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Re: LCD monitor power supply

 

Peter Morris:

I agree with most of what you claim.

But why try to repair something that can be replaced (exactly) for a few
bucks?

I don't how various people value their time, but breaking open a brick, and
replacing capacitors on a unit that has most likely outlived its
usefulness seems
to be a waste of time. The cost of the replacement electrolytics, shipping
included might even exceed the price of a new "brick"

Plug And Play.

If the spec. for a "brick" is 12VDC @ whatever amps, then just get a new
brick
for a few bucks and move on to something more exciting.

When I am confronted with a "sick brick" I just order a new one, rather
than doing
all of that cutting and digging and cracking open the case, etc, etc.

I guess that's why replacement bricks are so cheap and so easily obtainable.

No rocket science involved.

Roland F. Harriston, P.D.



Peter Morris wrote:



The reason that you can often get away with using the wrong "brick" is
because most of the monitor's internal circuitry requires voltages other
that 12 (usually 5 and 3.3 among others). The monitor has DC-DC converters
inside which will maintain a constant output voltage over a wide range of
input voltages. When using DC-Dc converters, the higher the input voltage,
the less current will be drawn from the supply. I'd be careful going too
high though, as there will be some devices requiring 12V (audio op-amps
spring to mind). Also, there are probably some electrolytic capacitors
across the 12V rail rated at either 16V, 25V, or 35V. If 16V - 19V "brick"
will kill them. With 25V - 19V will be close, but probably ok. If the caps
are 35V rated, then 19V won't harm them.

When choosing a replacement PSU (brick), the voltage is usually the most
important point of specification. If the original was 12V 4A, then the
replacement should be 12V (or close, eg. 11-14ish) and at least 4A. If the
monitor requires 4 amps, a 2 amp PSU won't be able to cope. A 12V 10A PSU
will work fine. A 20V 4A supply is not recommended.

As for repairing the old "brick", in my experience, the most common
cause of
failure of switch-mode PSUs is electrolytic capacitors 'drying out'.
This is
often because the PSUs are built to a pathetic budget, meaning the
cheapest
parts are used, not the most appropriate. Switch-mode PSUs operate at high
frequencies (usually in the region of 100KHz). With current flowing in and
out of the bulk electrolytic capacitors at these rates, ESR of the
capacitors becomes crucial in order to keep ripple on the output (and
instability as a result) low. When capacitors with high ESR are used, the
result is that the capacitors heat up while in use. This often causes the
top of the can to bulge until the weak point in the middle breaks. At this
point, the electrolyte will evaporate. As this happens, the effective
capacitance of the capacitor reduces to almost nothing. The ripple of the
PSU will increase and eventually, the PSU will no longer even start.

In short, when I am presented with a faulty piece of equipment which I
suspect may be the SMPS, I immediately visually inspect the
electrolytic for
signs of bulging. If there are any with even the slightest of bulges, I
replace them without question. 9 times out of 10, this has worked.
Just last
week, I repaired a PC which would power on and then power down straight
away. I took the cover off and there were 7 caps on the MoBo with bulging
tops. I replaced them and the PC now works fine.

Hope this is insightful for some of you. Please tell me if you think I
missed the point, or have just wasted a lot of your time reading this.

Thanks

Pipester

From: Electronics_101@...
<mailto:Electronics_101%40yahoogroups.com>
[mailto:Electronics_101@...
<mailto:Electronics_101%40yahoogroups.com>] On Behalf Of Roland F.
Harriston
Sent: 24 January 2011 15:41
To: Electronics_101@...
<mailto:Electronics_101%40yahoogroups.com>
Subject: Re: [Electronics_101] LCD monitor power supply

An excelllent source for a variety of power supplies is Marlin P. Jones
Associates, Inc., located in
Lake Park, Florida (www. mpja.com). Prices are very reasonable, and a
wide variety of linear and
switch-mode power supplies are available. MPJ is always my first choice
when I need a power
supply.

Another thought: "Wall Warts" are not (generally) NOT regulated. A
"nominal" voltage is usually
specified on the unit, but since they are not regulated, the actual
voltage delivered to the device
being powered can vary a great deal, proportionate to the V/I demand of
the device being powered.

Switch-mode power supplies are almost always regulated, and these are
they types of supplies
that are used with computer monitors, etc.

IMHO, using an unregulated "wall wart" to powrer some devices can lead
to drastic disaster
at worst, and poor and erratic operation at best.

MPJ usually has in stock, a variety of switch-mode, regulated "bricks"
that are reasonably priced.
I never attempt to repair a failed switch-mode brick..............it
just not economically worth the
effort........that is.........if you can ever actually repair the
blasted thing and get back to spec.

For example: MPJ shows several 12VDC bricks with 1 Amp, up to 4 Amp
capability at prices
around 10 to 15 bucks.

Can't beat MJP's prices, variety, and fast shipment.

Spend your time designing something that's fun and useful.

Roland F. Harriston, P.D.
****

Roland F. Harriston

Andrew Villeneuve wrote:



I've actually had this exact same problem ( 19" LCD with a 12V/4A power
brick that burnt out ), and since I had a pair of 12V/2A wall-warts
laying
around, I ganged them together in parallel. Seems to work great.

Barring that, my standard approach to these problems would just be
to hook
up a spare ATX power supply - you can usually find them for free in
old PCs
that people throw away because they're underpowered they don't know
how to
clean up their virus collection.

-Andrew

On Wed, Jan 19, 2011 at 11:27 AM, Reese <reeza@...
<mailto:reeza%40reeza.com>
<mailto:reeza%40reeza.com>
<mailto:reeza%40reeza.com>> wrote:



I have a bad news story. The 100-240 v input, 12v 4A output power
brick
that sends power to my 19" LCD monitor apparently took a dump
overnight.
An LED on the brick does not light up properly, I can't measure
anything
on the output side. I've already looked in my spare parts piles, I do
not have any power bricks or wallwarts that come close enough.

I'm in the process of opening the plastic case, to see if anything is
obviously wrong and can easily be fixed. It's glued (no screws) so it
is slow going with a hobbyist slitting saw:

<

600-h/413S586EGEL__SL500_AA280_.jpg
On the chance that the brick is properly toasted and cannot be fixed,
what are some other options for 12vdc @ 4a to power the monitor?

Yes, I can Google for something, but I thought I'd ask here first. If
something quick and easy makes for a good project build, why not do
that instead of rushing of to purchase a turnkey item?

Reese
Re: Offset standard .1 header Eagle PCB article with component library

 

Yes, it was definitely on the Sparkfun site - although I didn't try to look for it again. I use FreePCB, always design my own footprints, and ever since I read it I have always offset one of the holes on any of my .100" headers by 5 mils. It works great.

Bob

--- In Electronics_101@..., "vaclav_sal" <vaclav_sal@...> wrote:

When my younger brother cannot find his house slippers he always complains about his roommate hiding them from him. The roommate, German fellow, last name sound to the untrained ear as "old timer".
Well, this playful German fellow made it to our house.

I recall reading an article about offsetting the circuit board pads in standard .1 header circuit layout to make the pins actually connect to the feed thru material instead of just being in at random.
It forces the header to sit straight on the board.

Now I just cannot remember where was this published. I though on Spartkfun site , but I just cannot find it there.
.
Of course Mr Google does not want to help! I am stuck.

Anybody run over this article?
Reason I am looking for it - they did include the new developed component library for Eagle PCB.

Sorry to bug you with my forgetfulness.

Vaclav
Re: LCD monitor power supply

Peter Morris
 

The reason that you can often get away with using the wrong "brick" is
because most of the monitor's internal circuitry requires voltages other
that 12 (usually 5 and 3.3 among others). The monitor has DC-DC converters
inside which will maintain a constant output voltage over a wide range of
input voltages. When using DC-Dc converters, the higher the input voltage,
the less current will be drawn from the supply. I'd be careful going too
high though, as there will be some devices requiring 12V (audio op-amps
spring to mind). Also, there are probably some electrolytic capacitors
across the 12V rail rated at either 16V, 25V, or 35V. If 16V - 19V "brick"
will kill them. With 25V - 19V will be close, but probably ok. If the caps
are 35V rated, then 19V won't harm them.

When choosing a replacement PSU (brick), the voltage is usually the most
important point of specification. If the original was 12V 4A, then the
replacement should be 12V (or close, eg. 11-14ish) and at least 4A. If the
monitor requires 4 amps, a 2 amp PSU won't be able to cope. A 12V 10A PSU
will work fine. A 20V 4A supply is not recommended.



As for repairing the old "brick", in my experience, the most common cause of
failure of switch-mode PSUs is electrolytic capacitors 'drying out'. This is
often because the PSUs are built to a pathetic budget, meaning the cheapest
parts are used, not the most appropriate. Switch-mode PSUs operate at high
frequencies (usually in the region of 100KHz). With current flowing in and
out of the bulk electrolytic capacitors at these rates, ESR of the
capacitors becomes crucial in order to keep ripple on the output (and
instability as a result) low. When capacitors with high ESR are used, the
result is that the capacitors heat up while in use. This often causes the
top of the can to bulge until the weak point in the middle breaks. At this
point, the electrolyte will evaporate. As this happens, the effective
capacitance of the capacitor reduces to almost nothing. The ripple of the
PSU will increase and eventually, the PSU will no longer even start.



In short, when I am presented with a faulty piece of equipment which I
suspect may be the SMPS, I immediately visually inspect the electrolytic for
signs of bulging. If there are any with even the slightest of bulges, I
replace them without question. 9 times out of 10, this has worked. Just last
week, I repaired a PC which would power on and then power down straight
away. I took the cover off and there were 7 caps on the MoBo with bulging
tops. I replaced them and the PC now works fine.



Hope this is insightful for some of you. Please tell me if you think I
missed the point, or have just wasted a lot of your time reading this.



Thanks



Pipester



From: Electronics_101@...
[mailto:Electronics_101@...] On Behalf Of Roland F. Harriston
Sent: 24 January 2011 15:41
To: Electronics_101@...
Subject: Re: [Electronics_101] LCD monitor power supply





An excelllent source for a variety of power supplies is Marlin P. Jones
Associates, Inc., located in
Lake Park, Florida (www. mpja.com). Prices are very reasonable, and a
wide variety of linear and
switch-mode power supplies are available. MPJ is always my first choice
when I need a power
supply.

Another thought: "Wall Warts" are not (generally) NOT regulated. A
"nominal" voltage is usually
specified on the unit, but since they are not regulated, the actual
voltage delivered to the device
being powered can vary a great deal, proportionate to the V/I demand of
the device being powered.

Switch-mode power supplies are almost always regulated, and these are
they types of supplies
that are used with computer monitors, etc.

IMHO, using an unregulated "wall wart" to powrer some devices can lead
to drastic disaster
at worst, and poor and erratic operation at best.

MPJ usually has in stock, a variety of switch-mode, regulated "bricks"
that are reasonably priced.
I never attempt to repair a failed switch-mode brick..............it
just not economically worth the
effort........that is.........if you can ever actually repair the
blasted thing and get back to spec.

For example: MPJ shows several 12VDC bricks with 1 Amp, up to 4 Amp
capability at prices
around 10 to 15 bucks.

Can't beat MJP's prices, variety, and fast shipment.

Spend your time designing something that's fun and useful.

Roland F. Harriston, P.D.
****

Roland F. Harriston

Andrew Villeneuve wrote:



I've actually had this exact same problem ( 19" LCD with a 12V/4A power
brick that burnt out ), and since I had a pair of 12V/2A wall-warts laying
around, I ganged them together in parallel. Seems to work great.

Barring that, my standard approach to these problems would just be to hook
up a spare ATX power supply - you can usually find them for free in
old PCs
that people throw away because they're underpowered they don't know how to
clean up their virus collection.

-Andrew

On Wed, Jan 19, 2011 at 11:27 AM, Reese <reeza@...
<mailto:reeza%40reeza.com>
<mailto:reeza%40reeza.com>> wrote:



I have a bad news story. The 100-240 v input, 12v 4A output power brick
that sends power to my 19" LCD monitor apparently took a dump overnight.
An LED on the brick does not light up properly, I can't measure anything
on the output side. I've already looked in my spare parts piles, I do
not have any power bricks or wallwarts that come close enough.

I'm in the process of opening the plastic case, to see if anything is
obviously wrong and can easily be fixed. It's glued (no screws) so it
is slow going with a hobbyist slitting saw:

<

600-h/413S586EGEL__SL500_AA280_.jpg
On the chance that the brick is properly toasted and cannot be fixed,
what are some other options for 12vdc @ 4a to power the monitor?

Yes, I can Google for something, but I thought I'd ask here first. If
something quick and easy makes for a good project build, why not do
that instead of rushing of to purchase a turnkey item?

Reese
Re: Can Multisim automatically calculate resistance?

 

Especially for Howard Hansen.
Re: Can Multisim automatically calculate resistance?

 

Thanks all you guys!
I found the Grapher View a wonderful tool!
Inspiration for the 555 timer design contest

 

A couple of articles from EDN magazine about the 555 timer, including news of a
new version from Advanced Linear Devices, the ALD7555 and ALD7556. Sounds like
the CMOS version on steroids.







The contest:


I have something I was?already working on using 555 timers, nothing special but
I think I'll enter it in the Art portion. I have a few other ideas, too.
Probably more than I have time for.

?Steve Greenfield AE7HD
Re: question

lists
 

In article <ihkhf1+qpst@...>,
Herbert <herbbartley@...> wrote:
I have an old computer monitor in my garage. What would it take use it
for an o-scope display?
It's been done in the past but you get about a 100kHz bandwidth (if you're
lucky) and a lot of trials and tribulations - not counting the blood,
sweat and tears.

Most of the 'scope projects I've seen over the years at least started off
with something like an old WWII radar tube.

--
Stuart Winsor

Midland RISC OS show - Sat July 9th 2011
Re: Source for 5KV ac supply?

 

For an off the shelf high voltage Ac power supply see:


For DIY plans see:


You will find more information using the search term "high voltage AC
power supply"

Howard

On 1/23/2011 11:12 PM, DaveC wrote:

Googling gets many hits for dell, sony, and other power supply
replacements (5000 being a model number or part number, not an output
voltge...)

Anyone know of a surplus or other cheapie source? Or plans?

Extra points for variable...

Thanks,
Dave
Re: Source for 5KV ac supply?

 

Scrounge up an old-school neon sign transformer (i.e., "iron" as opposed
to a modern switching-type NST)
and feed it with a variac. Or possibly a microwave oven transformer
feeding a simple voltage doubler.
If you're going to draw significant current, you'll want to research how
to remove the metal "shunts" in
the core of microwave oven xfmrs.

Randy

On 1/24/2011 12:12 AM, DaveC wrote:

Googling gets many hits for dell, sony, and other power supply
replacements (5000 being a model number or part number, not an output
voltge...)

Anyone know of a surplus or other cheapie source? Or plans?

Extra points for variable...

Thanks,
Dave


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

No virus found in this message.
Checked by AVG - www.avg.com <>
Version: 10.0.1191 / Virus Database: 1435/3398 - Release Date: 01/23/11
Re: Offset standard .1 header Eagle PCB article with component library

 

I suspect you're thinking of this tutorial:

On Mon, Jan 24, 2011 at 8:56 AM, vaclav_sal <vaclav_sal@...> wrote:




I recall reading an article about offsetting the circuit board pads in
standard .1 header circuit layout to make the pins actually connect to the
feed thru material instead of just being in at random.
It forces the header to sit straight on the board.

Now I just cannot remember where was this published. I though on Spartkfun
site , but I just cannot find it there.
.
Of course Mr Google does not want to help! I am stuck.

Anybody run over this article?
Reason I am looking for it - they did include the new developed component
library for Eagle PCB.

Sorry to bug you with my forgetfulness.

Vaclav
Re: Source for 5KV ac supply?

 

What frequency, voltage and current rating?

Howard

On 1/23/2011 11:12 PM, DaveC wrote:

Googling gets many hits for dell, sony, and other power supply
replacements (5000 being a model number or part number, not an output
voltge...)

Anyone know of a surplus or other cheapie source? Or plans?

Extra points for variable...

Thanks,
Dave
Re: PCB house pricing comment - off subject

Mike Payson
 

Just a guess, but you were probably using the wrong site. The Gold Phoenix
Website is not the most intuitive, but it has always been reliable for me.

On Mon, Jan 24, 2011 at 8:33 AM, vaclav_sal <vaclav_sal@...> wrote:

Mike,
Nothing specific about Gold Phoenix site since I was getting only - link
error , site does not exist, empty page etc..
I just don't get why some companies have useless web sites.
Why bother.
I had a similar experience with nameless outfit advertizing voice
recognition chips they no longer made!
Vaclav




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

Please trim excess when replyingYahoo! Groups Links
Re: question

Stefan Trethan
 

A computer to connect it to and a USB oscilloscope ;-)

No seriously, there is very little point in pursuing this.
Analog scopes use electrostatic deflection, a monitor uses magnetic
deflection (coils).
Also there is probably a whole lot of other stuff wrong with the CRT to make
a useful scope out of it.

You'd end up with something much less useful than a $10 analog scope, after
a lot of work.

Many many years ago I was thinking along similar lines with an old B/W TV
set. Luckily some day when I was walking past the (of course opened) set
sitting on the floor my trouser leg caught on the little nub on the back of
the jug, which broke off as designed and let the vacuum out (or in). That
put a stop to that little project.

ST

On Mon, Jan 24, 2011 at 7:46 PM, Herbert <herbbartley@...> wrote:

I have an old computer monitor in my garage. What would it take use it for
an o-scope display?



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

Please trim excess when replyingYahoo! Groups Links
question

 

I have an old computer monitor in my garage. What would it take use it for an o-scope display?
Re: Plugging holes in bakelite.

James M. &#92;(Jim&#92;) Geidl
 

Actually, you make a good point. If the holes a little then any hard curing
epoxy should work fine. Bando isn't so bad it you trim it down with a knife
or chisel before it gets rock hard.

James "Jim" M. Geidl, K6JMG

No trees were harmed in the sending of this message; however, a large number
of electrons were terribly inconvenienced.

-----Original Message-----
From: Electronics_101@...
[mailto:Electronics_101@...] On Behalf Of Reese
Sent: Monday, January 24, 2011 8:56 AM
To: Electronics_101@...
Subject: RE: [Electronics_101] Plugging holes in bakelite.

At 11:48 24 01 11, James M. &#92;(Jim&#92;) Geidl wrote:

I think I'd use Bondo or equivalent and tint it.
I'm wondering why JB Weld, tinted if necessary, would not work.
Besides, JB Weld is more widely available in the smaller
quantities needed for a bakelite/circuit board repair. And
unless you have some of the newer easy-sanding body filler on
hand? The old Bondo is a cast-iron beeeeyatch to sand down.

Bondo, the newer easy-sanding fillers, and JB weld all use a
chemo- thermal curing process. The heat produced is not that
great, for any of them except in large quantities - which is
not an issue here.

Reese


-----Original Message-----
From: Electronics_101@...
[mailto:Electronics_101@...] On Behalf Of vaclav_sal
Sent: Monday, January 24, 2011 8:07 AM
To: Electronics_101@...
Subject: [Electronics_101] Plugging holes in bakelite.

For the new generations of electronics hobbyists here -
there was a
time when radio "boxes" were made from one of the first plastics
invented - bakelite. So this is related to electrons in
some strage
way.

I have a box made in early fifties - that is 1950's.
It has some unwanted holes I would like to fill.
The challenge is - bakelite is temperature unfriendly, so
I cannot
use any thermosetting goop.
Of course it also needs to be polished and colored to match.

Any experienced old time radio restorer lurks here ?

Vaclav
Offset standard .1 header Eagle PCB article with component library

 

When my younger brother cannot find his house slippers he always complains about his roommate hiding them from him. The roommate, German fellow, last name sound to the untrained ear as "old timer".
Well, this playful German fellow made it to our house.

I recall reading an article about offsetting the circuit board pads in standard .1 header circuit layout to make the pins actually connect to the feed thru material instead of just being in at random.
It forces the header to sit straight on the board.

Now I just cannot remember where was this published. I though on Spartkfun site , but I just cannot find it there.
.
Of course Mr Google does not want to help! I am stuck.

Anybody run over this article?
Reason I am looking for it - they did include the new developed component library for Eagle PCB.

Sorry to bug you with my forgetfulness.

Vaclav
Re: Plugging holes in bakelite.

 

At 11:48 24 01 11, James M. &#92;(Jim&#92;) Geidl wrote:

I think I'd use Bondo or equivalent and tint it.
I'm wondering why JB Weld, tinted if necessary, would not work.
Besides, JB Weld is more widely available in the smaller quantities
needed for a bakelite/circuit board repair. And unless you have
some of the newer easy-sanding body filler on hand? The old Bondo
is a cast-iron beeeeyatch to sand down.

Bondo, the newer easy-sanding fillers, and JB weld all use a chemo-
thermal curing process. The heat produced is not that great, for
any of them except in large quantities - which is not an issue here.

Reese


-----Original Message-----
From: Electronics_101@...
[mailto:Electronics_101@...] On Behalf Of vaclav_sal
Sent: Monday, January 24, 2011 8:07 AM
To: Electronics_101@...
Subject: [Electronics_101] Plugging holes in bakelite.

For the new generations of electronics hobbyists here - there
was a time when radio "boxes" were made from one of the first
plastics invented - bakelite. So this is related to electrons
in some strage way.

I have a box made in early fifties - that is 1950's.
It has some unwanted holes I would like to fill.
The challenge is - bakelite is temperature unfriendly, so I
cannot use any thermosetting goop.
Of course it also needs to be polished and colored to match.

Any experienced old time radio restorer lurks here ?

Vaclav


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

Please trim excess when replyingYahoo! Groups Links
Re: Plugging holes in bakelite.

James M. &#92;(Jim&#92;) Geidl
 

I think I'd use Bondo or equivalent and tint it.

James "Jim" M. Geidl, K6JMG

No trees were harmed in the sending of this message; however, a large number
of electrons were terribly inconvenienced.

-----Original Message-----
From: Electronics_101@...
[mailto:Electronics_101@...] On Behalf Of vaclav_sal
Sent: Monday, January 24, 2011 8:07 AM
To: Electronics_101@...
Subject: [Electronics_101] Plugging holes in bakelite.

For the new generations of electronics hobbyists here - there
was a time when radio "boxes" were made from one of the first
plastics invented - bakelite. So this is related to electrons
in some strage way.

I have a box made in early fifties - that is 1950's.
It has some unwanted holes I would like to fill.
The challenge is - bakelite is temperature unfriendly, so I
cannot use any thermosetting goop.
Of course it also needs to be polished and colored to match.

Any experienced old time radio restorer lurks here ?

Vaclav
Re: PCB house pricing comment - off subject

 

Mike,
Nothing specific about Gold Phoenix site since I was getting only - link error , site does not exist, empty page etc..
I just don't get why some companies have useless web sites.
Why bother.
I had a similar experience with nameless outfit advertizing voice recognition chips they no longer made!
Vaclav
Re: Schematic Symbols Book?

 

ARRL Ham radio handbook used to have a schematc section, but I have not look at recent one.
It aslo may be little too spendy just for schematic synbols.
(And since you have said you want a book I will not suggest
"google it" )

But you may try Eagle PCB software - it has an extensive component library you could retrieve symbols you want.

BTW I think there is no limit on schematic "size", you could use ti to build your schematic only.


Vaclav

PS I hope references to PCB software are legal here, if not I'll delete this if necessary and reply privately. I posted it to the group because I feel the group may benefit.
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