dirty speaker relay contacts. If it has output
relays. Sometimes you can pop the top off them to spray the contacts,
others are sealed and need to be replaced.

Signal relays do much the same thing by the way.

If you see any relays inside, try getting it in the state where the
speakers
aren't working and then start tapping them with a stick.

Yeah, that's what I think also. I even seem to recall this very receiver
having that problem back before dinosaurs.....

There are two relays with covers that pop off.

Thanks!

--- sam | Sci.Electronics.Repair FAQ: 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 Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above
is
ignored unless my full name AND either lasers or electronics is included
in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

Power it up and don't turn up the volume. Put a scope probe at either the
speaker relay input or the emitter resistors of the power transistors. Turn
the volume up slowly. If you see signal before the sound comes on then you
know it's either the relay, or speaker switch. If you see signal at the same
time the sound comes on, then you have a different problem.

I'm a little confused by your observation that the problem happens whether
or not the speakers are enabled. How can you hear anything with the speakers
disabled? Are you using headphones? Or do you mean you turn the volume up
and down with the speakers off, then turn the speakers on, and then
everything is ok?

--
David Farber
David Farber's Service Center
L.A., CA

 

[Deke]

"Martin" <funkychateauSPAM@yahoo.com> wrote in message
news:768f84c4-a322-4cdd-ac02-2a5f2a55b9bb@l42g2000hsc.googlegroups.com...

I'm wanting to build a regulated external power pack for my JVC EVERIO
MG155US, but I can't find a source for the oddball DC-power connector
that plugs into the camcorder. Anybody know where to get these?


http://i264.photobucket.com/albums/ii168/funkychateau/Craigslist/f0b8_1_b.jpg

thanks,

Martin

www.JVCAmerica.com

 

[David Farber]

"Sam Goldwasser" <sam@plus.seas.upenn.edu> wrote in message
news:6wbq3op978.fsf@plus.seas.upenn.edu...

"David Farber" <farberbear.unspam@aol.com> writes:

"Sam Goldwasser" <sam@plus.seas.upenn.edu> wrote in message
news:6wskx17h6d.fsf@plus.seas.upenn.edu...
"Gareth Magennis" <sound.service@btconnect.com> writes:

"Sam Goldwasser" <sam@plus.seas.upenn.edu> wrote in message
news:6w3ap19b1v.fsf@plus.seas.upenn.edu...
This receiver seems to work fine in every respect except that the
volume
knob has to be turned up to a modest value before the speakers
come
on.
This
will occur regardless of whether the speakers are actually
enabled.

After that, it will usually run at any volume until power cycled

It has been sitting unused for about 10 years but don't know if
this
was a problem back then.

Any common issues with this model?

Thanks.



Often this is down to dirty speaker relay contacts. If it has
output
relays. Sometimes you can pop the top off them to spray the
contacts,
others are sealed and need to be replaced.

Signal relays do much the same thing by the way.

If you see any relays inside, try getting it in the state where the
speakers
aren't working and then start tapping them with a stick.

Yeah, that's what I think also. I even seem to recall this very
receiver
having that problem back before dinosaurs.....

There are two relays with covers that pop off.

Thanks!

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/

Power it up and don't turn up the volume. Put a scope probe at either
the
speaker relay input or the emitter resistors of the power transistors.
Turn
the volume up slowly. If you see signal before the sound comes on then
you
know it's either the relay, or speaker switch. If you see signal at the
same
time the sound comes on, then you have a different problem.

Intend to do something like that, or just clean the relay contacts!

I'm a little confused by your observation that the problem happens
whether
or not the speakers are enabled. How can you hear anything with the
speakers
disabled? Are you using headphones? Or do you mean you turn the volume
up
and down with the speakers off, then turn the speakers on, and then
everything is ok?

Turn on and no sound. Turn off Speaker A switch. Turn up volume and turn
back down. Turn on Speaker A and it works at low volume.

--- sam | Sci.Electronics.Repair FAQ: 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 Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

I remember the Kenwood KR-4070 had the power switch piggy backed onto the
speaker selector switch. If yours has the same design, make sure the long,
skinny, metal piece that connects the rotary switches together has not
slipped out of place. That might be contributing to the problem. This is
where hooking up your oscilloscope will answer your question in a matter of
seconds.

Good luck.
--
David Farber
David Farber's Service Center
L.A., CA

 

[Mark D. Zacharias]

"Sam Goldwasser" <sam@plus.seas.upenn.edu> wrote in message
news:6wbq3op978.fsf@plus.seas.upenn.edu...

"David Farber" <farberbear.unspam@aol.com> writes:

"Sam Goldwasser" <sam@plus.seas.upenn.edu> wrote in message
news:6wskx17h6d.fsf@plus.seas.upenn.edu...
"Gareth Magennis" <sound.service@btconnect.com> writes:

"Sam Goldwasser" <sam@plus.seas.upenn.edu> wrote in message
news:6w3ap19b1v.fsf@plus.seas.upenn.edu...
This receiver seems to work fine in every respect except that the
volume
knob has to be turned up to a modest value before the speakers come
on.
This
will occur regardless of whether the speakers are actually enabled.

After that, it will usually run at any volume until power cycled

It has been sitting unused for about 10 years but don't know if
this
was a problem back then.

Any common issues with this model?

Thanks.



Often this is down to dirty speaker relay contacts. If it has output
relays. Sometimes you can pop the top off them to spray the
contacts,
others are sealed and need to be replaced.

Signal relays do much the same thing by the way.

If you see any relays inside, try getting it in the state where the
speakers
aren't working and then start tapping them with a stick.

Yeah, that's what I think also. I even seem to recall this very
receiver
having that problem back before dinosaurs.....

There are two relays with covers that pop off.

Thanks!

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/

Power it up and don't turn up the volume. Put a scope probe at either the
speaker relay input or the emitter resistors of the power transistors.
Turn
the volume up slowly. If you see signal before the sound comes on then
you
know it's either the relay, or speaker switch. If you see signal at the
same
time the sound comes on, then you have a different problem.

Intend to do something like that, or just clean the relay contacts!

I'm a little confused by your observation that the problem happens
whether
or not the speakers are enabled. How can you hear anything with the
speakers
disabled? Are you using headphones? Or do you mean you turn the volume up
and down with the speakers off, then turn the speakers on, and then
everything is ok?

Turn on and no sound. Turn off Speaker A switch. Turn up volume and turn
back down. Turn on Speaker A and it works at low volume.

--- sam | Sci.Electronics.Repair FAQ: 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 Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above
is
ignored unless my full name AND either lasers or electronics is included
in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

Just sounds like flaky relay contacts to me. Put a load on it look at a sine
wave output on a 'scope, and tap on the relay(s). Probably see one or more
of them cut out - could be solder connections there at the relay as well.

To David Farber:
This model isn't even CLOSE to the old KR-4070... that was an analog 40 w/ch
receiver from the '70s. This is a more modern surround receiver.

Mark Z.

 

[Gareth Magennis]

"Wiebe Cazemier" <wiebe@halfgaar.net> wrote in message
news:142d$481c37a1$d4cc82be$5908@cache6.tilbu1.nb.home.nl...

On Saturday 03 May 2008 06:57, David Farber wrote:

I remember the Kenwood KR-4070 had the power switch piggy backed onto the
speaker selector switch. If yours has the same design, make sure the
long,
skinny, metal piece that connects the rotary switches together has not
slipped out of place. That might be contributing to the problem. This is
where hooking up your oscilloscope will answer your question in a matter
of
seconds.

Good luck.

I have a KR4070 here, and that is probably not the problem. That pin
indeed
falls out sometimes, but it just results in not being able to turn the
speakers on; or the entire amplifier for that matter.

BTW I find it rather strange that dirty relay contacts would cause this
behavior, most notably because after the sound has kicked in, the low
volume
setting works again, and because turning up the volume with the speakers
disabled, also turns them on.

You may well find it strange, but that is in fact exactly what happens in
the real world. Last time I heard any kind of technical explanation, it
seemed to be little understood and/or quite a complex situation - often a
kind of diode junction is formed. Turning up the volume (voltage across the
junction) often seems to "punch through" the dirt and it will then behave
normally for a while. You could try Googling for technical information on
this. I did for about a minute and gave up.



Gareth.

If your relay experiment fails, try locating the power amplifier section
and
determine if the problem is present on the input signal, or only on the
power
output.

 

[Arfa Daily]

"Wiebe Cazemier" <wiebe@halfgaar.net> wrote in message
news:f110c$481c4333$d4cc82be$12621@cache1.tilbu1.nb.home.nl...

On Saturday 03 May 2008 01:33, Wiebe Cazemier wrote:
Just to confirm something: the CRT repair FAQ says this about K-G1
shorts:

Cathode to control grid (K-G1). Since the G1 electrodes for all the guns
are
connected together, this will affect not only the color of the guilty
cathode
but the others as well. The result may be a very bright overloaded
*negative*
picture with little, none, or messed up colors.

But [1] says that cathode to G1 can produce similar symptoms as
heater-cathode shorts. I ask, because I noticed that G1 is connected to
ground on the CRT socket board. I can imagine that one cathode can very
well
short to G1 without the others being affected. Is that a right assement?

Can I disconnect G1 to test if it's a cathode-G1 short? There are two
pins on
the CRT to which G1 connects (which I don't understand BTW).

And, what is the use of G1 being at ground potential...?

BTW, [1] also states a 25% success rate of blowing out cathode-heater
shorts
with the flyback...

[1] http://www.thegleam.com/ke5fx/crt/sencrt.pdf.

I just did a test. In off state, I can't measure any short. But when I
heat up
the heater with an external power supply, I can measure 1K resistance
between
G1 and any of the cathodes (R, G and B). As the heater heats up, the
resistance decreases. The strange thing is, even tough they all read 1K,
the
continuity meter only read complete short on red (that is, "0". The others
read "0.2"). I still couldn't measure anything between heater and
cathodes.

So, as far as I can see, it's a cathode-G1 short after all (that is, that
1K
resistance should be there, right?). The only thing that stands in the way
of
this conclusion, is the comment from the repair FAQ above.

Any comments on this are appreciated.

k to g1 is by far the most common leakage path as far as I recall - and I
have to say it's been a while since I have been into CRT based repairs at
this level, so what John said above about h-k shorts may well be true with
'modern' tubes, although I'm sure that I remember being able to remove h-k's
in some circumstances with my B&K 465. As far as what you are measuring,
there should be no reading between g1 and any cathode. If the grid
connection is indeed grounded, then the statement about all guns being
affected equally, is not valid in this case, and individual gun conditions
could be affected by individual shorts. What you have to remember, is that
it is irrelevant what *actual* potentials the individual electrodes are
connected to, as long as the correct *differentials* are maintained. Hence,
if the gun requires the grid to be say -40v to achieve cut-off, it doesn't
matter whether the cathode is at +40v and the grid at ground, or the grid at
+20v and the cathode at +60v, the differential of -40v is maintained, and
the bias conditions remain the same.

You questioned earlier what constituted a "firm rap". I really can't tell
you in terms of anything that you could take as 'definitive instructions'.
It's just one of those things that's a 'feel' that you gain over years of
doing it. When I was directly involved with CRT equipment repairs, it was
something you 'just did' on a daily basis, and you never actually broke a
neck as a result ... Let's say that if you rap your fingertips on the bench
just hard enough to get that sort of 'buzz' in them immediately after,
that's probably about the most force that you want to be hitting the neck
with. I would normally be using an old box spanner that I have, which has a
wooden handle, and is a bit 'kinder' to the glass. As far as putting the
monitor on its side or upside down when you do it, it's just a case of
propping or holding it in position whilst you do it. It sometimes allows
particles to dislodge under the effects of gravity coming at them from a
different direction.

Other than this, use the capacitor discharge method to try and vapourise the
particles. You might want to try this with the heater on, as you say that
the resistance of the short goes down as the heater warms up. This is
probably because the particle(s) causing the short get 'squeezed' tighter in
the k-g1 gap, as the cathode cylinder expands. A better contact between the
two electrodes, via the contamination, is likely to result in a higher
discharge current from the cap, and a better chance of vapourising the
material, rather than just dislodging it.

Arfa

 

[Gareth Magennis]

"jango2" <crow_slapper@yahoo.co.uk> wrote in message
news:aafbfc69-f4a7-4a3e-a235-492d90080cb4@w5g2000prd.googlegroups.com...

FREE TIBET

This made me laugh:
http://news.bbc.co.uk/2/hi/asia-pacific/7370903.stm




Gareth.

 

[Gareth Magennis]

"jango2" <crow_slapper@yahoo.co.uk> wrote in message
news:aafbfc69-f4a7-4a3e-a235-492d90080cb4@w5g2000prd.googlegroups.com...

FREE TIBET

This made me laugh:
http://news.bbc.co.uk/2/hi/asia-pacific/7370903.stm




Gareth.

 

[William Sommerwerck]

Any difference in voltage between the batteries will cause current to flow
from the higher-voltage battery to the lower-voltage one.

If this makes you feel uncomfortable, it should. It's not a good idea to run
batteries in parallel, unless there is some mechanism (such as a series
diode) to block this flow.

Lithium coin cells aren't horribly expensive, especially if you buy from a
mail-order supplier. You can use the opportunity to stock up on batteries
you need for other stuff you own.

 

[William Sommerwerck]

Any difference in voltage between the batteries will cause current to flow
from the higher-voltage battery to the lower-voltage one.

If this makes you feel uncomfortable, it should. It's not a good idea to run
batteries in parallel, unless there is some mechanism (such as a series
diode) to block this flow.

Lithium coin cells aren't horribly expensive, especially if you buy from a
mail-order supplier. You can use the opportunity to stock up on batteries
you need for other stuff you own.

 

[DaveM]

""Blattus Slafaly ? (3) ź "" <boobooililililil@roadrunner.com> wrote in
message news:481c590e$0$30484$4c368faf@roadrunner.com...

CharlesBlackstone wrote:
I am looking for manufacturer of good power supplies, preferrably a US-
based company.

I bought a Chinese Mastech 30v 10a CVCC power supply. It was cheap,
and upon arrival I see why. I'm new to this stuff and the manual is
pretty useless.

I would like to find a similar HP, Tektronix, or other high quality
comparable type power supply, so I can try to find/buy/download a
manual for one. I bet an HP manual would clear up how to use these
things.

Thanks a lot.


A power supply is a power supply. The cheapest one will do. I have good luck
with $18.00 power supplies. They either work or they don't. People who pay
$150 or $200 for a power supply are crazy. I've bought the cheapest for
decades. It don't have to last 200 years, I won't live that long and it will
be obsolete in a couple years anyway.



--
Blattus Slafaly ? 3 7/8

I think you're taking a fatalist attitude. I have to disagree with you on a few
points. Experimenters need a PS with constant current or current limiting
capabilities (in case the breadboarded circuit is miswired or designed
improperly). Metering is another necessity for experimenters. Yes, the user
can always use bench meters for that, but it's sure handy to have those meters
built into the PS. Keeps everything neat and easy to monitor, and frees your
bench meters for probing the circuit..
Also, as a general rule, I like linear supplies for analog experimenting.
Switchers can cause tremors in analog circuits that will drive you crazy unless
you are aware of the source. Dual tracking supplies are great for analog
circuits as well, since many designs need positive and negative sources. Again,
keeps everything neat and easy to monitor.
People aren't "crazy" for paying reasonable prices for good equipment. The
extra cost of a well featured power supply can easily pay for itself by avoiding
destruction of expensive components because the power supply couldn't limit or
control the output current. Good power supplies don't become obsolete in a
couple of years, as computers do. With proper use and a little care, they can
last for decades.

Back to the OP's post...
Constant Voltage (CV) operation is the basic mode of a power supply. It means
that the output voltage is constant, regardless of current being drawn from the
supply (within limits, of course). The output voltage of an unregulated supply
will vary, depending on the current being drawn.
Constant Current (CC) operation means that the power supply output is a constant
current, regardless of the load resistance (again, within limits). The power
supply will vary the output voltage on order to maintain the current at a
constant level.
If the unit has current limiting capabilities, that means that if you are
operating in CV mode, and the current demanded by the load exceeds the supply's
current setting, then it will switch into CC mode at the current limit setting,
or it will shut down, causing the voltage to go to zero volts (or to a very low
value).
You set the current limit by setting the supply's mode to CC, then setting the
output voltage to the maximum voltage that you want your circuit to feel. Short
(yes, SHORT) the output terminals together, and set the current control to the
amount of current you want to supply to the circuit, or for the limiting to
occur.

If your supply has dual tracking outputs, that means the when you set the output
voltage of the master output, the other output will follow that voltage setting.
You control both output voltages with one control setting. That mode is usually
controlled by a Tracking Mode (or similar label) switch.

That's pretty much the basics of PS operation.

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Some people are like Slinkies. Not really good for anything, but they bring a
smile to your face when pushed down the stairs.

 

[DaveM]

""Blattus Slafaly ? (3) ź "" <boobooililililil@roadrunner.com> wrote in
message news:481c590e$0$30484$4c368faf@roadrunner.com...

CharlesBlackstone wrote:
I am looking for manufacturer of good power supplies, preferrably a US-
based company.

I bought a Chinese Mastech 30v 10a CVCC power supply. It was cheap,
and upon arrival I see why. I'm new to this stuff and the manual is
pretty useless.

I would like to find a similar HP, Tektronix, or other high quality
comparable type power supply, so I can try to find/buy/download a
manual for one. I bet an HP manual would clear up how to use these
things.

Thanks a lot.


A power supply is a power supply. The cheapest one will do. I have good luck
with $18.00 power supplies. They either work or they don't. People who pay
$150 or $200 for a power supply are crazy. I've bought the cheapest for
decades. It don't have to last 200 years, I won't live that long and it will
be obsolete in a couple years anyway.



--
Blattus Slafaly ? 3 7/8

I think you're taking a fatalist attitude. I have to disagree with you on a few
points. Experimenters need a PS with constant current or current limiting
capabilities (in case the breadboarded circuit is miswired or designed
improperly). Metering is another necessity for experimenters. Yes, the user
can always use bench meters for that, but it's sure handy to have those meters
built into the PS. Keeps everything neat and easy to monitor, and frees your
bench meters for probing the circuit..
Also, as a general rule, I like linear supplies for analog experimenting.
Switchers can cause tremors in analog circuits that will drive you crazy unless
you are aware of the source. Dual tracking supplies are great for analog
circuits as well, since many designs need positive and negative sources. Again,
keeps everything neat and easy to monitor.
People aren't "crazy" for paying reasonable prices for good equipment. The
extra cost of a well featured power supply can easily pay for itself by avoiding
destruction of expensive components because the power supply couldn't limit or
control the output current. Good power supplies don't become obsolete in a
couple of years, as computers do. With proper use and a little care, they can
last for decades.

Back to the OP's post...
Constant Voltage (CV) operation is the basic mode of a power supply. It means
that the output voltage is constant, regardless of current being drawn from the
supply (within limits, of course). The output voltage of an unregulated supply
will vary, depending on the current being drawn.
Constant Current (CC) operation means that the power supply output is a constant
current, regardless of the load resistance (again, within limits). The power
supply will vary the output voltage on order to maintain the current at a
constant level.
If the unit has current limiting capabilities, that means that if you are
operating in CV mode, and the current demanded by the load exceeds the supply's
current setting, then it will switch into CC mode at the current limit setting,
or it will shut down, causing the voltage to go to zero volts (or to a very low
value).
You set the current limit by setting the supply's mode to CC, then setting the
output voltage to the maximum voltage that you want your circuit to feel. Short
(yes, SHORT) the output terminals together, and set the current control to the
amount of current you want to supply to the circuit, or for the limiting to
occur.

If your supply has dual tracking outputs, that means the when you set the output
voltage of the master output, the other output will follow that voltage setting.
You control both output voltages with one control setting. That mode is usually
controlled by a Tracking Mode (or similar label) switch.

That's pretty much the basics of PS operation.

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Some people are like Slinkies. Not really good for anything, but they bring a
smile to your face when pushed down the stairs.

 

[James Sweet]

I think you're taking a fatalist attitude. I have to disagree with you on
a few points. Experimenters need a PS with constant current or current
limiting capabilities (in case the breadboarded circuit is miswired or
designed improperly). Metering is another necessity for experimenters.
Yes, the user can always use bench meters for that, but it's sure handy to
have those meters built into the PS. Keeps everything neat and easy to
monitor, and frees your bench meters for probing the circuit..
Also, as a general rule, I like linear supplies for analog experimenting.
Switchers can cause tremors in analog circuits that will drive you crazy
unless you are aware of the source. Dual tracking supplies are great for
analog circuits as well, since many designs need positive and negative
sources. Again, keeps everything neat and easy to monitor.
People aren't "crazy" for paying reasonable prices for good equipment.
The extra cost of a well featured power supply can easily pay for itself
by avoiding destruction of expensive components because the power supply
couldn't limit or control the output current. Good power supplies don't
become obsolete in a couple of years, as computers do. With proper use
and a little care, they can last for decades.

Someone once told me, "buy good tools and only cry once" and I've found that
to be consistantly true. Not once have I looked back and thought dang, I
should have spent less money on this tool, but many times I've grumbled that
I should have bit the bullet and splurged on a better one.

 

[Mark D. Zacharias]

<tx7123@yahoo.com> wrote in message
news:92dc789c-7188-460c-aed3-e3df24b80df4@x41g2000hsb.googlegroups.com...
I have left the case open, and have the thing sitting on a shelf
vertically.
It worked flawlessly for about 3 days, then spontaneouslt the radio
went dead again.
I ever so gently tapped the heatsink that this transistor is on, and
once
again everything is fine. I have not lifted the board yet to look at
the solder
underneath. However I'm beginning to think that it is the transistor
itself
that is the problem. Can I find the exact replacement at radio shack?
If I'm going to lift the board, I'm thinking it's probably makes sense
to replace the
device.

Thanks

On Apr 29, 2:32 am, "JANA" <j...@NOSPAMca.inter.net> wrote:

I strongly suggest you find and fix the cold solder connection that
caused the fault. Or if the transistor is intermittant, replace it.

--

JANA
_____

tx7...@yahoo.com> wrote in message

news:a60fee7d-739c-427d-bf6c-301464aa4ceb@k37g2000hsf.googlegroups.com...
OK I took the thing apart and sure enough, there was a sanyo 313E
mounted on a V shaped piece of metal(heatsink?). When I tapped
gently on the metal, everything now works fine.
The small board in question is AWR-011A, which according
to the schematic is the power supply unit.
I would think that if this was the roblem it would effect
everything, not just theradio.
Anyway I will run it for awhile with the case open,
and see if the problem recurs.

On Apr 26, 11:50 am, "Bob Shuman" <no_spam_...@sbcglobal.net> wrote:



Sounds like something is intermittent in theradiosection (assumes
amplifier/auxiliary input/tape/etc. all are still working fine). I'd
start
by looking for cold/broken solder connections under a magnifying. Or
alternatively, if that does not work and you can get at the board
safely
while the unit is powered up, you can try pushing at various points
with a
wooden dowel or similar non-conductive item. This may help you isolate
the
area to take a closer look.

If these do not help, then you'll either need a schematic, a volt
meter,
scope, and some troubleshooting skills to check the power supply
voltages at
key points and then follow the signal through theradiosection or
take it
to someone to do the work for you.

Bob

tx7...@yahoo.com> wrote in message

news:facbbdcd-1b25-4648-a91b-6c409b7924d8@56g2000hsm.googlegroups.com...

I have apioneersx-727receiver, I'm the original owner (33 years).
Recently theradiostopped working.
Everything else works great.
FM, AM no difference does NOT work.
The tuning meter does not move as I turn the tuning dial.
If I turn the volume up, I can hear some static thru the speakers.
Occasionally theradiowill spontaneously work for a while,
and then return to this dead mode.
All the other inputs cd, turntable work fine.
Any ideas what the problem might be?
Thanks.- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Just resolder the transistor. You will see that the solder connections there
have ring cracks from age and heating / cooling over the course of time.
Common problem.

Mark Z.

 

[Arfa Daily]

"Wiebe Cazemier" <wiebe@halfgaar.net> wrote in message
news:8468e$481d95b8$d4cc82be$22722@cache4.tilbu1.nb.home.nl...

On Sunday 04 May 2008 02:54, Wiebe Cazemier wrote:
Thanks for your elaborate response.

I just had a revelation today, which also sheds light not only on this
issue,
but also with earlier issues I had with this monitor; that being that it
turned brighter and brighter over time, resulting in a very washed out
picture with visible retrace lines, when at default settings. The OSD
menu
allowed me to decrease cut-off and gain, but at some point that wasn't
enough
anymore, and I needed to decrease G2 value on the flyback. And now I
think I
know what's going on.

I think a leakage path between the cathodes and G1 has slowly been
forming,
which slowly increased beam current over the years, and therefore
brightness.
Now, I'm at a point where there is not just leakage, but a dead short now
and
again. Tapping therefore, will not solve the issue.

Another problem I had, was that the automatic color calibrator didn't
correct
for the washed out picture. And I suspect that is because the cathodes
pulled
the extra current directly from ground, and therefore the circuit which
measures the beam current was oblivious to it. However, this is just
speculation.

I think I will need a proper CRT rejuvenator to clear the leakage path
between cathode and G1. I could do it myself, by using the G2 voltage for
example, but googling reveals that modern CRTs are too fragile for this,
and
that professional rejuvenators are matched precisely for modern tubes.

It also appears that cathode-G1 shorts are one of the easier things to
fix,
so I think I can still avoid buying a TFT . The only thing is, that it
would be better to let a professional servicer do it, but I dread the
likely
outcome of it coming back with a calibration that is way off.

One more thing. I may just decide to try to fix it myself (I was planning
to
use the capacitor discharge method, starting with a few uF at about 230V
or
so). But I have a question:

Most pin-outs of CRTs I've seen, contain only one G1 pin. But the G1
connection
on this neck board connects to two pins on the CRT. And, with the socket
removed, I can also measure 0 Ohms resistance between those pins. Is it
normal
that there are two G1 pins? When zapping, should I connect them together?

Probably for no other reason than there being a 'spare' pin. If they read
zero to one another, then it's pretty safe to assume that they are both
connected to the same place. Can you not find a data sheet for the tube on
the 'net somewhere, or a schematic for the whole monitor ?
www.eserviceinfo.com might be a good place to look for one. As far as your
calibration fears go, I would suggest that when these shorts are removed, it
is going to want a good set-up anyway ...

Arfa

 

[James Sweet]

"JR North" <junkjasonrnorth@bigfoot.com> wrote in message
news:f7kr141srtacojhkqirfp9v2m9lci91d2l@4ax.com...

The distinguishing feature of this otherwise unremarkable video 8
camera is it's color viewfinder. Mine was working fine last week. Took
it out for the weekly power up I do with all my other video cameras,
and the viewfinder is B/W, and washed out. All other functions are
normal, and the video output to the TV is color.
Is this prolly a cap issue? Has anyone any experience with
dissassembly and repair of Sony boards? Are they smt? Is it practical
to consider a teardown of this device to attempt repair?
JR
HOME PAGE:
http://www.seanet.com/~jasonrnorth
--------------------------------------------------

Probably capacitors, the only more common problem I see in camcorders is a
tape transport mechanical issue.

 

[Jim Yanik]

Jamie <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in
news:ZUoTj.106$4J1.95@newsfe05.lga:

We have a second drive that created the same problem as a drive of
the same model but smaller in size we tost out 3 years due to a
"SC" error "Short circuit" as you place the drive in RUN mode.

This time, I would like to repair this one instead of tossing it.
I can't remember the exact model # at the moment, a 5xx something
VF drive.
what I have found is, the 2 DC bus caps "2000 uf, 400 VDC" only test
up to only ~1500 uf each. I really don't think this would be the cause
if the "SC" error in run mode. This error takes place with no delay even
before the drive would normally ramp up. Nothing is apparently shorted.

I did find how ever, on the optical isolated Gate driving circuit one
bad CAP "58 uf, 35VDC"

58 uF is a really ODD value. sure it's not just 50 uF?

which measures ~ 1 uf on the first phase, the
same caps in the phase 2 and 3 circuit measure around 35 uf and appears
to have leaked out fluid a bit over the SMT driving trannies.

not good.

The bad cap I found how ever does not appear to have leaked at all.
So confusion tells me to replace all of them to start with.

I agree.

Any ways, I applied voltage to the IGBT bridge and there isn't any
shorts even thought the CPU thinks there is so, I have drawn a
conclusion that maybe the gate firing driver circuit has fail and thus
the loop back monitoring isolation circuit isn't detecting a feed back
response due to the bad driving circuit not signaling the bridge on that
one leg and assuming a short..

Does this sound like a plausible train of thought ?

P.S.
I'm doing this with out a service print, it does not seem like its to
difficult to resolve this problem.

if a cap leaked electrolyte on the board,that will be conductive.
that stuff can get under ICs and other components.

It must be cleaned off and thouroughly dried.


--
Jim Yanik
jyanik
at
kua.net

 

[ROITHNER LASERTECHNIK]

yes, Sam, I understand your needs behind, but sorry I cannot help, so far!
What nice and tricky "high end" application could be created with this
complex optical part - outside a DVD player, of course. Are you sure, Sir,
that this part is yet not blacklisted from the DOD? Actually as a kind of
Laserschurkendevices? Read his lips...!!!

beamit
Andreas Roithner

"Sam Goldwasser" <sam@plus.seas.upenn.edu> schrieb im Newsbeitrag
news:6wzlr65hnd.fsf@plus.seas.upenn.edu...

Even a schematic of the area of the optical pickup from the JVC service
manual for the XL-FZ158BK would be helpful. That would at least identify
the pinout of the hologram laser IC.

Thanks.

--- sam | Sci.Electronics.Repair FAQ: 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 Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above
is
ignored unless my full name AND either lasers or electronics is included
in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.


Sam Goldwasser <sam@plus.seas.upenn.edu> writes:

(Part of this was posted Yesterday to sci.electronics.repair only.)

I'm looking for a datasheet with as much detail as possible on the
optical pickup in the JVC XL-FZ158BK. It's either from Philips or
Sony. The type of pickup is called a "hologram laser" by some
manufacturers as it uses a Holographic Optical Element (HOE) to produce
the 3 beams of the "three beam pickup" and to distribute the return
beams to the focusing and tracking photodiodes. It has 10 pins in a
flat package with the hologram part in the clear cover. What I'm
mainly interested in are the details of the optical arrangement to
identify
the photodiode locations. While conventional optical pickups using
discrete optics generally have a separate PD array with easily
identified
individual photodiodes, these hologram lasers may have the photodiodes
distributed in almost any pattern. And on this one, it's far from
obvous
even where they are, let alone the specific function of each.

It has a normal edge-emitting laser diode with its beam reflected by a
really tiny prism. But I can't visually identify either the monitor
photodiode, or the phodiiodes of the focusing/tracking/RF signal PD
array.

Here is a poor photo:

http://repairfaq.cis.upenn.edu/Misc/Diode%20and%20photo-diodes.jpg

13,14,15,16 are pads for the laser diode.

B is the angled mirror face.

A is the flat top of the prism. It is not known what, if anything,
is below this.

Pointers to any Philips or Sony combined laser/photodiode array optical
pickup datasheets would be desirable if this specific one doesn't ring
a bell.

Any info appreciated.

Thanks!

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/