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Today's topics:

* Blew another damn transformer on my Trane XB80 - 20 messages, 7 authors
http://groups.google.com/group/sci.electronics.repair/t/f883cd09a3a0b791?hl=en
* Help to identify capacitor please - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/df081010fd20fad8?hl=en
* LG refrigerator model LBN2251#** problems - 1 messages, 1 author
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==============================================================================
TOPIC: Blew another damn transformer on my Trane XB80
http://groups.google.com/group/sci.electronics.repair/t/f883cd09a3a0b791?hl=en
==============================================================================

== 1 of 20 ==
Date: Mon, Apr 11 2011 4:26 pm
From: don@manx.misty.com (Don Klipstein)

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.

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

One more thing: If there is a switch upstream of a capacitor across a
power line, then the switch may be in for severe contact pitting.

Then again, I doubt a voltage spike lasting long enough to burn out a
transformer will be absorbed by a 1 uF cap across a 120V AC line.

I would lean to looking for intermittent overload by the transformer's
load, the transformer's load intermittently drawing a large amount of DC
(such as by failing-open one diode in a bridge rectifier).

Or, the transformer being connected incorrectly.

(Such as a 120V/240V one with 2 primary winding sections needing both
primary sections to be connected in parallel with each other for full
power handling at 120V, but only 1 of them is being used.)

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

== 2 of 20 ==
Date: Mon, Apr 11 2011 4:34 pm
From: "Phil Allison"

"Don Klipstein"

> Then again, I doubt a voltage spike lasting long enough to burn out a
> transformer will be absorbed by a 1 uF cap across a 120V AC line.

** You missed the point entirely.

A voltage spike ( or a series of them) can easily cause insulation failure
in the enamel winding wire of the primary - then the energy to explode the
lead in and lead out wires comes from the 120 volt AC supply.

.... Phil

== 3 of 20 ==
Date: Mon, Apr 11 2011 4:37 pm
From: "Stormin Mormon"

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.

Reminds me of the time I got asked to change a thermostat.
New one needs common, old one did not. After several trips
to the roof, I got me some common sense. Still, it was a
rather long and tiring job. The first level of roof was
maybe 16 feet, and there was about a 4 foot rise to the next
level, so I ended up buying two ladders for that job. Worked
out, I've used both ladders several times since then.
Learned a lot, too.

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

"John Robertson" <spam@flippers.com> wrote in message
news:hMCdnUAET_PowD7QnZ2dnUVZ_vqdnZ2d@giganews.com...
Stormin Mormon wrote:
> What is this "old light bulb trick"?
>

Wire a 25W - 75W incandescent light bulb in series with the
load
(transformer primary). If the light is bright then there is
a short in
either the primary or secondary side output. If it is bright
for a
second then dims right down (power supply caps charging up)
then there
is no serious short.

Picture of one such setup:

http://www.flippers.com/images/OvercurrentTestJigFused.JPG

Note I recommend an isolation transformer. The fuse holder
is there so
the light can act as an indicator that the fuse has blown,
or remove the
fuse for "the light bulb test/trick".

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."

== 4 of 20 ==
Date: Mon, Apr 11 2011 5:00 pm
From: don@manx.misty.com (Don Klipstein)

In article <90f8dcFc4aU1@mid.individual.net>, Phil Allison wrote:
>
>"Jeff Thies"
> Phil Allison wrote:
>
>>>>> I suggest you provide the next replacement for that vulnerable tranny
>>>>> with
>>>>> some "protection" - firstly an in-line fuse of say 1/4 amp AND a
>>>>> capacitor wired across the primary of say 1uF rated for continuous use
>>>>> across the AC supply.
>>>>>
>>>>> If there is an overload on the tranny, the fuse will blow.
>>>>>
>>>>> The 1uF capacitor should suppress spike voltages enough to save the
>>>>> tranny from harm.
>>>>
>>>> 1 uF sounds a little high.
>>>
>>> ** No it ain't.
>>
>> I thought you had simply misspoke and that this was an honest error.
>>
>> The reactance of a 1uF cap at 60Hz is: 2652 ohms (1/(2*pi*F*C)
>> Online calculator:
>> http://www.kusashi.com/reactance-c.php?f=60&c=1&stage=results
>>
>> V^2/R = W
>>
>> Assuming primary, as why would you put it on the secondary:
>>
>> 120^2 / 2652 = 5.43 W
>>
>> Does that not seem wrong to you?
>
>** Completely.
>
>Such a cap dissipates no energy at all.
>
>What planet do you come from ??

With AC, volts times amps is not necessarily watts.

If determination of volts and amps are both "true RMS", (non-"true RMS"
meters are usually OK for line voltage and for current through a cap
across an AC line),

then volts times amps is "volt-amps". Ratio of power consumption (in
watts) to VA is power factor. Capacitors have very low, ideally zero,
power factor.

>> If not then go buy a 200V non polarized 1uF cap. It is no easy chore.
>
>** 1uF caps for use across the AC supply are cheap and plentiful.

Digi-Key has 3 easy enough to find 1uF ones with X1 or X2 rating, all
$3-plus plus shipping with minimum order requirement to avoid a surcharge.

Among those 3, my favorite is FC233820105, which is by Vishay/BC
Components. Its datasheet refers to 2 UL standards and 2 CSA ones, and has
a link to an application note making a claim that the referenced UL ones are
sufficient for achieving the "UL Recognized" ("backwards UR") mark.

>Typical examples are metallised polypropylene " class X2 " types and sell
>for $1 or $2 each.
>
>http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=399-5466-ND

That one needed me to delve into its datasheet to see that it claims to
meet the two relevant UL standards and that it has X2 rating. Its AC
voltage rating is 275 volts. 91 cents each plus shipping, with a minimum
order requirement to avoid a surcharge.

Any of the 4 capacitors above (2 mentioned specifically) look good, in
the unlikely event what is needed is a capacitor across the line.

>What planet do you come from ??

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

== 5 of 20 ==
Date: Mon, Apr 11 2011 5:03 pm
From: "Phil Allison"

"Don Klipstein"

>
> Any of the 4 capacitors above (2 mentioned specifically) look good, in
> the unlikely event what is needed is a capacitor across the line.

** You are one smug, fucking PITA aren't you ?

.... Phil

== 6 of 20 ==
Date: Mon, Apr 11 2011 5:10 pm
From: don@manx.misty.com (Don Klipstein)

In article <inv5oj$nkt$1@news.albasani.net>, Jeff Thies wrote:
>On 4/10/2011 11:29 PM, Phil Allison wrote:
>> "Jeff Thies"
>>> Phil Allison wrote:
>>>> "Jeff Thies"
>>>> Phil Allison wrote:
>>>>
>>>>>>>> I suggest you provide the next replacement for that vulnerable tranny
>>>>>>>> with
>>>>>>>> some "protection" - firstly an in-line fuse of say 1/4 amp AND a
>>>>>>>> capacitor wired across the primary of say 1uF rated for continuous
>>>>>>>> use
>>>>>>>> across the AC supply.
>>>>>>>>
>>>>>>>> If there is an overload on the tranny, the fuse will blow.
>>>>>>>>
>>>>>>>> The 1uF capacitor should suppress spike voltages enough to save the
>>>>>>>> tranny from harm.
>>>>>>>
>>>>>>> 1 uF sounds a little high.
>>>>>>
>>>>>>
>>>>>> ** No it ain't.
>>>>>
>>>>> I thought you had simply misspoke and that this was an honest error.
>>>>>
>>>>> The reactance of a 1uF cap at 60Hz is: 2652 ohms (1/(2*pi*F*C)
>>>>> Online calculator:
>>>>> http://www.kusashi.com/reactance-c.php?f=60&c=1&stage=results
>>>>>
>>>>> V^2/R = W
>>>>>
>>>>> Assuming primary, as why would you put it on the secondary:
>>>>>
>>>>> 120^2 / 2652 = 5.43 W
>>>>>
>>>>> Does that not seem wrong to you?
>>>>
>>>> ** Completely.
>>>>
>>>> Such a cap dissipates no energy at all.
>>>>
>>>> What planet do you come from ??
>>>
>>> What a jerk you are. You do realize that is 45mA running through that.
>>
>>
>> ** What sort of know nothing JERK thinks that capacitors dissipate energy
>> ??
>
>It doesn't have to dissipate energy to explode. That is a lot of joules.
>>
>> Then proceeds to calculate the reactive impedance and treat it the same as
>> resistance ??
>>
>> Big bad.
>
> So I left out the PF, so what?
>>
>> Zero out of ten.

PF of a capacitor suitable to connect across an AC line is usually less
than .01.

>My first encounter with you, but no doubt others have had the same
>reaction.
<Make that longish story shorter>

Phil Allison is well known in sci.electronics.design to be quick to
get brash, even calling people names and sometimes a little worse. If
only he would avoid that, a lot more people would think a lot more highly
of him than they do now, since he does fairly well know what he is talking
about when it's electrical.
--
- Don Klipstein (don@misty.com)

== 7 of 20 ==
Date: Mon, Apr 11 2011 5:12 pm
From: don@manx.misty.com (Don Klipstein)

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

== 8 of 20 ==
Date: Mon, Apr 11 2011 5:51 pm
From: don@manx.misty.com (Don Klipstein)

In article <90hhh6F3kgU1@mid.individual.net>, Phil Allison wrote:
>
>"Don Klipstein"
>
>> Then again, I doubt a voltage spike lasting long enough to burn out a
>> transformer will be absorbed by a 1 uF cap across a 120V AC line.
>
>** You missed the point entirely.
>
>A voltage spike ( or a series of them) can easily cause insulation failure
>in the enamel winding wire of the primary - then the energy to explode
>the lead in and lead out wires comes from the 120 volt AC supply.

Is the O.P. having other things in his house blowing from voltage spikes
severe enough to blow transformer primary winding insulation?

I have seen lots of things blow from line voltage surges, but no
transformers indoors blowing when line voltage spikes blow other things.

My experience is that usual 120V-primary step-down transformers can
produce pulses of 2 kilovolts when used on pulses in reverse. In fact, I
have done that with about 8 different transformers dozens of times each,
and none of them lost their ability to do that. (I am aware of line
voltage spikes being noted to get even higher.)

There is also the issue of line voltage surges not easily being loaded
down by capacitors for whatever reason. I have experience with them
blowing things that had capacitors, including a CFL that had probably a 22
or 47 uF capacitor across the output of its internal bridge rectifier as
they usually do. No transformer failures in the same house from the same
event, though there were electronics failures.

The usual solutions to absorb line voltage spikes are MOVs and other
devices that absorb voltage surges by becoming conductive in response to
excessive voltage.

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

== 9 of 20 ==
Date: Mon, Apr 11 2011 6:24 pm
From: "Phil Allison"

"Don Klipstein"
Phil Allison wrote:
>"Don Klipstein"
>>
>>> Then again, I doubt a voltage spike lasting long enough to burn out a
>>> transformer will be absorbed by a 1 uF cap across a 120V AC line.
>>
>>** You missed the point entirely.
>>
>>A voltage spike ( or a series of them) can easily cause insulation failure
>>in the enamel winding wire of the primary - then the energy to explode
>>the lead in and lead out wires comes from the 120 volt AC supply.
>
> Is the O.P. having other things in his house blowing from voltage spikes
> severe enough to blow transformer primary winding insulation?

** Totally irrelevant.

The furnace unit and the transformer in question are all we are discussing.

You have clearly not bothered to read my first or my other posts in this
thread.

Eg:

" High voltage spikes on the primary could also cause insulation failure
leading to the damage seen in the pics - lightning does this sort of thing.
So also could back emfs from the blower fan if the is a bad connection in
the AC supply feed."

Whenever AC power to that furnace is disconnected, the blower fan will
deliver a back emf spike - meanwhile that poor, little tranny is wired in
parallel with it. Other devices in the house are NOT involved.

Most AC supply transformers can tolerate repeated 2kV spikes on the primary
till the cows come home - but a badly wound one cannot. This is a specific
and fairly recent problem with small transformers made in China and
elsewhere in Asia where the makers are not fully aware of the issue of
insulation failure in the enamel windings.

Once there is a layer to layer insulation failure ( between adjacent wires)
in the primary of that tranny - the AC current draw will jump up to many
amps and may cause the feed in and out wires to explode - as seen in the
pics.

If the spike voltage is suppressed, the tranny will likely survive.

A 1uF cap provides a low impedance path for such a back emf spike, virtually
shorting it out.

OTOH a varistor provides no conduction path until its breakdown voltage is
exceeded, but is also a means of suppressing the spike voltage to a safe
value.

.... Phil

== 10 of 20 ==
Date: Mon, Apr 11 2011 6:31 pm
From: John Robertson

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 :-#)#

--
(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."

== 11 of 20 ==
Date: Mon, Apr 11 2011 6:46 pm
From: clare@snyder.on.ca

On Mon, 11 Apr 2011 15:48:43 +1000, "Phil Allison" <phil_a@tpg.com.au>
wrote:

>
><clare@snyder.on.ca>
>
>>>** The primary appears to be EXPLODING !!
>>>
>>> You ridiculous wanker.
>>>
>> Phil - your mamma should wash your mouth out with soap.
>
>
>** You need to get your hands off of it.
>
>
>> I SAID the other two scenarios were long shots ..
>
>** And I said they were ridiculous drivel.
>
>> - but so is everything else that has been suggested.
>
>** Your opinion is based on your ignorance only.
>
>> The windings of the trasnformer do not
>> APPEAR to be overheated - looks like just blackened at the connections
>> between the winding and the connecting wires.
>
>
>** See the vaporised metal coating deposited on the plastic cover next to
>the tranny?
>
>That is a damn EXPLOSION !!
>
>It happened very suddenly and made a loud bang too.
>
>I said:
>
>" High voltage spikes on the primary could also cause insulation failure
>leading to the damage seen in the pics - lightning does this sort of thing.
>So also could back emfs from the blower fan if the is a bad connection in
>the AC supply feed."
>
>If the insulation on the enamel wire of the primary is punctured by a HIGH
>VOLTAGE SPIKE, effectively shorting out most of the primary - then the
>120 AC supply ( no fuse exists remember ) will easily turn the two exposed
>wire ends into metal vapour !!!
>
>Cos they just became the fuses.
>
>It just so happens that many small transformers made in China, India & Sri
>Lanka etc are very prone to this sort of failure - due to bad manufacturing
>practices.
>
>
>
>.... Phil
>
>
So you are agreeing with what I said before - most likely problem is
cheap crap component.

We can be relatively sure it wasn't lightning 3 times.
If the back emf from the motor is causing the problem, the bad
connection to the motor should have made itself VERY evident by now.
Not saying it is NOT part of the problem - like you, I wasn't there
watching it fail - and neither you nor I heard the noise you speak of.

And IF the problem is what you say it is (and I'm not saying it is
not), then probing the old primary and getting to the winding beyond
where the solder joint "exploded" you should be able to measure a
significantly lower than normal primary resistance.

That measurement has not, as far as I know, been made and reported.

If it was mine, or if I had the transformer at hand, I'd have it apart
and analysed in no time. If the primary is shorted, I'd know, within
an hour or two of the failure..
And with that second primary, it would not be hard to determine if the
110 volt primary is shorted without even dissassembling the
transformer..

At this point no-one has actually posted FOR SURE what the primary
configuration is. Is it a mult-tapped primary, set for 115, 208, and
230 volts, or is it 2 independent primaries, or is it 2 primaries that
need to be connected either in series or parallel depending on the
voltage (115 or 230)

I don't know this, and you don't know either unless you are
clairvoyant, because it has not, to this point, been established and
reported.

So we are all guilty of the same thing - making ASSumptions.
>

== 12 of 20 ==
Date: Mon, Apr 11 2011 6:57 pm
From: clare@snyder.on.ca

On Mon, 11 Apr 2011 23:26:45 +0000 (UTC), don@manx.misty.com (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.
>
>===================================
>
> One more thing: If there is a switch upstream of a capacitor across a
>power line, then the switch may be in for severe contact pitting.
>
> Then again, I doubt a voltage spike lasting long enough to burn out a
>transformer will be absorbed by a 1 uF cap across a 120V AC line.
>
> I would lean to looking for intermittent overload by the transformer's
>load, the transformer's load intermittently drawing a large amount of DC
>(such as by failing-open one diode in a bridge rectifier).
>
> Or, the transformer being connected incorrectly.
>
> (Such as a 120V/240V one with 2 primary winding sections needing both
>primary sections to be connected in parallel with each other for full
>power handling at 120V, but only 1 of them is being used.)
I have to agree with Don. DC power component on secondary OR primary,
or not connected right are the 2 most likely problems after "cheap
crap component"

== 13 of 20 ==
Date: Mon, Apr 11 2011 6:59 pm
From: David Nebenzahl

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*?)

== 14 of 20 ==
Date: Mon, Apr 11 2011 7:01 pm
From: clare@snyder.on.ca

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.

== 15 of 20 ==
Date: Mon, Apr 11 2011 7:22 pm
From: "Phil Allison"

<clare@snyder.on.ca

> If the back emf from the motor is causing the problem, the bad
> connection to the motor should have made itself VERY evident by now.

** Not true at all.

> If it was mine, or if I had the transformer at hand, I'd have it apart
> and analysed in no time. If the primary is shorted, I'd know, within
> an hour or two of the failure..

** What is clear is that the primary has suddenly drawn a very large current
and that means there are SHORTED turns inside the primary.

Go away wanker.

..... Phil

== 16 of 20 ==
Date: Mon, Apr 11 2011 7:23 pm
From: "Phil Allison"

<clare@snyder.on.ca>
>
> I have to agree with Don. DC power component on secondary OR primary,

** You are both wrong.

> or not connected right are the 2 most likely problems after "cheap
> crap component"

** Which is no help to the OP.

.... Phil

== 17 of 20 ==
Date: Mon, Apr 11 2011 8:07 pm
From: Jeff Thies

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

== 18 of 20 ==
Date: Mon, Apr 11 2011 9:57 pm
From: don@manx.misty.com (Don Klipstein)

In article <90hnurFbhgU1@mid.individual.net>, Phil Allison wrote:
>
>"Don Klipstein"
> Phil Allison wrote:
>>"Don Klipstein"
>>>
>>>> Then again, I doubt a voltage spike lasting long enough to burn out a
>>>> transformer will be absorbed by a 1 uF cap across a 120V AC line.
>>>
>>>** You missed the point entirely.
>>>
>>>A voltage spike ( or a series of them) can easily cause insulation failure
>>>in the enamel winding wire of the primary - then the energy to explode
>>>the lead in and lead out wires comes from the 120 volt AC supply.
>>
>> Is the O.P. having other things in his house blowing from voltage spikes
>> severe enough to blow transformer primary winding insulation?
>
>** Totally irrelevant.
>
>The furnace unit and the transformer in question are all we are discussing.
>
>You have clearly not bothered to read my first or my other posts in this
>thread.
>
>Eg:
>
>" High voltage spikes on the primary could also cause insulation failure
>leading to the damage seen in the pics - lightning does this sort of thing.

Why would that be, in your words, "totally irrelevant" to whether or not
the O.P. had any electrical/electronic failures elsewhere in his home
attributable to voltage surges?

As opposed to 3 transformers blowing in the same appliance with nothing
else anywhere in the home running into trouble from voltage surges?

While I have experienced roughly 8 transformers surviving repeated
abusive pulse-in-reverse-direction developing about 2 KV across the
primary without any degradation against ability to do so?

>So also could back emfs from the blower fan if the is a bad connection in
>the AC supply feed."
>
>Whenever AC power to that furnace is disconnected, the blower fan will
>deliver a back emf spike - meanwhile that poor, little tranny is wired in
>parallel with it. Other devices in the house are NOT involved.

Why would the solution be deploying a capacitor, rather than repairing
the poor connection or deploying a voltage-dependent spike-absorbing
device such as an MOV?

>Most AC supply transformers can tolerate repeated 2kV spikes on the primary
>till the cows come home - but a badly wound one cannot. This is a specific
>and fairly recent problem with small transformers made in China and
>elsewhere in Asia where the makers are not fully aware of the issue of
>insulation failure in the enamel windings.

So, why should we hear about problems about that from only one customer
blowing 3 of them?

>Once there is a layer to layer insulation failure ( between adjacent wires)
>in the primary of that tranny - the AC current draw will jump up to many
>amps and may cause the feed in and out wires to explode - as seen in the
>pics.
>
>If the spike voltage is suppressed, the tranny will likely survive.
>
>A 1uF cap provides a low impedance path for such a back emf spike, virtually
>shorting it out.

Why should 1 uF protect the trannies in question while 22-47 uF fails to
protect a compact fluorescent lamp from a line voltage surge that blows
even other electronics in 2 houses but did not blow any in-home trannies?

>OTOH a varistor provides no conduction path until its breakdown voltage is
>exceeded, but is also a means of suppressing the spike voltage to a safe
>value.

Certainly protects against applying for even a microsecond more than
roughly 250-300 volts across transformer primaries, where it appears to me
that we agree that transformer primaries usually survive 2,000 volts pulse
voltage?

I seem to think that the trannies are probably blowing from either
improper wiring (connecting only 1 of the 2 primary winding sections
possibly noted for 120V usage), or from secondary load malfunction
including bridge rectifier failure in manner of a diode "failing open".

Or, extreme-oddball trouble such as sticking a magnet to the tranny.
But that's grasping-at-straws, like line voltage irregularities that blow
3 trannies in 1 piece of equipment but draw no other complaints such as
blowing of electronics downstream of the tranny in question, or elsewhere
in the house where one appliance blew 3 trannies.
--
- Don (don@misty.com)

== 19 of 20 ==
Date: Mon, Apr 11 2011 10:14 pm
From: "Phil Allison"

"Don Klipstein the Troll"

> Why would that be, in your words, "totally irrelevant"

** You posted under my words and it was not relevant to them.

> Why would the solution be deploying a capacitor, rather than repairing
> the poor connection or deploying a voltage-dependent spike-absorbing
> device such as an MOV?

** A suitable MOV is also a possible solution.

You still have not read all my posts in this thread.

> So, why should we hear about problems about that from only one customer
> blowing 3 of them?

** Stop making silly stuff up - you pathetic wanker.

> Why should 1 uF protect the trannies in question ...

** Already answered.

( snip bullshit story)

Keep on ignoring the evidence in the photos and you will never get close to
what sort of failure has occurred.

Facts are just like water off a ducks back to you - Don.

Co you fools like you believe whatever they fucking feel like.

.... Phil

== 20 of 20 ==
Date: Mon, Apr 11 2011 10:29 pm
From: don@manx.misty.com (Don Klipstein)

In article <90hre6FsgU1@mid.individual.net>, Phil Allison wrote:
>
><clare@snyder.on.ca>
>>
>> I have to agree with Don. DC power component on secondary OR primary,
>
>** You are both wrong.
>
>> or not connected right are the 2 most likely problems after "cheap
>> crap component"
>
>** Which is no help to the OP.

Please add helpfulness, as opposed to adding nothing but saying who
is wrong.

I chimed in explaining stuff every time. At this point that I respond
to, you are doing nothing but claiming who is wrong.

It appears to me, posting nothing but who is wrong is even lower than
my grasping-at-straws bit of any magnets on the transformer in question.

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

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

== 1 of 1 ==
Date: Mon, Apr 11 2011 4:53 pm
From: "Phil Allison"

"Nutcase Kook"

>
> 33* 10^4 pico farad, 250V but would have to be self-healing type, not
> polyester

** Really ?

So polyester caps are not " self healing " ??

.... Phil

==============================================================================
TOPIC: LG refrigerator model LBN2251#** problems
http://groups.google.com/group/sci.electronics.repair/t/a8a81578d072145d?hl=en
==============================================================================

== 1 of 1 ==
Date: Mon, Apr 11 2011 5:20 pm
From: klem kedidelhopper

On Apr 11, 11:53 am, nesesu <neil_sutcli...@telus.net> wrote:
> On Apr 10, 10:08 pm, Geoff <y...@email.com> wrote:
>
>
>
> > klem kedidelhopper <captainvideo462...@gmail.com> wrote in news:dd664d3b-
> > 3c48-492b-b116-20f9a8e7e...@v10g2000yqn.googlegroups.com:
>
> > > The refrigerator section is running at about 46 degrees and the
> > > freezer is at 42. We cleaned all the dust out of the back and there
> > > doesn't seem to be any improvement. I am an electronics technician
> > > however I don't know too much about refrigerators. All the food is
> > > spoiling and I' hope that someone can please point me in the right
> > > direction to troubleshoot this thing. We had a GE for 22 years and
> > > against my better judgment had to get rid of it because my wife didn't
> > > like the rust on the bottom. Now we're stuck with this non functioning
> > > pos. Thanks for any assistance. Lenny
>
> > Could be failure of defrost system, even if compressor is running. You can
> > check by removing the cover in the back of the freezer section, if that is
> > how you get to the freezer coill thingies, the aluminium bits.
>
> > This causes the ice that is there to slow the flow of air from the fans to
> > the fridge compartments. Next step is to find out why, if this is
> > happening.
>
> My Maytag uses an electronic "Adaptive Defrost Controller". This PC
> board is located in the upper right of the refridgerator compartment
> and ceased working a couple of years ago with the exact symptoms
> described by the OP. I had a tech come in and replace it [$150] but
> kept the old one to see what had happened. It turned out that the bulk
> filter cap [22uF 50V electrolytic] had gone high ESR, so I replaced it
> with a new high ripple cap and put the board away. A week or so ago I
> heard a buzzing like a chattering relay from the 'fridge and went a
> pressed on the panel in the freezer that covers the evaporator and
> felt frost on the coil so I guessed that the replacement board cap was
> failing. I went on line to find the instruction on how to access that
> board in my model and took it out and to the bench. Indeed tha same
> cap was high ESR, so I replaced it and then reinstalled the board into
> the 'fridge. Total time from start to finish of the removal, repair
> and re-installation was about 30 minutes. Problem seems to be
> resolved. So, if you have the same board [it seems to be used across
> many brands], you should not need to spend $43 for a new one, just
> replace the 22u cap with a better quality one.
> Neil S.
Hi everyone
Thank you to everyone who has responded and nice of you to once again
get involved in another one of my problems Neil.
I'm trying to figure out where this board, if my machine uses the
adaptive defrost controller might be on my model..When you open the
refrigerator door and look up sort of on the frame there is this
rectangular panel with separate freezer and refrigerator soft push
button controls The book recommends "4" for each section. Right now we
have the fridge set at 6 and the freezer which my wife set up all the
way is now set back to 4.The fridge runs between 40 and 45 and the
freezer is running at 45 as well. So the fridge is almost OK but we
lost the frozen stuff. My problem is that I don't really understand
the theory behind the operation of this machine so its very hard for
me to try to fix it. I think of thermostats as two wire devices not a
board. And unlike my old GE that came with a service manual and lasted
22 years,(it was still working when I donated it to the Boy Scouts
because my wife complained about the rust on the bottom) I have no
service or even parts layout for this thing.
Can anyone shed any light on the theory part and information perhaps
on where these parts might be located. Thanks, Lenny

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

== 1 of 2 ==
Date: Mon, Apr 11 2011 5:30 pm
From: a7yvm109gf5d1@netzero.com

On Apr 11, 2:41 am, "N_Cook" <dive...@tcp.co.uk> wrote:
> <a7yvm109gf...@netzero.com> wrote in message
>
> news:9e7527b4-b0af-4d2b-974a-cd7794accb9a@y26g2000yqd.googlegroups.com...
>
>
>
> > DS5102C, color LCD scope. When turned on, the leftmost quarter has
> > vertical stripes, the affected column is dead.
>
> > It looks like specific sub-pixels are not responding. R in one row is
> > dead, then G a few rows down, then B, repeat 10 times.
>
> >http://img593.imageshack.us/i/rigollcdscreen.jpg/
>
> > Thing is, after a few hour warm up, it works normally.
>
> > What is the most likely suspect before I go in and strip it down? Is
> > it likely to be simply a bad harness somewhere that needs reseating?
> > Or do I need to take apart the panel and fiddle arround with something
> > more arcane?
>
> > I don't think there's zebra strips in these things these days.
>
> I would get inside and lightly probe with fingers, either final bond to the
> LCD failed somewhere or solder problem on a demultiplexer chip. If bond
> failure , do not try debonding and rebonding . That plastic reticulated
> foam, pan scourer, pressed against the suspect area and padded/braced
> against something is about all you can expect to remedy, unlikely to be
> zebra strip.

Thanks, I haven't taken it apart yet but I think it's just a PS, a
mainboard and the front panel with the LCD, BNCs and buttons.
I'm hoping a simple reseating will fix it.
Thanks for the tips.

== 2 of 2 ==
Date: Mon, Apr 11 2011 8:59 pm
From: Jeff Liebermann

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.

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

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http://groups.google.com/group/sci.electronics.repair/t/9769eed384d5ac70?hl=en
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