sci.electronics.repair - 25 new messages in 10 topics - digest

sci.electronics.repair
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Today's topics:

==============================================================================
TOPIC: Gareth Magennis is xxxxxxxxxxxx
http://groups.google.com/group/sci.electronics.repair/t/aff797bedba2c908?hl=en
==============================================================================

== 1 of 6 ==
Date: Sat, Apr 9 2011 5:42 am
From: "Ian Field"

"Gareth Magennis" <sound.service@btconnect.com> wrote in message
news:V4Nnp.3394$9h6.2711@newsfe02.ams2...
>
>
> "Meat Plow" <mhywattt@yahoo.com> wrote in message
> news:pan.2011.04.08.23.25.40@lmao.lol.lol...
>> On Sat, 09 Apr 2011 00:12:23 +0100, Gareth Magennis wrote:
>>
>>> "Meat Plow" <mhywattt@yahoo.com> wrote in message
>>> news:pan.2011.04.08.17.26.17@lmao.lol.lol...
>>>> On Fri, 08 Apr 2011 10:17:06 +0100, Gareth Magennis wrote:
>>>>
>>>>> Interestingly the customer said that the amp went DC and fried his
>>>>> speaker - the amp has no relay or DC protection. My little bit or
>>>>> research so far indicates that dv/dt failure in industrial motor
>>>>> applications can be down to pulling the power cable off a stalled
>>>>> motor, zapping the gate/substrate connection in a nanosecond. Might
>>>>> this also apply to a faulty speaker in this kind of audio amp which
>>>>> burns short then eventually self disconnects?
>>>>>
>>>>> I also understand extremely electrically noisy environments can also
>>>>> induce this failure mode. The customer is daisy chaining this amp
>>>>> with another one via the FX send, I'm wondering if this has any chance
>>>>> of being the cause of the failure.
>>>>
>>>> Slaving another amp via the send isn't likely but a failing speaker or
>>>> poorly wired/connected load might be the reason.
>>>>
>>>>
>>>>
>>>
>>> Check this out, if just for educational purposes. Quite interesting.
>>>
>>> http://www.4qd.co.uk/serv/MOSFETfail.html
>>>
>>>
>>>
>>> Gareth.
>>
>> Mostly pertaining to motor control applications. My experience is limited
>> to audio applications. Some similarities exist thought. Still a good read
>> for failure modes.
>>
>>
>
>
> Isn't a speaker a motor?

Maybe the "speech coil" head actuators in old 5&1/4 FH HDDs blur the
distinction a bit.

== 2 of 6 ==
Date: Sat, Apr 9 2011 9:06 am
From: Meat Plow

On Sat, 09 Apr 2011 00:43:51 +0100, Gareth Magennis wrote:

> "Meat Plow" <mhywattt@yahoo.com> wrote in message
> news:pan.2011.04.08.23.25.40@lmao.lol.lol...
>> On Sat, 09 Apr 2011 00:12:23 +0100, Gareth Magennis wrote:
>>
>>> "Meat Plow" <mhywattt@yahoo.com> wrote in message
>>> news:pan.2011.04.08.17.26.17@lmao.lol.lol...
>>>> On Fri, 08 Apr 2011 10:17:06 +0100, Gareth Magennis wrote:
>>>>
>>>>> Interestingly the customer said that the amp went DC and fried his
>>>>> speaker - the amp has no relay or DC protection. My little bit or
>>>>> research so far indicates that dv/dt failure in industrial motor
>>>>> applications can be down to pulling the power cable off a stalled
>>>>> motor, zapping the gate/substrate connection in a nanosecond. Might
>>>>> this also apply to a faulty speaker in this kind of audio amp which
>>>>> burns short then eventually self disconnects?
>>>>>
>>>>> I also understand extremely electrically noisy environments can also
>>>>> induce this failure mode. The customer is daisy chaining this amp
>>>>> with another one via the FX send, I'm wondering if this has any
>>>>> chance of being the cause of the failure.
>>>>
>>>> Slaving another amp via the send isn't likely but a failing speaker
>>>> or poorly wired/connected load might be the reason.
>>>>
>>>>
>>>>
>>>>
>>> Check this out, if just for educational purposes. Quite interesting.
>>>
>>> http://www.4qd.co.uk/serv/MOSFETfail.html
>>>
>>>
>>>
>>> Gareth.
>>
>> Mostly pertaining to motor control applications. My experience is
>> limited to audio applications. Some similarities exist thought. Still a
>> good read for failure modes.
>>
>>
>>
>
> Isn't a speaker a motor?
>
>
>
> Gareth.

It can be perceived as a sound motor.

--
Live Fast Die Young, Leave A Pretty Corpse

== 3 of 6 ==
Date: Sat, Apr 9 2011 9:12 am
From: Meat Plow

On Sat, 09 Apr 2011 09:42:02 +1000, Phil Allison wrote:

> "Gareth Magennis"
>
>> Check this out, if just for educational purposes. Quite interesting.
>>
>> http://www.4qd.co.uk/serv/MOSFETfail.html
>
>
> ** Got nothing WHATSOEVER to do with LATERAL mosfets !!!
>
> These are completely different animals to switching mosfets.
>
> Originally invented by Hitachi and sold in TO3 packs as 2SK ( N ch) and
> 2SJ ( P ch) numbers as the perfect output devices for audio amplifiers.
> Power amp makers in the UK, Australia and NZ pounced on them and for a
> while in the mid 1980s, MOSFET amps were the industry standard.

I cried the day Hitachi quit manufacturing the 2SK49 / 2SJ135 pairs. I
have one old SCS 350w/ch power amp that uses them. I acquired it with a
blow channel back in the late 90's. It wasn't easy back then to find
replacements. I imagine it's probably a lot easier these days to find NOS
replacements. Maybe even a sub is made today?

--
Live Fast Die Young, Leave A Pretty Corpse

== 4 of 6 ==
Date: Sat, Apr 9 2011 12:23 pm
From: "Gareth Magennis"

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:909l0uFrhoU1@mid.individual.net...
>
> "Gareth Magennis"
>>
>> Isn't a speaker a motor?
>
>
> ** And chaulk an cheese are the same too.
>
> Fuckwit.
>
>
> ... Phil
>

Oh and there's me thinking a motor is a device that converts electrical
energy into mechanical energy.

Fuckwit.

== 5 of 6 ==
Date: Sat, Apr 9 2011 1:23 pm
From: David Nebenzahl

On 4/9/2011 9:06 AM Meat Plow spake thus:

> On Sat, 09 Apr 2011 00:43:51 +0100, Gareth Magennis wrote:
>
>> "Meat Plow" <mhywattt@yahoo.com> wrote in message
>> news:pan.2011.04.08.23.25.40@lmao.lol.lol...
>>
>>> On Sat, 09 Apr 2011 00:12:23 +0100, Gareth Magennis wrote:
>>>
>>>> "Meat Plow" <mhywattt@yahoo.com> wrote in message
>>>> news:pan.2011.04.08.17.26.17@lmao.lol.lol...
>>>>
>>>>> On Fri, 08 Apr 2011 10:17:06 +0100, Gareth Magennis wrote:
>>>>>
>>>>>> Interestingly the customer said that the amp went DC and
>>>>>> fried his speaker - the amp has no relay or DC protection.
>>>>>> My little bit or research so far indicates that dv/dt
>>>>>> failure in industrial motor applications can be down to
>>>>>> pulling the power cable off a stalled motor, zapping the
>>>>>> gate/substrate connection in a nanosecond. Might this also
>>>>>> apply to a faulty speaker in this kind of audio amp which
>>>>>> burns short then eventually self disconnects?
>>>>>>
>>>>>> I also understand extremely electrically noisy environments
>>>>>> can also induce this failure mode. The customer is daisy
>>>>>> chaining this amp with another one via the FX send, I'm
>>>>>> wondering if this has any chance of being the cause of the
>>>>>> failure.
>>>>>
>>>>> Slaving another amp via the send isn't likely but a failing
>>>>> speaker or poorly wired/connected load might be the reason.
>>>>>
>>>> Check this out, if just for educational purposes. Quite
>>>> interesting.
>>>>
>>>> http://www.4qd.co.uk/serv/MOSFETfail.html
>>>
>>> Mostly pertaining to motor control applications. My experience is
>>> limited to audio applications. Some similarities exist thought.
>>> Still a good read for failure modes.
>>
>> Isn't a speaker a motor?
>
> It can be perceived as a sound motor.

It *is*, in fact, a motor. Which, technically speaking, is anything that
converts electrical energy to mechanical motion. So by this definition,
even solenoids and piezo transducers are motors.

Now, it's not a motor in the conventionally-understood sense--something
that produces rotary motion--but it is, nonetheless, a perfectly good motor.

--
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*?)

== 6 of 6 ==
Date: Sat, Apr 9 2011 1:53 pm
From: Meat Plow

On Sat, 09 Apr 2011 13:23:48 -0700, David Nebenzahl wrote:

> On 4/9/2011 9:06 AM Meat Plow spake thus:
>
>> On Sat, 09 Apr 2011 00:43:51 +0100, Gareth Magennis wrote:
>>
>>> "Meat Plow" <mhywattt@yahoo.com> wrote in message
>>> news:pan.2011.04.08.23.25.40@lmao.lol.lol...
>>>
>>>> On Sat, 09 Apr 2011 00:12:23 +0100, Gareth Magennis wrote:
>>>>
>>>>> "Meat Plow" <mhywattt@yahoo.com> wrote in message
>>>>> news:pan.2011.04.08.17.26.17@lmao.lol.lol...
>>>>>
>>>>>> On Fri, 08 Apr 2011 10:17:06 +0100, Gareth Magennis wrote:
>>>>>>
>>>>>>> Interestingly the customer said that the amp went DC and fried his
>>>>>>> speaker - the amp has no relay or DC protection. My little bit or
>>>>>>> research so far indicates that dv/dt failure in industrial motor
>>>>>>> applications can be down to pulling the power cable off a stalled
>>>>>>> motor, zapping the gate/substrate connection in a nanosecond.
>>>>>>> Might this also apply to a faulty speaker in this kind of audio
>>>>>>> amp which burns short then eventually self disconnects?
>>>>>>>
>>>>>>> I also understand extremely electrically noisy environments can
>>>>>>> also induce this failure mode. The customer is daisy chaining
>>>>>>> this amp with another one via the FX send, I'm wondering if this
>>>>>>> has any chance of being the cause of the failure.
>>>>>>
>>>>>> Slaving another amp via the send isn't likely but a failing speaker
>>>>>> or poorly wired/connected load might be the reason.
>>>>>>
>>>>> Check this out, if just for educational purposes. Quite
>>>>> interesting.
>>>>>
>>>>> http://www.4qd.co.uk/serv/MOSFETfail.html
>>>>
>>>> Mostly pertaining to motor control applications. My experience is
>>>> limited to audio applications. Some similarities exist thought. Still
>>>> a good read for failure modes.
>>>
>>> Isn't a speaker a motor?
>>
>> It can be perceived as a sound motor.
>
> It *is*, in fact, a motor. Which, technically speaking, is anything that
> converts electrical energy to mechanical motion. So by this definition,
> even solenoids and piezo transducers are motors.
>
> Now, it's not a motor in the conventionally-understood sense--something
> that produces rotary motion--but it is, nonetheless, a perfectly good
> motor.

My reference was to the failure modes of motor speed control mosfets.
They aren't the ideal comparison to the failure modes found in audio
power amps using lateral or bipolar mosfets. None the less the 4QD read
was enlightening.

Lots of things can be considered motors if you think outside the box.
Anything that conveys motion can be considered a motor.

--
Live Fast Die Young, Leave A Pretty Corpse

==============================================================================
TOPIC: Heathkit SB-1000 problem
http://groups.google.com/group/sci.electronics.repair/t/bf1179ee58e02a68?hl=en
==============================================================================

== 1 of 2 ==
Date: Sat, Apr 9 2011 6:10 am
From: "Christopher Hall"

I am the second owner of a Heathkit SB-1000 that was built in the late
1980s. It was working great until I accidentally tried to tune it into a
mistuned antenna and I saw a flash through the ventilation screen on the
left side somewhere around the rectifier/filter section and there is now no
power output. The amp powers up, the fan runs, the meter lamps light and the
tube lights up. The amps multimeter shows 3400 volts on the high voltage
position (a little high maybe but it has always been like that). With no
drive, when the amp is keyed there is no plate current and no grid current.
Keyed with drive there is grid current, but no plate current and no power
output. These conditions are the same regardless of which band the amp is
set to. I had thought that the zener diode might have failed so I replaced
it, but nothing has changed. I would appreciate any thoughts as to what may
be the problem and how to fix it.

73
Chris
VE9ZX

== 2 of 2 ==
Date: Sat, Apr 9 2011 9:16 am
From: "Dave M"

Christopher Hall wrote:
> I am the second owner of a Heathkit SB-1000 that was built in the late
> 1980s. It was working great until I accidentally tried to tune it
> into a mistuned antenna and I saw a flash through the ventilation
> screen on the left side somewhere around the rectifier/filter section
> and there is now no power output. The amp powers up, the fan runs,
> the meter lamps light and the tube lights up. The amps multimeter
> shows 3400 volts on the high voltage position (a little high maybe
> but it has always been like that). With no drive, when the amp is
> keyed there is no plate current and no grid current. Keyed with drive
> there is grid current, but no plate current and no power output.
> These conditions are the same regardless of which band the amp is set
> to. I had thought that the zener diode might have failed so I
> replaced it, but nothing has changed. I would appreciate any thoughts
> as to what may be the problem and how to fix it.
> 73
> Chris
> VE9ZX

The first thing to check is to see if HV is present on the plate of the
final. If not, there's something blown open, likely in the HV rectifier
circuit. Check rectifiers and capacitors on the HV rectifier and HV filter
boards. Also, make sure there's continuity from the HV rectifier to the
plate of the final. An open circuit there means an open resistor or
inductor between the plate and HV rectifier/filter.

Cheers,
--
David
dgminala at mediacombb dot net

==============================================================================
TOPIC: Composite video from Compaq Armada e500 to Panasonic LCD TV TC-20LA1.
http://groups.google.com/group/sci.electronics.repair/t/bf86e0e27f847377?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, Apr 9 2011 6:19 am
From: TomC

Try changing the refresh rate or the display driver for the screen display.
Seems like the OS is loading something that the tv doesn't understand.

Peter <peasthope@shaw.ca> wrote in news:9498e99f-253d-464e-8876-
e77629918307@r13g2000yqk.googlegroups.com:

> Folk,
>
> This is an arcane question of application rather than repair but I
> don't know of a better place to ask.
>
> I've connected the composite video output from a Compaq Armada e500
> running Debian Squeeze, to a Panasonic LCD TV TC-20LA1. The display
> on the TV works for the COMPAQ logo, the BIOS, and the console
> startup messages. When X takes over, the TV appears to lose sync.
> Nothing helpful is evident in the BIOS of the Armada.
>
> The Armada was donated without the original software. I'll guess
> that there was software designed to drive the composite video output,
> independently of the laptop screen.
>
> I'm thinking of trying this in /etc/X11/xorg.conf.
> Section "Monitor"
> ...
> VertRefresh 60.0
> EndSection
>
> Can a setting in xorg.conf harm the laptop hardware? Any advice or
> comments or instructions to get a display on the TV suitable for
> watching a movie?
>
> Thanks, ... Peter E.

==============================================================================
TOPIC: Found: Schematics (ftp).
http://groups.google.com/group/sci.electronics.repair/t/d9cc653e0394359e?hl=en
==============================================================================

== 1 of 2 ==
Date: Sat, Apr 9 2011 5:55 am
From: "Ian Field"

"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:4acvp6p9m64l24a5g8rgve1iv5dgunv99t@4ax.com...
> On Fri, 8 Apr 2011 22:01:19 +0100, "Ian Field"
> <gangprobing.alien@ntlworld.com> wrote:
>
>>ftp://81.200.26.182/radio/RADIO/?????
>
> Chuckle:
> <ftp://81.200.26.182/index.htm>
> which Google translates to:
> My ftp-server is only adequate for all people!
>
> However, if you use HTTP instead of FTP, you get a
> partly finished and badly translated Joomla CMS page:
> <http://81.200.26.182>
>
> Thanks, maybe.

Unfortunately it seems like Russia is the best place to find free
schematics, so it shouldn't come as a complete surprise that some of the
schematics are in Russian.

I sampled some of the PDFs and found that some are in English, in some cases
it doesn't matter what language the text is in - a schematic is a schematic
and there are times when a Russian one is better than nothing at all.

== 2 of 2 ==
Date: Sat, Apr 9 2011 12:15 pm
From: Baron

Ian Field Inscribed thus:

>
> "Jeff Liebermann" <jeffl@cruzio.com> wrote in message
> news:4acvp6p9m64l24a5g8rgve1iv5dgunv99t@4ax.com...
>> On Fri, 8 Apr 2011 22:01:19 +0100, "Ian Field"
>> <gangprobing.alien@ntlworld.com> wrote:
>>
>>>ftp://81.200.26.182/radio/RADIO/?????
>>
>> Chuckle:
>> <ftp://81.200.26.182/index.htm>
>> which Google translates to:
>> My ftp-server is only adequate for all people!
>>
>> However, if you use HTTP instead of FTP, you get a
>> partly finished and badly translated Joomla CMS page:
>> <http://81.200.26.182>
>>
>> Thanks, maybe.
>
> Unfortunately it seems like Russia is the best place to find free
> schematics, so it shouldn't come as a complete surprise that some of
> the schematics are in Russian.
>
> I sampled some of the PDFs and found that some are in English, in some
> cases it doesn't matter what language the text is in - a schematic is
> a schematic and there are times when a Russian one is better than
> nothing at all.

Chrome will offer to translate it for you !

--
Best Regards:
Baron.

==============================================================================
TOPIC: OT: Video - 650 hp 2011 Ford Fiesta and an unlimited tire budget
http://groups.google.com/group/sci.electronics.repair/t/9bee7611fb66d405?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, Apr 9 2011 6:54 am
From: RoadRunner

http://wp.me/p184Gt-1Qa

==============================================================================
TOPIC: Stark 9-66 tube tester repair
http://groups.google.com/group/sci.electronics.repair/t/8bf2519188d6af07?hl=en
==============================================================================

== 1 of 4 ==
Date: Sat, Apr 9 2011 7:59 am
From: Lou

On Apr 7, 9:48 pm, "fabian_hart...@yahoo.ca" <fabian_hart...@yahoo.ca>
wrote:
> Amazing Barry and you are astonishingly right! A detailed calibration
> guide is presented here.
>
> http://bama.edebris.com/manuals/hickok/533%28a%29/
>
> However, while the 533A has a good parts list, only the transformer is
> specified being possible COTS. I think I read somewhere that the
> dynamic mutual conductance test was rather proprietary here? Well, I
> have roughed in these parts by only using a hand wound guesstimate.
> The original parts where in such bad shape that the number of windings
> could not be counted from the shape I received this unit in. BTW I
> used a micrometer to center in on the wire gauge which seemed rather
> sensible to me.
>
> One of the repairs I did was rather precise though. I sub'ed in a 5K
> pot given below and shunted it with a 7.5K resistor to correct for a
> solidly seized BIAS pot. 3K on the nose too... and it works just
> dandy.
>
> http://uk.farnell.com/colvern/clr400111s5k0k/potentiometer-5k/dp/1210...http://uk.farnell.com/ohmite/23j7k5e/resistor-wirewound-7-5kohm-3w-5/...
>
> These parts can also be imported through Newark. The lead time on the
> pot was rather insane though when they were not in stock
>
> I appreciate all your help guys. I would have thought this coil
> information would be easy to come by after all this time? While this
> unit is testing out triodes well (eg. 12AX7), it is not giving me
> impressive results on a tetrode (EL84/6BQ5) or a beam power tube
> (6L6). Something is fishy here because I otherwise believe at least
> the 6L6 is good. Sounds like a real cal problem here to me!!!!!
>
> Take care and many thanks.
>
> Fabe
> CBS, Newfoundland, CA
> fabian_hart...@yahoo.ca

Unfortunately that won't work for this pot. It was made with a special
taper and only an original will work.

== 2 of 4 ==
Date: Sat, Apr 9 2011 10:08 am
From: "fabian_hartery@yahoo.ca"

This what happens when you are too old to be new? I confess... I never
heard of spool resistors before but the concept makes sense to me in a
circuit. You see, I am of the age of select on test when 'only one
certain part' will do. To those souls out there... you understand the
process of dating before marriage.

I have restored TO's for the most part so I am in the breed of novice
to you guys. I guess it's back to the drawing board for me. I only see
four though. Two may be considered as doubles being wound on the same
phenolic core?

> Unfortunately that won't work for this pot. It was made with a special
> taper and only an original will work.

I do have this pot physically apart. It does seems like a linear taper
and the install says it electrically works fine. Accuracy? This maybe
a hung jury here based on these comments. The scale is linear but
given a wet towel snap on what I thought were inductors... anything is
possible.

Thanks for your input all.

== 3 of 4 ==
Date: Sat, Apr 9 2011 12:07 pm
From: Lou

On Apr 9, 1:08 pm, "fabian_hart...@yahoo.ca" <fabian_hart...@yahoo.ca>
wrote:
> This what happens when you are too old to be new? I confess... I never
> heard of spool resistors before but the concept makes sense to me in a
> circuit. You see, I am of the age of select on test when 'only one
> certain part' will do. To those souls out there... you understand the
> process of dating before marriage.
>
> I have restored TO's for the most part so I am in the breed of novice
> to you guys. I guess it's back to the drawing board for me. I only see
> four though. Two may be considered as doubles being wound on the same
> phenolic core?
>
> > Unfortunately that won't work for this pot. It was made with a special
> > taper and only an original will work.
>
> I do have this pot physically apart. It does seems like a linear taper
> and the install says it electrically works fine. Accuracy? This maybe
> a hung jury here based on these comments. The scale is linear but
> given a wet towel snap on what I thought were inductors... anything is
> possible.
>
> Thanks for your input all.

Well, if it's the same as a 533A then it wouldn't be a linear pot. Did
you go through the calibration procedure? Here is a typical case, the
DC voltage at 22 on the dial is only 3 volts.
http://web.archive.org/web/20060214215607/www.0wned.org/~hstraub/cal600.htm

== 4 of 4 ==
Date: Sat, Apr 9 2011 1:42 pm
From: "fabian_hartery@yahoo.ca"

Indeed this 3K value is totally non standard, hence the 7.5K shunt on
a 5K pot. If I can find a decent work around to repair this unit in
such precarious predicaments, I will post this information for free. I
always have in other places.

If I could post an internal postmortem pic of a dissected pot, you
would see pot appears to be an linear wire wound. All repairs do take
time and needs the advise of very many good friends.

Once again, thanks for helping out.

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

== 1 of 2 ==
Date: Sat, Apr 9 2011 11:24 am
From: Jim Yanik

"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

== 2 of 2 ==
Date: Sat, Apr 9 2011 11:51 am
From: "N_Cook"

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

No reply from owner on that yet.
Previous repair of this model, that owner had noticed the exhaust air was
hotter than normal and some time later it failed. Presumably spread over
some time rather than immediately prior to failure.
Someone else , in that situation, may have thought a fan problem and got it
changed.

==============================================================================
TOPIC: ALL THE HOTTEST VIDEOS CAMS AND WOMEN! JOIN FREE WITH THIS INVITATION!
YOU MAY EVEN WIN A TRIP TO VEGAS!
http://groups.google.com/group/sci.electronics.repair/t/1305ed14f431745b?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, Apr 9 2011 2:51 pm
From: jack daniels

http://www.fubar.com/join_w1.php?friend=3550556

==============================================================================
TOPIC: Recommendation for electronics forums?
http://groups.google.com/group/sci.electronics.repair/t/a2a97ca7806d8277?hl=en
==============================================================================

== 1 of 2 ==
Date: Sat, Apr 9 2011 4:11 pm
From: Wiebe Cazemier

Michael A. Terrell wrote:

>> >
>>
>> I've run out of bandwidth...
>
>
> You need a wider pipe...
>
>

That's what the plumber said...

== 2 of 2 ==
Date: Sat, Apr 9 2011 4:38 pm
From: "Michael A. Terrell"

Wiebe Cazemier wrote:
>
> Michael A. Terrell wrote:
>
> >> >
> >>
> >> I've run out of bandwidth...
> >
> >
> > You need a wider pipe...
> >
> >
>
> That's what the plumber said...

The 'Watergate plumbers' used tape.

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

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

== 1 of 4 ==
Date: Sat, Apr 9 2011 4:59 pm
From: "robb"

"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?
>

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

== 2 of 4 ==
Date: Sat, Apr 9 2011 5:29 pm
From: Jim Yanik

"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?

--
Jim Yanik
jyanik
at
localnet
dot com

== 3 of 4 ==
Date: Sat, Apr 9 2011 6:45 pm
From: clare@snyder.on.ca

On Sat, 09 Apr 2011 19:29:30 -0500, Jim Yanik <jyanik@abuse.gov>
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.

Or just another crappy transformer.
You do not just ASSume it is the transformer
>>>
>>
>> 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?

Transient overvoltages of less than 20% or there-abouts are unlikely
to blow the transformer primary of the furnace without manifesting
themselves elsewhere in the house - and over 20% would definitely
manifest themselves elsewhere.

== 4 of 4 ==
Date: Sat, Apr 9 2011 6:55 pm
From: Steve Turner

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.

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