sci.electronics.repair@googlegroups.com

Today's topics:

* Blew another damn transformer on my Trane XB80 - 17 messages, 11 authors
http://groups.google.com/group/sci.electronics.repair/t/f883cd09a3a0b791?hl=en
* Rigol scope LCD problem - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/f09ee6418c07d961?hl=en
* Phil Allison is fucking INSANE - 2 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/aff797bedba2c908?hl=en
* Help to identify capacitor please - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/df081010fd20fad8?hl=en
* Servis M6712W (washing machine) - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/96927913b917139e?hl=en
* PAYPAL WHOLESALE all BRAND(UGG BOOTS,SHOES,CLOTHES,HANDBAG,WATCH,JEANS,
JERSEY,T-SHIRT,SHIRTS,HOODY,EYEGLASS,CAP,SHAWL,WALLT) and so on http://www.24
hours-online.com/. - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/8cb7e30537b683c3?hl=en

==============================================================================
TOPIC: Blew another damn transformer on my Trane XB80
http://groups.google.com/group/sci.electronics.repair/t/f883cd09a3a0b791?hl=en
==============================================================================

== 1 of 17 ==
Date: Tues, Apr 12 2011 12:38 am
From: "Phil Allison"

"Don Klipstein"

** FOAD - you stupid, ridiculous arsehole.

== 2 of 17 ==
Date: Tues, Apr 12 2011 2:38 am
From: "Stormin Mormon"

There you go, again. Completely mistaken about what I'd
reccomend in the way of diagnostic. Just making up garbage,
and then trying to assign it to me. Well, you should do that
more often. Then, everyone can see what your true character
is like. Please write often, and lengthy. The more you
write, the better I look.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
.

"David Nebenzahl" <nobody@but.us.chickens> wrote in message
news:4da3b1e4$0$15512$822641b3@news.adtechcomputers.com...
On 4/11/2011 4:37 PM Stormin Mormon spake thus:

> OK, that makes a bit of sense. Seems like a bit of bother
> for what you can track down, with a VOM and some common
> sense.

As usual, being an ignoramus, you completely miss the point.

The light bulb not only allows you to detect if there's a
short causing
too high a current draw, but it also *saves the device under
test* from
releasing the magic smoke if there is such a smoke.

If you use some other method of measuring current--break
circuit and
insert ammeter, or use clamp-on-meter, the meter will tell
you there's a
short, all right, at about the same time the transformer
erupts in a
ball of smoke and fire.

--
The current state of literacy in our advanced civilization:

yo
wassup
nuttin
wan2 hang
k
where
here
k
l8tr
by

- from Usenet (what's *that*?)

== 3 of 17 ==
Date: Tues, Apr 12 2011 7:46 am
From: Tony Miklos

On 4/11/2011 9:31 PM, John Robertson wrote:
> Tony Miklos wrote:
>> On 4/9/2011 10:06 PM, John Robertson wrote:
>>> Steve Turner wrote:
>>>> On 4/9/2011 7:29 PM, Jim Yanik wrote:
>>>>> "robb"<some@where.on.net> wrote in
>>>>> news:WfKdnQOvu_d2bz3QnZ2dnUVZ_uadnZ2d@earthlink.com:
>>>>>
>>>>>> "Steve Turner" wrote in message news:inoakf$qin$1@dont-email.me...
>>>>>>
>>>>>>> A continuation of the "Why does the 115V->24V transformer keep
>>>>>>> blowing on my Trane XB80?" discussion I started on 04/02/2011.
>>>>>>>
>>>>>>> Yep, My A/C unit blew another transformer. Pictures (and wiring
>>>>>>> diagram) here:
>>>>>>>
>>>>>>> http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
>>>>>>>
>>>>>>> Trane's manual for the unit is here (for perhaps better viewing of
>>>>>>> the wiring diagrams that I also copied to my above flickr site as
>>>>>>> jpg images):
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>> http://www.trane.com/webcache/un/furnaces%20%28furn%29/product/22-1666-
>>>>>>
>>>>>> 07_04012009.pdf
>>>>>>>
>>>>>>> As you can probably see in the pictures, there is visible charring
>>>>>>> of the 115V leads going into the transformer, and of course the 115V
>>>>>>> circuit is open (again). If you didn't see my first thread, this is
>>>>>>> the third transformer the unit has blown. In the previous
>>>>>>> discussion, it was discussed that perhaps the first one just blew
>>>>>>> because of old age (6 years), and the second blew because it wasn't
>>>>>>> a proper replacement (poor quality, made in China, etc.). This
>>>>>>> third unit is most certainly a proper replacement, and it's most
>>>>>>> certainly indicative of a real problem I have somewhere else in the
>>>>>>> unit. I didn't see any such charring on the previous two units, at
>>>>>>> least not like this.
>>>>>>>
>>>>>>> I never got a real chance to test out the system after installing
>>>>>>> this third transformer. We had cool weather for several days, and I
>>>>>>> never tried to force the system to come on so I could monitor it;
>>>>>>> that was probably a mistake. Unfortunately, I was also absent from
>>>>>>> the premises during the extended times when the unit was most likely
>>>>>>> operational, so that didn't help either. However, my family tells me
>>>>>>> that it WAS working and cooling the house rather nicely, for at
>>>>>>> least a day, perhaps two. I'm getting 115V in all the right places,
>>>>>>> so it doesn't look like an over-voltage condition to me. Perhaps
>>>>>>> it's an overheating condition? It looks to me like the only real
>>>>>>> load on this circuit is the blower motor; could the motor be causing
>>>>>>> this? The blower spins freely when I turn it by hand. Start
>>>>>>> capacitor on the motor maybe? Relay on the control board perhaps?
>>>>>
>>>>> a bad start cap would not affect the 24v control transformer,that just
>>>>> powers the controller board and relays.
>>>>> either something is loading the transformer or a problem with input
>>>>> voltage.
>>>>>>>
>>>>>>
>>>>>> Just a thought,
>>>>>>
>>>>>> When you put the new transformer in does the "Diagnostic Light" LED
>>>>>> turn on ?
>>>>>> Does the LED blink or flash in one of the patterns indicated in the
>>>>>> "diagnostic codes" section that you posted a link to ?
>>>>>>
>>>>>> The "diagnostic codes" imply that the control board can detect
>>>>>> several of the problems mentioned by others.
>>>>>> Maybe a good starting point as there is not enough time to test with
>>>>>> test equipment.
>>>>>>
>>>>>> robb
>>>>>>
>>>>>>
>>>>>
>>>>> a line voltage monitor may be needed to see if there's some short-term
>>>>> overvoltage applied to the transformer,and a oscilloscope may
>>>>> determine if
>>>>> the input waveform is sinusoidal or otherwise,because 60hz iron core
>>>>> tranformers don't like extreme distortion on their input,it gets
>>>>> converted
>>>>> to heat,not output voltage. a DMM will not show line distortion or
>>>>> short
>>>>> term overvoltages.
>>>>> are the wires burned close to the transformer,or over their entire
>>>>> length?
>>>>
>>>> I peeled the insulation back from the hot and neutral wires and the
>>>> burning only occurred right at the terminals, no more than 1/4" into
>>>> the wiring.
>>>>
>>>
>>> So the problem is the joint of the transformer wiring to the lugs. They
>>> may have cold solder joints, or the lug may be slightly loose - enough
>>> to crack the solder connection over time. Your transformer may still be
>>> good!
>>>
>>> When you are examining the transformer wire make sure it is stripped
>>> enough to get good solder coverage. Burn off the insulation (enamel) -
>>> do not sand, scrape, or try to erode it because if you scratch the wire
>>> it will break at the scratch.
>>>
>>> Re-solder the transformer connectors after first making sure the wire
>>> has at least two complete wraps around the solder lug and the solder
>>> makes a good meniscus joint to the wire and lug. Also use a good grade
>>> of solder, not regular 60/40, find some 63/37 solder (Kester is best) -
>>> this solder resists cold solder joints due to movement when cooling by
>>> solidifying very fast.
>>>
>>> John :-#)#
>>
>> Hi John, fancy meeting you here! Wait, I didn't realize this is cross
>> posted to sci.electronics.repair Now I know why you are here. Glad you
>> liked the package.
>>
>> Tony
>
> Hi Tony,
>
> Yes, we enjoyed the peanut brittle...
>
> I do not think the original poster noticed my suggestion above, that
> failure mode is really not going to be too much load or some weird AC
> situation - it's either a short to the metal case the transformer is
> mounted in or a problem with the wire to solder lug joint.
>
> Would be nice to know if that idea was checked out...
>
> John :-#)#
>
Yes, the thread got too long. If you saw the photo, and know the
primary went open on 3 transformers, it sure looks like a problem on the
primary side. If the load was too much, those wires on the secondary
side would most likely have been at the very least discolored from the heat.

Tony

== 4 of 17 ==
Date: Tues, Apr 12 2011 8:06 am
From: Tony Miklos

On 4/11/2011 7:26 PM, Don Klipstein wrote:
> In<intmki$cmm$1@news.albasani.net>, Jeff Thies wrote:
>
> <SNIP to getting a nonpolarized 1uF cap suitable for 120 VAC>
>
>> If not then go buy a 200V non polarized 1uF cap. It is no easy chore.
>>
>> http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=131081
>
> 200V DC rating is not enough, despite 120 VAC having a peak voltage
> of only 169 volts.
>
> AC does make things worse, by rapidly repeated severe voltage swings
> combined with some development of heat.
>
> The capacitor needs to have an actual AC rating, and one that includes
> your AC voltage with a comfortable safety margin. If it has a DC rating,
> chances are that will be around 400 volts DC. And not every cap rated
> 400 VDC is dsafe for use with 120 VAC, even if non-polarized.
>
> Preferably, it should be "UL recognized" or the like, for some assurance
> that it is reasonably reliable against failure, or at least an unsafe
> failure.
>
> Back in the early 1980's, in an experimental sodium lamp ballast, I have
> blown an 800VDC cap and two 600 VDC ones with 240-260 VAC 60 Hz with less
> than 10 operating hours of this combined among the three of them. One of
> those capacitor blowups was a spectacular one that left a major oil stain
> on the ceiling above. I learned the hard way that actual AC ratings are
> required here.

Yes, many moons ago I was playing with adding a mylar cap in series with
the primary of a neon sign transformer. It worked great for making the
neon dimmer which was my attempt, but I recall measuring a much higher
voltage across the cap due to the reactence and impedence of them in
series. I'm guessing but I think it was up in the 400vac or so range
maybe higher. Not good for the transformer winding either. I didn't
blow them but stopped using them after reading the voltages.

== 5 of 17 ==
Date: Tues, Apr 12 2011 9:34 am
From: clare@snyder.on.ca

On Tue, 12 Apr 2011 17:37:15 +1000, "Phil Allison" <phil_a@tpg.com.au>
wrote:

>
>Got a fucking clue how much current it takes to vaporise copper wires like
>that ?
>
>Obviously fucking not.

How about "more than 15 amps"?

And it didn't blow the circuit breaker or fuse.
So the current came from somewhere other than the mains?
OK - the only other source is back emf from the motor -
Not saying it cannot be.
But why does the insulation on the transformer fail, and not the
insulation in the motor windings??
Most likely, if your scenario is correct, because there is something
wrong with the quality of the transformer windings.

And what is the solution????? Other than a transformer that can stand
up to real world abuse?
Find and repair the power connection problem that is causing the
back-emf problem before it causes other problems (like a fire from an
overheated power connection to a 1/2 HP motor)

NOT by putting a capacitor which may or may not have any effect across
the primary of the transformer. And MAY have the wrong effect.

Now, you need to locate the bad connection (if that is what it is)
Where do you start looking? It pretty well needs to be in the part of
the circuit that is always connected to both the motor and the
transformer - in other words upstream from wherever the transformer
and motor are connected (in common) to the mains, or else the back emf
would be "sunk" by the load on the mains, and the grid itself. - so
you are talking bad breaker, bad connection at the panel, bad shut-off
switch, or bad connections between the panel and the switch - not bad
relays, connections at the relays, or connections at or in the motor.

You would THINK there would be other symptoms - like the furnace
intermittently not running, noises, smoke, etc from the arcing
connection?

Again, not saying you are wrong - but you are not being very helpfull,
and you are sure being obstinate and dissagreeable
>
>Facts are just like water off a duck's back to you - Don.
>
>Cos fuckwits like you believe whatever they fucking feel like.
>
>
>FOAD
>
> - you useless, autistic, PITA turd.
>
>
>
>.... Phil
>
>
>
>
>
>
>

== 6 of 17 ==
Date: Tues, Apr 12 2011 10:40 am
From: John Robertson

Tony Miklos wrote:
> On 4/11/2011 9:31 PM, John Robertson wrote:
>> Tony Miklos wrote:
>>> On 4/9/2011 10:06 PM, John Robertson wrote:
>>>> Steve Turner wrote:
>>>>> On 4/9/2011 7:29 PM, Jim Yanik wrote:
>>>>>> "robb"<some@where.on.net> wrote in
>>>>>> news:WfKdnQOvu_d2bz3QnZ2dnUVZ_uadnZ2d@earthlink.com:
>>>>>>
>>>>>>> "Steve Turner" wrote in message news:inoakf$qin$1@dont-email.me...
>>>>>>>
>>>>>>>> A continuation of the "Why does the 115V->24V transformer keep
>>>>>>>> blowing on my Trane XB80?" discussion I started on 04/02/2011.
>>>>>>>>
>>>>>>>> Yep, My A/C unit blew another transformer. Pictures (and wiring
>>>>>>>> diagram) here:
>>>>>>>>
>>>>>>>> http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
>>>>>>>>
>>>>>>>> Trane's manual for the unit is here (for perhaps better viewing of
>>>>>>>> the wiring diagrams that I also copied to my above flickr site as
>>>>>>>> jpg images):
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>> http://www.trane.com/webcache/un/furnaces%20%28furn%29/product/22-1666-
>>>>>>>
>>>>>>>
>>>>>>> 07_04012009.pdf
>>>>>>>>
>>>>>>>> As you can probably see in the pictures, there is visible charring
>>>>>>>> of the 115V leads going into the transformer, and of course the
>>>>>>>> 115V
>>>>>>>> circuit is open (again). If you didn't see my first thread, this is
>>>>>>>> the third transformer the unit has blown. In the previous
>>>>>>>> discussion, it was discussed that perhaps the first one just blew
>>>>>>>> because of old age (6 years), and the second blew because it wasn't
>>>>>>>> a proper replacement (poor quality, made in China, etc.). This
>>>>>>>> third unit is most certainly a proper replacement, and it's most
>>>>>>>> certainly indicative of a real problem I have somewhere else in the
>>>>>>>> unit. I didn't see any such charring on the previous two units, at
>>>>>>>> least not like this.
>>>>>>>>
>>>>>>>> I never got a real chance to test out the system after installing
>>>>>>>> this third transformer. We had cool weather for several days, and I
>>>>>>>> never tried to force the system to come on so I could monitor it;
>>>>>>>> that was probably a mistake. Unfortunately, I was also absent from
>>>>>>>> the premises during the extended times when the unit was most
>>>>>>>> likely
>>>>>>>> operational, so that didn't help either. However, my family
>>>>>>>> tells me
>>>>>>>> that it WAS working and cooling the house rather nicely, for at
>>>>>>>> least a day, perhaps two. I'm getting 115V in all the right places,
>>>>>>>> so it doesn't look like an over-voltage condition to me. Perhaps
>>>>>>>> it's an overheating condition? It looks to me like the only real
>>>>>>>> load on this circuit is the blower motor; could the motor be
>>>>>>>> causing
>>>>>>>> this? The blower spins freely when I turn it by hand. Start
>>>>>>>> capacitor on the motor maybe? Relay on the control board perhaps?
>>>>>>
>>>>>> a bad start cap would not affect the 24v control transformer,that
>>>>>> just
>>>>>> powers the controller board and relays.
>>>>>> either something is loading the transformer or a problem with input
>>>>>> voltage.
>>>>>>>>
>>>>>>>
>>>>>>> Just a thought,
>>>>>>>
>>>>>>> When you put the new transformer in does the "Diagnostic Light" LED
>>>>>>> turn on ?
>>>>>>> Does the LED blink or flash in one of the patterns indicated in the
>>>>>>> "diagnostic codes" section that you posted a link to ?
>>>>>>>
>>>>>>> The "diagnostic codes" imply that the control board can detect
>>>>>>> several of the problems mentioned by others.
>>>>>>> Maybe a good starting point as there is not enough time to test with
>>>>>>> test equipment.
>>>>>>>
>>>>>>> robb
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> a line voltage monitor may be needed to see if there's some
>>>>>> short-term
>>>>>> overvoltage applied to the transformer,and a oscilloscope may
>>>>>> determine if
>>>>>> the input waveform is sinusoidal or otherwise,because 60hz iron core
>>>>>> tranformers don't like extreme distortion on their input,it gets
>>>>>> converted
>>>>>> to heat,not output voltage. a DMM will not show line distortion or
>>>>>> short
>>>>>> term overvoltages.
>>>>>> are the wires burned close to the transformer,or over their entire
>>>>>> length?
>>>>>
>>>>> I peeled the insulation back from the hot and neutral wires and the
>>>>> burning only occurred right at the terminals, no more than 1/4" into
>>>>> the wiring.
>>>>>
>>>>
>>>> So the problem is the joint of the transformer wiring to the lugs. They
>>>> may have cold solder joints, or the lug may be slightly loose - enough
>>>> to crack the solder connection over time. Your transformer may still be
>>>> good!
>>>>
>>>> When you are examining the transformer wire make sure it is stripped
>>>> enough to get good solder coverage. Burn off the insulation (enamel) -
>>>> do not sand, scrape, or try to erode it because if you scratch the wire
>>>> it will break at the scratch.
>>>>
>>>> Re-solder the transformer connectors after first making sure the wire
>>>> has at least two complete wraps around the solder lug and the solder
>>>> makes a good meniscus joint to the wire and lug. Also use a good grade
>>>> of solder, not regular 60/40, find some 63/37 solder (Kester is best) -
>>>> this solder resists cold solder joints due to movement when cooling by
>>>> solidifying very fast.
>>>>
>>>> John :-#)#
>>>
>>> Hi John, fancy meeting you here! Wait, I didn't realize this is cross
>>> posted to sci.electronics.repair Now I know why you are here. Glad you
>>> liked the package.
>>>
>>> Tony
>>
>> Hi Tony,
>>
>> Yes, we enjoyed the peanut brittle...
>>
>> I do not think the original poster noticed my suggestion above, that
>> failure mode is really not going to be too much load or some weird AC
>> situation - it's either a short to the metal case the transformer is
>> mounted in or a problem with the wire to solder lug joint.
>>
>> Would be nice to know if that idea was checked out...
>>
>> John :-#)#
>>
> Yes, the thread got too long. If you saw the photo, and know the
> primary went open on 3 transformers, it sure looks like a problem on the
> primary side. If the load was too much, those wires on the secondary
> side would most likely have been at the very least discolored from the
> heat.
>
> Tony

Yes, I looked at the pictures (rather poor resolution). The failure
looks like a connection issue because there is no evidence of windings
overheating. If the output was shorted the transformer would burn up -
assuming it could sink enough current, but it would be unlikely to flare
at one spot. This is a pretty standard 115VAC transformer, I've seen
many of them...

If someone tried to pump 5000 volts into the transformer then possibly
you could get an arc like that to the transformer frame, so that would
mean a serious miss-wiring of the furnace where the igniter somehow was
connected to the primary of the transformer and then turned on.

Hard to see that happening as the transformer powers the logic board
that would enable the igniter to fire up!

John :-#)#

--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

== 7 of 17 ==
Date: Tues, Apr 12 2011 10:54 am
From: Meat Plow

On Mon, 11 Apr 2011 23:07:50 -0400, Jeff Thies wrote:

> On 4/11/2011 10:01 PM, clare@snyder.on.ca wrote:
>> On Tue, 12 Apr 2011 00:12:48 +0000 (UTC), don@manx.misty.com (Don
>> Klipstein) wrote:
>>
>>> In article<invbun$64h$1@news.albasani.net>, Jeff Thies wrote:
>>>> On 4/11/2011 11:25 AM, Smitty Two wrote:
>>>>> In article<inv5oj$nkt$1@news.albasani.net>,
>>>>> Jeff Thies<jeff_thies@att.net> wrote:
>>>>>
>>>>>> My first encounter with you
>>>>>
>>>>> Jeff, since you don't hang out on s.e.r., I'll clue you in about
>>>>> Phil. Regardless of what he knows or doesn't know, he calls everyone
>>>>> a fuckwit, and worse, all the time. Virtually every sentence of
>>>>> every post is chock full of derision. If you choose to dialogue with
>>>>> him, you'll get great heaping portions of his demented abuse. So
>>>>> don't take it personally.
>>>>
>>>> Thanks. That's about what I surmised. A North American version of
>>>> Rod
>>>> Speed.
>>>
>>> I think Rod Speed is much worse. Meanwhile, it appears to me in my
>>> experience in s.e.d. that P.A. is, like R.S., an Aussie.
>> That would go a long ways to explaining his potty mouth.
>
> Perhaps that goes all the way. Hey, I learned something about Oz today.
> Funny the guys from NZ I know seem quite nice. I suppose it was a surly
> lot they are descended from... or is it the climate? No matter.
>
> Jeff

A friend traveled to NZ then to OZ in 2004. He said when he got off the
plane in NZ he thought the pilot had landed in China because 99% of the
people around were Asian. I have relatives living near Sidney and they
said this isn't the case there.

--
Live Fast Die Young, Leave A Pretty Corpse

== 8 of 17 ==
Date: Tues, Apr 12 2011 11:51 am
From: David Nebenzahl

On 4/12/2011 2:38 AM Stormin Mormon spake thus:

> There you go, again. Completely mistaken about what I'd
> reccomend in the way of diagnostic. Just making up garbage,
> and then trying to assign it to me. Well, you should do that
> more often. Then, everyone can see what your true character
> is like. Please write often, and lengthy. The more you
> write, the better I look.

In your mind, perhaps.

--
The current state of literacy in our advanced civilization:

yo
wassup
nuttin
wan2 hang
k
where
here
k
l8tr
by

- from Usenet (what's *that*?)

== 9 of 17 ==
Date: Tues, Apr 12 2011 2:28 pm
From: don@manx.misty.com (Don Klipstein)

In <tru8q6hhouec3fkd0s528a4g6ajbhf8a3j@4ax.com>, clare@snyder.on.ca wrote:
>On Tue, 12 Apr 2011 17:37:15 +1000, "Phil Allison" <phil_a@tpg.com.au>
>wrote:
>
>>Got a fucking clue how much current it takes to vaporise copper wires like
>>that ?
>>
>>Obviously fucking not.
>
>How about "more than 15 amps"?
>
>And it didn't blow the circuit breaker or fuse.
>So the current came from somewhere other than the mains?

I don't remember any V-A rating stated for the tranny in question since
the number of posts in the 2 threads is huge. Though, I have the
impression it's around 40 or 50 or so.

A 120V one this size usually has its primary around AWG 24 or 26, and a
240V one or a dual-primary 120/240V one usually has primary winding size
around AWG 28. Properly connected for 120V, that means 2 roughly-AWG-28
strands in parallel, effectively around AWG 25.

A transformer winding this size can gradually get charring hot at as
little as 1 or 1.5 amps or so.

Leads of this size get charring hot within a minute at several amps.

The CRC Handbook says fusing current for copper wire is 20 amps for AWG
26, 30 amps for AWG 24. Though these figures are only approximate, I
usually hear that these fusing current charts are for bare wire in free air.
Fusing current will be less for a wire next to another turn of overheating
wire.

Meanwhile, I doubt a 15 amp slow-blow fuse or slow-acting breaker will
keep a 26 or 24 AWG wire from fusing. One thing to keep in mind is that a
15 amp fuse or breaker normally passes 15 amps without opening, and may
take a few seconds or more to open at 20 amps.

I think the overcurrent that caused charring here came from the power
line without opening the breaker/fuse. Back EMF won't do that, though it
could cause insulation failure. However, I doubt that explains 3 blown
transformers and nothing else blown.

--
- Don Klipstein (don@misty.com)

== 10 of 17 ==
Date: Tues, Apr 12 2011 3:06 pm
From: don@manx.misty.com (Don Klipstein)

In article <90j6ugFluoU1@mid.individual.net>, Tony Miklos wrote:

>Yes, the thread got too long. If you saw the photo, and know the
>primary went open on 3 transformers, it sure looks like a problem on the
>primary side. If the load was too much, those wires on the secondary
>side would most likely have been at the very least discolored from the
>heat.

This makes me think the most likely causes are:

* Improperly connecting the transformer (such as using only 1 of the 2
primaries of a 120/240V dual primary transformer)

* DC flowing through the secondary. That can occur if the tranny's load
has a fullwave rectifier with one diode open. If the fullwave
rectifier has discrete diodes or a dual diode, the problem may be a bad
solder joint at one of the diodes.

DC through the secondary is well known to be able to cause transformer
cores to saturate. That can lead to the primary drawing excessive
current.

* Less likely - there is a magnet on the transformer core. That
combined with the tranny's normal magnetic flux can cause core
saturation, similar to the effect of DC in a winding although this
usually only causes part of the core to saturate.

However, a magnet on the core appears to me "probably unlikely to be
an actual problem" unless the tranny is of marginal design, line voltage
is on the high side, or the magnet is especially powerful.

There is the matter of voltage spikes on the primary blowing the
insulation. However, I consider that unlikely if nothing else has been
blown while 3 transformers blew.

--
- Don Klipstein (don@misty.com)

== 11 of 17 ==
Date: Tues, Apr 12 2011 4:43 pm
From: "Dave M"

Don Klipstein wrote:
> In article <90j6ugFluoU1@mid.individual.net>, Tony Miklos wrote:
>
>> Yes, the thread got too long. If you saw the photo, and know the
>> primary went open on 3 transformers, it sure looks like a problem on
>> the primary side. If the load was too much, those wires on the
>> secondary side would most likely have been at the very least
>> discolored from the heat.
>
> This makes me think the most likely causes are:
>
> * Improperly connecting the transformer (such as using only 1 of
> the 2 primaries of a 120/240V dual primary transformer)
>
> * DC flowing through the secondary. That can occur if the tranny's
> load has a fullwave rectifier with one diode open. If the fullwave
> rectifier has discrete diodes or a dual diode, the problem may be a
> bad solder joint at one of the diodes.
>

That's not true. an open rectifier does not allow DC current to flow
through the secondary. It's just 1/2 of the power line cycle. During the
opposite half of the cycle, no current flows in the secondary. True, it's
unidirectional current, but it's an intermittent current, not constant DC.
If your statement were true, then half-wave rectifiers wouldn't be feasible.

--
David
dgminala at mediacombb dot net

== 12 of 17 ==
Date: Tues, Apr 12 2011 4:57 pm
From: "Phil Allison"

"Dave M"
>
>
> That's not true. an open rectifier does not allow DC current to flow
> through the secondary. It's just 1/2 of the power line cycle. During the
> opposite half of the cycle, no current flows in the secondary.

** So the average value is non zero and that means there is a DC component
to the current.

> True, it's unidirectional current, but it's an intermittent current, not
> constant DC.

** It will show a nice, steady reading on a DC current meter.

The interesting thing is how there is no corresponding DC component in the
primary current.

.... Phil

== 13 of 17 ==
Date: Tues, Apr 12 2011 4:58 pm
From: "Michael A. Terrell"

Stormin Mormon wrote:
>
> OK, that makes a bit of sense. Seems like a bit of bother
> for what you can track down, with a VOM and some common
> sense.

The 'Dimbulb tester' will show a transformer that is in saturation,
or one that has a shorted turn. Your VOM can't.

--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

== 14 of 17 ==
Date: Tues, Apr 12 2011 5:49 pm
From: don@manx.misty.com (Don Klipstein)

In article <9fOdnZZQwKACfjnQnZ2dnUVZ_rmdnZ2d@giganews.com>, Dave M wrote:
>Don Klipstein wrote:
>> In article <90j6ugFluoU1@mid.individual.net>, Tony Miklos wrote:
>>
>>> Yes, the thread got too long. If you saw the photo, and know the
>>> primary went open on 3 transformers, it sure looks like a problem on
>>> the primary side. If the load was too much, those wires on the
>>> secondary side would most likely have been at the very least
>>> discolored from the heat.
>>
>> This makes me think the most likely causes are:
>>
>> * Improperly connecting the transformer (such as using only 1 of
>> the 2 primaries of a 120/240V dual primary transformer)
>>
>> * DC flowing through the secondary. That can occur if the tranny's
>> load has a fullwave rectifier with one diode open. If the fullwave
>> rectifier has discrete diodes or a dual diode, the problem may be a
>> bad solder joint at one of the diodes.
>>
>
>That's not true. an open rectifier does not allow DC current to flow
>through the secondary. It's just 1/2 of the power line cycle. During the
>opposite half of the cycle, no current flows in the secondary. True, it's
>unidirectional current, but it's an intermittent current, not constant DC.
>If your statement were true, then half-wave rectifiers wouldn't be feasible.

A unidirectional pulsing waveform has a DC component.

That analyzes to a sum of DC, fundamental frequency AC, and AC at
harmonic frequencies. The average as averaged over a whole cycle is the
DC component.

It is fairly well known that a transformer driving a halfwave rectified
load can run into core saturation problems from the DC component in the
unidirectionally pulsing current waveform.

--
- Don Klipstein (don@misty.com)

== 15 of 17 ==
Date: Tues, Apr 12 2011 7:05 pm
From: clare@snyder.on.ca

On Tue, 12 Apr 2011 10:40:02 -0700, John Robertson <spam@flippers.com>
wrote:

>>>
>> Yes, the thread got too long. If you saw the photo, and know the
>> primary went open on 3 transformers, it sure looks like a problem on the
>> primary side. If the load was too much, those wires on the secondary
>> side would most likely have been at the very least discolored from the
>> heat.
>>
>> Tony
>
>Yes, I looked at the pictures (rather poor resolution). The failure
>looks like a connection issue because there is no evidence of windings
>overheating. If the output was shorted the transformer would burn up -
>assuming it could sink enough current, but it would be unlikely to flare
>at one spot. This is a pretty standard 115VAC transformer, I've seen
>many of them...
>
>If someone tried to pump 5000 volts into the transformer then possibly
>you could get an arc like that to the transformer frame, so that would
>mean a serious miss-wiring of the furnace where the igniter somehow was
>connected to the primary of the transformer and then turned on.
>
>Hard to see that happening as the transformer powers the logic board
>that would enable the igniter to fire up!
>
>John :-#)#
And the FACT that the furnace in question uses a hot plate ignitor
further removes that scenario from any semplance of possibility

== 16 of 17 ==
Date: Tues, Apr 12 2011 7:14 pm
From: clare@snyder.on.ca

On Wed, 13 Apr 2011 09:57:33 +1000, "Phil Allison" <phil_a@tpg.com.au>
wrote:

>
>"Dave M"
>>
>>
>> That's not true. an open rectifier does not allow DC current to flow
>> through the secondary. It's just 1/2 of the power line cycle. During the
>> opposite half of the cycle, no current flows in the secondary.
>
>** So the average value is non zero and that means there is a DC component
>to the current.
>
>> True, it's unidirectional current, but it's an intermittent current, not
>> constant DC.
>
>** It will show a nice, steady reading on a DC current meter.
>
>The interesting thing is how there is no corresponding DC component in the
>primary current.
>
>
>.... Phil

Unless the half wave rectifier is on the PRIMARY side.
I don't see any evidence of that on any of the diagrams I saw, but is
there something else on this furnace circuit? By code there cannot be
- but we don't know know this to be the case - or what is on the
circuit if there is.
>
>
>
>
>
>
>
>
>
>
>
>

== 17 of 17 ==
Date: Tues, Apr 12 2011 7:32 pm
From: Mark

To the OP...
another long shot..

it looks like the primary of the transformer is wired in series with
the door safety switch. Is it possible that the door safety switch
is loose and arcing. This could cause a high voltage to appear at the
transformer and cause the insulation to fail...

Mark

==============================================================================
TOPIC: Rigol scope LCD problem
http://groups.google.com/group/sci.electronics.repair/t/f09ee6418c07d961?hl=en
==============================================================================

== 1 of 1 ==
Date: Tues, Apr 12 2011 7:19 am
From: Jim Yanik

Jeff Liebermann <jeffl@cruzio.com> wrote in
news:i8j7q6dd45ut6ro2cu2e84jef5edus4m5k@4ax.com:

> On Mon, 11 Apr 2011 17:42:27 -0400, Jamie
><jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:
>
>> Use circuit cooler on suspected areas after warm up to recreate the
>>problem.
>
> Good idea, but keep the cooler spray away from the CCFL lamp(s). I
> sprayed one while it was running and instantly cracked the tube. I
> don't know if this is a one-time problem, or is typical, but it might
> pay to be careful. Maybe a hot air gun (on low heat) when the panel
> is cool, or just massaging the circuitry looking for intermittents,
> might be equally productive.
>

I used to spray the cooler on a Q-tip swab and apply the swab to a
suspect component I wanted to chill.

or you could rig some short of paper shield to keep the spray away from
other parts.

--
Jim Yanik
jyanik
at
localnet
dot com

==============================================================================
TOPIC: Phil Allison is fucking INSANE
http://groups.google.com/group/sci.electronics.repair/t/aff797bedba2c908?hl=en
==============================================================================

== 1 of 2 ==
Date: Tues, Apr 12 2011 12:24 pm
From: Mike Tomlinson

In article <pan.2011.04.07.18.42.29@lmao.lol.lol>, Meat Plow
<mhywattt@yahoo.com> writes

>It's everyone who isn't Phil "fucking insane" Allison.

That's the product of transportation of thieves, rapists and murderers
to van Diemen's land and 200 years of enthusiastic inbreeding since.

--
(\__/)
(='.'=)
(")_(")

== 2 of 2 ==
Date: Tues, Apr 12 2011 12:26 pm
From: Mike Tomlinson

In article <RaudnfDVDpYleAPQnZ2dnUVZ8ludnZ2d@bt.com>, Gareth Magennis
<sound.service@btconnect.com> writes

>Decision is made, I'm not touching this.

Think you're right. Not worth the comeback if it fails again.

--
(\__/)
(='.'=)
(")_(")

==============================================================================
TOPIC: Help to identify capacitor please
http://groups.google.com/group/sci.electronics.repair/t/df081010fd20fad8?hl=en
==============================================================================

== 1 of 2 ==
Date: Tues, Apr 12 2011 12:12 pm
From: Markt

'Phil Allison[_2_ Wrote:
> ;2626915']"Markt"-
> Please can anyone help me to identify a capacitor.
>
> It is fitted to an MK Sentry RCD socket, it is fitted in position C6
> and
> is used as the mains dropper to power the RCD circuitry.
>
> It's only markings are 334K250 on the top line and NIS~S82 on the
> bottom
> line.
> -
>
> ** Its a 330 nF cap rated at 250 volts DC - a very poor choice by the
> maker.
>
>
> ...... Phil

Thanks Phil

I take it that you mean the working voltage is to low, what voltage
would be appropriate?

Mark

--
Markt

== 2 of 2 ==
Date: Tues, Apr 12 2011 5:01 pm
From: "Phil Allison"

"Markt"
>
> 'Phil Allison:
>>
>> ** Its a 330 nF cap rated at 250 volts DC - a very poor choice by the
>> maker.
>
> I take it that you mean the working voltage is to low, what voltage
> would be appropriate?

** Film caps rated for continuous use across the AC supply are special
types - known as class X1 or class X2

They are AC voltage rated, usually at 150 or 275 volts and carry logos from
agencies like UL.

..... Phil

==============================================================================
TOPIC: Servis M6712W (washing machine)
http://groups.google.com/group/sci.electronics.repair/t/96927913b917139e?hl=en
==============================================================================

== 1 of 2 ==
Date: Tues, Apr 12 2011 2:59 pm
From: Jack00

I have this machine which works fine until at the end of the cycle it
makes a ticking noise which is very annoying. Does anyone have a
solution?

Thanks

== 2 of 2 ==
Date: Tues, Apr 12 2011 3:18 pm
From: "William Sommerwerck"

> I have this machine which works fine until at the end
> of the cycle it makes a ticking noise which is very
> annoying. Does anyone have a solution?

It's common for electromechanical timers to make clicking noises, especially
between cycles. If the machine completes the full wash cycle, there's
nothing to worry about.

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hours-online.com/.
http://groups.google.com/group/sci.electronics.repair/t/8cb7e30537b683c3?hl=en
==============================================================================

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