sci.electronics.repair@googlegroups.com

Today's topics:

* Blew another damn transformer on my Trane XB80 - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/f883cd09a3a0b791?hl=en
* Repairing a USB 2.0 hub - 17 messages, 10 authors
http://groups.google.com/group/sci.electronics.repair/t/65c09081f950fabc?hl=en
* Behringer MDX2200 - 2 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/689edcf5c79b72ba?hl=en
* Free mobile to mobile - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/10bc6ae1579761f8?hl=en
* Ampeg BA600 - 115 bass amp combo, 6 months old, ROHS - 3 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/bc6178fc14fcf982?hl=en

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

== 1 of 2 ==
Date: Thurs, Apr 14 2011 9:58 pm
From: "Phil Allison"

"Don Klipstein is Full of Bull "

>
> Measure both AC and DC current through the secondary of the transformer.
> If putting a multimeter into DC current mode gets a reading around or over
> 50 milliamps (,05 amp), then something is wrong with the load.
> If DC secondary current is near or over 200 milliamps, then,
> "Houston, we have a problem"!

** Simply fitting that DAMN 1/4 amp s-b fuse will tell you immediately if
any such problem exists.

Significant DC in the secondary will causes high current to flow in the
primary ( due to core saturation) and BLOW the fuse !!!

If the 1/4 amp fuse holds and the tranny does not get stinking hot - all is
OK.

.... Phil

== 2 of 2 ==
Date: Fri, Apr 15 2011 7:51 am
From: "David"

>
> Measure both AC and DC current through the secondary of the
> transformer.
> If putting a multimeter into DC current mode gets a reading
> around or over
> 50 milliamps (,05 amp), then something is wrong with the load.
> If DC secondary current is near or over 200 milliamps, then,
> "Houston, we have a problem"!

I have been (sort of) following this conversation. I assume this
transformer also drives the contactor for the AC compressor.
Maybe there is a short in that circuit and the transformer
secondary gets shorted when the thermostat calls for cooling.

David

==============================================================================
TOPIC: Repairing a USB 2.0 hub
http://groups.google.com/group/sci.electronics.repair/t/65c09081f950fabc?hl=en
==============================================================================

== 1 of 17 ==
Date: Fri, Apr 15 2011 2:35 am
From: Man-wai Chang

What most likely kill the hub? Could it be repaired in general?

It's a Samsung PUH-7000NB.

--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and Farce be with you!
/( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.38.2
^ ^ 17:31:01 up 11:42 0 users load average: 1.07 1.07 1.05
不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA):
http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa

== 2 of 17 ==
Date: Fri, Apr 15 2011 3:02 am
From: "larry moe 'n curly"

Man-wai Chang wrote:
>
> What most likely kill the hub? Could it be repaired in general?
>
> It's a Samsung PUH-7000NB.

Zapped by static electricity, despite the 12,000 volt rating of the
chips?

A surge of current? I had an NEC-based USB 2.0 card lose 2 of its 4
ports because the tiny chip that was supposed to protect against
current surges was damaged by one.

I'd try resoldering the connectors, including the one for the cable.
Also there may be a blown fuse, which could look like a resistor or a
surface mount part.

Sometimes Windows just won't recognize a USB device, so try booting
the computer with an Ubuntu Linux CD.

== 3 of 17 ==
Date: Fri, Apr 15 2011 4:38 am
From: "William Sommerwerck"

Hubs are so cheap -- most are made in <ahem> China -- you might as well
replace it.

This might also be a good time to put a USB 3.0 card in the computer.

== 4 of 17 ==
Date: Fri, Apr 15 2011 5:05 am
From: Sylvia Else

On 15/04/2011 7:35 PM, Man-wai Chang wrote:
>
> What most likely kill the hub? Could it be repaired in general?
>
> It's a Samsung PUH-7000NB.
>

Presumably it's powered by a plugpack, which may have died, and be
replacable with something equivalent from your local electronics store.

Otherwise I'd expect it to be beyond salvage.

Sylvia.

== 5 of 17 ==
Date: Fri, Apr 15 2011 5:10 am
From: "trader4@optonline.net"

On Apr 15, 8:05 am, Sylvia Else <syl...@not.here.invalid> wrote:
> On 15/04/2011 7:35 PM, Man-wai Chang wrote:
>
>
>
> > What most likely kill the hub? Could it be repaired in general?
>
> > It's a Samsung PUH-7000NB.
>
> Presumably it's powered by a plugpack, which may have died, and be
> replacable with something equivalent from your local electronics store.
>
> Otherwise I'd expect it to be beyond salvage.
>
> Sylvia.

The ones I've seen are all powered off the USB connection. And given
the low cost of these not worth trying to fix, even if that were
possible, which I'd say is not
possible. Most likely it's the IC that's bad. Not much else there.

== 6 of 17 ==
Date: Fri, Apr 15 2011 5:20 am
From: Bob Villa

On Apr 15, 4:35 am, Man-wai Chang <toylet.toy...@gmail.com> wrote:
> What most likely kill the hub? Could it be repaired in general?
>
> It's a Samsung PUH-7000NB.
>
> --
> @~@ Might, Courage, Vision, SINCERITY.
> / v \ Simplicity is Beauty! May the Force and Farce be with you!
> /( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.38.2
> ^ ^ 17:31:01 up 11:42 0 users load average: 1.07 1.07 1.05
> 不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA):http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa

Considering your location...what would it cost you to replace?

== 7 of 17 ==
Date: Fri, Apr 15 2011 5:43 am
From: Man-wai Chang

> Considering your location...what would it cost you to replace?

Don't wanna waste it *IF* it could be repaired easily... :)

--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and Farce be with you!
/( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.38.2
^ ^ 20:51:01 up 15:02 0 users load average: 1.04 1.08 1.12
不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA):
http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa

== 8 of 17 ==
Date: Fri, Apr 15 2011 6:34 am
From: Sylvia Else

On 15/04/2011 10:43 PM, Man-wai Chang wrote:
>> Considering your location...what would it cost you to replace?
>
> Don't wanna waste it *IF* it could be repaired easily... :)
>

If you take it apart, you'll likely find that it consists of a single IC
and four USB sockets soldered to a board. There *might* be some capacitors.

There's not a lot there to repair.

You did try a different cable didn't you?

Sylvia.

== 9 of 17 ==
Date: Fri, Apr 15 2011 6:37 am
From: Tony Hwang

Man-wai Chang wrote:
>
> What most likely kill the hub? Could it be repaired in general?
>
> It's a Samsung PUH-7000NB.
>
Hii,
Is you time that cheap? New one may cost ~5 bucks.

== 10 of 17 ==
Date: Fri, Apr 15 2011 7:06 am
From: "Ian Field"

"Man-wai Chang" <toylet.toylet@gmail.com> wrote in message
news:io9f4c$bhv$2@dont-email.me...
>> Considering your location...what would it cost you to replace?
>
> Don't wanna waste it *IF* it could be repaired easily... :)

Do you have local recycling centers?

Bribe the site operator to let you have a few discarded hubs, you'll almost
guaranteed find a few are GWO - that way you can save several other people
wasting good hubs and have a couple spare.

== 11 of 17 ==
Date: Fri, Apr 15 2011 7:26 am
From: Jeff Liebermann

On Fri, 15 Apr 2011 17:35:40 +0800, Man-wai Chang
<toylet.toylet@gmail.com> wrote:

>What most likely kill the hub? Could it be repaired in general?
>It's a Samsung PUH-7000NB.

I haven't done any autopsies on USB hubs. I've never seen one with
just one blown port (unless it was mechanically damaged). What I have
seen are problems caused by:
1. Plugging in the wrong power supply.
2. Applying power to a powered hub from a miswired adapter.
3. Bad electrolytic caps.
4. Miserable ROHS soldering usually combined with flux all over the
PCB.
5. Probable package leakage on the chip.
6. Sometimes, the connectors are hand soldered, which leaves room for
some sloppy soldering.
7. Counterfeit ID code causing operating system to install the wrong
driver. Yes, you need a driver (USBhub.sys) to run a USB hub in
Windoze.

From what I've seen, the last is the most common followed closesly by
the bad soldering.

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

== 12 of 17 ==
Date: Fri, Apr 15 2011 7:31 am
From: Jeff Liebermann

On Fri, 15 Apr 2011 20:43:34 +0800, Man-wai Chang
<toylet.toylet@gmail.com> wrote:

>Don't wanna waste it *IF* it could be repaired easily... :)

Thank you. It's good to see someone else interested in keeping
electronics out of the landfill by repairing things, instead of just
replacing them.

Much can be learned by simply disassembling the hub. With an
inspection magnifying glass, look for bad soldering. Look for debris
between the IC leads. Twist the board looking for intermittents.
Check if 5VDC power is arriving at the chip. If the board looks
dirty, clean it.

Good luck.

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

== 13 of 17 ==
Date: Fri, Apr 15 2011 7:44 am
From: Jeff Liebermann

On Fri, 15 Apr 2011 04:38:14 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

>Hubs are so cheap -- most are made in <ahem> China -- you might as well
>replace it.
>
>This might also be a good time to put a USB 3.0 card in the computer.

Yes, if it has a PCI-E connector on the motherboard.

So, at what point do I recycle and replace, instead of repair? Well,
I allegedly charge $75/hr. Fixing even the most trivial device will
take about 30 minutes, most of which is cleaning up the mess on the
bench, and doing the inevitable paperwork. That makes the break even
point about $40. Anything worth less than $40 cannot be profitably
fixed. So, I'm suppose to toss mice, keyboards, numerous small PC
cards, disk drives less than 120GB, calculators, floppy drives,
speakers, wall warts, and USB hubs. No wonder I'm losing money and
have too much junk.

Extra credit: Calculate the cost of handling a zero cost repair.
That's a repair job that requires zero time and materials to fix, but
still requires, handling, paperwork, overhead, and possibly shipping.
The last time I did that, based on 200 working daze per year and an 8
hr day, I needed to charge about $100 for a zero cost fix.

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

== 14 of 17 ==
Date: Fri, Apr 15 2011 8:09 am
From: "William Sommerwerck"

> Extra credit: Calculate the cost of handling a zero cost repair.
> That's a repair job that requires zero time and materials to fix, but
> still requires, handling, paperwork, overhead, and possibly shipping.
> The last time I did that, based on 200 working daze per year and an 8
> hr day, I needed to charge about $100 for a zero cost fix.

We are caught in a dilemma... If stuff is made to a high quality standard,
then it won't break down very often, and won't need the repair. But -- to
some degree -- we need stuff to break down to encourage people to buy new
technology, which appears at an ever-faster rate.

== 15 of 17 ==
Date: Fri, Apr 15 2011 8:50 am
From: Smitty Two

In article <jolgq6hellbj1ug76n25hj2u7k8vchhooi@4ax.com>,
Jeff Liebermann <jeffl@cruzio.com> wrote:

> I allegedly charge $75/hr. Fixing even the most trivial device will
> take about 30 minutes, most of which is cleaning up the mess on the
> bench, and doing the inevitable paperwork. That makes the break even
> point about $40.

Paperwork, sure. But charging your customers to clean up the mess on
your bench? I wouldn't be advertising that ...

== 16 of 17 ==
Date: Fri, Apr 15 2011 10:15 am
From: Jeff Liebermann

On Fri, 15 Apr 2011 08:09:56 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

>> Extra credit: Calculate the cost of handling a zero cost repair.
>> That's a repair job that requires zero time and materials to fix, but
>> still requires, handling, paperwork, overhead, and possibly shipping.
>> The last time I did that, based on 200 working daze per year and an 8
>> hr day, I needed to charge about $100 for a zero cost fix.
>
>We are caught in a dilemma... If stuff is made to a high quality standard,
>then it won't break down very often, and won't need the repair. But -- to
>some degree -- we need stuff to break down to encourage people to buy new
>technology, which appears at an ever-faster rate.

The company motto is: "If this stuff worked, you wouldn't need me".
It's on all my stationary and business cards. Nobody has disagreed in
the last 30 years.

Designed obsolescence is one of the unpleasant side effects of CAD
(computah aided design). When it is possible to model the lifetime of
a product on a computah, one can easily design a product for a
specific life. For example, electrolytic capacitors can be selected
for a target lifetime based on temperature, ripple current, and
voltage rating. The life of power semiconductors can be estimated by
dissipation, temperatures, and the number of power (thermal) cycles.
If I offer a 1 year warranty, I would probably design for a 2-3 year
life. For a 5 year warranty, I would use better parts and run at
lower temperatures. Sometimes, I wonder if the bad-caps problem is
the result of manufacturers realizing that having products blow up
after some predictable time isn't a bad idea, and intentionally using
junk caps. (Everything is a conspiracy).

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

== 17 of 17 ==
Date: Fri, Apr 15 2011 10:31 am
From: Jeff Liebermann

On Fri, 15 Apr 2011 08:50:13 -0700, Smitty Two
<prestwhich@earthlink.net> wrote:

>In article <jolgq6hellbj1ug76n25hj2u7k8vchhooi@4ax.com>,
> Jeff Liebermann <jeffl@cruzio.com> wrote:
>
>> I allegedly charge $75/hr. Fixing even the most trivial device will
>> take about 30 minutes, most of which is cleaning up the mess on the
>> bench, and doing the inevitable paperwork. That makes the break even
>> point about $40.
>
>Paperwork, sure. But charging your customers to clean up the mess on
>your bench? I wouldn't be advertising that ...

I have yet to see any business from my usenet rants, so I'm not
worried. In theory, I should charge for literally everything. It
would not show up as a line item on the invoice, but would be part of
the hourly labor charge. The only labor I charge for separately are
travel time, expedite fees, waiting for the customer to get out of a
meeting, nobody home charge, and entertainment value[1].

The entertainment value discount requires a bit of explanation. I
will sometimes charge $1 million, on the invoice, for some effrontery
such as interrupting dinner, not following instructions, failing to
make a backup, or wasting my time. However, none of my customer are
expected to pay $1 million, so I balance out these charges with an
entertainment value discount of $1 million. I don't make any money on
this, but it does get their attention. Unfortunately, I don't do this
any more because my bookkeeper got irritated and thought that an
auditor might be equally irritated.

My guess(tm) is that I burn about 30 minutes per working day doing
nothing more than keeping my messy office and workbench from fatally
degenerating into an unusable mess. Someone has to pay for this waste
of time, and it's NOT going to be me.

[1] I've had only 1 bounced check in 30 years, so I don't bother with
the usual bounced check charge.

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

==============================================================================
TOPIC: Behringer MDX2200
http://groups.google.com/group/sci.electronics.repair/t/689edcf5c79b72ba?hl=en
==============================================================================

== 1 of 2 ==
Date: Fri, Apr 15 2011 4:29 am
From: Ron

Has anyone got a circuit diagram for a Behringer MDX2200 composer Pro
please?

C/dags for Alto ACL2Pro would probably be the same.

Ron

== 2 of 2 ==
Date: Fri, Apr 15 2011 4:48 am
From: Ron

On 15/04/2011 12:29, Ron wrote:
> Has anyone got a circuit diagram for a Behringer MDX2200 composer Pro
> please?
>
> C/dags for Alto ACL2Pro would probably be the same.
>
> Ron

Belay that, Alto circuits found

Ron

==============================================================================
TOPIC: Free mobile to mobile
http://groups.google.com/group/sci.electronics.repair/t/10bc6ae1579761f8?hl=en
==============================================================================

== 1 of 1 ==
Date: Fri, Apr 15 2011 7:56 am
From: Jeff Liebermann

On Wed, 13 Apr 2011 15:15:52 -0400, LSMFT <boleyn7@aol.com> wrote:

>What do cell companies mean by that? Are they saying mobile to land
>line is NOT free? Are they this crooked?

Perhaps an FAQ might help?
<http://wirelesssupport.verizon.com/faqs/Calling+Plans/faq_in_calling.html?t=4>
If you're not on Verizon, please disclose which vendor you're using.

"Mobile to Mobile Calling allows you to call any of our more than
80 million customers nationwide whenever you want, and talk as
long as you want without having to worry about using your minutes."

Note that it does NOT apply to pre-paid plans.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

==============================================================================
TOPIC: Ampeg BA600 - 115 bass amp combo, 6 months old, ROHS
http://groups.google.com/group/sci.electronics.repair/t/bc6178fc14fcf982?hl=en
==============================================================================

== 1 of 3 ==
Date: Fri, Apr 15 2011 8:11 am
From: boardjunkie1

On Apr 14, 7:51 am, "N_Cook" <dive...@tcp.co.uk> wrote:
> Cannot find that 20mm long screw lurking anywhere and extremely unlikely to
> jump through the grommeted lead ports into other section of amp and then
> fall out. Straight on , top and bottom x30 viewing of all TO220 soldering
> looks ok, surprisingly. Did find some nasty rework/fudge. 2 standard radial
> legged 10uF 50V, C19 and C54 soldered to standard SM pads, no thru board
> holes. Near it a SM cap, C61 measuring 15.2nF, had been soldered over
> conformal coating with one end not soldered to trace, as coating under.
> Owner has owned from new. 4x IRF450N power FET for 600W ?

Its prob'ly that class D junk....

== 2 of 3 ==
Date: Fri, Apr 15 2011 8:38 am
From: "N_Cook"

boardjunkie1 <boardjunkie1@gmail.com> wrote in message
news:bc9ee389-e2ca-4a1b-9335-29f5d700751d@w7g2000pre.googlegroups.com...
On Apr 14, 7:51 am, "N_Cook" <dive...@tcp.co.uk> wrote:
> Cannot find that 20mm long screw lurking anywhere and extremely unlikely
to
> jump through the grommeted lead ports into other section of amp and then
> fall out. Straight on , top and bottom x30 viewing of all TO220 soldering
> looks ok, surprisingly. Did find some nasty rework/fudge. 2 standard
radial
> legged 10uF 50V, C19 and C54 soldered to standard SM pads, no thru board
> holes. Near it a SM cap, C61 measuring 15.2nF, had been soldered over
> conformal coating with one end not soldered to trace, as coating under.
> Owner has owned from new. 4x IRF450N power FET for 600W ?

Its prob'ly that class D junk....

+++++++

Valid point, it does use 2x Int Rect IRS20955S, each one driving a pair of
FETs and
there is an IR application note out there for those being used in Class D.
That
would explain the socking great inductor/choke well out of scale with all
the SM on that board. Will check that inductor is at the output and try and
locate a clock line , presumably back to the SMPS.

== 3 of 3 ==
Date: Fri, Apr 15 2011 8:42 am
From: "N_Cook"

A generic problem with these will be mechanical noise from vibrating control
pots.
7 of the 9 were loose , in 6 months of non-commercial use. Not brass
cylinders over the bushes but are stop-ledged/ partial threaded leaving not
enough space for chassis thickness, nut and normal star washer so they used
thin plain washers. Luckily I have managed to fudge some thin star washers.

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