Toshiba TV29C90 problem; Image fades to black...

[Dave Martindale]

hatespam@hatespam.com (Fiat Sparks) writes:

Mostly less! My Panasonic inverter unit just released the magic
smoke. First the magenetron died, and then after I replaced that, an
IGBT in the switcher shorted and did a fair bit of collateral damage.

Ouch. We have one that's only a few months old; I hope it does better
than that. I love it because all of the power settings from "3" to "10"
actually vary the magnetron RF output while keeping it on continuously.
At "3", I can cook a single egg in the oven without it exploding.

Conventional microwaves set to "3" run the magnetron about 4.5 seconds
at full power followed by about 10.5 seconds off, and 4.5 seconds of
full power into a single egg generates enough steam for an explosion.

(On the Panasonic, settings of "1" and "2" actually run the magnetron at
30% power, using 1/3 and 2/3 on time).

So, $100 in parts later, I now have a working microwave again. And, if
I get tired of it, I can sell it on Craigslist for at least $35! :-/

For that much, I'd be tempted to scrap it and buy a new oven.

Dave

 

[Dave Martindale]

moroney@world.std.spaamtrap.com (Michael Moroney) writes:

Yes the inability to go to the nearest WallyWorld and buy a 240V 4kW
cooker/microwave/whatever is a big problem. European appliance could be
got, but I'd worry about anything with a motor (50 Hz), clock (do their
electronic clocks operate off the line frequency like some in the US?),
microwaves (don't they use frequency-dependent constant voltage
transformers?).

A motor designed for 50 Hz would run fast on 60 Hz, which might
overload something like a fan motor. A clock would run fast. On the
other hand, more iron is needed for 50 Hz motors (at a given voltage
and number of turns), so the motor is actually overbuilt for 60 Hz
operation. Same goes for ordinary transformers.

I've taken a number of microwave ovens apart over the years, and none of
them used constant-voltage transformers. They do have a magnetic shunt
to give them somewhat of a constant *current* characteristic, and that
might reduce the magnetron current some when operated from 60 Hz.
The magnetron itself operates from half-wave rectified DC, so it
shouldn't care.

Some Panasonic microwave ovens use an inverter to generate the HV supply
for the tube. Feeding it 60 Hz instead of 50 Hz should not be a
problem; it will just reduce the ripple at the output of the initial
rectifier.

Dave

 

[Dave Martindale]

David Lesher <wb8foz@panix.com> writes:

Someone one mentioned they were F-R, and a casual look seemed to confirm
that, so I never questioned it. A F-R is also current limited; short the
output and it delivers rated current, period..

They look similar. Both transformers have magnetic shunts, and there's
a big capacitor near the transformer. But the circuits are different.

The FR transformer puts the capacitor across the secondary winding, or
two secondary windings in series, and the windings plus capacitor
resonate at the designed line frequency. This causes the voltage to
rise above what you'd expect from the turns ratio alone, but the voltage
is limited by the portion of the core that the secondary is wound on
going into saturation. Sometimes the secondary voltage waveform looks
pretty square because of this peak clipping, but sometimes there's a
third winding that (somehow) reduces the second harmonic and gives
something closer to a sine wave.

There's a magnetic shunt between the primary and secondary windings so
that the primary current doesn't go through the roof when the iron in
the secondary saturates. It limits the shorted output current to about
*twice* the rated current, not equal to the rated current.

Still, the FR transformer runs hot with no load, dissipating about 20%
of its full output rating as heat.

In comparison, the capacitor in the microwave is wired as part of a
voltage doubler; it doesn't resonate with the transformer secondary.
The transformer iron is not designed to saturate (though, as an
intermittent-duty transformer that is fan-cooled in use, it is
apparently designed to operate close to saturation to minimize the
amount of iron).

Dave

 

[Fiat Sparks]

davem@cs.ubc.ca (Dave Martindale) wrote:

Ouch. We have one that's only a few months old; I hope it does better
than that. I love it because all of the power settings from "3" to "10"
actually vary the magnetron RF output while keeping it on continuously.
At "3", I can cook a single egg in the oven without it exploding.

Mine lasted about eight years with daily use for a family of 5. So,
hopefully you've got a ways to go. I agree, it does cook nicely, which
is why I even bothered to repair it.

So, $100 in parts later, I now have a working microwave again. And, if
I get tired of it, I can sell it on Craigslist for at least $35! :-/

For that much, I'd be tempted to scrap it and buy a new oven.

You know, that's what the wife said!

Had I known it was going to go out again after the magenetron died, I
probably would have. But, my pride was at stake!

 

[Fiat Sparks]

davem@cs.ubc.ca (Dave Martindale) wrote:

Ouch. We have one that's only a few months old; I hope it does better
than that. I love it because all of the power settings from "3" to "10"
actually vary the magnetron RF output while keeping it on continuously.
At "3", I can cook a single egg in the oven without it exploding.

Mine lasted about eight years with daily use for a family of 5. So,
hopefully you've got a ways to go. I agree, it does cook nicely, which
is why I even bothered to repair it.

So, $100 in parts later, I now have a working microwave again. And, if
I get tired of it, I can sell it on Craigslist for at least $35! :-/

For that much, I'd be tempted to scrap it and buy a new oven.

You know, that's what the wife said!

Had I known it was going to go out again after the magenetron died, I
probably would have. But, my pride was at stake!

 

[bz]

davem@cs.ubc.ca (Dave Martindale) wrote in news:g1pa8d$ljv$2
@swain.cs.ubc.ca:

Conventional microwaves set to "3" run the magnetron about 4.5 seconds
at full power followed by about 10.5 seconds off, and 4.5 seconds of
full power into a single egg generates enough steam for an explosion.

Saw something in a catalogue: a plastic 'Egg' shaped chamber that holds 4
eggs and some water. I am guessing that it is a 'plastic pressure cooker'.
Anyway, they claim you can hard boil eggs in it in a microwave oven.



--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap

 

[bz]

davem@cs.ubc.ca (Dave Martindale) wrote in news:g1pa8d$ljv$2
@swain.cs.ubc.ca:

Conventional microwaves set to "3" run the magnetron about 4.5 seconds
at full power followed by about 10.5 seconds off, and 4.5 seconds of
full power into a single egg generates enough steam for an explosion.

Saw something in a catalogue: a plastic 'Egg' shaped chamber that holds 4
eggs and some water. I am guessing that it is a 'plastic pressure cooker'.
Anyway, they claim you can hard boil eggs in it in a microwave oven.



--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap

 

[Michael Kennedy]

"Sparkey" <wwspage@aol.com> wrote in message
news:57e159d5-646c-495a-8363-e7bf7a891fb2@f36g2000hsa.googlegroups.com...

On May 29, 5:20 am, JW <n...@dev.null> wrote:
On Wed, 28 May 2008 18:43:46 -0700 (PDT) Sparkey <wwsp...@aol.com> wrote
in Message id:
4e0f732f-60a4-411a-8f8a-610c01ed7...@x35g2000hsb.googlegroups.com>:



On May 28, 4:40 pm, Sparkey <wwsp...@aol.com> wrote:
On May 28, 5:38 am, JW <n...@dev.null> wrote:

On Tue, 27 May 2008 19:34:51 -0700 (PDT) Sparkey <wwsp...@aol.com
wrote
in Message id:
b995d753-8b98-4bd8-8fcb-78e3af8a2...@d77g2000hsb.googlegroups.com>:

I need to figure out which smd class this ic chip is.
If you take a look at this
pichttp://members.aol.com/ta7205/MVC-181f

The 8 pin chip with the red dot is the one I need to replace.
I have an SOIC 8 version sitting just to the left of the chip.
Its quite a bit smaller.

Even increasing the picture size wouldn't allow me to see the
writing on
the device. Can you post exactly what is on the chip?

It took a lot of magnification but
4LC 1728 1Q5 is the number on the chip.
I reloaded the pic under a different name. The green arrow points to
the IC in question. http://members.aol.com/ta7205/chip.jpg

Thanks,
Spark

SO-8..... That's sounds right from the lit. I've been looking at.

Do you know of an easy way to use an SOIC 20 chip in a 20 pin DIP
socket ?

I'm not sure why you'd want to do such a thing. What exactly are you
trying to do? I'm assuming that you need a replacement chip for the board
in question, right? If so, what is the function of the board, and what
markings are on the chip to the left of the device in question?

The function of the original pc board with the SO-8 chip is a
wireless router I'm repairing for a friend. She gave me the SOIC 8
chip to swap out.

I'm sorry, this SOIC 20 question was for a different problem.

I purchased an HIP 4080 (full bridge FET driver) 20 pin DIP to repair
another unrelated problem with a car amplifier.

I ordered the IC from Mouser (it seems they were the only ones I could
find that carried it as it is discontinued) They sent me the SOIC 20
version of the HIP 4080 and said that is the only version they have.

I now am stuck with making the SOIC 20 work in the circuit.
I hope that clarifies my problems. I didn't mean to be confusing but
that's my other problem.

thanks again for your help.
Spark

I'm not trying to be negative, but I have a hard time believeing reparing a
wireless router can be worth the investment of time and money required to
fix it unless it is something extremely simple. You can get some routers for
almost nothing these days. You can eaisly find a used one on ebay for less
than $30. Buy a linksys and put DD-WRT on it and then you have a top notch
router and also a cheap fix.

Mike

 

[Michael Kennedy]

"Sparkey" <wwspage@aol.com> wrote in message
news:57e159d5-646c-495a-8363-e7bf7a891fb2@f36g2000hsa.googlegroups.com...

On May 29, 5:20 am, JW <n...@dev.null> wrote:
On Wed, 28 May 2008 18:43:46 -0700 (PDT) Sparkey <wwsp...@aol.com> wrote
in Message id:
4e0f732f-60a4-411a-8f8a-610c01ed7...@x35g2000hsb.googlegroups.com>:



On May 28, 4:40 pm, Sparkey <wwsp...@aol.com> wrote:
On May 28, 5:38 am, JW <n...@dev.null> wrote:

On Tue, 27 May 2008 19:34:51 -0700 (PDT) Sparkey <wwsp...@aol.com
wrote
in Message id:
b995d753-8b98-4bd8-8fcb-78e3af8a2...@d77g2000hsb.googlegroups.com>:

I need to figure out which smd class this ic chip is.
If you take a look at this
pichttp://members.aol.com/ta7205/MVC-181f

The 8 pin chip with the red dot is the one I need to replace.
I have an SOIC 8 version sitting just to the left of the chip.
Its quite a bit smaller.

Even increasing the picture size wouldn't allow me to see the
writing on
the device. Can you post exactly what is on the chip?

It took a lot of magnification but
4LC 1728 1Q5 is the number on the chip.
I reloaded the pic under a different name. The green arrow points to
the IC in question. http://members.aol.com/ta7205/chip.jpg

Thanks,
Spark

SO-8..... That's sounds right from the lit. I've been looking at.

Do you know of an easy way to use an SOIC 20 chip in a 20 pin DIP
socket ?

I'm not sure why you'd want to do such a thing. What exactly are you
trying to do? I'm assuming that you need a replacement chip for the board
in question, right? If so, what is the function of the board, and what
markings are on the chip to the left of the device in question?

The function of the original pc board with the SO-8 chip is a
wireless router I'm repairing for a friend. She gave me the SOIC 8
chip to swap out.

I'm sorry, this SOIC 20 question was for a different problem.

I purchased an HIP 4080 (full bridge FET driver) 20 pin DIP to repair
another unrelated problem with a car amplifier.

I ordered the IC from Mouser (it seems they were the only ones I could
find that carried it as it is discontinued) They sent me the SOIC 20
version of the HIP 4080 and said that is the only version they have.

I now am stuck with making the SOIC 20 work in the circuit.
I hope that clarifies my problems. I didn't mean to be confusing but
that's my other problem.

thanks again for your help.
Spark

I'm not trying to be negative, but I have a hard time believeing reparing a
wireless router can be worth the investment of time and money required to
fix it unless it is something extremely simple. You can get some routers for
almost nothing these days. You can eaisly find a used one on ebay for less
than $30. Buy a linksys and put DD-WRT on it and then you have a top notch
router and also a cheap fix.

Mike

 

[David Lesher]

moroney@world.std.spaamtrap.com (Michael Moroney) writes:

I've never heard of such as manual regulators so I assume they are
automatic.

Earlier in this thread it was mentioned the automatic ones are expensive
and only used for big substations, not for long runs of distribution
systems like that one. Before I read that I assumed they must be
automatic.

I know mine [which look to be very similar to the picture..] are
automatic -- after my PSC complaint, the PEPCO phone droid read off the
trouble report where the lineman went out, found higher-than-wanted
voltage on my phase and set it to manual until the correct person could
fix the regulator.

Alas, the first repair didn't work, as a week later, I was awoken
again....

Later conversations with lineman in the area confirmed both that detail;
and the fact their standard pole-pigs do NOT have a choice of taps.
[They replaced the pig serving me with a larger one a few years back.]


--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

 

[David Lesher]

moroney@world.std.spaamtrap.com (Michael Moroney) writes:

I've never heard of such as manual regulators so I assume they are
automatic.

Earlier in this thread it was mentioned the automatic ones are expensive
and only used for big substations, not for long runs of distribution
systems like that one. Before I read that I assumed they must be
automatic.

I know mine [which look to be very similar to the picture..] are
automatic -- after my PSC complaint, the PEPCO phone droid read off the
trouble report where the lineman went out, found higher-than-wanted
voltage on my phase and set it to manual until the correct person could
fix the regulator.

Alas, the first repair didn't work, as a week later, I was awoken
again....

Later conversations with lineman in the area confirmed both that detail;
and the fact their standard pole-pigs do NOT have a choice of taps.
[They replaced the pig serving me with a larger one a few years back.]


--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

 

[bz]

James Sweet <jamessweet1@trashmail.net> wrote in news:HT%%j.670$BV.298
@trndny05:

With a Variac on the input, this is a handy for working on line
operated devices that might have a line-to-chassis defect.

Do you actually use a setup like that? I'd think that for any sort
of current, the filament windings would be melting down even though
they are made of fat wire. For example, at 300 VA of output, you're
looking at ~100 A in the filament winding.




Connecting the HV windings together would probably work a lot better.
Would want to knock out the magnetic shunts too, that can be tricky but
I've done it on several without damaging the windings.

I wanted some heavy copper wire to wind a coil with so I tore xxxx started
to tear up an old microwave transformer.
Found out that pretty copper wire was aluminum with a copper colored layer
on top of it.




--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap

 

[Smitty Two]

In article <19530-4840AA04-565@storefull-3252.bay.webtv.net>,
cuhulin@webtv.net wrote:

There is, or was a guy in Alabama and he built and sold some high
powered super duper CB Radios.I heard about him when I was listening to
CB radio over ten years ago.The amplifiers for those radios required
several alternators.He mostly sold those suped up radios to 18 wheeler
truck drivers.I once heard tell if the CB radio's antenna was aimed at a
car, it would fry the car's electronics and stop the engine stone cold
dead.
Have any of y'all ever heard of that guy before?
cuhulin

Heard of him? Hell, dude, that was my cousin. Those monster amplifiers
really could fry a car's electronics. The cops still use 'em down in
Mississippi to stop people who are trying to run from them. Too bad
they're illegal in all the other states.

They've also been known to knock the fillings right out of your teeth,
and cause women to have spontaneous orgasms. The "Big Daddy" version
used to sell for $28,000, and it put out 50,000 watts. Of course it had
a bank of sixteen KT88s with solid gold pins.

Anyway, my cousin passed away six years ago, syphilis you know, so you
can't get those things anymore. Saw one on eBay a couple years back, but
it sold for $90,000 to some collector in Eastern Europe.

 

[JANA]

From what you are indicating, your power supply is under sized. The
voltage is correct, but there is another very important issue. If your
unit is asking for a supply of 2.4 Amps, and your supply is able to only
put out 400 ma, there will be a problem. Your supply will not last very
long.

When your unit is in a USB port, it probably can sense that and the
limitations are regarded. When you connect the external supply, it will
expect a very different spec.

--

JANA
_____


"Marcel" <conique.opdencamp@gmail.com> wrote in message
news:0cd234c2-eda5-486f-9c15-ddc457587720@t54g2000hsg.googlegroups.com...
Hi,

We bought a Creative ZEN V mp3 player. It comes with a USB-cable to
charge the li-ion battery through a pc. I want to charge this player
with a power supply (220V in). I think the ZEN needs 5 V at 2.4A (max)
it says at the internet. I do have already a power supply witch says:
input 100-240V-50/60Hz 120mA, output 5V === 400mA. Is this save to
use??? Will it work?

Thanks for helping

Marcel

 

[N_Cook]

JW <none@dev.null> wrote in message
news:v00544hl1tbvhcn46d26uj4pbbn96qq6jv@4ax.com...

Hello all, I am repairing a Keithley 617 that has a blown input JFET Q308
which is no longer available. Looking at the service manual, I am unable
to determine what a good sub would be, as the part # is a Keithley house
numbered part (617-606) The manual is here:
http://www.keithley.com/data?asset=1062 Schematic is on page 161 and the
parts list is on pg. 155. Could anyone please suggest a good sub for this
part? Thank you for any help.

Is it dual gate or dual FET?
If the latter then just tie 2 basic ones together with some white goo
between would probably be adequate for all but the most stringent of uses.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

[Dave Platt]

Hello all, I am repairing a Keithley 617 that has a blown input JFET Q308
which is no longer available. Looking at the service manual, I am unable
to determine what a good sub would be, as the part # is a Keithley house
numbered part (617-606) The manual is here:
http://www.keithley.com/data?asset=1062 Schematic is on page 161 and the
parts list is on pg. 155. Could anyone please suggest a good sub for this
part? Thank you for any help.

Is it dual gate or dual FET?
If the latter then just tie 2 basic ones together with some white goo
between would probably be adequate for all but the most stringent of uses.

In this application, I don't think that this approach would work
well... at least, not without some preparation. It looks as if this
dual-JFET is being used as a high-Z buffer in a sort-of-differential
input stage. Matching of the two JFETs in the package (for Idss,
transconductance, pinchoff voltage, etc.) is probably important.

The original Q308 part probably had good matching between the two
JFETs. It may also have been hand-selected by Keithley for a specific
range of Idss.

There's enough process variation in JFET manufacture that two single
JFETs, with the same number and from the same manufacturing batch, are
likely to vary in Idss by quite a bit (tens of percent). This might
unbalance the input stage enough to affect its accuracy. Tying the
JFETs together thermally will certainly minimize thermal drift, but if
they aren't already well-matched this might not help matters.

JW - are both sides of the existing dual JFET blown, or did just the
left-hand size (pins 1-3) get fried? If the right side is still
intact, you could measure the Idss, pinchoff voltage, and
transconductance and thus get a better sense as to what you'd need to
replace it.

I'd offer two practical alternatives to replacing it:

[1] Try what N_Cook suggested - use two single JFETs glued together.
Grab a bagful, measure them for Idss and pinchoff voltage, and
pick a pair which are well-matched.

[2] Try a U440 or U441. These have gate-voltage matching to within 10
or 20 millivolts. Newark has both types in stock... the U441 with
its 20 mV matching is less painfully priced and I suspect it'd do
the job.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Pilgrim]

In article
<8b4c9d2f-f411-44a9-af8f-2e3b15c789fb@b1g2000hsg.googlegroups.com>,
Red <RedAlt5@hotmail.com> wrote:

A rheostat is in a simple series circuit with another component. The
input is connected to one end of the rheostat. The output is taken
from the wiper terminal. Some schematics show the remaining other end
of the rheostat left unconnected and others show the wiper and
remaining terminal connected together. Is there any advantage of one
way over the other?

Red

Just paranoia. If the wiper should fail you would still have the full R
in the circuit.

Chuck P.

 

[Pilgrim]

In article <48430FF9.5080805@prodigy.net>, CJT <abujlehc@prodigy.net>
wrote:

Pilgrim wrote:

In article
8b4c9d2f-f411-44a9-af8f-2e3b15c789fb@b1g2000hsg.googlegroups.com>,
Red <RedAlt5@hotmail.com> wrote:


A rheostat is in a simple series circuit with another component. The
input is connected to one end of the rheostat. The output is taken
from the wiper terminal. Some schematics show the remaining other end
of the rheostat left unconnected and others show the wiper and
remaining terminal connected together. Is there any advantage of one
way over the other?

Red


Just paranoia. If the wiper should fail you would still have the full R
in the circuit.

Chuck P.

It doesn't have to fail -- just momentarily lose contact (think
wirewound).

Good point.

Chuck P.

 

[Deke]

Do a Google on Jensen TS2050J.
You will find that it sold new for $95 at Best Buy, where to
get a replacement remote, its a Made in China elcheapo TV, and it has a poor
performance history.
Good Luck!


<stokesbr@cox.net> wrote in message
news:1204db57-ea2c-47fb-9258-313d13b3b34a@b1g2000hsg.googlegroups.com...

Hi group. I have searched for threads and came up empty on this set.
Same with my repair database. This is a model #TS2050J. Televsion was
working fine. Unplugged it, moved to another room, plugged back in and
now only get a blue screen at power up with a display "C24". I don't
know what this means. Left set unplugged for 24 hours and tried again,
with same results. Is this a micro problem or something I can reset.
Buttons on the front panel don't respond. Also don't have remote, and
can't find code for my all in one. Anyone here have a guess as to what
I should check? Thanks as always.

 

[Deke]

Do a Google on Jensen TS2050J.
You will find that it sold new for $95 at Best Buy, where to
get a replacement remote, its a Made in China elcheapo TV, and it has a poor
performance history.
Good Luck!


<stokesbr@cox.net> wrote in message
news:1204db57-ea2c-47fb-9258-313d13b3b34a@b1g2000hsg.googlegroups.com...

Hi group. I have searched for threads and came up empty on this set.
Same with my repair database. This is a model #TS2050J. Televsion was
working fine. Unplugged it, moved to another room, plugged back in and
now only get a blue screen at power up with a display "C24". I don't
know what this means. Left set unplugged for 24 hours and tried again,
with same results. Is this a micro problem or something I can reset.
Buttons on the front panel don't respond. Also don't have remote, and
can't find code for my all in one. Anyone here have a guess as to what
I should check? Thanks as always.