sci.electronics.repair@googlegroups.com

Today's topics:

* White coating over part of surface mount amp - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/150806fccb06a046?hl=en
* hai - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/1cb6858b0d9b5f98?hl=en
* Blew another damn transformer on my Trane XB80 - 21 messages, 10 authors
http://groups.google.com/group/sci.electronics.repair/t/f883cd09a3a0b791?hl=en
* LG refrigerator model LBN2251#** problems - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/a8a81578d072145d?hl=en
* Rigol scope LCD problem - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/f09ee6418c07d961?hl=en

==============================================================================
TOPIC: White coating over part of surface mount amp
http://groups.google.com/group/sci.electronics.repair/t/150806fccb06a046?hl=en
==============================================================================

== 1 of 1 ==
Date: Sun, Apr 10 2011 1:14 am
From: "N_Cook"

N_Cook <diverse@tcp.co.uk> wrote in message
news:inrm3t$gnq$1@dont-email.me...
> Jim Yanik <jyanik@abuse.gov> wrote in message
> news:Xns9EC292B4E862Bjyaniklocalnetcom@216.168.3.44...
> > "N_Cook" <diverse@tcp.co.uk> wrote in news:inph8p$h89$1@dont-email.me:
> >
> > > The 500 class D amp shown component level on eservice is near enough
> > > the same as the 300 with scaling down of ratings of components.
> > > Overlay numbering 7... for transistors, 6... for diodes, 5... for
> > > inductors. The large lump that looks like a transformer is 30uH output
> > > filter choke. Will replace the powerfets with mica'd IRF740 and 0.056R
> > > "fuses" with a small piece of resistance wire, previous such repair of
> > > this model of amp never bounced back but otherwise unknown .
> > > I see the replacement FETs for the 2SK3607 is IRF640 which gives me
> > > more confidence.
> > > Will try and find from the owner how they knew and why they replaced
> > > the output fan. But will do my previous retrofit fudge of bending up
> > > the corner of the chassis top cover over the fan ouput and a 5mm
> > > nylon standoff under the fixing screw to at least double/halve the
> > > "choked" fan . Otherwise the ridiculous air flow design? of this amp
> > > is to try and make a compressor out of these little 12V fans.
> > > I will assume heat build up was failure mode as quite a bit of dust
> > > inside, even under the 1/4 inch sockets etc where air prefers to
> > > ingress rather than the designed? row of tiny holes in the chassis
> > > cover. The crack in the FET gate solder was just a partial PbF crack ,
> > > bending the leg to force the "crack" open failed to do so , so not
> > > through to the pad/trace. Plus usaul suspects of PbF dealt with JIC.
> > >
> > >
> > >
> >
> > the fan may have been replaced because it's bearings wore out and got
> > noisy.
> >
> > --
> > Jim Yanik
> > jyanik
> > at
> > localnet
> > dot com
>
> T'was a noisey fan. Still I find it suspicious the same fault outcome,
both
> powerfets shorted all round but just one 0.056R "fuse" blown in the
negative
> rail supply. The fan must be overloaded as well as poor amp ventilation.
> Allowing for central core of fan but not the fan blades themselves, area
> across duct within the 2 inch fan is 420 sq mm.
> Ignoring aerodynamic braking effects of forcing the outcoming air to
> immediately do a confined right angle, a wall 10 mm beyonfd the face of
the
> fan, and vortexing effects from forcing througth 2mm wide slots, the
> combined area of the outlet slots is 170 sq mm. So more like a compressor
> than ventilator. Not only will I be lifting the outlet grill to double or
> treble the area for the outlet air, but drilling out every other inlet
hole
> as well perhaps.
>
>

There must be a ventilation problem with these tiny amps
http://www.luthermusic.com/uat/luthermusic_class/prod/765_1_preview.jpg

The outlet grill , on this presumably later version, is under the master
control in the pic orientation.
This pic shows about twice the number of slots as the one I have here, so in
recent years they have punched more slots. This one is just the slots in the
black area of that pic, not the continuation towards the master control. I'm
not in the position to retrofit slots, but can lift that corner with a
standoff.
The inlet holes are a line of 1.5mm holes , directly under the top handle in
that pic, so obscured.

==============================================================================
TOPIC: hai
http://groups.google.com/group/sci.electronics.repair/t/1cb6858b0d9b5f98?hl=en
==============================================================================

== 1 of 1 ==
Date: Sun, Apr 10 2011 7:03 am
From: vijay balan

http://123maza.com/75/model419/

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

== 1 of 21 ==
Date: Sun, Apr 10 2011 7:25 am
From: Jeff Thies

On 4/9/2011 10:22 PM, Phil Allison wrote:
> "robb"
>
>>
>> Yep, My A/C unit blew another transformer. Pictures (and wiring diagram)
>> here:
>>
>> http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
>>
>> 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).
>
>
> ** From the damage to the tranny visible in the photos - the primary has
> developed an internal short ( due to insulation failure) and since there is
> no fuse link in series, the resulting current was high enough to make an
> exposed wire leading to the terminals explode.
>
> An internal short could develop due to heat alone because of an overload on
> the tranny - but this requires a fault to exist on the secondary side which
> seems not to be the case.
>
> 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.
>
> 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.

I would think .01 uF at 400V would be a better bet. Or an MOV (metal
oxide varistor) or three (across the line and then from each side to
ground).

I don't think this is a voltage spike problem though. Voltage spikes
take out other components first.

Jeff
>
>
>
> ..... Phil
>
>
>
>
>
>
>

== 2 of 21 ==
Date: Sun, Apr 10 2011 7:43 am
From: "trader4@optonline.net"

On Apr 9, 8:29 pm, Jim Yanik <jya...@abuse.gov> wrote:
> "robb" <s...@where.on.net> wrote innews:WfKdnQOvu_d2bz3QnZ2dnUVZ_uadnZ2d@earthlink.com:
>
>
>
>
>
> > "Steve Turner"  wrote in messagenews: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.
>
>

It also could be powering a thermostat. Some of them will take power
from the transformer circuit. For example, I have a Honeywell
VisionPro
that has an optional 24V connection to power the thermostat, with
batteries then being the backup. Doing it that way allows the display
to be backlit 24/7 too.

Also, it's not unusual to have humdifiers tied into the 24V circuit
too.

Again, he needs to start doing some basic current measurements,
starting at the transformer and find out how much current the whole
thing is drawing and then if it's high, work to isolate it. If the
current
is normal, then I'd put in a 1.5 amp fuse in the secondary
temporarily.
Contrary to the suggestions to use a fast blow, I'd probably just use
a regular one, as whatever is capable of destroying a transformer
should be most capable of opening any fuse.

>
>
>
>
>
> > 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.

That's a good idea too.

>
> > 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.

I don't see how he could have a waveform that is so out of shape that
it
burns up this one specific transformer, yet there are no apparent
complaints of any other problems in the house. Or how you'd get
such a badly distorted waveform in the house in the first place.

> a DMM will not show line distortion or short
> term overvoltages.
> are the wires burned close to the transformer,or over their entire length?
>
> --
> Jim Yanik
> jyanik
> at
> localnet
> dot com- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -

== 3 of 21 ==
Date: Sun, Apr 10 2011 8:21 am
From: Mark

To OP
this is a long shot but...
I noticed on the Trane wiring diagram that you posted that the
connections for the IGNITION circuit are shown to be near to the
connections for the primary of the transformer.

If there is some insulation problem on the ignition wires and the VERY
high voltage from the ignition circuit is sparking or jumping over to
the transformer primary circuit, this could cause the symptoms you are
seeing.

Make sure the wires that are part of the ignition circuit are not even
close to the anything else. and inspect them (with the power off) for
any sigh of cracks or other faults. These have very high voltage
like in a car spark plug and can jump several inches if there is an
insulation problem. And the problem would be intermittent. The
transformer primary voltage would look perfect except when the high
voltage spark jumps over to it and this could easily damage the
insulation on the transformer which is not designed for very high
voltages.

If you are an electrical novice, you may want to think about calling
in for some help at this point.

Mark
>

== 4 of 21 ==
Date: Sun, Apr 10 2011 8:55 am
From: "David"

>"Mark" wrote in message
>news:fe82a1bf-396e-4db1-96be-bdbc0d47798e@e9g2000vbk.googlegroups.com...
>To OP
>this is a long shot but...
>I noticed on the Trane wiring diagram that you posted that the
>connections for the IGNITION circuit are shown to be near to the
>connections for the primary of the transformer.
<snip>
>Mark

Everything I see on the diagrams says this is a HSI (Hot Surface
Igniter) type of furnace. There is no high voltage in that type
of igniter.
David

== 5 of 21 ==
Date: Sun, Apr 10 2011 9:18 am
From: Smitty Two

In article <fs62q6djakj0jdki52906m5s27fdp59knt@4ax.com>,
Grant <omg@grrr.id.au> wrote:

>
> Is that a dual primary 115V (230V) xformer? Did you wire both primaries
> in parallel for 115V operation?
>
> Grant.

This thread started on a.h.r (alt.home.repair) and I'm not sure the OP
monitors s.e.r. Someone cross-posted it here, but the bulk of the thread
(several hundred posts) is on a.h.r. only.

So if you want to be helpful, you might wander over there. ISTR reading
that the OP taped off two wires.

== 6 of 21 ==
Date: Sun, Apr 10 2011 10:08 am
From: Jim Yanik

Grant <omg@grrr.id.au> wrote in
news:fs62q6djakj0jdki52906m5s27fdp59knt@4ax.com:

> On Sat, 09 Apr 2011 20:55:37 -0500, Steve Turner
> <bbqboyee@swtacobell.net.invalid> 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/22-16
>>>> 66- 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.
>
> Is that a dual primary 115V (230V) xformer? Did you wire both
> primaries in parallel for 115V operation?
>
> Grant.
>

another poster on the alt.home.repair NG made that suggestion/comment.
A very good one,that I had overlooked. good catch!

--
Jim Yanik
jyanik
at
localnet
dot com

== 7 of 21 ==
Date: Sun, Apr 10 2011 10:36 am
From: Mark

On Apr 10, 11:55 am, "David" <some...@somewhere.com> wrote:
> >"Mark"  wrote in message
> >news:fe82a1bf-396e-4db1-96be-bdbc0d47798e@e9g2000vbk.googlegroups.com...
> >To OP
> >this is a long shot but...
> >I noticed on the Trane wiring diagram that you posted that the
> >connections for the IGNITION circuit are shown to be near to the
> >connections for the primary of the transformer.
> <snip>
> >Mark
>
> Everything I see on the diagrams says this is a HSI (Hot Surface
> Igniter) type of furnace. There is no high voltage in that type
> of igniter.
> David

David,
I think you are right...

well it sounded good anyway....

regards
Mark

== 8 of 21 ==
Date: Sun, Apr 10 2011 4:47 pm
From: "Phil Allison"

"Jeff Thies"
Phil Allison wrote:
>> "robb"
>>
>>>
>>> Yep, My A/C unit blew another transformer. Pictures (and wiring
>>> diagram)
>>> here:
>>>
>>> http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
>>>
>>> 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).
>>
>>
>> ** From the damage to the tranny visible in the photos - the primary has
>> developed an internal short ( due to insulation failure) and since there
>> is
>> no fuse link in series, the resulting current was high enough to make an
>> exposed wire leading to the terminals explode.
>>
>> An internal short could develop due to heat alone because of an overload
>> on
>> the tranny - but this requires a fault to exist on the secondary side
>> which
>> seems not to be the case.
>>
>> 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.
>>
>> 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 would think .01 uF at 400V would be a better bet.

** Think again.

> Or an MOV (metal oxide varistor) or three (across the line and then from
> each side to ground).

** Bad idea.

> I don't think this is a voltage spike problem though. Voltage spikes take
> out other components first.

** Not on the AC supply they don't.

..... Phil

== 9 of 21 ==
Date: Sun, Apr 10 2011 5:05 pm
From: Tony Miklos

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

== 10 of 21 ==
Date: Sun, Apr 10 2011 5:14 pm
From: Tony Miklos

On 4/9/2011 10:22 PM, Phil Allison wrote:
> "robb"
>
>>
>> Yep, My A/C unit blew another transformer. Pictures (and wiring diagram)
>> here:
>>
>> http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
>>
>> 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).
>
>
> ** From the damage to the tranny visible in the photos - the primary has
> developed an internal short ( due to insulation failure) and since there is
> no fuse link in series, the resulting current was high enough to make an
> exposed wire leading to the terminals explode.
>
> An internal short could develop due to heat alone because of an overload on
> the tranny - but this requires a fault to exist on the secondary side which
> seems not to be the case.

Oh my gawd, someone agrees with me. Looking at the picture says a lot.
Burnt on the primary side, looks like new on the secondary. And this
is the third transformer with an open primary!

I don't know about a the 1uF cap, seems way too high so I'll delete what
was below and pretend I didn't see it.

== 11 of 21 ==
Date: Sun, Apr 10 2011 5:19 pm
From: "Phil Allison"

"Tony Miklos don't know much"

>
>> ** From the damage to the tranny visible in the photos - the primary has
>> developed an internal short ( due to insulation failure) and since there
>> is
>> no fuse link in series, the resulting current was high enough to make an
>> exposed wire leading to the terminals explode.
>>
>> An internal short could develop due to heat alone because of an overload
>> on
>> the tranny - but this requires a fault to exist on the secondary side
>> which
>> seems not to be the case.
>
> Oh my gawd, someone agrees with me. Looking at the picture says a lot.
> Burnt on the primary side, looks like new on the secondary. And this is
> the third transformer with an open primary!
>
>
> I don't know about a the 1uF cap, seems way too high

** Why ?????

It ( likely ) needs to absorb a transient back emf generated by a powerful
blower fan.

Non puny size cap will ever do that and using 1uF cases no harm whatsoever.

> so I'll delete what was below and pretend I didn't see it.

** Nothing like doing the old Ostrich trick when the brain gets overloaded.

Wot a jerk off.

.... Phil

== 12 of 21 ==
Date: Sun, Apr 10 2011 5:39 pm
From: "Ron D."

Put 3A automotive fuse on secondary. Use light bulb trick to find
shorts. Two 12 V light bulbs in series that draw no more than 40 VA.

== 13 of 21 ==
Date: Sun, Apr 10 2011 6:47 pm
From: Jeff Thies

On 4/10/2011 7:47 PM, Phil Allison wrote:
> "Jeff Thies"
> Phil Allison wrote:
>>> "robb"
>>>
>>>>
>>>> Yep, My A/C unit blew another transformer. Pictures (and wiring
>>>> diagram)
>>>> here:
>>>>
>>>> http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
>>>>
>>>> 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).
>>>
>>>
>>> ** From the damage to the tranny visible in the photos - the primary has
>>> developed an internal short ( due to insulation failure) and since there
>>> is
>>> no fuse link in series, the resulting current was high enough to make an
>>> exposed wire leading to the terminals explode.
>>>
>>> An internal short could develop due to heat alone because of an overload
>>> on
>>> the tranny - but this requires a fault to exist on the secondary side
>>> which
>>> seems not to be the case.
>>>
>>> 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.
>>>
>>> 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?

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

Jeff

== 14 of 21 ==
Date: Sun, Apr 10 2011 7:37 pm
From: Tony Miklos

On 4/10/2011 9:47 PM, Jeff Thies wrote:
> On 4/10/2011 7:47 PM, Phil Allison wrote:
>> "Jeff Thies"
>> Phil Allison wrote:
>>>> "robb"
>>>>
>>>>>
>>>>> Yep, My A/C unit blew another transformer. Pictures (and wiring
>>>>> diagram)
>>>>> here:
>>>>>
>>>>> http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
>>>>>
>>>>> 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).
>>>>
>>>>
>>>> ** From the damage to the tranny visible in the photos - the primary
>>>> has
>>>> developed an internal short ( due to insulation failure) and since
>>>> there
>>>> is
>>>> no fuse link in series, the resulting current was high enough to
>>>> make an
>>>> exposed wire leading to the terminals explode.
>>>>
>>>> An internal short could develop due to heat alone because of an
>>>> overload
>>>> on
>>>> the tranny - but this requires a fault to exist on the secondary side
>>>> which
>>>> seems not to be the case.
>>>>
>>>> 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.
>>>>
>>>> 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?
>
> If not then go buy a 200V non polarized 1uF cap. It is no easy chore.

I have some big ass mylars, I think they are 4uF @ 200v.

== 15 of 21 ==
Date: Sun, Apr 10 2011 7:46 pm
From: "Phil Allison"

"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 ??

> 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.

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

What planet do you come from ??

.... Phil

== 16 of 21 ==
Date: Sun, Apr 10 2011 7:48 pm
From: "Phil Allison"

"Tony Miklos"

> I have some big ass mylars, I think they are 4uF @ 200v.

** They won't last long if connected across the AC supply.

.... Phil

== 17 of 21 ==
Date: Sun, Apr 10 2011 7:55 pm
From: Tony Miklos

On 4/10/2011 10:48 PM, Phil Allison wrote:
> "Tony Miklos"
>
>> I have some big ass mylars, I think they are 4uF @ 200v.
>
>
> ** They won't last long if connected across the AC supply.
>
>
>
> .... Phil
>
>

I know, I was just about to reply to my post saying that the voltage
rating is VDC.

== 18 of 21 ==
Date: Sun, Apr 10 2011 8:01 pm
From: "Phil Allison"

"Tony Miklos"
Phil Allison wrote:

>>
>>> I have some big ass mylars, I think they are 4uF @ 200v.
>>
>>
>> ** They won't last long if connected across the AC supply.
>>
>
> I know, I was just about to reply to my post saying that the voltage
> rating is VDC.

** Film caps rated at 600VDC will generally last a fair while wired across a
120 volt AC supply ( but not with a 240VAC supply ) - but is it far better
to use a purpose designed and agency approved "class X1" or "classX2"
capacitor.

... Phil

== 19 of 21 ==
Date: Sun, Apr 10 2011 8:15 pm
From: clare@snyder.on.ca

On Sun, 10 Apr 2011 12:22:13 +1000, "Phil Allison" <phil_a@tpg.com.au>
wrote:

>
>"robb"
>
>>
>> Yep, My A/C unit blew another transformer. Pictures (and wiring diagram)
>> here:
>>
>> http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
>>
>> 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).
>
>
>** From the damage to the tranny visible in the photos - the primary has
>developed an internal short ( due to insulation failure) and since there is
>no fuse link in series, the resulting current was high enough to make an
>exposed wire leading to the terminals explode
>
>An internal short could develop due to heat alone because of an overload on
>the tranny - but this requires a fault to exist on the secondary side which
>seems not to be the case.
>
>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.

>
>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.
>
>

A capacitor across an AC supply??????????????? As a surge
protector????
Have not heard of that before.

A capacitor across the AC line would appear as a load - and could
form a resonant l/ci tank circuit, which would also appear as a low
resistance -causing high current to flow

There are 2 other POSSIBLE issues here though - - -.

Both are perhaps long shots - but mabee worth investigating.

The transformer primary APPEARS to be saturating.
Primary current on an unloaded transformer CAN, in some cases, excede
full load current. Possibly the transformer requires MORE load on the
secondary than it is getting.

An example is a microwave oven transformer. With no load on either the
high voltage or low voltage secondary, the primary will generally
saturate and overheat. If you remove the high voltage secondary and
add your own windings to make a "custom" transformer, it is not
uncommon for the primary to saturate at no/low loads - overheating the
transformer.

Like I said - a long shot, but possibly worth investigating. adding a
small 24 volt pilot light across the secondary MAY solve that kind of
a problem.

The other POSSIBILITY is a DC bias on the primary, which WILL cause
saturation on 1/2 cycle of the AC. Need a scope to check that
effectively - or something like a 10uf nonpolarized capacitor and a
100K ohm 1/2 watt resistor in series across the primary, with a DC
voltmeter connected across the cap. Make all connections BEFORE
turning on the mains power. You should expect to see readings of +/-
approx 25-35mv across the cap in a normal residential situation.

Lets say you read 275mv DC on the line, and the transformer primary
resistance is 2 ohms.. That will put a DC current of 137.5ma through
the primary - which when added to the normal AC current on the one
half cycle will greatly excede the saturation current of the primary.

A half wave rectified load on the same circuit could put a DC
component across the line.

An AC (nonpolarized) capacitor IN SERIES with the primary would
remove the DC component from the primary winding, but finding a
capacitor that would ballast the primary properly (allow full rated
primary current) while not causing a series resonance (which would
appear as a short circuit across the mains) is not something I would
try to calculate.
>
>..... Phil
>
>
>
>
>
>

== 20 of 21 ==
Date: Sun, Apr 10 2011 8:25 pm
From: "Phil Allison"

<clare@snyder.on.ca>
"Phil Allison"
>
>
>>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.
>
>>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.
>>
>>
>
> A capacitor across an AC supply??????????????? As a surge
> protector????
> Have not heard of that before.

** Then your ignorance is showing.

The stated reason for the capacitor was in relation to the "blower fan"
inside the same unit as the small tranny.

The event the cap has to deal with is a back emf surge generated by that
fan when the AC supply is suddenly disconnected - for whatever reason.

> A capacitor across the AC line would appear as a load

** Draws 45mA continuously.

Yawnnnnnnn....

> - and could form a resonant l/ci tank circuit,

** Yawnnnnnn....

(snip absurd drivel)

> There are 2 other POSSIBLE issues here though - - -.
>
> Both are perhaps long shots - but mabee worth investigating.
>
> The transformer primary APPEARS to be saturating.

** The primary appears to be EXPLODING !!

You ridiculous wanker.

.... Phil

== 21 of 21 ==
Date: Sun, Apr 10 2011 8:27 pm
From: Jeff Thies

On 4/10/2011 10:46 PM, 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.

Jeff

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

== 1 of 2 ==
Date: Sun, Apr 10 2011 4:42 pm
From: klem kedidelhopper

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

== 2 of 2 ==
Date: Sun, Apr 10 2011 7:50 pm
From: Smitty Two

In article
<dd664d3b-3c48-492b-b116-20f9a8e7ef64@v10g2000yqn.googlegroups.com>,
klem kedidelhopper <captainvideo462009@gmail.com> wrote:

> 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

Lots of troubleshooting guides on the net, but the easiest thing to try
first is a 24 hour defrost.

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

== 1 of 1 ==
Date: Sun, Apr 10 2011 8:13 pm
From: a7yvm109gf5d1@netzero.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.

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

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