sci.electronics.repair - 19 new messages in 8 topics - digest

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

sci.electronics.repair@googlegroups.com

Today's topics:

==============================================================================
TOPIC: Sony DSC-P3 has Error Code 61;00
http://groups.google.com/group/sci.electronics.repair/t/59d8a0c9abbbf9c7?hl=en
==============================================================================

== 1 of 2 ==
Date: Mon, Oct 24 2011 9:24 pm
From: "hrhofmann@att.net"

On Oct 24, 1:31 pm, abrsvc <dansabrservi...@yahoo.com> wrote:
> On Oct 23, 11:34 pm, "hrhofm...@att.net" <hrhofm...@att.net> wrote:
>
> > On Oct 23, 8:08 pm, "William Sommerwerck" <grizzledgee...@comcast.net>
> > wrote:
>
> > > The last time you transferred pictures to your computer... Did you properly
> > > eject the memory stick before removing it? If not, you could have damaged
> > > the stick.
>
> > I transferred using the USB connector on the camera to download to the
> > computer.
>
> Pne of the most common causes of this error is poor contacts on the
> memory stick. Remove the stick and burnish the contacts a little. Re-
> insert the stick and try again. It doesn't take much to cause a
> questionable connection at the pins. The contacts can fatigue a bit
> as well.
>
> Update this with your progress.
>
> Dan

Well---I put the camera on the charger for a couple of hours while I
was doing household chores. Then about 1/2 hour ago, I connected a
USB cable to my computer, and turned the camera on. To my pleasant
surprise, the camera turned on normally and there was no error
mesage. Now I have turned the camera off, disconnected the USB cable
and set it aside until tomorrow morning. We'll see what happens. I
didn't take the camera card out since I did look at the card earlier
today, and was still getting error messages after I replaced the
card. Contacts looked fine when I had it out, and I didn't see
anything that looked like dirt inside the card housing and its
contacts. So, we'll see what happens tomorrow
and will report back. Thanks for your suggeston.

== 2 of 2 ==
Date: Tues, Oct 25 2011 12:38 pm
From: "hrhofmann@att.net"

On Oct 24, 11:24 pm, "hrhofm...@att.net" <hrhofm...@att.net> wrote:
> On Oct 24, 1:31 pm, abrsvc <dansabrservi...@yahoo.com> wrote:
>
>
>
>
>
> > On Oct 23, 11:34 pm, "hrhofm...@att.net" <hrhofm...@att.net> wrote:
>
> > > On Oct 23, 8:08 pm, "William Sommerwerck" <grizzledgee...@comcast.net>
> > > wrote:
>
> > > > The last time you transferred pictures to your computer... Did you properly
> > > > eject the memory stick before removing it? If not, you could have damaged
> > > > the stick.
>
> > > I transferred using the USB connector on the camera to download to the
> > > computer.
>
> > Pne of the most common causes of this error is poor contacts on the
> > memory stick. Remove the stick and burnish the contacts a little. Re-
> > insert the stick and try again. It doesn't take much to cause a
> > questionable connection at the pins. The contacts can fatigue a bit
> > as well.
>
> > Update this with your progress.
>
> > Dan
>
> Well---I put the camera on the charger for a couple of hours while I
> was doing household chores. Then about 1/2 hour ago, I connected a
> USB cable to my computer, and turned the camera on. To my pleasant
> surprise, the camera turned on normally and there was no error
> mesage. Now I have turned the camera off, disconnected the USB cable
> and set it aside until tomorrow morning. We'll see what happens. I
> didn't take the camera card out since I did look at the card earlier
> today, and was still getting error messages after I replaced the
> card. Contacts looked fine when I had it out, and I didn't see
> anything that looked like dirt inside the card housing and its
> contacts. So, we'll see what happens tomorrow
> and will report back. Thanks for your suggeston.- Hide quoted text -
>
> - Show quoted text -

Turned camera on twice today, everything appears to be normal, sure
would like to know what happened, but very happy it is working again.

==============================================================================
TOPIC: unassembling external drive enclosure
http://groups.google.com/group/sci.electronics.repair/t/d976fe30b90ef802?hl=en
==============================================================================

== 1 of 3 ==
Date: Tues, Oct 25 2011 4:21 am
From: Ninho

Hi! Got a problem, which I've been advised to submit to this Group's
experienced users. Please pardon me if I made an error posting, also,
bear with less than adequate English !

So, a 6/7 years old 80-gigabyte disk in an external USB 2.0
enclosure has failed me. I suspect the drive itself could be OK but
the USB interface or other electronics/connectics of the case might
have fail (it had been acting weird sometimes)

Now I would like to separate the drive from this enclosure and
connect it straight to the MoBoard for testing.

Brand stamped on the pretty, sturdy case is "QPS multimedia" ("made
in China"). Disk inside is Maxtor 80 Gb, probably pATA.

Disk + enclosure came as a unit, and the problem is, I can't seem to
be able to disassemble it even after removing screws :=(
I don't think I've missed any hidden screws.

The disk itself is a 80Gb Maxtor, I assume pATA.

Googling hasn't served very much, nor did Youtube help. The "QPS"
brand is no longer manufacturing those articles it seems.

I hope someone can point me to a site with instructions or hints for
disassembly.

--
Ninho

== 2 of 3 ==
Date: Tues, Oct 25 2011 4:25 am
From: "N_Cook"

Ninho <don't.use!@this.is.invalid> wrote in message
news:XnF9F8987F397CBBG6R6C1N@193.252.117.183...
> Hi! Got a problem, which I've been advised to submit to this Group's
> experienced users. Please pardon me if I made an error posting, also,
> bear with less than adequate English !
>
> So, a 6/7 years old 80-gigabyte disk in an external USB 2.0
> enclosure has failed me. I suspect the drive itself could be OK but
> the USB interface or other electronics/connectics of the case might
> have fail (it had been acting weird sometimes)
>
> Now I would like to separate the drive from this enclosure and
> connect it straight to the MoBoard for testing.
>
> Brand stamped on the pretty, sturdy case is "QPS multimedia" ("made
> in China"). Disk inside is Maxtor 80 Gb, probably pATA.
>
> Disk + enclosure came as a unit, and the problem is, I can't seem to
> be able to disassemble it even after removing screws

> I don't think I've missed any hidden screws.
>
> The disk itself is a 80Gb Maxtor, I assume pATA.
>
> Googling hasn't served very much, nor did Youtube help. The "QPS"
> brand is no longer manufacturing those articles it seems.
>
> I hope someone can point me to a site with instructions or hints for
> disassembly.
>
> --
> Ninho

Any label hiding a fixing ? heat off with hot air perhaps

== 3 of 3 ==
Date: Tues, Oct 25 2011 4:56 am
From: Bob_Villa

On Oct 25, 6:21 am, Ninho <don't.u...@this.is.invalid> wrote:
> Hi! Got a problem, which I've been advised to submit to this Group's
> experienced users. Please pardon me if I made an error posting, also,
> bear with less than adequate English !
>
> So, a 6/7 years old 80-gigabyte disk in an external USB 2.0
> enclosure has failed me. I suspect the drive itself could be OK but
> the USB interface or other electronics/connectics of the case might
> have fail (it had been acting weird sometimes)
>
> Now I would like to separate the drive from this enclosure and
> connect it straight to the MoBoard for testing.
>
> Brand stamped on the pretty, sturdy case is "QPS multimedia" ("made
> in China"). Disk inside is Maxtor 80 Gb, probably pATA.
>
> Disk + enclosure came as a unit, and the problem is, I can't seem to
> be able to disassemble it even after removing screws :=(
> I don't think I've missed any hidden screws.
>
> The disk itself is a 80Gb Maxtor, I assume pATA.
>
> Googling hasn't served very much, nor did Youtube help. The "QPS"
> brand is no longer manufacturing those articles it seems.
>
> I hope someone can point me to a site with instructions or hints for
> disassembly.
>
> --
> Ninho

I believe (if it's like mine) the screws are under the bottom label.
And you can almost bet if it's Maxtor...its bad!

==============================================================================
TOPIC: home-brew Freon TF substitutes?
http://groups.google.com/group/sci.electronics.repair/t/f66a71610e41b61d?hl=en
==============================================================================

== 1 of 3 ==
Date: Tues, Oct 25 2011 6:16 am
From: "Orson Cart"

isw <isw@witzend.com> wrote:

>
>At least some (perhaps not all) methylated hydrocarbons are completely
>
>non-flammable, and also are heavier than water and will not mix with
>it.
>I am sure that is true of methylene chloride.
>
>Be careful, though; it is a powerful solvent, removing, among other
>
>things, *all* the oil from your skin, if you have much contact with
>it.
>It is absorbed through the skin, too, and hurts/burns.
>
>It may also neatly soften or dissolve a lot of the plastics used in
>
>electronics; I don't know.
>
>Isaac

Methylene chloride is definitely not for electronic components.
It is used a paint stripper. I am sure it would require rinsing
off quickly with another solvent, otherwise your PCB would be
fuggered.
The sadly-missed chloro/fluoro-carbon cleaners would not damage the useful
stuff like plastics, rubber, lacquer, metal, paper et ecetera.

== 2 of 3 ==
Date: Tues, Oct 25 2011 3:06 pm
From: Jim Yanik

gregz <zekor@comcast.net> wrote in news:326610463341166402.448206zekor-
comcast.net@news.eternal-september.org:

> Jeff Layman <JMLayman@invalid.invalid> wrote:
>> On 24/10/2011 13:33, Nomen Nescio wrote:
>>> I last saw this in the mid 1990s. I knew a warehouse that still
>>> had some drums hidden away...
>>> Bloody best cleaner ever. Although some liked Genklene,
>>> now also banned.
>>> There are some commercial spray cleaners that claim to be
>>> almost as good. I would like something in bulk for dipping
>>> computer boards. Isopropyl alchohol is suggested by some,
>>> but has 9% water usually.
>>
>> Not sure where you are, but isopropyl alcohol is usually available 99.9%
>> pure, with a negligible water content.
>
>
> And by the time it's dried, it's picked up a lot of water.
>
> Greg
>

Mass Air Flow sensor cleaner,available at Wal-Mart of auto stores.
CRC makes a spray can of it. # 05110

--
Jim Yanik
jyanik
at
localnet
dot com

== 3 of 3 ==
Date: Tues, Oct 25 2011 6:08 pm
From: "Arfa Daily"

"Jeff Layman" <JMLayman@invalid.invalid> wrote in message
news:j83vnf$cjh$2@news.albasani.net...
> On 24/10/2011 13:33, Nomen Nescio wrote:
>> I last saw this in the mid 1990s. I knew a warehouse that still
>> had some drums hidden away...
>> Bloody best cleaner ever. Although some liked Genklene,
>> now also banned.
>> There are some commercial spray cleaners that claim to be
>> almost as good. I would like something in bulk for dipping
>> computer boards. Isopropyl alchohol is suggested by some,
>> but has 9% water usually.
>
> Not sure where you are, but isopropyl alcohol is usually available 99.9%
> pure, with a negligible water content.
>
> --
>
> Jeff

I'd go along with that. The stuff specified as 'electronics grade' is
typically at least 99.7% to get that rating

Arfa

==============================================================================
TOPIC: SEXY HOT PHOTOS & VIDEOS
http://groups.google.com/group/sci.electronics.repair/t/da6826d6cd08a4ee?hl=en
==============================================================================

== 1 of 1 ==
Date: Tues, Oct 25 2011 7:35 am
From: SRAVANTHI LOVE

FOR GOOD JOBS SITES TO YOU
http://goodjobssites.blogspot.com/

==============================================================================
TOPIC: Repair Projects
http://groups.google.com/group/sci.electronics.repair/t/272a3ad8423db5af?hl=en
==============================================================================

== 1 of 3 ==
Date: Tues, Oct 25 2011 8:16 am
From: Scott Smith

Great Organizer Software, PIM, Lister, Record Keeper, ToDo SW, Ultra
Easy to Use, ListerPro, 12 Programmable Different Catagory Listboxes
(Titles, Entries and Colors), Unlimited Entries Per ListBox, Add,
Delete, Edit and Clear Functions, Backup Load / Save /Clear Options,
Import Load / Save / Clear / Delete Options, One Entry Counter Per
Listbox, Programmable ListBox Names, Latest Version 3.8, Free Version
timed Demo Link Below, Unlimited Support For Registered Users
http://www.sharewaresoftware.info/listerpro/listerpro.htm

== 2 of 3 ==
Date: Tues, Oct 25 2011 2:08 pm
From: "Michael A. Terrell"

Scott Smith wrote:
>
> Great Spam.

--
You can't have a sense of humor, if you have no sense.

== 3 of 3 ==
Date: Tues, Oct 25 2011 10:20 pm
From: Sofa Slug

On 10/25/2011 8:16 AM, Scott Smith wrote:
> Great Organizer Software, PIM, Lister, Record Keeper, ToDo SW, Ultra
> Easy to Use, ListerPro, 12 Programmable Different Catagory Listboxes
> (Titles, Entries and Colors), Unlimited Entries Per ListBox, Add,
> Delete, Edit and Clear Functions, Backup Load / Save /Clear Options,
> Import Load / Save / Clear / Delete Options, One Entry Counter Per
> Listbox, Programmable ListBox Names, Latest Version 3.8, Free
> Version timed Demo Link Below, Unlimited Support For Registered
> Users http://www.junksoftware.info/whocares/listcrap.htm

I'm sure the spambots would love to have your email address ...let's
give it to them!: scott93727@aol.com

==============================================================================
TOPIC: SMPS design ...
http://groups.google.com/group/sci.electronics.repair/t/fafbacc4bb94c7c0?hl=en
==============================================================================

== 1 of 3 ==
Date: Tues, Oct 25 2011 1:35 pm
From: "Ian Field"

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:rq6dnSPqhbfurzvTnZ2dnUVZ_h-dnZ2d@earthlink.com...
>
> Arfa Daily wrote:
>>
>> "petrus bitbyter" <petrus.bitbyter@hotmail.com> wrote in message
>> news:4ea31dff$0$482$e4fe514c@dreader26.news.xs4all.nl...
>> >
>> > "Arfa Daily" <arfa.daily@ntlworld.com> schreef in bericht
>> > news:zDooq.16012$tk5.4043@newsfe13.ams2...
>> >>
>> >>>>>
>> >>>>>
>> >>>
>> >>> Didn't you walk right into the problem? It seems that by a yet
>> >>> unknown
>> >>> cause the circuit sometimes runs into some state that makes it
>> >>> oscillate
>> >>> or in some other way fries the resistors. This kind of intermitted
>> >>> faults are the most difficult to solve as most of the times there
>> >>> seems
>> >>> to be no problem. Even your observations with the scope may mislead
>> >>> you
>> >>> as connecting the probe may change the circuit enough to change its
>> >>> behavior.
>> >>>
>> >>> petrus bitbyter
>> >>>
>> >>
>> >> Yes, there may indeed be some kind of intermittent problem. I will put
>> >> them all back up again on Monday, and see how they perform this time.
>> >> As
>> >> to my 'scope muddying the waters, it's generally pretty well behaved
>> >> in
>> >> that respect. It's a high quality 100 MHz job, which is always used
>> >> with
>> >> a x 10 low capacitance probe. If that is having much of an effect on
>> >> the
>> >> circuit, then it must for sure be a pretty poor design. To be honest,
>> >> I
>> >> still think that the problem lies with me somehow. Something that I
>> >> did
>> >> differently between the first and second times that I tried them, but
>> >> I'm
>> >> not sure what ...
>> >>
>> >> Arfa
>> >
>> > Off course you may have made a mistake. Humans make mistakes, even I
>> > sometimes do :)
>> > But if so, what on earth fried those resistors the first time?
>> >
>> > petrus bitbyter
>> >
>> >
>>
>> Every example that I've seen so far, has the resistors badly discoloured
>> and
>> the print and substrate scorched. On some, one of the resistors has been
>> open, so the network has not been doing the job it was put there for, at
>> all. They are 3 watt resistors, and even when the supply *appears* to be
>> running correctly, they get hot enough for you to say that they are
>> probably
>> dissipating a good 3 watts, and maybe a bit more, so I would guess that
>> you
>> would have to say that from that angle, it's a badly designed bit of
>> circuitry. I am fairly convinced that the purpose of the network is to
>> attenuate the big spike that occurs on the leading edge of the switching
>> waveform. This would tie in with why they have used about the biggest
>> film
>> resistors they could get, rather than using a higher power wirewound
>> type,
>> which would have a fair bit of inductance. I would also surmise that they
>> have used two x 150 ohm resistors rather than a single 330 ohm, to try to
>> spread the dissipation a bit.
>>
>> When you replace the resistors, they still run hot, with no visible signs
>> on
>> the 'scope of any 'RF' on the waveform, so you'd have to say that it *is*
>> working correctly. What led to this thread in the first place was that
>> when
>> I was initially evaluating these supplies for the company that wants them
>> repairing, after I replaced the resistors, they ran very hot when the
>> supply
>> was loaded, but seemed to just run 'acceptably' hot when it was idling.
>> Likewise, when loaded, the switching FET got very hot, but was almost
>> cold
>> at idle.
>>
>> However, when I next tried them - same conditions for i/p voltage and
>> load,
>> as far as I was aware - they now seemed to be working much better in that
>> the resistors were just acceptably hot for all conditions, loaded or not,
>> and the FET remained cool also. So this has now led me to believe that it
>> must have been something I was doing differently - and wrongly - when it
>> was
>> running very hot. So, a mistake ? Yes, probably. As you say, we all make
>> them, and this has got to be one of the easiest trades for doing it in.
>>
>> I've just heard from the company that they are sending a bunch more up
>> this
>> week, so if there's some more of this type amongst them, I'll have some
>> more
>> 'untouched' ones to see what happens this time.
>
>
> Are you using metal or carbon film resistors? You could have a
> resonance with a cap & metal film.

There's allways low inductance thick film resistors, but they have to be
generously rated to minimise heating - they were a constant hassle in the
video O/P stage in one of the TCE CTVs, running too hot and repeated thermal
cycling took its toll on the pins attachment pads.

== 2 of 3 ==
Date: Tues, Oct 25 2011 2:07 pm
From: "Michael A. Terrell"

Ian Field wrote:
>
> "Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
> news:rq6dnSPqhbfurzvTnZ2dnUVZ_h-dnZ2d@earthlink.com...
> >
> > Arfa Daily wrote:
> >>
> >> "petrus bitbyter" <petrus.bitbyter@hotmail.com> wrote in message
> >> news:4ea31dff$0$482$e4fe514c@dreader26.news.xs4all.nl...
> >> >
> >> > "Arfa Daily" <arfa.daily@ntlworld.com> schreef in bericht
> >> > news:zDooq.16012$tk5.4043@newsfe13.ams2...
> >> >>
> >> >>>>>
> >> >>>>>
> >> >>>
> >> >>> Didn't you walk right into the problem? It seems that by a yet
> >> >>> unknown
> >> >>> cause the circuit sometimes runs into some state that makes it
> >> >>> oscillate
> >> >>> or in some other way fries the resistors. This kind of intermitted
> >> >>> faults are the most difficult to solve as most of the times there
> >> >>> seems
> >> >>> to be no problem. Even your observations with the scope may mislead
> >> >>> you
> >> >>> as connecting the probe may change the circuit enough to change its
> >> >>> behavior.
> >> >>>
> >> >>> petrus bitbyter
> >> >>>
> >> >>
> >> >> Yes, there may indeed be some kind of intermittent problem. I will put
> >> >> them all back up again on Monday, and see how they perform this time.
> >> >> As
> >> >> to my 'scope muddying the waters, it's generally pretty well behaved
> >> >> in
> >> >> that respect. It's a high quality 100 MHz job, which is always used
> >> >> with
> >> >> a x 10 low capacitance probe. If that is having much of an effect on
> >> >> the
> >> >> circuit, then it must for sure be a pretty poor design. To be honest,
> >> >> I
> >> >> still think that the problem lies with me somehow. Something that I
> >> >> did
> >> >> differently between the first and second times that I tried them, but
> >> >> I'm
> >> >> not sure what ...
> >> >>
> >> >> Arfa
> >> >
> >> > Off course you may have made a mistake. Humans make mistakes, even I
> >> > sometimes do :)
> >> > But if so, what on earth fried those resistors the first time?
> >> >
> >> > petrus bitbyter
> >> >
> >> >
> >>
> >> Every example that I've seen so far, has the resistors badly discoloured
> >> and
> >> the print and substrate scorched. On some, one of the resistors has been
> >> open, so the network has not been doing the job it was put there for, at
> >> all. They are 3 watt resistors, and even when the supply *appears* to be
> >> running correctly, they get hot enough for you to say that they are
> >> probably
> >> dissipating a good 3 watts, and maybe a bit more, so I would guess that
> >> you
> >> would have to say that from that angle, it's a badly designed bit of
> >> circuitry. I am fairly convinced that the purpose of the network is to
> >> attenuate the big spike that occurs on the leading edge of the switching
> >> waveform. This would tie in with why they have used about the biggest
> >> film
> >> resistors they could get, rather than using a higher power wirewound
> >> type,
> >> which would have a fair bit of inductance. I would also surmise that they
> >> have used two x 150 ohm resistors rather than a single 330 ohm, to try to
> >> spread the dissipation a bit.
> >>
> >> When you replace the resistors, they still run hot, with no visible signs
> >> on
> >> the 'scope of any 'RF' on the waveform, so you'd have to say that it *is*
> >> working correctly. What led to this thread in the first place was that
> >> when
> >> I was initially evaluating these supplies for the company that wants them
> >> repairing, after I replaced the resistors, they ran very hot when the
> >> supply
> >> was loaded, but seemed to just run 'acceptably' hot when it was idling.
> >> Likewise, when loaded, the switching FET got very hot, but was almost
> >> cold
> >> at idle.
> >>
> >> However, when I next tried them - same conditions for i/p voltage and
> >> load,
> >> as far as I was aware - they now seemed to be working much better in that
> >> the resistors were just acceptably hot for all conditions, loaded or not,
> >> and the FET remained cool also. So this has now led me to believe that it
> >> must have been something I was doing differently - and wrongly - when it
> >> was
> >> running very hot. So, a mistake ? Yes, probably. As you say, we all make
> >> them, and this has got to be one of the easiest trades for doing it in.
> >>
> >> I've just heard from the company that they are sending a bunch more up
> >> this
> >> week, so if there's some more of this type amongst them, I'll have some
> >> more
> >> 'untouched' ones to see what happens this time.
> >
> >
> > Are you using metal or carbon film resistors? You could have a
> > resonance with a cap & metal film.
>
> There's always low inductance thick film resistors, but they have to be
> generously rated to minimise heating - they were a constant hassle in the
> video O/P stage in one of the TCE CTVs, running too hot and repeated thermal
> cycling took its toll on the pins attachment pads.

Carbon film is less inductive. Carbon comp would be ideal, but most
EEs these days don't know they exist. Low power SMD metal film
resistors do a lot better at UHF and Microwave frequencies. We used
them at 10 GHz, with no problems. Larger, high power metal film on a
round core are a spiral of metal.

--
You can't have a sense of humor, if you have no sense.

== 3 of 3 ==
Date: Tues, Oct 25 2011 2:51 pm
From: "Ian Field"

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:cKOdnVfqb_OHuDrTnZ2dnUVZ_oqdnZ2d@earthlink.com...
>
> Ian Field wrote:
>>
>> "Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
>> news:rq6dnSPqhbfurzvTnZ2dnUVZ_h-dnZ2d@earthlink.com...
>> >
>> > Arfa Daily wrote:
>> >>
>> >> "petrus bitbyter" <petrus.bitbyter@hotmail.com> wrote in message
>> >> news:4ea31dff$0$482$e4fe514c@dreader26.news.xs4all.nl...
>> >> >
>> >> > "Arfa Daily" <arfa.daily@ntlworld.com> schreef in bericht
>> >> > news:zDooq.16012$tk5.4043@newsfe13.ams2...
>> >> >>
>> >> >>>>>
>> >> >>>>>
>> >> >>>
>> >> >>> Didn't you walk right into the problem? It seems that by a yet
>> >> >>> unknown
>> >> >>> cause the circuit sometimes runs into some state that makes it
>> >> >>> oscillate
>> >> >>> or in some other way fries the resistors. This kind of intermitted
>> >> >>> faults are the most difficult to solve as most of the times there
>> >> >>> seems
>> >> >>> to be no problem. Even your observations with the scope may
>> >> >>> mislead
>> >> >>> you
>> >> >>> as connecting the probe may change the circuit enough to change
>> >> >>> its
>> >> >>> behavior.
>> >> >>>
>> >> >>> petrus bitbyter
>> >> >>>
>> >> >>
>> >> >> Yes, there may indeed be some kind of intermittent problem. I will
>> >> >> put
>> >> >> them all back up again on Monday, and see how they perform this
>> >> >> time.
>> >> >> As
>> >> >> to my 'scope muddying the waters, it's generally pretty well
>> >> >> behaved
>> >> >> in
>> >> >> that respect. It's a high quality 100 MHz job, which is always used
>> >> >> with
>> >> >> a x 10 low capacitance probe. If that is having much of an effect
>> >> >> on
>> >> >> the
>> >> >> circuit, then it must for sure be a pretty poor design. To be
>> >> >> honest,
>> >> >> I
>> >> >> still think that the problem lies with me somehow. Something that I
>> >> >> did
>> >> >> differently between the first and second times that I tried them,
>> >> >> but
>> >> >> I'm
>> >> >> not sure what ...
>> >> >>
>> >> >> Arfa
>> >> >
>> >> > Off course you may have made a mistake. Humans make mistakes, even I
>> >> > sometimes do :)
>> >> > But if so, what on earth fried those resistors the first time?
>> >> >
>> >> > petrus bitbyter
>> >> >
>> >> >
>> >>
>> >> Every example that I've seen so far, has the resistors badly
>> >> discoloured
>> >> and
>> >> the print and substrate scorched. On some, one of the resistors has
>> >> been
>> >> open, so the network has not been doing the job it was put there for,
>> >> at
>> >> all. They are 3 watt resistors, and even when the supply *appears* to
>> >> be
>> >> running correctly, they get hot enough for you to say that they are
>> >> probably
>> >> dissipating a good 3 watts, and maybe a bit more, so I would guess
>> >> that
>> >> you
>> >> would have to say that from that angle, it's a badly designed bit of
>> >> circuitry. I am fairly convinced that the purpose of the network is to
>> >> attenuate the big spike that occurs on the leading edge of the
>> >> switching
>> >> waveform. This would tie in with why they have used about the biggest
>> >> film
>> >> resistors they could get, rather than using a higher power wirewound
>> >> type,
>> >> which would have a fair bit of inductance. I would also surmise that
>> >> they
>> >> have used two x 150 ohm resistors rather than a single 330 ohm, to try
>> >> to
>> >> spread the dissipation a bit.
>> >>
>> >> When you replace the resistors, they still run hot, with no visible
>> >> signs
>> >> on
>> >> the 'scope of any 'RF' on the waveform, so you'd have to say that it
>> >> *is*
>> >> working correctly. What led to this thread in the first place was that
>> >> when
>> >> I was initially evaluating these supplies for the company that wants
>> >> them
>> >> repairing, after I replaced the resistors, they ran very hot when the
>> >> supply
>> >> was loaded, but seemed to just run 'acceptably' hot when it was
>> >> idling.
>> >> Likewise, when loaded, the switching FET got very hot, but was almost
>> >> cold
>> >> at idle.
>> >>
>> >> However, when I next tried them - same conditions for i/p voltage and
>> >> load,
>> >> as far as I was aware - they now seemed to be working much better in
>> >> that
>> >> the resistors were just acceptably hot for all conditions, loaded or
>> >> not,
>> >> and the FET remained cool also. So this has now led me to believe that
>> >> it
>> >> must have been something I was doing differently - and wrongly - when
>> >> it
>> >> was
>> >> running very hot. So, a mistake ? Yes, probably. As you say, we all
>> >> make
>> >> them, and this has got to be one of the easiest trades for doing it
>> >> in.
>> >>
>> >> I've just heard from the company that they are sending a bunch more up
>> >> this
>> >> week, so if there's some more of this type amongst them, I'll have
>> >> some
>> >> more
>> >> 'untouched' ones to see what happens this time.
>> >
>> >
>> > Are you using metal or carbon film resistors? You could have a
>> > resonance with a cap & metal film.
>>
>> There's always low inductance thick film resistors, but they have to be
>> generously rated to minimise heating - they were a constant hassle in the
>> video O/P stage in one of the TCE CTVs, running too hot and repeated
>> thermal
>> cycling took its toll on the pins attachment pads.
>
>
> Carbon film is less inductive. Carbon comp would be ideal, but most
> EEs these days don't know they exist. Low power SMD metal film
> resistors do a lot better at UHF and Microwave frequencies. We used
> them at 10 GHz, with no problems. Larger, high power metal film on a
> round core are a spiral of metal.

Why do you think I suggested thick film!

==============================================================================
TOPIC: A cordless phone question
http://groups.google.com/group/sci.electronics.repair/t/dbf17b88cb06d8a8?hl=en
==============================================================================

== 1 of 2 ==
Date: Tues, Oct 25 2011 5:08 pm
From: Jeff Urban

I got a couple of Unidens that interchange just fine. They do it
digitally so once you stick one in the other base, the remaaining base
and handset will not work until plugged in once. When the charge light
comes on it flickers a bit after about a half a second, that is the
handshake I would assume.

Years ago a buddy of mine bought a couple of Vtechs that did the same
thing, but he had them connected to different phone lines. That has
it's own set of advantages but mine are still hooked to the same line.
I just switch them when a battery starts dying.

However when one dies there is a loud audio noise until one of the
handsets goes on the base that was in use. Then being reinitialized of
course it hangs up, so you have to take another phone off hook to make
the transistion.

They wil also work simultaneously, they sidestep each others'
channel.

They are getting old now, the battery life is not what it once was but
I like the phones themselves. There is also a problem if I use a
certain wireless camera because it's also only 2.4 Ghz.

== 2 of 2 ==
Date: Tues, Oct 25 2011 6:53 pm
From: Ken

Jeff Urban wrote:
> I got a couple of Unidens that interchange just fine. They do it
> digitally so once you stick one in the other base, the remaaining base
> and handset will not work until plugged in once. When the charge light
> comes on it flickers a bit after about a half a second, that is the
> handshake I would assume.
>
> Years ago a buddy of mine bought a couple of Vtechs that did the same
> thing, but he had them connected to different phone lines. That has
> it's own set of advantages but mine are still hooked to the same line.
> I just switch them when a battery starts dying.
>
> However when one dies there is a loud audio noise until one of the
> handsets goes on the base that was in use. Then being reinitialized of
> course it hangs up, so you have to take another phone off hook to make
> the transistion.
>
> They wil also work simultaneously, they sidestep each others'
> channel.
>
> They are getting old now, the battery life is not what it once was but
> I like the phones themselves. There is also a problem if I use a
> certain wireless camera because it's also only 2.4 Ghz.
>
> J

Thanks for your comments. Thanks to everyone I have several ideas now
that I did not have before.

==============================================================================
TOPIC: Mixing 4 audio channels to 3?
http://groups.google.com/group/sci.electronics.repair/t/a9c921002b2ed750?hl=en
==============================================================================

== 1 of 2 ==
Date: Tues, Oct 25 2011 11:58 pm
From: DaveC

I want to connect the audio out (headphone jack) of 2 computer sound cards to
a desktop & woofer speaker-amp combination. (The original input was via USB
only and I'm modifying this for analog audio input.)

This is my guess at the necessary resistors to mix down these 4 outputs to
the 3 inputs in the amplifier (L, R, sub):

<http://i41.tinypic.com/97mpud.jpg>

The data sheet for the Philips TDA8510J amp IC shows an application for 2
channel input:

<http://i40.tinypic.com/5ets9w.jpg>

Suggestions welcome.

Thanks.

== 2 of 2 ==
Date: Tues, Oct 25 2011 11:59 pm
From: DaveC

If I'm on the right track, what are the suggested values for resistors?

Thahks.

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

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

Electronics

sci.electronics.repair - 19 new messages in 8 topics - digest

No Response to "sci.electronics.repair - 19 new messages in 8 topics - digest"

Post a Comment

Blog Roll

Blog Archive