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

sci.electronics.repair@googlegroups.com

Today's topics:

* Benq G2420HD power supply heat issue? - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/5535843582121d59?hl=en
* Roland Cube 30 - 4 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/a23b78ce21495f68?hl=en
* How to properly feed GPS navigation prompts into a bluetooth earpiece? - 2
messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/ff70bbb8288b005e?hl=en
* HP Laserjet 4000 paper jam and other issues. [FIXED] - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/8620b1cad620b4b9?hl=en
* How do I get Voice-to-Text back in my Android 4.3 for SMS texting? - 6
messages, 6 authors
http://groups.google.com/group/sci.electronics.repair/t/73bd95f6d9063aaf?hl=en
* Panasonic VCR model AG1980P no HiFi sound on record or Playbac - 2 messages,
2 authors
http://groups.google.com/group/sci.electronics.repair/t/7c7728604ad33148?hl=en
* Magnetic door holders question - 7 messages, 7 authors
http://groups.google.com/group/sci.electronics.repair/t/21eb21515055e1fe?hl=en
* Trying to understand the current draw of a Samsung Galaxy S3 under GPS & low
battery - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/1dceb0f9a68c6f2d?hl=en

==============================================================================
TOPIC: Benq G2420HD power supply heat issue?
http://groups.google.com/group/sci.electronics.repair/t/5535843582121d59?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, Feb 8 2014 9:00 am
From: Michael Black


On Sat, 8 Feb 2014, 2phar wrote:

> On 2/8/2014 1:16 AM, Michael Black wrote:
>>
>> Are you sure you got all the capacitors?
>>
>> I dragged a 19" Acer monitor home, and it worked fine, or so it seemed.
>> But if I left it on, it would go into standby and then I couldn't get it
>> activated again, the Acer logo would go on and nothing more. I changed
>> the obvious capacitors and it's fine. So it was resetting because one
>> of those bigger electrolytics in the power supply wasn't quite right. I
>> nitially thought it was something else, but changed the capacitors
>> because it was easy.
>>
>> Michael
>>
>
> I replaced them all except the big 450V one.. mainly cos its not even
> included in capacitor repair kits and everyone seems to say failure of it is
> extremely rare.
>
It wouldn't. That one is just running at 60Hz (50Hz in some countries),
which requires less effort on the part of the capacitor. It can go bad,
but not in the same way as the capacitors on the output of the supply.

A switching supply is a feedback system, so if a capacitor goes bad, what
the problem is may not immediately be obvious. So I was thinking if a
small value electrolytic was overlooked, it might be more problem than
would seem from the small value.

Phil's comment about bad solder joints is good. You have to look
carefully.

Michael








==============================================================================
TOPIC: Roland Cube 30
http://groups.google.com/group/sci.electronics.repair/t/a23b78ce21495f68?hl=en
==============================================================================

== 1 of 4 ==
Date: Sat, Feb 8 2014 9:34 am
From: N_Cook


Applying bench ps to pin 38 isolated from all else, then for .2A, 1.3V
dropped and 10 deg C rise of the chip.




== 2 of 4 ==
Date: Mon, Feb 10 2014 7:05 am
From: N_Cook


before consigning to the mule park , investigated the JAPN IC a bit
5 pin,
p1&2 gnd, 3 N/C unless hidden in an interlayer,4 to large Boss R03015201
p21, p5 absent, p6 3.3V
Power-on reset IC?




== 3 of 4 ==
Date: Mon, Feb 10 2014 8:38 am
From: "Gareth Magennis"



"N_Cook" <diverse@tcp.co.uk> wrote in message
news:ldaps1$9s$1@dont-email.me...
> before consigning to the mule park , investigated the JAPN IC a bit
> 5 pin,
> p1&2 gnd, 3 N/C unless hidden in an interlayer,4 to large Boss R03015201
> p21, p5 absent, p6 3.3V
> Power-on reset IC?




That IC is S80130ANMC. Voltage supervisor with built in delay.



Gareth.






== 4 of 4 ==
Date: Mon, Feb 10 2014 1:04 pm
From: "Gareth Magennis"




"N_Cook" wrote in message news:ldaps1$9s$1@dont-email.me...

before consigning to the mule park , investigated the JAPN IC a bit
5 pin,
p1&2 gnd, 3 N/C unless hidden in an interlayer,4 to large Boss R03015201
p21, p5 absent, p6 3.3V
Power-on reset IC?




The schematic designates the output of this chip to be Reset0, and becomes
Reset1 after R19.

Reset0 goes to logic chip IC1, Reset1 goes to CN U2 pin6, CN U2 being
designated Not Utilised.


I can't see any direct connections of these reset lines to the main CPU.



Gareth.






==============================================================================
TOPIC: How to properly feed GPS navigation prompts into a bluetooth earpiece?
http://groups.google.com/group/sci.electronics.repair/t/ff70bbb8288b005e?hl=en
==============================================================================

== 1 of 2 ==
Date: Sat, Feb 8 2014 2:25 pm
From: Jim Rusling


Danny D'Amico <danny@is.invalid> wrote:

>On Fri, 07 Feb 2014 20:11:55 -0600, Jim Rusling wrote:
>
>> Your bluetooth playback device has to support the A2DP functions. This
>> is for stereo and play controls. There are quite a few single earpiece
>> that will also handle A2DP.
>
>I'm a little confused because I had not known anything about "A2DP".
>
>Googling, "Advanced Audio Distribution Profile", I find this:
> http://www.ebay.com/gds/What-is-A2DP-for-bluetooth-/10000000004035086/g.html
>
>Which says there are two channels for bluetooth, one for phone, and,
>essentially, the other for GPS.
>
>That article kept using the word "profile", so, looking that up, I find:
> http://en.wikipedia.org/wiki/Bluetooth_profile
>
>While this stuff is new to me, do I have this right yet?
>
>Q: What do I need to get GPS voice over a bluetooth earpiece?
>A: (tentative) Bluetooth 2.0 + A2DP ???
>
>Is that what I should look for in an earpiece to get GPS voice?

If you GPS will work with a bluetooth speaker, then it should work
with a bluetooth earpiece that supports A2DP. I use an ICON ERA to
listen to audiobooks and navigation from my phone.
--
Jim Rusling
More or Less Retired
Mustang, OK
My local Weather http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KOKMUSTA4




== 2 of 2 ==
Date: Sun, Feb 9 2014 4:27 am
From: Danny D'Amico


On Sat, 08 Feb 2014 16:25:31 -0600, Jim Rusling wrote:

> If your GPS will work with a bluetooth speaker, then it should work with a
> bluetooth earpiece that supports A2DP.

I like the flip-boom earpieces that Motorola sells (because they're trivially
easy to shut off and turn on); but unfortunately, my H730 doesn't appear to
have A2DP.
https://www.motorola.com/us/Motorola-H730-Bluetooth-Headset/71260.html

Googling for Motorola flip-boom H2DP earpieces, I find an alphabet soup here:
http://www.motorola.com/us/accessories-bluetooth-headsets/Boom-Wireless-Headset/boom-wireless-headset.html

Do any of these Bluetooth "profiles" add any value to me for GPS listening?
A2DP 1.2, Hands Free (HFP), AVRCP 1.4, HFP 1.6

Does the "version" of A2DP (i.e., 1.2) matter or can *any* version work?






==============================================================================
TOPIC: HP Laserjet 4000 paper jam and other issues. [FIXED]
http://groups.google.com/group/sci.electronics.repair/t/8620b1cad620b4b9?hl=en
==============================================================================

== 1 of 2 ==
Date: Sat, Feb 8 2014 4:30 pm
From: "David Farber"



"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:a733f9pk6s1oba16ujieobj9dbeo64hcvv@4ax.com...
> On Tue, 4 Feb 2014 01:24:19 -0800, "David Farber"
> <farberbear.unspam@aol.com> wrote:
>
>>I did clean (though probably not well enough) the sticky stuff off of the
>>solenoid which is used to control the lower "D" rollers. I used some
>>electrical tape as was suggested in the fix. Is the purpose of the felt or
>>electrical tape to muffle the sound when the solenoid is energized or is
>>there a mechanical reason as well? I'll take it out again, put some dc on
>>it, and see how it operates. I'll also replace the rubber parts.
>
> Don't use electrical tape. My original version of the fix indicated
> to use 2 layers of electrical tape. That worked for about 3 months,
> when the tape got warm and fell off. I had to rework about 8 printers
> where I had used tape. The felt has lasted much longer.
>
> There are various thicknesses of felt available at the local hardware
> store. The stuff in the photo is 2mm thick (including the backing
> paper and NOT compressed). I also have some felt that's about 1mm
> thick. Both work just fine but I would NOT go any thicker than 2mm.
>
> The main purpose of the felt to reduce the sound, but it also may have
> a secondary purpose. Running the solenoids off DC tends to magnetize
> the cores. If the armature comes in contact with the core, it will
> stick. See video at:
> <http://www.learnbydestroying.com/jeffl/crud/hp2200-solenoid.wmv>
> The felt provides the necessary air gap so that the armature doesn't
> stick.
>
> If replacing all the rubber parts and fixing the sticky solenoid
> doesn't do the trick, there are some obscure problems that should be
> investigates. The clutch that runs the feed roller (the one above the
> paper tray) gets dirty and doesn't release. Tear it apart, clean out
> the metal dust, and it should be ok. Another common problem is a
> sticky paper height sensor. That's also above the tray. Clean with a
> paint brush.
>
> Good luck.
> --
> 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

Hi Jeff,

I purchased the package of felt you suggested (picture at the bottom of this
page http://www.learnbydestroying.com/jeffl/hp2200/hp2200.html) and put it
on the solenoid. It was just the right thickness to allow the relay to
close. However after reassembly, the printer still was spitting out blank
pages. In other words, the solenoid somehow was not releasing. I did some
more web searching and finally found a link to the step by step procedure to
do the repair. Long story short, I finally realized I had pulled the wrong
solenoid. The one I was working on was for the upper tray #1, not tray #2
(the drawer that slides out). I went back to the service manual and figured
out how to get access to that solenoid. It was stuck shut of course. I
removed the stickiness from the components and put the felt on. For some
reason, this solenoid would not close when I manually tried to close it. The
felt was too thick. I removed the felt, put some electrical tape on it, and
now it works great. As for the electrical tape, if it fails again, at least
I know exactly where to find that solenoid. If anyone is interested, what
follows below is a very concise list of steps you can follow to get somewhat
easy access to the solenoid on the 4000 model.

Thanks for your help.
--
David Farber
Los Osos, CA

From
http://www.petri.co.il/forums/showpost.php?s=d0803b95688f2018c531d8c0cbc0d171&p=262315&postcount=6

I found that accessing the solenoid is much less complicated than described
above.
1- You only need to remove the rear right side cover. Just slide it to the
rear.
2- Remove the formatter assembly, the formatter pan and unplug the large
cable that is behind the pan and remove the cable wire bundle from its
retainer.
3- Open Tray 1 on the front and unscrew 2 long screws that attach the
printer to the Tray 2 assembly; they are located on each side of the Tray 1
pickup assembly. (They are 4 1/2 inches long and oriented in an upright
position) They are not easy to see on first inspection. The left one is
recessed in a hole on the left side. The right one is behind a cover which
you can flip open on the right side. The left screw can be left in place
once it is unscrewed.
4- Remove the screw that is on the left side of the printer just below the
cooling fan. There is a hole in the left cover specifically for this
purpose.
5- Lift the printer straight up off of the Tray 2 assembly. This is about
2/3 of the total unit and will lift off easily.
6- Remove the cover plate on the Tray 2 assembly.
7- Loosen the Tray 2 gear train assembly from the Tray 2 housing. There is
just one screw holding it in place and this screw is recessed in the inner
right side. Make sure to first remove the solenoid wires (2 wires) from
their routing channel before removing the assembly. I would NOT recommend
unplugging these wires from the controller as they are small and seem
fragile.
8- Lift out the gear assembly. The solenoid is now available to remove and
service. Make sure to remove all of the glue residue. I found the glue to be
quite tenacious and required extra care to remove it all.
Just 2 notes on reassembly:
1- Take care to be sure that the solenoid is well seated in its proper
position when screwing it back on.
2- When placing the printer back on the Tray 2 assembly, check that the
large cable is out of the way.






== 2 of 2 ==
Date: Sat, Feb 8 2014 5:07 pm
From: Jeff Liebermann


On Sat, 8 Feb 2014 16:30:39 -0800, "David Farber"
<farberbear.unspam@aol.com> wrote:

>I finally realized I had pulled the wrong
>solenoid. The one I was working on was for the upper tray #1, not tray #2
>(the drawer that slides out).

Oops. The URL I supplied was for the Tray 1 solenoid.

>I went back to the service manual and figured
>out how to get access to that solenoid. It was stuck shut of course. I
>removed the stickiness from the components and put the felt on. For some
>reason, this solenoid would not close when I manually tried to close it. The
>felt was too thick.

Hmmm... That's odd. I've been using the 2mm thick felt for HP
solenoids without difficulties. There is a solenoid in the HP2550n
color laser that requires 1mm thick felt, which I was able to find at
the local $1 store.

The neighboring office has an HP4000 that is going to the recyclers
shortly. I'll take a closer look at the solenoid (time permitting).

>I removed the felt, put some electrical tape on it, and
>now it works great. As for the electrical tape, if it fails again, at least
>I know exactly where to find that solenoid.

If my experience is any indication of future performance, the glue
will either melt or evaporate. Old electrical tape becomes brittle
and non-sticky after a few years. Either way, I believe that the
electrical tape will eventually fall off. I predict you'll be digging
in again in a few months.

Did you check for a magnetized solenoid?

>If anyone is interested, what
>follows below is a very concise list of steps you can follow to get somewhat
>easy access to the solenoid on the 4000 model.

Thanks. I'll plagiarize it for when I eventually do an HP4000
instruction page.

>Thanks for your help.

Congrats and sorry for the confusion.

--
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: How do I get Voice-to-Text back in my Android 4.3 for SMS texting?
http://groups.google.com/group/sci.electronics.repair/t/73bd95f6d9063aaf?hl=en
==============================================================================

== 1 of 6 ==
Date: Sun, Feb 9 2014 12:40 pm
From: josephkk


On Fri, 7 Feb 2014 14:58:23 +0000 (UTC), Danny D'Amico <danny@is.invalid>
wrote:

>On Fri, 07 Feb 2014 06:18:47 -0700, RobertMacy wrote:
>
>> get a gmail account with voicemail capability. the telephone number you
>> get converts voice to text and emails you the message.
>
>I apologize for not being specific enough in the request.
>
>What I'm trying to accomplish, is, speaking into the phone, using the
>microphone of the phone instead of the keyboard, and having that spoken
>sentence transcribed into an SMS text message.
>
>I'm pretty sure "something" deep inside the operating system is
>corrupted, since I've uninstalled and re-installed multiple keyboards,
>and a half-dozen voice-to-sms programs, and all those speech-to-text
>programs complain about a missing underlying hook:
> RuntimeError: No activity found to handle intent
> {act=android.speech.action.RECOGNIZE_SPEECH (has extras)}
>
>At this point, I probably need to either find someone who knows what that
>underlying program actually is; or, if it's an inconspicuous part of the
>Android operating system, then I need to re-install the OS.
>
>Is there a way to update the Android operating system on a T-Mobile
>Samsung Galaxy S3 running Android 4.3 when the operating system is
>slightly corrupted (but otherwise up to date already)?

Call me crazy but didn't your problems start when you upgraded Android
itself? Maybe the answer is a downgrade?

?-)




== 2 of 6 ==
Date: Sun, Feb 9 2014 3:03 pm
From: Danny D'Amico


On Sun, 09 Feb 2014 13:43:13 -0800, josephkk wrote:

> Call me crazy but didn't your problems start when you upgraded Android
> itself? Maybe the answer is a downgrade?

Unfortunatly, I've installed so much on this Android phone that I really
do not know /when/ the problems started.

While cleaning things up, /think/ I may have uninstalled a Google "service"
that apparently controls the voice recognition.

So, what I really need to figure out is how to get a system /back/ to
where it was, with respect to all the /required/ services.

Does anyone know if there is a way to check for all the required
services (because clearly I'm missing one of them)?





== 3 of 6 ==
Date: Sun, Feb 9 2014 3:13 pm
From: ~BD~ <~BD~@nomail.afraid.org>


Danny D'Amico wrote:
> On Sun, 09 Feb 2014 13:43:13 -0800, josephkk wrote:
>
>> Call me crazy but didn't your problems start when you upgraded Android
>> itself? Maybe the answer is a downgrade?
>
> Unfortunatly, I've installed so much on this Android phone that I really
> do not know /when/ the problems started.
>
> While cleaning things up, /think/ I may have uninstalled a Google "service"
> that apparently controls the voice recognition.
>
> So, what I really need to figure out is how to get a system /back/ to
> where it was, with respect to all the /required/ services.
>
> Does anyone know if there is a way to check for all the required
> services (because clearly I'm missing one of them)?

Have you tried 'settings'? - http://www.wikihow.com/Reset-Your-Android-Phone

Good luck!

-




== 4 of 6 ==
Date: Sun, Feb 9 2014 4:17 pm
From: Sjouke Burry


On 10.02.14 0:03, Danny D'Amico wrote:
> On Sun, 09 Feb 2014 13:43:13 -0800, josephkk wrote:
>
>> Call me crazy but didn't your problems start when you upgraded Android
>> itself? Maybe the answer is a downgrade?
>
> Unfortunatly, I've installed so much on this Android phone that I really
> do not know /when/ the problems started.
>
> While cleaning things up, /think/ I may have uninstalled a Google "service"
> that apparently controls the voice recognition.
>
> So, what I really need to figure out is how to get a system /back/ to
> where it was, with respect to all the /required/ services.
>
> Does anyone know if there is a way to check for all the required
> services (because clearly I'm missing one of them)?
>
Easy. Make a backup before you start experimenting.
No backup? In that case you are sure out of luck.




== 5 of 6 ==
Date: Mon, Feb 10 2014 7:07 am
From: chuck


On Mon, 10 Feb 2014 01:17:31 +0100, Sjouke Burry
<burrynulnulfour@ppllaanneett.nnll> wrote:

>On 10.02.14 0:03, Danny D'Amico wrote:
>> On Sun, 09 Feb 2014 13:43:13 -0800, josephkk wrote:
>>
>>> Call me crazy but didn't your problems start when you upgraded Android
>>> itself? Maybe the answer is a downgrade?
>>
>> Unfortunatly, I've installed so much on this Android phone that I really
>> do not know /when/ the problems started.
>>
>> While cleaning things up, /think/ I may have uninstalled a Google "service"
>> that apparently controls the voice recognition.
>>
>> So, what I really need to figure out is how to get a system /back/ to
>> where it was, with respect to all the /required/ services.
>>
>> Does anyone know if there is a way to check for all the required
>> services (because clearly I'm missing one of them)?
>>
>Easy. Make a backup before you start experimenting.
>No backup? In that case you are sure out of luck.


If the android device is rooted, Titanium Backup does a very good back
up and restore.




== 6 of 6 ==
Date: Mon, Feb 10 2014 7:10 am
From: dave


On 02/09/2014 03:03 PM, Danny D'Amico wrote:
> On Sun, 09 Feb 2014 13:43:13 -0800, josephkk wrote:
>
>> Call me crazy but didn't your problems start when you upgraded Android
>> itself? Maybe the answer is a downgrade?
>
> Unfortunatly, I've installed so much on this Android phone that I really
> do not know /when/ the problems started.
>
> While cleaning things up, /think/ I may have uninstalled a Google "service"
> that apparently controls the voice recognition.
>
> So, what I really need to figure out is how to get a system /back/ to
> where it was, with respect to all the /required/ services.
>
> Does anyone know if there is a way to check for all the required
> services (because clearly I'm missing one of them)?
>

Every carrier has its own suite of installed apps. I have a Credo phone.
I get Google Play, Plus Samsung and Sprint Stores. You should be able to
flash it back to Factory. Backup your data files onto a removeable.
Remove it. Then Restore.





==============================================================================
TOPIC: Panasonic VCR model AG1980P no HiFi sound on record or Playbac
http://groups.google.com/group/sci.electronics.repair/t/7c7728604ad33148?hl=en
==============================================================================

== 1 of 2 ==
Date: Mon, Feb 10 2014 8:37 am
From: captainvideo462009@gmail.com


I own six of these machines which I picked up several years ago for a dollar apiece at an auction. I've been using four of them around the house and until recently they have been great machines. These had belonged to a town cable TV access station and it was my understanding that despite the fact that they were in pristine condition when I received them the town was simply upgrading to DVR's and had considered these obsolete. I now have three of them with the same problem. They will not record or play back in Hi Fi mode. Is anyone aware of this being a common known problem with these machines? I only have an operating manual for these but truthfully I've never chased a Hi Fi problem in a VCR so I don't really know where to look. Thanks for any help or advice. Lenny




== 2 of 2 ==
Date: Mon, Feb 10 2014 9:10 am
From: jurb6006@gmail.com


The first thing to do is confirm the problem. this might sound stupid but it's easiy to overlook. Make sure you have the problem on both record ansd playback. Taker a tape from a bad one and put it in a good one, in fact note whether or not the machine indicates it is a hifi recodring or not. Determine if it recording an unmoduilatd carrier or no carrier at all. Also take a known good tape in hifi and see if the defective machines play it in hifi and/or if they even recognize the hifi carrier.

If you truly have no carrier on either machine as well as no rsponse to a tapae with a hifi carrier, that points on a certain direction. On VHS ifi is handled by its own heads and therefore its own associated preamps and recording amps. The problem could well be riht there and you don't have to mess with the actual hifi circuitry, just treat it as another set of rotary video haeds, just at a lower frequency.

At this URL :

http://forum.videohelp.com/threads/329513-Fixing-my-Panasonic-AG-1980-NV-FS200

Right clock on the omage in post #5 to download the service manual. It's abour 10MB in PDF format. I just opened it so it is good.

For the most part, the chips that do the DBX encode and decode as well as the FM modulation/freq switching are dual purpose. (I didn't look, they simply almost ALL are). They encode and a line goes high or low and they decode. You could be losing moidulation or demodulation in any of them, but only certain parts of it will lose you the carrier.

That is what we need to know. Is the entire hifi subsystem dead as far as the carrie goes ? If so, one direction, if not you go in another direction. And do check all the machines and make sure they have the exact same problem.

There are alot of parts in those things made of unobtainium, mainly the hybrid ICs. Some of those have enntsy teensy caps on them that can leak and corrode the traces. If that happens welcome to the world of linear audio. If that's the case in all if the affected units your days are numbered on the rest of them. As such, pick up a DVD recorder and dub baby dub, all your stuff that means anything. If you CAN fix one you can probably fix them all. I still recommend dubbing anythig important to DVD. In fact now they have long life DVDs because even the regular kind have a finite life. Either still outlasts any video tape though.






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

== 1 of 7 ==
Date: Mon, Feb 10 2014 9:32 am
From: captainvideo462009@gmail.com


I work on commercial fire alarm systems mostly in apartment houses. Many of these buildings in the common hallways employ electromagnetic units mounted on the walls and an iron disk on the back corner of the doors. When the doors are opened and the disks are mated with the electromagnet the doors are held open in place. These doors all have pneumatic closers on them as well which are always applying a force in the opposite direction to try to close the door.

When the alarm is activated the 24VDC is removed from the coils and the doors are supposed to be automatically pulled closed by the force of the pneumatic unit. This doesn't always work because in spite of the opposing force applied by the pneumatic unit, in many cases the electromagnets seem to hold enough residual magnetism to keep disks from releasing and the doors from closing. It often becomes necessary to increase the opposing pneumatic force tremendously in order to overcome this.

I have discussed this with various manufacturers of these electromagnetic units and in all but one instance have received the same bullshit answer that they've "never heard of this".

The one exception was one tech who ventured that perhaps momentarily reversing polarity on alarm before DC drop out might work, however he had never tried it. Does anyone have any ideas about this? Thanks, Lenny




== 2 of 7 ==
Date: Mon, Feb 10 2014 9:38 am
From: Ken


captainvideo462009@gmail.com wrote:
> I work on commercial fire alarm systems mostly in apartment houses.
> Many of these buildings in the common hallways employ electromagnetic
> units mounted on the walls and an iron disk on the back corner of the
> doors. When the doors are opened and the disks are mated with the
> electromagnet the doors are held open in place. These doors all have
> pneumatic closers on them as well which are always applying a force
> in the opposite direction to try to close the door.
>
> When the alarm is activated the 24VDC is removed from the coils and
> the doors are supposed to be automatically pulled closed by the force
> of the pneumatic unit. This doesn't always work because in spite of
> the opposing force applied by the pneumatic unit, in many cases the
> electromagnets seem to hold enough residual magnetism to keep disks
> from releasing and the doors from closing. It often becomes necessary
> to increase the opposing pneumatic force tremendously in order to
> overcome this.
>
> I have discussed this with various manufacturers of these
> electromagnetic units and in all but one instance have received the
> same bullshit answer that they've "never heard of this".
>
> The one exception was one tech who ventured that perhaps momentarily
> reversing polarity on alarm before DC drop out might work, however he
> had never tried it. Does anyone have any ideas about this? Thanks,
> Lenny
>
Couldn't you place something over the metal disks to reduce the magnetic
coupling with the magnet? I would think you could find a point where it
would still hold the door when needed, and release it when 24v is removed.




== 3 of 7 ==
Date: Mon, Feb 10 2014 10:16 am
From: Cydrome Leader


captainvideo462009@gmail.com wrote:
> I work on commercial fire alarm systems mostly in apartment houses. Many of these buildings in the common hallways employ electromagnetic units mounted on the walls and an iron disk on the back corner of the doors. When the doors are opened and the disks are mated with the electromagnet the doors are held open in place. These doors all have pneumatic closers on them as well which are always applying a force in the opposite direction to try to close the door.
>
> When the alarm is activated the 24VDC is removed from the coils and the doors are supposed to be automatically pulled closed by the force of the pneumatic unit. This doesn't always work because in spite of the opposing force applied by the pneumatic unit, in many cases the electromagnets seem to hold enough residual magnetism to keep disks from releasing and the doors from closing. It often becomes necessary to increase the opposing pneumatic force tremendously in order to overcome this.
>
> I have discussed this with various manufacturers of these electromagnetic units and in all but one instance have received the same bullshit answer that they've "never heard of this".
>
> The one exception was one tech who ventured that perhaps momentarily reversing polarity on alarm before DC drop out might work, however he had never tried it. Does anyone have any ideas about this? Thanks, Lenny

feed them less than 24 volts, or maybe put a layer of packing tape over
the plate to add some space, or get somebody to "accidentally" paint over
the mating surfaces, although this is likely to make them stick as well.






== 4 of 7 ==
Date: Mon, Feb 10 2014 11:06 am
From: "hrhofmann@sbcglobal.net"


On Monday, February 10, 2014 11:32:26 AM UTC-6, captainvi...@gmail.com wrote:
> I work on commercial fire alarm systems mostly in apartment houses. Many of these buildings in the common hallways employ electromagnetic units mounted on the walls and an iron disk on the back corner of the doors. When the doors are opened and the disks are mated with the electromagnet the doors are held open in place. These doors all have pneumatic closers on them as well which are always applying a force in the opposite direction to try to close the door. When the alarm is activated the 24VDC is removed from the coils and the doors are supposed to be automatically pulled closed by the force of the pneumatic unit. This doesn't always work because in spite of the opposing force applied by the pneumatic unit, in many cases the electromagnets seem to hold enough residual magnetism to keep disks from releasing and the doors from closing. It often becomes necessary to increase the opposing pneumatic force tremendously in order to overcome this. I have discussed this with various manufacturers of these electromagnetic units and in all but one instance have received the same bullshit answer that they've "never heard of this". The one exception was one tech who ventured that perhaps momentarily reversing polarity on alarm before DC drop out might work, however he had never tried it. Does anyone have any ideas about this? Thanks, Lenny

Ken and Cydrome's idea to put a thin spacer on the disc to make it easier to release sounds like a good idea. My experience has always been that the magnetism was not strong enough to hold the door open, not that it would not release.





== 5 of 7 ==
Date: Mon, Feb 10 2014 11:11 am
From: Tim R


On Monday, February 10, 2014 2:06:37 PM UTC-5, hrho...@sbcglobal.net wrote:
> Ken and Cydrome's idea to put a thin spacer on the disc to make it easier to >release sounds like a good idea. My experience has always been that the >magnetism was not strong enough to hold the door open, not that it would not >release.

I've never seen this and I have a fair amount of experience with these doors in hospitals.

It is more commonly hard to get them to stay open.

I would suspect a door closer problem first.





== 6 of 7 ==
Date: Mon, Feb 10 2014 12:39 pm
From: RobertMacy


On Mon, 10 Feb 2014 10:32:26 -0700, <captainvideo462009@gmail.com> wrote:

>> ...snip...
> The one exception was one tech who ventured that perhaps momentarily
> reversing polarity on alarm before DC drop out might work, however he
> had never tried it. Does anyone have any ideas about this? Thanks, Lenny


I've always found that having ferrous metal in a DC field touching each
other is not a good idea. Add a 3 mil layer of kapton tape between the
two. the extra distance will prevent the 'residual' magnetism from having
enough strength to hold and keep the doors open. More likely difficulty
keeping them open.




== 7 of 7 ==
Date: Mon, Feb 10 2014 12:47 pm
From: adrian@poppyrecords.invalid.invalid (Adrian Tuddenham)


<captainvideo462009@gmail.com> wrote:

> I work on commercial fire alarm systems mostly in apartment houses. Many
> of these buildings in the common hallways employ electromagnetic units
> mounted on the walls and an iron disk on the back corner of the doors.
> When the doors are opened and the disks are mated with the electromagnet
> the doors are held open in place. These doors all have pneumatic closers
> on them as well which are always applying a force in the opposite
> direction to try to close the door.
>
> When the alarm is activated the 24VDC is removed from the coils and the
> doors are supposed to be automatically pulled closed by the force of the
> pneumatic unit. This doesn't always work because in spite of the opposing
> force applied by the pneumatic unit, in many cases the electromagnets seem
> to hold enough residual magnetism to keep disks from releasing and the
> doors from closing. It often becomes necessary to increase the opposing
> pneumatic force tremendously in order to overcome this.
>
> I have discussed this with various manufacturers of these electromagnetic
> units and in all but one instance have received the same bullshit answer
> that they've "never heard of this".
>
> The one exception was one tech who ventured that perhaps momentarily
> reversing polarity on alarm before DC drop out might work, however he had
> never tried it. Does anyone have any ideas about this? Thanks, Lenny

That last idea is an elegant one which would probably work quite well;
however, it has one very big drawback:

The safety of the whole system depends on the doors closing if anything
goes wrong. If the wires were burned through, the control box would
lose contact with the magnets and could not demagnetise them. The
fail-safe aspect of the system would be lost.


The usual method is to insert a non-magnetic shim of some kind, but this
can wear down and fail after a few years. A more subtle way is to
abrade or machine down one of the pole faces so that it is not quite in
the same plane as the other. If these are 'pot' magnets, you could skim
a thou or so off the centre pole if you have access to a lathe.
Unfortunately this would destroy any anti-corrosion plating on the
metal, but that might not matter if the buildings are dry.

An alternative would be to 'dish' the armature plate so that the concave
side was towards the magnet. To do this you would need to take it off
the door and stand it outside on a solid foundation (or an anvil, if you
have one). A supporting ring to back up the outer edge can be
improvised from a piece of hard wood with a hole in it or a short offcut
of steel pipe. To dish it slightly you will need a steel bar or other
hard object with one end slightly rounded - and a sledge hammer to hit
it with. Try to do it in one hit, so as to avoid peening the surface.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk





==============================================================================
TOPIC: Trying to understand the current draw of a Samsung Galaxy S3 under GPS &
low battery
http://groups.google.com/group/sci.electronics.repair/t/1dceb0f9a68c6f2d?hl=en
==============================================================================

== 1 of 2 ==
Date: Mon, Feb 10 2014 12:12 pm
From: artleknock


Going back to original query.
Ignoring all of the technical jargon, it could be that the GPS is
using power faster than it can be replaced.
According to the battery utility app on my Samsung Note 10.1 it takes
a very low battery in excess of 2.5hrs to charge on a mains charger,
but with a full battery the GPS will only function for 1hr and
39minutes. So the GPS is using power faster than even a mains
connection can replace it, it would be even faster with a USB
connection.




== 2 of 2 ==
Date: Mon, Feb 10 2014 12:24 pm
From: Juan Wei


Danny D. has written on 2/1/2014 10:45 PM:
> On Sat, 01 Feb 2014 05:17:38 -0600, Capt Rick wrote:
>
>> No need to sacrifice a USB cable.
>> Measure the current going into the
>> cigarette lighter adapter.
>
> Now why hadn't I thought of that!
>
> I can just hook an ammeter across the fuse
> for the cigarette lighter socket, which
> will give me the current being consumed
> with, and without the phone being charged!

(If you hook it across the fuse, you won't get the current you want.
Remove the fuse and connect the ammeter to the fuse terminals.)




==============================================================================

You received this message because you are subscribed to the Google Groups "sci.electronics.repair"
group.

To post to this group, visit http://groups.google.com/group/sci.electronics.repair?hl=en

To unsubscribe from this group, send email to sci.electronics.repair+unsubscribe@googlegroups.com

To change the way you get mail from this group, visit:
http://groups.google.com/group/sci.electronics.repair/subscribe?hl=en

To report abuse, send email explaining the problem to abuse@googlegroups.com

==============================================================================
Google Groups: http://groups.google.com/?hl=en