Toshiba TV29C90 problem; Image fades to black...

[Jeff Thies]

On 4/11/2011 2:46 PM, Meat Plow wrote:

On Mon, 11 Apr 2011 11:30:33 -0700, David Nebenzahl wrote:

On 4/11/2011 8:25 AM Smitty Two spake thus:

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.

That's true, and it's also true that he often acts--seriously, no
joke--like he's off his meds.

But it's also true that he knows more about electronics than probably
all the "experts" here (a.h.r.) put together.

That's debatable. Phil is a troll

he does have the outward symptoms.

with decent knowledge in electronics.

He sets traps like a spider spins a web then comes back to pounce on
those in the trap.

I have no time for playing games. Anyone sending me down that path is
not worth the time consumed.

I think he is more than a little looney about the whole 1mF cap
business. Not that I'm an expert on appliances but there are plenty of
good reasons why such a thing is not used in other commercial and home
electronics. I've been inside thousands of different line driven
electronics and I've never seen anyone reflect his thinking. It makes me
doubt his practical background, and that is an understatement.


I think Phil gets a lot of his knowledge on Google.

Not a clue on that. I'll leave him in your group where he can foster
as much contempt as he desires.

Jeff

 

[John Robertson]

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."

 

[Meat Plow]

On Mon, 11 Apr 2011 11:30:33 -0700, David Nebenzahl wrote:

On 4/11/2011 8:25 AM Smitty Two spake thus:

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.

That's true, and it's also true that he often acts--seriously, no
joke--like he's off his meds.

But it's also true that he knows more about electronics than probably
all the "experts" here (a.h.r.) put together.

That's debatable. Phil is a troll with decent knowledge in electronics.
He sets traps like a spider spins a web then comes back to pounce on
those in the trap. I think Phil gets a lot of his knowledge on Google.



--
Live Fast Die Young, Leave A Pretty Corpse

 

[Meat Plow]

On Mon, 11 Apr 2011 14:08:47 -0500, The Daring Dufas wrote:

On 4/11/2011 1:46 PM, Meat Plow wrote:
On Mon, 11 Apr 2011 11:30:33 -0700, David Nebenzahl wrote:

On 4/11/2011 8:25 AM Smitty Two spake thus:

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.

That's true, and it's also true that he often acts--seriously, no
joke--like he's off his meds.

But it's also true that he knows more about electronics than probably
all the "experts" here (a.h.r.) put together.

That's debatable. Phil is a troll with decent knowledge in electronics.
He sets traps like a spider spins a web then comes back to pounce on
those in the trap. I think Phil gets a lot of his knowledge on Google.


Google? Is that some new kind of mind altering drug? ^_^

TDD

Sometimes it seems that's the case.



--
Live Fast Die Young, Leave A Pretty Corpse

 

[Meat Plow]

On Mon, 11 Apr 2011 15:28:09 -0400, Jeff Thies wrote:

On 4/11/2011 2:46 PM, Meat Plow wrote:
On Mon, 11 Apr 2011 11:30:33 -0700, David Nebenzahl wrote:

On 4/11/2011 8:25 AM Smitty Two spake thus:

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.

That's true, and it's also true that he often acts--seriously, no
joke--like he's off his meds.

But it's also true that he knows more about electronics than probably
all the "experts" here (a.h.r.) put together.

That's debatable. Phil is a troll

he does have the outward symptoms.

with decent knowledge in electronics.
He sets traps like a spider spins a web then comes back to pounce on
those in the trap.

I have no time for playing games. Anyone sending me down that path is
not worth the time consumed.

I think he is more than a little looney about the whole 1mF cap
business. Not that I'm an expert on appliances but there are plenty of
good reasons why such a thing is not used in other commercial and home
electronics. I've been inside thousands of different line driven
electronics and I've never seen anyone reflect his thinking. It makes me
doubt his practical background, and that is an understatement.


I think Phil gets a lot of his knowledge on Google.

Not a clue on that. I'll leave him in your group where he can foster
as much contempt as he desires.

The sad part is Phil usually is right with things involving pro-audio
gear. I would take his word hands down on guitar and power amps. But you
cannot know everything about any kind of electronic device like he would
like others to believe he does. And why he traps people with one decent
reply then comes back scathing is beyond me.




--
Live Fast Die Young, Leave A Pretty Corpse

 

[Phil Allison]

"Jeff Thies"
Phil Allison

** What sort of know nothing JERK thinks that capacitors dissipate
energy
??

Then proceeds to calculate the reactive impedance and treat it the same
as
resistance ??

Big bad.

Zero out of ten.

** Jeff - you are much worse than merely a know nothing idiot.

You are one colossally narcissistic fool and a public menace.

God knows what it is you DO know something about - but certainly
electricity and electronics are not among them.

Piss off and stop TROLLING .


..... Phil

 

[Phil Allison]

"Smitty Shitty Two"

Jeff Thies

My first encounter with you

Jeff, since you don't hang out on s.e.r., I'll clue you in about Phil.

**As if you have the metal capacity for any such thing.

Regardless of what he knows or doesn't know, he calls everyone a
fuckwit, and worse, all the time.

** Blatant lies.

I only call fuckwits fuckwits.

Shame is, the whole of usenet has been taken over by them.


..... Phil

 

[Phil Allison]

"Jeff Thies is a Moron "

** Piss off - you fuckwit WANKER !!!

I think he is more than a little looney about the whole 1mF cap business.

** FFS IMBECILE -

I suggested a capacitor of " 1uF rated for continuous use across the AC
supply"

Standard practice with inductive loads for decades.

Not that I'm an expert on appliances ...

** Only thing a fool like YOU is expert on is puling your tiny cock in
public.


FUCK OFF - DAMN TROLL !!

 

[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

 

[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."

 

[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

 

[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

 

[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)

 

[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)

 

[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)

 

[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)

 

[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)

 

[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."

 

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.
>

 

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"