sci.electronics.repair
http://groups.google.com/group/sci.electronics.repair?hl=en

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Today's topics:

* Magnetic door holders question - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/21eb21515055e1fe?hl=en
* Identifying buck-boost transformer windings? - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/401048ec1c4ab948?hl=en
* Loss of preset settings on LCD monitor - 4 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/a04d8e22e7d8fc34?hl=en
* 75 ohm Termination Question - 14 messages, 8 authors
http://groups.google.com/group/sci.electronics.repair/t/be000fe11979bff2?hl=en
* Do remote keypads sweat silcone oil? - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/c14d8e962b605e97?hl=en
* Comprehensive test banks and solution manuals for sale - 1 messages, 1
author
http://groups.google.com/group/sci.electronics.repair/t/8e2e7a53cd376039?hl=en
* Phase Linear 400 output transistors - 3 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/d0cb28fa4ada674c?hl=en

==============================================================================
TOPIC: Magnetic door holders question
http://groups.google.com/group/sci.electronics.repair/t/21eb21515055e1fe?hl=en
==============================================================================

== 1 of 1 ==
Date: Thurs, Feb 13 2014 4:14 am
From: "Michael A. Terrell"



Adrian Tuddenham wrote:
>
> Michael A. Terrell <mike.terrell@earthlink.net> wrote:
>
> > Adrian Tuddenham wrote:
> > >
> > > Michael A. Terrell wrote:
> > > >
> > > >
> > > > All I've seen in use, use AC to prevent this problem.
> > >
> > > ...except that A.C. doesn't prevent it. I've seen enough stuck
> > > contactors with A.C. coils to be quite certain of that.
> >
> >
> > They are not contactors. Some hold the door open for years between
> > operations. Contactors get beat to death by repeatedly slamming the pole
> > piece into the metal on the moving contacts.
> >
> >
> > You're comparing apples to water melons.
>
> These D.C. magnets with flat pole faces are getting stuck because of
> residual magnetism - A.C. contactors with laminated pole faces which
> have become hammered flat, get stuck in exactly the same way.
>
> This is not because the contactors have had to do a lot of work in order
> to develop flat pole faces, it is because the residual magnetism is the
> same, regardless of whether it resulted from D.C. or the last half-cycle
> of A.C.

The old sliding fire doors on slanted rollers that used a rope and
weights were pretty much foolproof. They didn't need electricity, and
there was little you could do to screw them up. Once they were moving,
you couldn't hold them open.

Those laminated contactors take thousands and thousands of operations
to flatten into a solid face.

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.





==============================================================================
TOPIC: Identifying buck-boost transformer windings?
http://groups.google.com/group/sci.electronics.repair/t/401048ec1c4ab948?hl=en
==============================================================================

== 1 of 1 ==
Date: Thurs, Feb 13 2014 5:05 am
From: "Michael A. Terrell"



Salmon Egg wrote:
>
> In article
> <0001HW.CF1FBCBB056C00BCB01029BF@news.eternal-september.org>,
> DaveC <invalid@invalid.net> wrote:
>
> > Imagine you are asked to install a used buck-boost transformer. Imagine you
> > could normally do this in a few minutes. Except if the leads were cut short
> > such that identifying characters on the leads' insulation were missing.
> >
> > Identifying 2 leads belonging to any one winding is straightforward ohm meter
> > work. Maybe use of a ESR meter might help separate the X windings from the H
> > windings?. But identifying which specific winding is which and which end is
> > which--not so straightforward. For me.
> >
> > How would you go about identifying the windings? Maybe use a Variac to input
> > voltage to each of the windings then measure the output of the others? What
> > outputs should I expect at, for example, the H3/H4 winding with a voltage on
> > H1/H2 winding? How to identify backward connection of a winding?
> >
> > Are the two H windings identical? The two X windings?
> >
> > Suggestions welcome.
> >
> > This is a 208 -> 230 (ie, 12 & 24 v buck-boost voltage) single-phase
> > autotransformer in N. America.
> >
> > Thanks.
>
> I am intrigued by this post and the replies. The post has little useful
> information and the replies are based on assumption that that may have
> little connection to reality. From the description, I have no idea if
> there really is an auto transformer, completely separate windings, or a
> combination of both. Also I have no idea what a description "H3/H4
> winding" means. I refuse to guess. Try to understand this communication
> is in writing and not telepathic.
>
> 1. An ohmmeter can separate one set of connected windings from other
> such sets. If there are taps, you might even find the ends of the
> windings and and the order of the taps.
>
> 2. Put all these winding sets in series.
>
> 3. Using your Variac, energize one winding (without saturating).
>
> 4. From voltage measurements you should be able to find the turn ratios
> amongst the various windings.
>
> 5. You should also be able to locate which ends of a winding are in
> phase or out of phase with the ends of your excited winding.
>
> In the future, realize that good communication requires good grammar and
> little ambiguity.


There is no ambiguity. A typical datasheet will tell you that 'X' is a
high voltage lead, and that 'H' is a low voltage lead.

If you'd ever installed one you would know that they have two
primaries and two secondaries, all four isolated. For 120, you parallel
the primaries in phase. The secondaries are connected in series with the
load. The phase affects the addition to or subtraction from the line
voltage. It isn't rocket science. I recently installed one on a pipe
bender at a factory, right after the company had moved to a larger
building.

That machine had two problems. It was built for 240 volts, and they
had 208. The other problem was that the so called industrial electrician
they hired wired it for 120 V because he was too damned lazy to go back
to the shop and get the right breaker. A boost transformer and the right
breaker had it working better than it had at their old location, where
it had been on a 208 volt circuit.


For your transformer, all you need is an ohm meter to identify each
winding, and an AC voltmeter to figure out the phasing of each winding.


The logical steps are:


1: Identify the pairs of the thin leads with an ohm meter. These are
the primaries.

2: Identify the pairs of the thick leads with an Ohm meter. These are
the Secondaries.

(BTW, I would put a cable tie around each pair of leads, near the
transformer to keep track of each pair in case you need to reuse it in
the suture.)

3: For 208, connect the two sets of primary wires in series. If you
have 12 volts on the outputs, they are in phase. If not, reverse one set
of the primary leads.

4: Connect a pair of the secondary leads in series. If you get 24
volts, you can use it for 24 volts. If you get zero, connect the
remaining two leads together will give you 12 volts. Just keep in mind
that you only get half the current at 24 volts.


Page 93 of this PDF shows the primaries wired for 120 or 240 and the
secondaries in series or parallel to give 12 or 24 volts boost or buck

<http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=16&cad=rja&ved=0CFwQFjAP&url=http%3A%2F%2Fwww.hammondpowersolutions.com%2Ffiles%2FHPS_Catalog_BuckBoost_Section2.pdf&ei=nr_8Uri1A_fNsQT11YAY&usg=AFQjCNEyTy77_co5ZMOQii2jkEUDw8W1Cw&sig2=-VF-Fyg1XsdHDckcm9EIjw>

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.





==============================================================================
TOPIC: Loss of preset settings on LCD monitor
http://groups.google.com/group/sci.electronics.repair/t/a04d8e22e7d8fc34?hl=en
==============================================================================

== 1 of 4 ==
Date: Thurs, Feb 13 2014 7:06 am
From: Ken


I have a Dell 1907FPVt monitor that often loses its preset settings for
brightness, color, etc. It is not a problem in that I have found a way
around it, but I was wondering if there is a better solution than the
one I found.

The above monitor will come on without pressing the power switch if one
were to simply plug it in to AC. That is simply a characteristic of the
monitor as I discovered through a search for that model. I have the
monitor attached to a UPS along with my computer, so if I remove power
completely by shutting down the UPS, when I power it up the monitor
automatically turns on. It appears that when the monitor powers up in
this way, it sometimes (20% of the time) fails to assume the preset
settings. Once it is powered up, I can set the settings to factory
settings and the monitor responds properly.

Since it appeared to me to be a situation where power had perhaps not
risen fast enough to read the retained settings, I opened up the monitor
looking for a cap that was weak. Using a ESR meter, I found none. I
did not trace out the standby voltage circuit and perhaps I should have,
but I had no schematic and it appeared to be more work than I was
prepared to do.

What I have discovered as I was suspecting, is that the monitor never
loses its settings if the monitor remains plugged in and it is turned
off via the switch on the monitor. So it appears that the standby
voltage is not coming up fast enough.

So my questions are these: Has anyone else experienced a similar
problem? And if so, were you able to solve it? Or am I locked into
keeping the monitor attached to AC so it maintained the standby voltage
and use the switch on the monitor to turn it on? I find the latter
solution awkward as it defeats the purpose of the UPS, and I would need
to change the monitor power cable to one attached to the UPS when a
power interruption occurs.




== 2 of 4 ==
Date: Thurs, Feb 13 2014 7:12 am
From: N_Cook


On 13/02/2014 15:06, Ken wrote:
> I have a Dell 1907FPVt monitor that often loses its preset settings for
> brightness, color, etc. It is not a problem in that I have found a way
> around it, but I was wondering if there is a better solution than the
> one I found.
>
> The above monitor will come on without pressing the power switch if one
> were to simply plug it in to AC. That is simply a characteristic of the
> monitor as I discovered through a search for that model. I have the
> monitor attached to a UPS along with my computer, so if I remove power
> completely by shutting down the UPS, when I power it up the monitor
> automatically turns on. It appears that when the monitor powers up in
> this way, it sometimes (20% of the time) fails to assume the preset
> settings. Once it is powered up, I can set the settings to factory
> settings and the monitor responds properly.
>
> Since it appeared to me to be a situation where power had perhaps not
> risen fast enough to read the retained settings, I opened up the monitor
> looking for a cap that was weak. Using a ESR meter, I found none. I
> did not trace out the standby voltage circuit and perhaps I should have,
> but I had no schematic and it appeared to be more work than I was
> prepared to do.
>
> What I have discovered as I was suspecting, is that the monitor never
> loses its settings if the monitor remains plugged in and it is turned
> off via the switch on the monitor. So it appears that the standby
> voltage is not coming up fast enough.
>
> So my questions are these: Has anyone else experienced a similar
> problem? And if so, were you able to solve it? Or am I locked into
> keeping the monitor attached to AC so it maintained the standby voltage
> and use the switch on the monitor to turn it on? I find the latter
> solution awkward as it defeats the purpose of the UPS, and I would need
> to change the monitor power cable to one attached to the UPS when a
> power interruption occurs.

ESR does not necessarily find low capicitance caps, try a 1KHz RLC meter
set on C if the circuit allows it




== 3 of 4 ==
Date: Thurs, Feb 13 2014 8:07 am
From: stratus46@yahoo.com



Many times you'll find a small ceramic in parallel with the 'lytic. The ceramic cap will 'fool' the ESR meter. If it reads bad with an ESR meter it is bad. If it reads good you need to remove it, let it cool off (heat improves it ) and measure it again. There's a good chance the cap is bad. In switching supplies the caps need to be perfect. There is no 'good enough'. Make sure you buy caps with lowest E$R / highest ripple current.

G²




== 4 of 4 ==
Date: Fri, Feb 14 2014 3:55 am
From: Ken


Thanks for the replies, I shall look closer at the caps should I open up
the monitor again.





==============================================================================
TOPIC: 75 ohm Termination Question
http://groups.google.com/group/sci.electronics.repair/t/be000fe11979bff2?hl=en
==============================================================================

== 1 of 14 ==
Date: Thurs, Feb 13 2014 10:40 am
From: Bennett


A friend replaced her Comcast TV box with an over-the-air antenna but
continues to use Comcast Internet service. This leaves her
Comcast-supplied splitter with an unterminated socket - does it matter?
Should I bother to terminate it?

(A barrel connector isn't a good replacement for the splitter as the
splitter provides a grounding point.)

---
This email is free from viruses and malware because avast! Antivirus protection is active.
http://www.avast.com





== 2 of 14 ==
Date: Thurs, Feb 13 2014 11:18 am
From: dplatt@coop.radagast.org (David Platt)


>A friend replaced her Comcast TV box with an over-the-air antenna but
>continues to use Comcast Internet service. This leaves her
>Comcast-supplied splitter with an unterminated socket - does it matter?
>Should I bother to terminate it?
>
>(A barrel connector isn't a good replacement for the splitter as the
>splitter provides a grounding point.)

It is a good idea to do so.

Cable-TV systems often use frequencies on the cable that are assigned
to non-television services for over-the-air use (e.g. aircraft, ham
band, etc.). If you have loose or unterminated cable connections,
some of the cable-TV signal will "leak" out and can be radiated. This
can cause interference in those other services.

The cable companies usually have "signal leak" detection teams driving
around occasionally, looking for emission from their cable
transmissions which ought not to be present. I've heard of people
who've had their cable company employees arrive at their door, and
insist that their in-home wiring either be fixed or disconnected.

Also, if you don't terminate a splitter port, you'll create an
impedance mismatch at that point, and this can cause a signal
"reflection" within the cable. Depending on the quality of the
splitter (its port-to-port isolation) this reflection can cause
"ghosts" in an analog TV transmission, multipath distortion in analog
FM, and inter-symbol interference (leading to a higher bit-error rate
and possible dropouts) in digital TV.

75-ohm F-connector terminators are cheap and widely available. It's
good practice to use them on all otherwise-unused splitter ports.






== 3 of 14 ==
Date: Thurs, Feb 13 2014 11:29 am
From: "Geoffrey S. Mendelson"


David Platt wrote:
>
> The cable companies usually have "signal leak" detection teams driving
> around occasionally, looking for emission from their cable
> transmissions which ought not to be present. I've heard of people
> who've had their cable company employees arrive at their door, and
> insist that their in-home wiring either be fixed or disconnected.

If the FCC catches them (usually because of a complaint from the user
of those frequencies) they can be heavily fined, so usually they are
agressive at tracking down "leakage".

Geoff.


--
Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379





== 4 of 14 ==
Date: Thurs, Feb 13 2014 3:25 pm
From: "hrhofmann@sbcglobal.net"


On Thursday, February 13, 2014 12:40:26 PM UTC-6, Bennett wrote:
> A friend replaced her Comcast TV box with an over-the-air antenna but continues to use Comcast Internet service. This leaves her Comcast-supplied splitter with an unterminated socket - does it matter? Should I bother to terminate it? (A barrel connector isn't a good replacement for the splitter as the splitter provides a grounding point.) --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com

COMCAST might even furnish your friend with a splitter.




== 5 of 14 ==
Date: Thurs, Feb 13 2014 3:25 pm
From: "hrhofmann@sbcglobal.net"


Oops, I meant furnish your friend a terminator




== 6 of 14 ==
Date: Thurs, Feb 13 2014 5:17 pm
From: Jeff Liebermann


On Thu, 13 Feb 2014 10:40:26 -0800, Bennett <bjprice@cal.berkeley.edu>
wrote:

>A friend replaced her Comcast TV box with an over-the-air antenna but
>continues to use Comcast Internet service. This leaves her
>Comcast-supplied splitter with an unterminated socket - does it matter?

Yes, it matters.

>Should I bother to terminate it?

Yes, you should terminate it.

>(A barrel connector isn't a good replacement for the splitter as the
>splitter provides a grounding point.)

Sorta. Apparently she has a 2 way splitter installed with one port
left unterminated. A barrel connector is a very good replacement.
However, you're correct that you'll need to do something about the
grounding point. If this is indoors, just remove the grounding wire,
wrap it around the barrel connector, and hold it in place with a small
hose clamp. For outdoors, use a proper grounding clamp:
<http://www.solidsignal.com/pview.asp?p=pvgb1&d=perfect-vision-pvgb1-single-grounding-blocks-%28pvgb1%29>
<https://www.google.com/search?tbm=isch&q=cable+tv+grounding+block>
For outdoors, also don't forget to recreate the coax drip loop so that
water doesn't run into the connector block, or into the house.
<http://activerain.com/blogsview/3168531/drip-loop-really-do-you-need-it-wenatchee-and-leavenworth-home-inspection>
<http://images.meredith.com/diy/images/2009/03/p_SCW_240_02.jpg>
--
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




== 7 of 14 ==
Date: Thurs, Feb 13 2014 5:31 pm
From: Jeff Liebermann


On Thu, 13 Feb 2014 15:25:34 -0800 (PST), "hrhofmann@sbcglobal.net"
<hrhofmann@sbcglobal.net> wrote:

>Oops, I meant furnish your friend a terminator

Careful. Comcast has an early termination fee.

--
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




== 8 of 14 ==
Date: Thurs, Feb 13 2014 5:41 pm
From: Bennett


On 2/13/2014 5:17 PM, Jeff Liebermann wrote:
> On Thu, 13 Feb 2014 10:40:26 -0800, Bennett <bjprice@cal.berkeley.edu>
> wrote:
>
>> A friend replaced her Comcast TV box with an over-the-air antenna but
>> continues to use Comcast Internet service. This leaves her
>> Comcast-supplied splitter with an unterminated socket - does it matter?
>
> Yes, it matters.
>
>> Should I bother to terminate it?
>
> Yes, you should terminate it.
>
>> (A barrel connector isn't a good replacement for the splitter as the
>> splitter provides a grounding point.)
>
> Sorta. Apparently she has a 2 way splitter installed with one port
> left unterminated. A barrel connector is a very good replacement.
> However, you're correct that you'll need to do something about the
> grounding point. If this is indoors, just remove the grounding wire,
> wrap it around the barrel connector, and hold it in place with a small
> hose clamp. For outdoors, use a proper grounding clamp:
> <http://www.solidsignal.com/pview.asp?p=pvgb1&d=perfect-vision-pvgb1-single-grounding-blocks-%28pvgb1%29>
> <https://www.google.com/search?tbm=isch&q=cable+tv+grounding+block>
> For outdoors, also don't forget to recreate the coax drip loop so that
> water doesn't run into the connector block, or into the house.
> <http://activerain.com/blogsview/3168531/drip-loop-really-do-you-need-it-wenatchee-and-leavenworth-home-inspection>
> <http://images.meredith.com/diy/images/2009/03/p_SCW_240_02.jpg>
>
Thanks for all your replies. It's an indoor splitter. Since I had a 68
ohm resistor and appropriate connector (but no hose clamp), I just built
a terminator. Factory-builts are cheap - if you want 10, 25 or 100 but
I only needed one.




== 9 of 14 ==
Date: Thurs, Feb 13 2014 6:07 pm
From: Jeff Liebermann


On Thu, 13 Feb 2014 17:41:28 -0800, Bennett <bjprice@cal.berkeley.edu>
wrote:

>On 2/13/2014 5:17 PM, Jeff Liebermann wrote:
>> On Thu, 13 Feb 2014 10:40:26 -0800, Bennett <bjprice@cal.berkeley.edu>
>> wrote:
>>
>>> A friend replaced her Comcast TV box with an over-the-air antenna but
>>> continues to use Comcast Internet service. This leaves her
>>> Comcast-supplied splitter with an unterminated socket - does it matter?
>>
>> Yes, it matters.
>>
>>> Should I bother to terminate it?
>>
>> Yes, you should terminate it.
>>
>>> (A barrel connector isn't a good replacement for the splitter as the
>>> splitter provides a grounding point.)
>>
>> Sorta. Apparently she has a 2 way splitter installed with one port
>> left unterminated. A barrel connector is a very good replacement.
>> However, you're correct that you'll need to do something about the
>> grounding point. If this is indoors, just remove the grounding wire,
>> wrap it around the barrel connector, and hold it in place with a small
>> hose clamp. For outdoors, use a proper grounding clamp:
>> <http://www.solidsignal.com/pview.asp?p=pvgb1&d=perfect-vision-pvgb1-single-grounding-blocks-%28pvgb1%29>
>> <https://www.google.com/search?tbm=isch&q=cable+tv+grounding+block>
>> For outdoors, also don't forget to recreate the coax drip loop so that
>> water doesn't run into the connector block, or into the house.
>> <http://activerain.com/blogsview/3168531/drip-loop-really-do-you-need-it-wenatchee-and-leavenworth-home-inspection>
>> <http://images.meredith.com/diy/images/2009/03/p_SCW_240_02.jpg>

>Thanks for all your replies. It's an indoor splitter. Since I had a 68
>ohm resistor and appropriate connector (but no hose clamp), I just built
>a terminator. Factory-builts are cheap - if you want 10, 25 or 100 but
>I only needed one.

Not good enough. If you just crammed a 68 ohm resistor into the
F-connector jack, you probably have a fairly good approximation of an
antenna. It's going to radiate junk, and pickup more junk (ingres).
If you insist on doing it like that, wrap the resistor with some
insulating tape, and then cover it with aluminum foil.

Yeah, you're right that nobody sells them in small quantities. The
best I can do on eBay is 10 pcs for $3.85 including shipping.
<http://www.ebay.com/itm/261230167868>

Looks like you're semi-local. Send me a mailing address and I'll
stuff a few into an envelope for you. You could also buy one of the
outdoor grounding blocks, and use it indoors. Lots of options that
doesn't involve a leaky do-it-thyself terminator.

--
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




== 10 of 14 ==
Date: Thurs, Feb 13 2014 7:32 pm
From: Michael Black


On Thu, 13 Feb 2014, Jeff Liebermann wrote:

> On Thu, 13 Feb 2014 17:41:28 -0800, Bennett <bjprice@cal.berkeley.edu>
> wrote:
>
>> On 2/13/2014 5:17 PM, Jeff Liebermann wrote:
>>> On Thu, 13 Feb 2014 10:40:26 -0800, Bennett <bjprice@cal.berkeley.edu>
>>> wrote:
>>>
>>>> A friend replaced her Comcast TV box with an over-the-air antenna but
>>>> continues to use Comcast Internet service. This leaves her
>>>> Comcast-supplied splitter with an unterminated socket - does it matter?
>>>
>>> Yes, it matters.
>>>
>>>> Should I bother to terminate it?
>>>
>>> Yes, you should terminate it.
>>>
>>>> (A barrel connector isn't a good replacement for the splitter as the
>>>> splitter provides a grounding point.)
>>>
>>> Sorta. Apparently she has a 2 way splitter installed with one port
>>> left unterminated. A barrel connector is a very good replacement.
>>> However, you're correct that you'll need to do something about the
>>> grounding point. If this is indoors, just remove the grounding wire,
>>> wrap it around the barrel connector, and hold it in place with a small
>>> hose clamp. For outdoors, use a proper grounding clamp:
>>> <http://www.solidsignal.com/pview.asp?p=pvgb1&d=perfect-vision-pvgb1-single-grounding-blocks-%28pvgb1%29>
>>> <https://www.google.com/search?tbm=isch&q=cable+tv+grounding+block>
>>> For outdoors, also don't forget to recreate the coax drip loop so that
>>> water doesn't run into the connector block, or into the house.
>>> <http://activerain.com/blogsview/3168531/drip-loop-really-do-you-need-it-wenatchee-and-leavenworth-home-inspection>
>>> <http://images.meredith.com/diy/images/2009/03/p_SCW_240_02.jpg>
>
>> Thanks for all your replies. It's an indoor splitter. Since I had a 68
>> ohm resistor and appropriate connector (but no hose clamp), I just built
>> a terminator. Factory-builts are cheap - if you want 10, 25 or 100 but
>> I only needed one.
>
> Not good enough. If you just crammed a 68 ohm resistor into the
> F-connector jack, you probably have a fairly good approximation of an
> antenna. It's going to radiate junk, and pickup more junk (ingres).
> If you insist on doing it like that, wrap the resistor with some
> insulating tape, and then cover it with aluminum foil.
>
One time I was looking into switches that couldn't be accidentally
toggled, and I thought of type F connectors.

I'm sure I took a bit of wire for the center conductor, then a bit of thin
copper sheet. PUt the wire into the centre of the copper sheet, soldered
it, then soldered the copper sheet to the outer part of the connector.
So switching was by screwing in the connector or unscrewing it.

I'm blank about soldering the copper sheet to the outer part of the
conenctor though, but I can picture the finished connector.


> Yeah, you're right that nobody sells them in small quantities. The
> best I can do on eBay is 10 pcs for $3.85 including shipping.
> <http://www.ebay.com/itm/261230167868>
>
That's why I tend to keep junk. Terminators may seem like the most
mundane thing found in a pile of junk on the sidewalk, but if you need
one, you actually save money and effort, while the 60gig iPod that I found
somewhere else needs a battery in order to be useful.

Michael






== 11 of 14 ==
Date: Thurs, Feb 13 2014 7:48 pm
From: Jeff Liebermann


On Thu, 13 Feb 2014 22:32:15 -0500, Michael Black <et472@ncf.ca>
wrote:

>One time I was looking into switches that couldn't be accidentally
>toggled, and I thought of type F connectors.

No need to build your own. Most switch manufacturers make "locking
lever" type of switches. I've used them in various devices where I
didn't want any accidentally toggling. They're also common in
aerospace and military equipment:
<http://infinityaerospace.com/LL_Toggle_Sw_for_Preoiler.jpg>
<http://www.chiefaircraft.com/edm-7103k2zqe.html>
<http://www.ebay.com/bhp/locking-toggle-switch>

--
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




== 12 of 14 ==
Date: Fri, Feb 14 2014 6:38 am
From: dave


On 02/13/2014 06:07 PM, Jeff Liebermann wrote:
> On Thu, 13 Feb 2014 17:41:28 -0800, Bennett <bjprice@cal.berkeley.edu>

>
> Not good enough. If you just crammed a 68 ohm resistor into the
> F-connector jack, you probably have a fairly good approximation of an
> antenna. It's going to radiate junk, and pickup more junk (ingres).
> If you insist on doing it like that, wrap the resistor with some
> insulating tape, and then cover it with aluminum foil.
>

Do you have any idea what the wavelength is at 600MHz? It's half a meter
(Meters times megaHertz equals 300). That makes the length of a quarter
wave is 1/8 meter or about 5". A tiny resistor is not going to radiate
efficiently enough. If the "splitter" is a hybrid the unterminated port
will cause higher attenuation through the splitter. Maybe a single dB.
Not important when receiving.

You'd be better off getting a DC block. The splitter loses at least 3 dB.





== 13 of 14 ==
Date: Fri, Feb 14 2014 7:24 am
From: "Michael A. Terrell"



dave wrote:
>
> On 02/13/2014 06:07 PM, Jeff Liebermann wrote:
> > On Thu, 13 Feb 2014 17:41:28 -0800, Bennett <bjprice@cal.berkeley.edu>
>
> >
> > Not good enough. If you just crammed a 68 ohm resistor into the
> > F-connector jack, you probably have a fairly good approximation of an
> > antenna. It's going to radiate junk, and pickup more junk (ingres).
> > If you insist on doing it like that, wrap the resistor with some
> > insulating tape, and then cover it with aluminum foil.
> >
>
> Do you have any idea what the wavelength is at 600MHz? It's half a meter
> (Meters times megaHertz equals 300). That makes the length of a quarter
> wave is 1/8 meter or about 5". A tiny resistor is not going to radiate
> efficiently enough. If the "splitter" is a hybrid the unterminated port
> will cause higher attenuation through the splitter. Maybe a single dB.
> Not important when receiving.
>
> You'd be better off getting a DC block. The splitter loses at least 3 dB.


A DC Block is nothing more than a capacitor between two connectors.
Some use more than one capacitor to extend the usable frequencies. I've
used up to five to have a flat response from <100 KHz to >1400 MHz at 50
Ohms for a production test line. The insertion loss was about .1 dB at
each end of the usable range.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.




== 14 of 14 ==
Date: Fri, Feb 14 2014 9:03 am
From: Jeff Liebermann


On Fri, 14 Feb 2014 06:38:54 -0800, dave <ricketzz@earthlink.net>
wrote:

>On 02/13/2014 06:07 PM, Jeff Liebermann wrote:
>> On Thu, 13 Feb 2014 17:41:28 -0800, Bennett <bjprice@cal.berkeley.edu>
>
>>
>> Not good enough. If you just crammed a 68 ohm resistor into the
>> F-connector jack, you probably have a fairly good approximation of an
>> antenna. It's going to radiate junk, and pickup more junk (ingres).
>> If you insist on doing it like that, wrap the resistor with some
>> insulating tape, and then cover it with aluminum foil.

>Do you have any idea what the wavelength is at 600MHz? It's half a meter
>(Meters times megaHertz equals 300). That makes the length of a quarter
>wave is 1/8 meter or about 5". A tiny resistor is not going to radiate
>efficiently enough.

Whether it radiates efficiently or inefficiently, it still radiates.
Assuming a 1/2 watt resistor, with one lead wrapped around the
grounding screw, and the other shoved into the F-connector center
wire, there will be about 1/4" of exposed wire between the center pin
and the 60 ohm resistor. That's not much, can probably be tolerated,
and will be sufficient to slightly increase base line noise level in
the area. I would hate to think what might happen if EVERYONE decided
to use leaky terminators.[1]

I like to play ham radio (VHF/UHF) in my vehicle when driving. I
constantly hear the digital hash as I drive repeatedly by specific
locations. At first, I assumed that these were leaks from the
overhead cable plant. Nope. When I started banging on doors, I found
some really creative wiring and connector crimping. Most were caused
by distribution amps with unterminated cables, where the coax cable
becomes somewhat of an antenna. I also found either a defective drop
or tap on the pole (Comcast didn't tell me what they found, but they
did fix it).

Obviously, a leaky cable is a much longer length of wire than 1/4" of
exposed center conductor. Yet, after the gross leaks were fixed, I
still could still hear the test tones on the borrowed Trilithic
something leakage detector. I had to install terminators on literally
everything to reduce it to zero. Admittedly, I was working well below
the FCC Part 76.605 leakage limits:
<http://transition.fcc.gov/mb/engineering/605.html>
<http://www.cablefax.com/tech/sections/columns/broadband/Broadband-Signal-Leakage-in-an-All-Digital-Network_33882.html>
<http://www.cablefax.com/tech/deployment/bestpractices/A-Leak-Is-A-Leak&hellip%20Or-Is-It_52272.html>
but I needed to get the radiated junk down to a level where I could
use my radios in the neighborhood. Overkill yes, but necessary.

It's also a problem in the other direction, which is called ingress.
Nearby transmitters, such as mine, can easily get into the cable
system, and interfere with reception. Once it gets in, there's no
easy way to get rid of the signal. The best approach is proper
shielding. It isn't just my transmitters, but broadcast stations,
intermod with cordless phones, RF remotes, wireless security cameras,
and other RF devices. Mostly, they cause problems with cable modems,
which use the higher RF frequencies, but in extreme cases, can affect
TV reception. It's also difficult to see with a spectrum analyzer:
<http://www.jdsu.com/ProductLiterature/DSAM-D3-Spectrum-Analyzer-App-Note.pdf>
Can you see it? Spoiler:
<http://blogs.jdsu.com/hfc/Lists/Photos/dd6cc9ceb7e6a11e1006e1ad654edd7f.jpg>

More:
"Characterizing Signal Leakage from an All-Digital Cable Network"
<http://www.incospec.com/resources/webinars/files/Characterizing%20Signal%20Leakage%20from%20an%20All-Digital%20Cable%20NetworkMS.pdf>

>If the "splitter" is a hybrid the unterminated port
>will cause higher attenuation through the splitter. Maybe a single dB.
>Not important when receiving.

Without a termination, the splitter begins to resonate with the coax
cable which can be made to radiate. I'm not sure of the unterminated
losses, but I suspect it's more than 1dB. I'll try it on the bench
when I have time (mostly to clean off the accumulated junk from the
bench).
<http://802.11junk.com/jeffl/pics/home/slides/test-equip-mess.html>

>You'd be better off getting a DC block. The splitter loses at least 3 dB.

A DC block won't do anything useful except block DC. I think you
might have meant a straight through barrel connector.



[1] Incidentally, you might be amused to look at my study of monopole
antenna gains versus length.
<http://802.11junk.com/jeffl/antennas/Monopole/index.html>
The title includes the wavelength. For example, 0_750 is 3/4
wavelength long and 5_250 is 5.25 wavelengths long. If you look at
the antenna gains, you'll notice that the gain doesn't really drop
very much for shortened antennas. From the antenna patterns:
Wavelength Gain dBi
0.250 5.19
0.125 4.85
0.050 4.75
That's a 0.45dB gain loss in an antenna that's 1/5th the length of a
1/4 wave radiator. That might explain why I'm concerned about even
small amounts of exposed center conductor.


--
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: Do remote keypads sweat silcone oil?
http://groups.google.com/group/sci.electronics.repair/t/c14d8e962b605e97?hl=en
==============================================================================

== 1 of 2 ==
Date: Thurs, Feb 13 2014 3:19 pm
From: whit3rd


On Friday, December 8, 2000 5:18:05 PM UTC-8, Michael Shell wrote:
> Ok folks I think I have an answer!
>
> Daniel Malik noticed that the keys (and remotes) that are used more
> often, tend to have more oil problems. This is in agreement with my
> observations.
>
> One thing I have to make clear is that I *_KNOW_ * that whatever is
> going on is NOT due to spillage or other external contamination. If I
> had not seen it with my own eyes, I would not believe it either!...

> The oil behaves a bit differently from most normal household
> (and hand) oils.
>
> 1. It is not sticky in the least
> 2. It is VERY clear.
> 3. It is VERY hydrophobic and detergent action is noticeably less
> than with most petroleum based oils.
>
> I would not have noticed these fine points except for the fact that
> I have worked with Silicone (DOT 5) brake fluid...

Probably, the rubbery key material is compounded with a plasticizer.
The oil is really the plasticizer material oozing out.

Plasticizers are additives that keep plastics flexible or springy, and
they can come out of the plastic as it ages (gummed-up old vinyl power
cords are a familiar example).

Brake fluid contains a plasticizer (to keep the o-rings and seals
properly rubbery).




== 2 of 2 ==
Date: Thurs, Feb 13 2014 7:25 pm
From: Michael Black


On Thu, 13 Feb 2014, whit3rd wrote:

> On Friday, December 8, 2000 5:18:05 PM UTC-8, Michael Shell wrote:
>> Ok folks I think I have an answer!
>>
>> Daniel Malik noticed that the keys (and remotes) that are used more
>> often, tend to have more oil problems. This is in agreement with my
>> observations.
>>
>> One thing I have to make clear is that I *_KNOW_ * that whatever is
>> going on is NOT due to spillage or other external contamination. If I
>> had not seen it with my own eyes, I would not believe it either!...
>
>> The oil behaves a bit differently from most normal household
>> (and hand) oils.
>>
>> 1. It is not sticky in the least
>> 2. It is VERY clear.
>> 3. It is VERY hydrophobic and detergent action is noticeably less
>> than with most petroleum based oils.
>>
>> I would not have noticed these fine points except for the fact that
>> I have worked with Silicone (DOT 5) brake fluid...
>
> Probably, the rubbery key material is compounded with a plasticizer.
> The oil is really the plasticizer material oozing out.
>
> Plasticizers are additives that keep plastics flexible or springy, and
> they can come out of the plastic as it ages (gummed-up old vinyl power
> cords are a familiar example).
>
> Brake fluid contains a plasticizer (to keep the o-rings and seals
> properly rubbery).
>
I'm pretty sure something about this is in the FAQ. No reason to agree to
a 14 year old post. The guy isn't here anymore.

Michael






==============================================================================
TOPIC: Comprehensive test banks and solution manuals for sale
http://groups.google.com/group/sci.electronics.repair/t/8e2e7a53cd376039?hl=en
==============================================================================

== 1 of 1 ==
Date: Thurs, Feb 13 2014 3:50 pm
From: lakshman.maddineni@gmail.com


Modern Database Management, 11E Hoffer solution manual
Modern Database Management, 11E Hoffer Test Bank

I need these two...

Can you tell me how i can get those from you.






==============================================================================
TOPIC: Phase Linear 400 output transistors
http://groups.google.com/group/sci.electronics.repair/t/d0cb28fa4ada674c?hl=en
==============================================================================

== 1 of 3 ==
Date: Fri, Feb 14 2014 2:23 am
From: georgesantel@gmail.com


On Sunday, June 1, 1997 3:00:00 AM UTC-4, John Whitmore wrote:
> I've recently acquired a Phase Linear 400. This was
> an historically important audio amp, as it was the first of the
> wave of high-powered amplifiers that came out of the 1970's.
>
> This unit, though, has been through some tough times.
> I've found lots of shorted and fried components, but the
> main difficulty is in the output transistors.
>
> There are four different types plugged in to the
> sixteen TO-3 sockets. The outputs are four composite-Darlington
> transistors, each having a single driver feeding three
> paralleled output transistors. Someone in the past
> replaced some of the paralleled outputs with various types.
> So, I don't trust the types of transistors I see there.
> Also, I don't know what the original drivers were.
>
> Driver types: GE-37, DTS-701, RCA410
> The first two are 700V, 1A; the third is 300V, 5A rated.
>
> Output types: GE-37, PL-909
> The first is clearly inappropriate in this application,
> and the second is (apparently) a Fairchild special part
> number for Phase Linear. I assume it's intended to be
> a high current type, and possibly similar to 2N5264
> (a Fairchild power transistor of the right era).
>
> From the emitter degeneration resistance (0.22 ohms)
> I suspect the output transistors should be roughly 5A rated.
> Does anyone know? Should I just jam in MJ15003's?
> Or maybe MJ410's (very similar to the RCA410)?
>
> And as for the drivers; should they all be the same
> type as the outputs? What were the original drivers?
>
> Thanks for any info; this can't interest many folk,
> so e-mail is preferred.
>
> John Whitmore
> whit@hipress.phys.washington.edu


If interested I have some XPL909 for sale
georgesantel@gmail.com




== 2 of 3 ==
Date: Fri, Feb 14 2014 8:22 am
From: Smarty


On 2/14/2014 5:23 AM, georgesantel@gmail.com wrote:
> On Sunday, June 1, 1997 3:00:00 AM UTC-4, John Whitmore wrote:
>> I've recently acquired a Phase Linear 400. This was
>> an historically important audio amp, as it was the first of the
>> wave of high-powered amplifiers that came out of the 1970's.
>>
>> This unit, though, has been through some tough times.
>> I've found lots of shorted and fried components, but the
>> main difficulty is in the output transistors.
>>
>> There are four different types plugged in to the
>> sixteen TO-3 sockets. The outputs are four composite-Darlington
>> transistors, each having a single driver feeding three
>> paralleled output transistors. Someone in the past
>> replaced some of the paralleled outputs with various types.
>> So, I don't trust the types of transistors I see there.
>> Also, I don't know what the original drivers were.
>>
>> Driver types: GE-37, DTS-701, RCA410
>> The first two are 700V, 1A; the third is 300V, 5A rated.
>>
>> Output types: GE-37, PL-909
>> The first is clearly inappropriate in this application,
>> and the second is (apparently) a Fairchild special part
>> number for Phase Linear. I assume it's intended to be
>> a high current type, and possibly similar to 2N5264
>> (a Fairchild power transistor of the right era).
>>
>> From the emitter degeneration resistance (0.22 ohms)
>> I suspect the output transistors should be roughly 5A rated.
>> Does anyone know? Should I just jam in MJ15003's?
>> Or maybe MJ410's (very similar to the RCA410)?
>>
>> And as for the drivers; should they all be the same
>> type as the outputs? What were the original drivers?
>>
>> Thanks for any info; this can't interest many folk,
>> so e-mail is preferred.
>>
>> John Whitmore
>> whit@hipress.phys.washington.edu
>
> If interested I have some XPL909 for sale
> georgesantel@gmail.com


Service manuals for Phase Linear 400s, 700s, etc. with schematics, PCB
layouts, instructions, are available at numerous places for free. A
Google search turned this one up, among others:

http://www.vintageshifi.com/repertoire-pdf/Phase-Linear.php










== 3 of 3 ==
Date: Fri, Feb 14 2014 8:52 am
From: jurb6006@gmail.com


There is a website for these.

http://thecarversite.com/

THAT is where you get information on these. I bought one with a fried right channel a couple years ago and due to improper servicing it had blown it all the way back to the current limiters. Surprisingly it did not blow the drivers, but it did blow one predriver. I forgot what I used for those but I DID look at spec sheets etc. because you don't just go to NTE and get transistors for something like this. If you need anything other than the outputs I will find you the correct transistors, don't trust anyone on this. A couple of them are germanium.

The current correct output transistor type is MJ15024 available from Digikey for reasonable, about five bucks each. Replace them ALL in one bank, no exceptions. Each in a bank of three has to equally share the current, and rated down to four ohms with 85 volts rails that pretty much stay put, you don't need any current hogs. That's what happened to mine, it blew the emitter resistor on the one in a bank used for current detection. This is why it blew the predrivrs but not the drivers.

Remove the transistors for checking, all the resistances are too low in the whole thig to do it in circuit. Check ALL emitter resistors. After all is said and done, you can run it on the bench without a load connected with all of the outputs removed and it should look right on a scope, with possible SLIGHT early clipping on one side of the waveform.

There are two types of these, most use all NPN outputs and drivers, the other uses complemmentary. As far as I know only some of the Series Two amps were complementary. If it has the LED meters you don't know, those were built around 1979 and 1980 right after Pioneer bought the company. These have an IC on the board rather than the usual diff pair at the input.

The older ones with the analog meters as fas as I know all used all NPN outputs and drivers.

After I got the right channel fixed I was jamming it and the damn left channel fried. The reason was that where the heavy wires act as a bus and connects all the collectors together in one of the banks of outputs had come loose, it broke the solder over the years. Check ALL connections to ALL outputs because even one of them off can fry the whole channel.

Really, if you are not used to working on high power amps like this, you could waste alot of silicon.

The price break on the MJ15024s comes at ten pieces, so just get twelve and replace them all. With any luck they will all be from the same batch so matching will not be a big problem. There is a matching procedure required after replacing the outputs to assure they are properly matched. If not they could fail prematurely when pushed hard, and you buy this amp to push it hard.

A short at the output terminals should not fry this amp, but connecting it to certain low impedance loads can. The book says never go below four ohms, but many four ohm systems do just that. Bob Carver knew this and set the current limiting to handle probably down to about three ohms because of those gnarly woofers and infinite baffle systems of the day, but any lower and it is vulnerable.

Aso note these amps have abslutely no speaker protection whatsoever, no relay no nothing. They recommend you use speaker fuses calculated to your particular speaker handling capabilities, the formula is in the book.

If you buy the manual you have been scammed, it is available for free not only from carversite, but a few other places. I think you can get it at bama as well, but the best one with the addendums etc. is at carversite. There is a note about certain Infinity speakers that use some ungodly high value cap in their crossover that affects the power down of these amps and can result in a transient if turned back on too quickly. If you got this, you got the right manual. Also note that you do have to sift through that manual as more than one version is covered.

When you get it working you probably won't want to sell it. Even at flat response it sounds better due to an extraordinarily high damping factor. This is one of the few amps that can really benefit from heavy guage (and short) speaker wires. The cones of the speakers act like servomotors actually. Mine is not for sale except under extreme duress, and I mean for alot more than it's worth. You can't buy an amp like this for less than twice what you could sell it for.

So fix it right.

There is a guy on eBay who claims to fix these right for about $350 no matter what is wrong with them. Of course two way shipping is probably extra. The point is, there is a reason people don't fix these things for a hundred bucks.

Get the ohmmeter out before even plugging the thing in and keep us posted.




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