sci.electronics.repair@googlegroups.com

Today's topics:

* NiMH new battery conditioning - 5 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/642feb09361f607e?hl=en
* Stupid question - 5 messages, 4 authors
http://groups.google.com/group/sci.electronics.repair/t/f7521ebc46223e72?hl=en
* Fuse: fast blown vs slow blown - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/075c97d6b6b6e1f0?hl=en
* free shipping wholesale CLOTHING jacket T-shirt long sleeve suit and hoody(
Franklin Marshall,Monclereiderdown,nike,adidas,a&f,d&g,ed harday,bape,bbc,lv,
gucci,armani,polo, poul smith and so on)/http://www.24hours-online.com/ - 1
messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/531daf8b11ca41f0?hl=en
* Video distortion on TV tube - 3 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/54b6737faa12803b?hl=en
* Lost in VIDEO signal - 4 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/9ac11c52da1a87d4?hl=en

==============================================================================
TOPIC: NiMH new battery conditioning
http://groups.google.com/group/sci.electronics.repair/t/642feb09361f607e?hl=en
==============================================================================

== 1 of 5 ==
Date: Wed, Jun 1 2011 11:50 am
From: Jeff Liebermann

On Wed, 1 Jun 2011 10:31:48 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

>"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
>news:ddpcu69fvgl4lb0fml8hsultltcmslgehi@4ax.com...
>> On Wed, 1 Jun 2011 09:06:40 -0700, "William Sommerwerck"
>> <grizzledgeezer@comcast.net> wrote:
>
>>> Much to my surprise, I discovered that the rechargeable cells powered the
>>> unit as long as the throwaways. This means I'd break even after only 10
>>> recharges. Even if I was off by 50%, I'd still need only 20 recharges.
>
>> Headphone amps sound like a light load. Got a number for the average
>> current drain?
>
>The operative word here is STAX -- as in high-voltage electrostatic
>earphones. I never measured the drain, but neither set of cells lasted much
>more than four hours.

$2,000 for earphones and you're worrying about the price of
rechargeable batteries? Argh.

There seems to be two amps. One with tubes and the other presumably
IC's.
<http://www.stax.co.jp/Export/ExportProducts.html>
55 watts and 46 watts power consumption from an internal 117VAC power
supply. No batteries in sight. Wrong unit?

>We still don't have a rational answer as to why some people don't have
>problems with rapid self-discharge.

Oh, that's easy. How many charge cycles would you guess you get on a
set of NiMH before they're ready to recycle? You probably don't know
and neither does Joe Sixpack. I don't even know because nobody is
counting. So, Joe Sixpack may get 2 years of service out his NiMH
battery pack, but has only charged it perhaps 20 times before it died.
I vaguely know someone that maintains TV camera battery packs for one
of the major networks. Current technology is Li-Ion but in the not so
distant past, it was NiMH and NiCd. He keeps meticulous records. I
must admit that I wasn't paying attention when he showed me the
numbers, but it seemed to me that even for identical battery packs,
the numbers were almost random. Some would last on a few charge
cycles, while other would last seemingly forever. He attributed this
mostly to depth of charge and storage temperature. Even the best
battery, stored hot, will die prematurely. This is a known problem
with Li-Ion, but I'm not sure if storage temperature has any effect on
NiMH. Mine are all in the fridge, just in case. Depth of charge is
the biggie. A battery that is only discharged to perhaps 75% of full
charge, can be charge cycled many more times than one that is fully
discharged before recharging. However, if the charger is too
aggressive, a battery that's discharged to 75% might be overcharged,
while the one that's fully discharged is less likely to be
overcharged.

>I don't shoot every day, so I can charge-up the night before. I have two
>chargers, which makes things easier.

I have 3 fast chargers. House, office, and vehicle. The one in the
vehicle seems to get the most use.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

== 2 of 5 ==
Date: Wed, Jun 1 2011 12:12 pm
From: "William Sommerwerck"

"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:gk1du65nn8ipkgboqqji1b9gkhmtds5in0@4ax.com...
> On Wed, 1 Jun 2011 10:31:48 -0700, "William Sommerwerck"
> <grizzledgeezer@comcast.net> wrote:

>> The operative word here is STAX -- as in high-voltage electrostatic
>> earphones. I never measured the drain, but neither set of cells
>> lasted much more than four hours.

> $2,000 for earphones and you're worrying about the price of
> rechargeable batteries? Argh.

No, they were more like $350. I said earphones, not headphones.

> There seems to be two amps. One with tubes and the other presumably
> IC's.
> <http://www.stax.co.jp/Export/ExportProducts.html>
> 55 watts and 46 watts power consumption from an internal 117VAC power
> supply. No batteries in sight. Wrong unit?

Wrong units. This is a pocket-sized transformerless energizer that runs off
two AA cells. It works with a tiny pair of electrostatic earphones.

> >We still don't have a rational answer as to why some people don't have
> >problems with rapid self-discharge.

> Oh, that's easy. How many charge cycles would you guess you get on a
> set of NiMH before they're ready to recycle? You probably don't know
> and neither does Joe Sixpack. I don't even know because nobody is
> counting. So, Joe Sixpack may get 2 years of service out his NiMH
> battery pack, but has only charged it perhaps 20 times before it died.
> I vaguely know someone that maintains TV camera battery packs for one
> of the major networks. Current technology is Li-Ion but in the not so
> distant past, it was NiMH and NiCd. He keeps meticulous records. I
> must admit that I wasn't paying attention when he showed me the
> numbers, but it seemed to me that even for identical battery packs,
> the numbers were almost random. Some would last on a few charge
> cycles, while other would last seemingly forever. He attributed this
> mostly to depth of charge and storage temperature. Even the best
> battery, stored hot, will die prematurely. This is a known problem
> with Li-Ion, but I'm not sure if storage temperature has any effect on
> NiMH. Mine are all in the fridge, just in case. Depth of charge is
> the biggie. A battery that is only discharged to perhaps 75% of full
> charge, can be charge cycled many more times than one that is fully
> discharged before recharging. However, if the charger is too
> aggressive, a battery that's discharged to 75% might be overcharged,
> while the one that's fully discharged is less likely to be
> overcharged.

That's extremely useful information, but I'm still not sure it answers the
question -- unless you're suggesting that the people who have problems with
rapid self-discharge have damaged their cells.

== 3 of 5 ==
Date: Wed, Jun 1 2011 5:30 pm
From: Jeff Liebermann

On Wed, 1 Jun 2011 12:12:03 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

>No, they were more like $350. I said earphones, not headphones.

Pardon my ignorance, but what is the difference between earphones and
headphones? I use the terms interchangeably.

>That's extremely useful information, but I'm still not sure it answers the
>question -- unless you're suggesting that the people who have problems with
>rapid self-discharge have damaged their cells.

Nope. A one line summary would be that most users don't remember how
many times they have charged their NiMH cells, don't recall how old
they are, and have no clue as what constitutes normal lifetime. If
someone has a battery killer in the form of a battery charger, they
would just continue to use it, killing battery after battery, without
ever doing the math needed to determine if something is wrong.

Even simpler... do *YOU* record the number of charge cycles of your
rechargeable batteries? If not, then you have no accurate way to
determine if you're getting the normal number of charge cycles
(400-800) from the NiMH batteries (unless you have a really good
memory).

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS

== 4 of 5 ==
Date: Wed, Jun 1 2011 6:08 pm
From: "William Sommerwerck"

"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:eqldu6lt7hdi9jp2hh5ai4u7a752pqunqp@4ax.com...
> On Wed, 1 Jun 2011 12:12:03 -0700, "William Sommerwerck"
> <grizzledgeezer@comcast.net> wrote:

>> No, they were more like $350. I said earphones, not headphones.

> Pardon my ignorance, but what is the difference between earphones
> and headphones? I use the terms interchangeably.

Headphones sit on your head. Earphones go in your ears. Sennheiser 600s are
headphones. Etymotics are earphones.

>> That's extremely useful information, but I'm still not sure it answers
the
>> question -- unless you're suggesting that the people who have problems
>> with rapid self-discharge have damaged their cells.

> Nope. A one line summary would be that most users don't remember
> how many times they have charged their NiMH cells, don't recall how
> old they are, and have no clue as what constitutes normal lifetime. If
> someone has a battery killer in the form of a battery charger, they
> would just continue to use it, killing battery after battery, without
> ever doing the math needed to determine if something is wrong.

That makes sense. However, the question was about rapid self-discharge --
NOT the total number of charge/discharge cycles.

> Even simpler... do *YOU* record the number of charge cycles of your
> rechargeable batteries? If not, then you have no accurate way to
> determine if you're getting the normal number of charge cycles
> (400-800) from the NiMH batteries (unless you have a really good
> memory).

None of my NiMH cells has had gone through more than 100 cycles -- most a
lot less.

Again, the issue is "rapid" self-discharge. I don't see where the gradual
loss of capacity necessarily results in more-rapid self-discharge.

The complaints about NiMH cells were with respect to nicads. I'm assuming
(perhaps incorrectly) that the plaintiffs were comparing relatively new NiMH
cells with older nicads -- which should have been in worse condition, and
therefore subject to more-rapid self-discharge.

== 5 of 5 ==
Date: Wed, Jun 1 2011 9:39 pm
From: "Wild_Bill"

My experience with newer NIMH high capacity cells indicates that their
capacity improves considerably, after at least several charge/discharge
cycles.
If I hadn't been aware of the NIMH chemistry's low initial capacity before I
purchased them, I would've been seriously disappointed at their initial test
results.

I've also seen, but not tried, cells that are claimed to be
pre-conditioned.. so they're supposedly ready for use after the first
charge.

My testing was controlled, and didn't perform any deep discharging, like
that which could happen with a cordless power tool, for example.

The cells I'm presently using are Powerizer 4500 mAh sub-C cells (in packs
of 5) and Tenergy 10,000 mAh D cells (also in packs of 5).

For the first couple of cycles, the capacity is about 50% and gradually
improves to full capacity after 5 or more cycles (at reasonable rates).
I'm using 1A charge rate for the 4500, and 2A for the 10k packs now..
although I wouldn't consider higher rates of 2A and 4A to be detrimental, as
long as the cells don't heat up.

The MRC Super Brain 977 will provide a reading for the discharge mAh, and
prevents damaging deep discharges.
Readouts will include rate, time and mAh.. so test results can be noted and
compared.
Charging and discharge rates are completely adjustable, which makes this
model fairly versatile.. and it can be input with vehicle 12V for charging
packs of less than 12V.

I also bought a MRC 992, which has a port for a USB cable (which I don't
have), and since the 992 doesn't have the discharge capability, I don't care
much about plotting charging cycles.

Sophisticated chargers can detect problems in charging rates and then shut
down, but less advanced chargers will continue to supply charging current.

I have experienced fault Errors with both of the MRC units, which I consider
a valuable feature.. there were 2 questionable older AA cells in the 4-cell
holder, and I'd marked those 2 cells previously becaue they had elevated
temperatures when charged with a different charger in the past.

I also have some negative-pulse chargers which continuously monitor the
state of charge. For these chargers, I just write the begin time on a
sticker, to see how long the packs have charged when they're finished.

Another handy item is a continuous rate discharging unit, made for cycling
commercial ENG camera batteries, as part of a conditioning cycle. Anton
Bauer ADM is a 2A rate for 12-14V packs.

As mentioned numerous times in the past, there are many different grades of
cells, and certain cell types have specific features that the others don't.
Traditionally, the best quality rechargeable cells are from Japan, and those
cell makers provide lots of specifications for their products.

I'm convinced that overheating cells is damaging, and precautions should be
taken to prevent overheating.
Unattended charging is generally high risk, as many battery pack temperature
cutouts are rated so high (65 C), that by the time the air in the plastic
housing reaches the cutout temp, the core temps of the cells are already
beyond a safe/reasonable range.

--
Cheers,
WB
.............

"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:aap8u6h1p0po506lfennu3kri5nnngh0ij@4ax.com...
> Per a previous discussion, I decided to test whether new NiMH
> batteries need to be conditioned or charged several times before
> reaching their rated capacity. Apparently they do.
>
> The test setup is a West Mtn Radio CBA-IIv1 battery analyzer.
> <http://802.11junk.com/jeffl/NiMH/cba-II.jpg>
> I didn't want to wait 20 hrs per test to get the official rated
> capacity, so I elected to run the tests at 1C which resulted in about
> a 45 minute test, but also resulted in a much lower capacity result.
> It also caused some unexpected errors. The design of the CBA-II does
> not include a Kelvin probe connection to eliminate any losses in the
> cables and connectors. It measures the voltage at the load, instead
> of at the battery. This is not a problem at low load currents, but at
> 2 amps, results in considerable error.
>
> Two new (out of the package) batteries were used. An Energizer NiMH
> 2300 ma-hr cell, and a Duracell 2050 ma-hr cell. Between tests, the
> batteries were quick charged in a Radio Shack 23-1305 NiMH quick
> charger (15 min). Each battery was discharged 3 times and the
> discharge curves plotted.
>
> Note that the Energizer package says 2450 ma-hr, while the battery is
> marked 2300 ma-hrs.
> <http://802.11junk.com/jeffl/NiMH/energizer.jpg>
>
> The Energizer cell showed no change in capacity between discharges.
> <http://802.11junk.com/jeffl/NiMH/Energizer-NiMH-2300.jpg>
> Using 1.0VDC as the end point, the measured cell capacity is:
> Run 1 1785 ma-hr
> Run 2 1890 ma-hr
> Run 3 1895 ma-hr
>
> The Duracell cell showed a larger change.
> <http://802.11junk.com/jeffl/NiMH/Duracelll-NiMH-2050.jpg>
> Using 1.0VDC as the end point, the measured cell capacity is:
> Run 1 1200 ma-hr
> Run 2 1270 ma-hr
> Run 3 1385 ma-hr
>
> The net improvement over 3 charge-discharge runs is about 10% for the
> Energizer and 15% for the Duracell. Not huge, but certainly
> measurable. Whether it is worth the effort conditioning the battery
> before use, is debatable.
>
> --
> Jeff Liebermann jeffl@cruzio.com
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

==============================================================================
TOPIC: Stupid question
http://groups.google.com/group/sci.electronics.repair/t/f7521ebc46223e72?hl=en
==============================================================================

== 1 of 5 ==
Date: Wed, Jun 1 2011 11:59 am
From: Jeff Liebermann

On Wed, 1 Jun 2011 11:47:18 -0700 (PDT), klem kedidelhopper
<captainvideo462009@gmail.com> wrote:

>Lately I've had more than a few flat screens in the shop with bulged
>capacitors in the power supply.

Shhhh... replacing such parts is what's keeping me in business.

>I've noticed that in many of these
>sets there might be for instance two or three 1000UF caps in parallel.
>Is there any reason in the manufacturing process to parallel three
>1000UF capacitors when one 3300UF would do the job? Lenny

Height. Flat panel LCD monitors tend to be rather thin. Everyone
wants low profile thin products these daze. 3300uF caps tend to be
taller than 1000uF caps. I don't know exactly why, but it seems to do
with the way the foil and insulators are wrapped inside the can. I
haven't seen any short and fat PCB mount caps. While it's possible to
use axial leaded caps instead of radial, the robotic insertion
hardware greatly prefers radial leads.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

== 2 of 5 ==
Date: Wed, Jun 1 2011 12:10 pm
From: Jamie

klem kedidelhopper wrote:

> Lately I've had more than a few flat screens in the shop with bulged
> capacitors in the power supply. I've noticed that in many of these
> sets there might be for instance two or three 1000UF caps in parallel.
> Is there any reason in the manufacturing process to parallel three
> 1000UF capacitors when one 3300UF would do the job? Lenny
You get better ESR results with smaller cap values.

Jamie

== 3 of 5 ==
Date: Wed, Jun 1 2011 1:38 pm
From: "Ian Field"

"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in message
news:e1wFp.19195$pi2.17799@newsfe11.iad...
> klem kedidelhopper wrote:
>
>> Lately I've had more than a few flat screens in the shop with bulged
>> capacitors in the power supply. I've noticed that in many of these
>> sets there might be for instance two or three 1000UF caps in parallel.
>> Is there any reason in the manufacturing process to parallel three
>> 1000UF capacitors when one 3300UF would do the job? Lenny
> You get better ESR results with smaller cap values.

More to the point, the difference in ESR is not directly proportional to the
different sizes of capacitor, so 3x 1000uF has ESR of not much more than 1/3
that of a single 3000uF.

== 4 of 5 ==
Date: Wed, Jun 1 2011 2:59 pm
From: "Charles"

"Ian Field" wrote in message news:OqxFp.28874$A05.2940@newsfe13.ams2...

"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in message
news:e1wFp.19195$pi2.17799@newsfe11.iad...
> klem kedidelhopper wrote:
>
>> Lately I've had more than a few flat screens in the shop with bulged
>> capacitors in the power supply. I've noticed that in many of these
>> sets there might be for instance two or three 1000UF caps in parallel.
>> Is there any reason in the manufacturing process to parallel three
>> 1000UF capacitors when one 3300UF would do the job? Lenny
> You get better ESR results with smaller cap values.

More to the point, the difference in ESR is not directly proportional to the
different sizes of capacitor, so 3x 1000uF has ESR of not much more than 1/3
that of a single 3000uF.

It's the form factor, as Jeff has suggested.

== 5 of 5 ==
Date: Wed, Jun 1 2011 10:20 pm
From: Jeff Liebermann

On Wed, 1 Jun 2011 17:59:44 -0400, "Charles"
<charlesschuler@comcast.net> wrote:

>More to the point, the difference in ESR is not directly proportional to the
>different sizes of capacitor, so 3x 1000uF has ESR of not much more than 1/3
>that of a single 3000uF.

Easy enough to test, or so I thought. First, I spend 10 minutes
rescuing my Dick Smith ESR meter from the Gordian Knot of tangled
cables behind my test equipment wall. I then find an old PCB (Okidata
320 printer board) with 3300uf 35v and 1000uf 35v Rubyeon
electrolytics. Carefully measuring the ESR, I get;
1000 uF 35v = 0.05 ohms
3300 uf 35v = 0.04 ohms
So much for the 3x theory. I'll see if I can find some 6.3v or 10v
caps, which should (hopefully) give higher ESR readings that are not
at the extreme of the meter range.

>It's the form factor, as Jeff has suggested.

Well, maybe not. The 3300 uf is only about 1mm taller than the 1000
uF cap, and a little less than twice as wide.
<http://802.11junk.com/jeffl/crud/ESR-test-01.jpg>
I would have thought the 3300 uF would be somewhat larger.

I just hate it when my measurements don't agree with my guesswork.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

==============================================================================
TOPIC: Fuse: fast blown vs slow blown
http://groups.google.com/group/sci.electronics.repair/t/075c97d6b6b6e1f0?hl=en
==============================================================================

== 1 of 2 ==
Date: Wed, Jun 1 2011 12:12 pm
From: Jamie

Winston wrote:

> Phil Allison wrote:
>
> (...)
>
>> Piss off wanker.
>
>
> You are so beautiful when you are angry, Phil.
>
> --Winston :)
no, he's not angry, he's being Phil.

Jamie

== 2 of 2 ==
Date: Wed, Jun 1 2011 1:05 pm
From: Winston

Jamie wrote:
> Winston wrote:
>
>> Phil Allison wrote:
>>
>> (...)
>>
>>> Piss off wanker.
>>
>>
>> You are so beautiful when you are angry, Phil.
>>
>> --Winston :)
> no, he's not angry, he's being Phil.

http://en.wikipedia.org/wiki/Coprolalia

I see.

--Winston

==============================================================================
TOPIC: free shipping wholesale CLOTHING jacket T-shirt long sleeve suit and
hoody(Franklin Marshall,Monclereiderdown,nike,adidas,a&f,d&g,ed harday,bape,
bbc,lv,gucci,armani,polo, poul smith and so on)/http://www.24hours-online.com/
http://groups.google.com/group/sci.electronics.repair/t/531daf8b11ca41f0?hl=en
==============================================================================

== 1 of 1 ==
Date: Wed, Jun 1 2011 6:36 pm
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==============================================================================
TOPIC: Video distortion on TV tube
http://groups.google.com/group/sci.electronics.repair/t/54b6737faa12803b?hl=en
==============================================================================

== 1 of 3 ==
Date: Wed, Jun 1 2011 8:16 pm
From: "hrhofmann@att.net"

On Jun 1, 10:54 am, "Dave" <db5...@hotmail.com> wrote:
> Okay, I've fixed the vertical hold problem mentioned in another string of
> posts, and now the bottom of the picture is overlaid or superimposed over
> the top of the picture, at the top of the screen,.  I was thinking this is
> most likely an adjustment, but couldn't find the pot that affected it and
> ended up pulling the CRT out to gain access to and adjust a variable
> inductor at the back middle of the PC board.  So now the problem is not as
> bad, but it's still there.  I'm guessing this is some sort of wrap-around,
> but have no idea as to what to do about it.  Any suggestions? Surely this
> isn't the first time something like this as happened with a TV.  There are
> four pots on this board, but one of them doesn't seem to do anything to the
> picture, so I am trying to leave it where it was.  If anyone has any ideas,
> I'm all ears.
>
> Thanks bunches.
>
> Dave

How about a make model, year age info, etc?????

== 2 of 3 ==
Date: Wed, Jun 1 2011 9:49 pm
From: spamtrap1888

On Jun 1, 8:54 am, "Dave" <db5...@hotmail.com> wrote:
> Okay, I've fixed the vertical hold problem mentioned in another string of
> posts, and now the bottom of the picture is overlaid or superimposed over
> the top of the picture, at the top of the screen,.  I was thinking this is
> most likely an adjustment, but couldn't find the pot that affected it and
> ended up pulling the CRT out to gain access to and adjust a variable
> inductor at the back middle of the PC board.  So now the problem is not as
> bad, but it's still there.
>

Sounds like your original problem was height or linearity, not
vertical hold.

http://books.google.com/books?id=XOMDAAAAMBAJ&pg=PA170&lpg=PA170&source=bl&ots=SMB4elO4c3&sig=JTviy4TLebvoDdYd5Ky9ObZsrzs&hl=en&ei=owznTYvhI4nRiALXofnNCQ&sa=X&oi=book_result&ct=result&resnum=2&ved=0CCQQ6AEwATgK#v=onepage&q&f=false

== 3 of 3 ==
Date: Wed, Jun 1 2011 10:04 pm
From: stratus46@yahoo.com

On Jun 1, 8:54 am, "Dave" <db5...@hotmail.com> wrote:
> Okay, I've fixed the vertical hold problem mentioned in another string of
> posts, and now the bottom of the picture is overlaid or superimposed over
> the top of the picture, at the top of the screen,.  I was thinking this is
> most likely an adjustment, but couldn't find the pot that affected it and
> ended up pulling the CRT out to gain access to and adjust a variable
> inductor at the back middle of the PC board.  So now the problem is not as
> bad, but it's still there.  I'm guessing this is some sort of wrap-around,
> but have no idea as to what to do about it.  Any suggestions? Surely this
> isn't the first time something like this as happened with a TV.  There are
> four pots on this board, but one of them doesn't seem to do anything to the
> picture, so I am trying to leave it where it was.  If anyone has any ideas,
> I'm all ears.
>
> Thanks bunches.
>
> Dave

Replace the bad electrolytics in the vertical output particularly if
it's inside the feedback look. Sony 8" color monitors are notorious
for this. Don't screw with the pots but I'm sure you already did. If
you ever need to move things more than 10% it's broken or somebody did
what you're doing now. Diddling but it won't take long to correct once
the bad caps are gone. And don't buy cheap crap. Look for highest
ripple current.

G²

==============================================================================
TOPIC: Lost in VIDEO signal
http://groups.google.com/group/sci.electronics.repair/t/9ac11c52da1a87d4?hl=en
==============================================================================

== 1 of 4 ==
Date: Wed, Jun 1 2011 8:18 pm
From: "hrhofmann@att.net"

On Jun 1, 10:55 am, benitos <poth...@cae.ca> wrote:
> On Jun 1, 10:38 am, "Phil Allison" <phi...@tpg.com.au> wrote:
>
> > "benitos"
>
> > I cannot connect the AMP to the CAM side , only at the Display
> > side. That's an issue.
>
> > ** How are you getting power to the camera  ?
>
> >   ( runs on 12V DC or 24VAC at about 4 watts )
>
> > ...  Phil
>
> I put 24VAC to the CAM now.
>
> On DC12 , cable is too long ,was getting 6.5 volts to the CAM.

Putting an amp at the dislay end just amplifies signal plus noise, it
must be closer to the camera so that it only amplifies signal and not
noise.....

== 2 of 4 ==
Date: Wed, Jun 1 2011 9:22 pm
From: "Phil Allison"

<hrhofmann@att.net>
"Phil Allison" :
>
> > "benitos"
>
> > I cannot connect the AMP to the CAM side , only at the Display
> > side. That's an issue.

Putting an amp at the dislay end just amplifies signal plus noise, it
must be closer to the camera so that it only amplifies signal and not
noise.....

** Where is this mysterious extra noise coming from ??

The self noise of a 75 ohm source in a 5 MHz bandwidth ( circa 1uV ) is not
relevant to a 1 volt video signal.

The antenna problem, where one is dealing with uV level signals, is another
kettle of fish.

.... Phil

== 3 of 4 ==
Date: Wed, Jun 1 2011 10:03 pm
From: Jeff Liebermann

On Wed, 1 Jun 2011 20:18:06 -0700 (PDT), "hrhofmann@att.net"
<hrhofmann@att.net> wrote:

>Putting an amp at the dislay end just amplifies signal plus noise, it
>must be closer to the camera so that it only amplifies signal and not
>noise.....

It's not a S/N problem. It's the change in group delay across the
video frequency range that's distorting the parts of the NTSC video.
Throw in a -6dB/octave loss to trash the amplitude. See the photos
near the bottom of:
<http://www.intersil.com/data/fn/fn6739.pdf>

Instead of an adaptive equalizer, it can be done with a passive
equalizer, followed by an amplifier to compensate for the losses. The
adaptive equalizer adjusts itself, while the passive equalizer and amp
design requires level adjustment. When something changes in the
cabling, the levels need to be re-adjusted.

Typical video distribution amplifier:
<http://www.multidyne.com/amps.html>
Claims "3000 feet of Belden RG59U to within +/-0.05dB at 5MHz".
Probably overkill for a security camera.

This design works to 250ft. More amplifier gain will be required for
1500ft.
<http://cds.linear.com/docs/Design%20Note/dn92.pdf>

Here's another example. Claims 1000ft or more:
<http://www.decadenet.com/cab/cab.html>

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

== 4 of 4 ==
Date: Wed, Jun 1 2011 10:18 pm
From: "Phil Allison"

"benitos"
>
> We have a CCTV cam (Bosh WZ18) that is 1500 feet from the LCD display.
>
> The cable that was used is a RG59 and having 2 splices (2 junctions).
>
> The video signal is poor , we can see tha image but with lines and
> it's noisy.

** That sounds like you have a ground loop in the cabling passing noise into
the shield of the RG59.

Your 24VAC may well be the source.

Or possibly injection from AC power cables running along with the RG59.

Whatever, the pic should not contain noise or lines.

.... Phil

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