sci.electronics.repair - 16 new messages in 5 topics - digest

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

sci.electronics.repair@googlegroups.com

Today's topics:

* Repairing a USB 2.0 hub - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/65c09081f950fabc?hl=en
* Blew another damn transformer on my Trane XB80 - 5 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/f883cd09a3a0b791?hl=en
* Electric mower battery - 7 messages, 7 authors
http://groups.google.com/group/sci.electronics.repair/t/a079faa9f877be2f?hl=en
* SEXY HOT GIRLS - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/87d23ed6b04c5fa7?hl=en
* Ampeg BA600 - 115 bass amp combo, 6 months old, ROHS - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/bc6178fc14fcf982?hl=en

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

== 1 of 2 ==
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

== 2 of 2 ==
Date: Fri, Apr 15 2011 11:48 am
From: "A. Baum" <50kiloton@net.not>

On Fri, 15 Apr 2011 17:35:40 +0800, Man-wai Chang wrote:

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

I have two 2.0 hubs I'll send you for free.

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

== 1 of 5 ==
Date: Fri, Apr 15 2011 11:49 am
From: Meat Plow

On Fri, 15 Apr 2011 14:04:11 +1000, Phil Allison wrote:

> "Tony Hwang"
>
>
>> This isunthinkab;e crazy idea but is the x-former being put in
>> backward?
>
> ** You must be totally schizo.

Ironic statement of the year candidate!

--
Live Fast Die Young, Leave A Pretty Corpse

== 2 of 5 ==
Date: Fri, Apr 15 2011 6:25 pm
From: Tony Miklos

On 4/14/2011 9:52 PM, Tony Hwang wrote:
>
>
> John Robertson wrote:
>> Steve Turner wrote:
>>> On 4/14/2011 2:54 PM, trader4@optonline.net wrote:
>>>> On Apr 14, 2:37 pm, Steve Turner<bbqbo...@swtacobell.net.invalid>
>>>> wrote:
>>>>> On 4/14/2011 12:06 PM, Smitty Two wrote:
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>> In article<io785f$t8...@dont-email.me>,
>>>>>> Steve Turner<bbqbo...@swtacobell.net.invalid> wrote:
>>>>>
>>>>>>> On 4/14/2011 12:41 AM, Smitty Two wrote:
>>>>>>>> In article<io5tea$b6...@dont-email.me>,
>>>>>>>> Steve Turner<bbqbo...@swtacobell.net.invalid> wrote:
>>>>>
>>>>>>>>> Just mentioned elsewhere that I have a new transformer on order
>>>>>>>>> and I
>>>>>>>>> can't
>>>>>>>>> really do anything until that arrives.
>>>>>
>>>>>>>> Sure you could. You could open up those other two transformers
>>>>>>>> and check
>>>>>>>> for an open thermal fuse. As I recall, you said neither of them
>>>>>>>> failed
>>>>>>>> in the same manner as the third. I still say you could have 3
>>>>>>>> distinct,
>>>>>>>> unrelated failures.
>>>>>
>>>>>>> The design of the first transformer makes it virtually impossible
>>>>>>> to open it
>>>>>>> up
>>>>>>> (remove the tape) without destroying the windings, (which I did)
>>>>>>> so there is
>>>>>>> no
>>>>>>> possibility of "repairing" it by installing a thermal fuse (as some
>>>>>>> suggested).
>>>>>>> There is evidence of burning at the input contactors just like
>>>>>>> there is on
>>>>>>> the third transformer (the one I took pictures of), but not quite
>>>>>>> as bad. I
>>>>>>> wouldn't call it an "explosion". There is no evidence of a thermal
>>>>>>> fuse.
>>>>>
>>>>>>> On the second transformer (a completely different brand and style)
>>>>>>> there was
>>>>>>> no
>>>>>>> evidence of burning. Again, it too was virtually impossible to
>>>>>>> open up with
>>>>>>> destroying it, so I didn't bother. However, because everyone has
>>>>>>> been so
>>>>>>> curious, I just did open it up (destroying it in the process) and
>>>>>>> there IS a
>>>>>>> thermal fuse on the input side; it is open, which explains why
>>>>>>> there is no
>>>>>>> burning.
>>>>>
>>>>>>> The third transformer is similar to the first in design (except
>>>>>>> for the extra
>>>>>>> 208 and 240 legs, which, per the instructions, I taped off and
>>>>>>> ignored). It
>>>>>>> is
>>>>>>> also virtually impossible to remove the tape to gain access to the
>>>>>>> primary
>>>>>>> windings without breaking through the wires, but I did, and again
>>>>>>> there is no
>>>>>>> evidence of a thermal fuse.
>>>>>
>>>>>>> I see no reason to conclude there are "3 distinct, unrelated
>>>>>>> failures".
>>>>>
>>>>>> Just because you can't fix something, it doesn't mean that failure
>>>>>> analysis is moot. I'd be doing serious exploratory surgery on all
>>>>>> 3 of
>>>>>> those transformers to try to understand what the hell happened.
>>>>>
>>>>>> I'm not "concluding" that there are 3 distinct unrelated failures,
>>>>>> I'm
>>>>>> suggesting it as a possibility.
>>>>>
>>>>>> The first, OEM transformer lasted 6 years. The second transformer
>>>>>> lasted
>>>>>> a few days, and by your own admission was a cheap knockoff that may
>>>>>> not
>>>>>> have been suited for your application at all.
>>>>>
>>>>> Others sorta concluded that for me. It was "Made in China" and has a
>>>>> bit of a
>>>>> different form factor, but that's the only evidence I have so say it
>>>>> might not
>>>>> have been "suitable". The transformer was similarly rated, and
>>>>> internally it
>>>>> doesn't look much different from the others, so I still have no real
>>>>> reason to
>>>>> believe it shouldn't have worked.
>>>>>
>>>>>> And the 3rd transformer may well have failed due to improper
>>>>>> wiring, or
>>>>>> a loose connection leading to excessive current leading to insulation
>>>>>> breakdown and a hard short, or as has been suggested repeatedly, a
>>>>>> fault
>>>>>> somewhere on the secondary side.
>>>>>
>>>>>> You've also agreed that there are wire color discrepancies and
>>>>>> several
>>>>>> respondents have opined that both halves of the primary should,
>>>>>> perhaps,
>>>>>> have been wired in parallel to accommodate the current requirements.
>>>>>
>>>>> I brought the old transformer to a local HVAC supply house, and the
>>>>> sales
>>>>> person (whom I perceived to be at least somewhat of an expert), gave
>>>>> me the
>>>>> third transformer as a suitable replacment. I chose to connect the
>>>>> transformer
>>>>> according to the instructions, and not according to any speculation
>>>>> "opined" in
>>>>> this group.
>>>>>
>>>>>> So, I too am curious, have you acquired some appropriate fuses,
>>>>>> figured
>>>>>> out how to monitor the current, and been able to schedule some time
>>>>>> off
>>>>>> from your other responsibilities so that you can actually work
>>>>>> through
>>>>>> this puzzle once the new xformer arrives? Are you equipped to bench
>>>>>> test
>>>>>> the new transformer to verify wiring color scheme before you
>>>>>> install it?
>>>>>> Do you know how to test that bridge rectifier? Seems like you have a
>>>>>> *lot* you could be doing while waiting for the UPS guy.
>>>>>
>>>>> I'm sorry you feel that I'm not "doing" anything or that I'm leaving
>>>>> you
>>>>> hanging, but I'll be making the repairs on my own schedule, as time
>>>>> permits.
>>>>> My own place of employ has me working 12 and 16 hour days, so I
>>>>> can't be
>>>>> everywhere at once. Plus, the weather here is pleasant and there's
>>>>> been no
>>>>> real need to run the air conditioner, and the house has two A/C
>>>>> units anyway so
>>>>> I'm in no hurry. I don't have the fuses or fuse holders yet, but the
>>>>> transformer isn't going in without them, so it will be taken care
>>>>> of. My
>>>>> common sense tells me that I really shouldn't *have* to test and
>>>>> verify the
>>>>> living daylights out of a new transformer, but I will most certainly
>>>>> get
>>>>> bitched out here if I don't, so yes, that will be done. I don't
>>>>> really recall
>>>>> the discussion about the bridge rectifier, but I'll look for it. I
>>>>> will be
>>>>> reviewing the entire discussion and make a checklist of all the
>>>>> steps I need to
>>>>> perform.
>>>>>
>>>>> Anything else?- Hide quoted text -
>>>>>
>>>>> - Show quoted text -
>>>>
>>>> After you put it in, measure the current and voltages in both
>>>> the primary and secondary. I'd measure them both with the
>>>> AC running and with it not running.
>>>>
>>>> Also, not sure if anyone ever covered this, but when the transformers
>>>> have failed have they all been in cooling mode, heating, or both?
>>>
>>> Yep, I'll do that. It's only in cooling mode that the transformers
>>> have failed, but I'm in Texas and we're long past the point where
>>> we'll be needing the heater for a while, so it's hard to say whether
>>> or not running the heat would also trigger the problem.
>>>
>>
>> Steve, As said before the best thing to do is to fuse both the primary
>> and secondary windings.
>>
>> If you have the recommended (original) transformer ratings handy that
>> should make it easy to figure out. For example, if the secondary (24VAC
>> as I recall) is rated at 1A, then the primary fuse is 1/5 of that
>> (24:120 - plus a fudge factor) suggesting that a 0.25A slo-blo should
>> last fairly well, and a 1A slo-blo on the secondary winding. If the
>> secondary is rated at 2A, then I'd go with a 0.5A slo-blo on the
>> primary, along with a 2A slo-blo on the secondary.
>>
>> Two fuse holders should be fine - one for the 120VAC side and one for
>> the 24VAC side.
>>
>> Hope this helps - at least it will reduce the cost of replacing
>> transformers!
>>
>> John :-#)#
>>
> Hi,
> Giving up for real solution? Just band aid fix? VChanging blown x-former
> to blown fuse? If I am having problem like that I'd fix it for sure
> dragging out all the tools I need. O'scope, clamp ammeter, DVM, etc.
> Maybe it is asked already but is happening all of sudden or been like
> that since the system got installed? Every symptom has cause.

It's the first step in determining if the problem is on the primary or
secondary. Ever hear of "divide and conquer"? Fuses will hopefully cut
the troubleshooting in half. That's the first step since he can't
monitor voltage and current for hours or days at a time.

== 3 of 5 ==
Date: Fri, Apr 15 2011 6:33 pm
From: Tony Miklos

On 4/14/2011 11:18 PM, Tony Hwang wrote:
>
>
> Phil Allison wrote:
>> <clare@snyder.on.ca>
>>
>>> The fuse is not being put forward as a solution - just to avoid
>>> blowing the transformer while finding the real problem.
>>
>>
>> ** The fuse will actually help you diagnose the problem.
>>
>> If the fuse opens soon as AC power is applied - the tranny is being
>> overloaded.
>>
>> If the fuse opens after some time because insulation in the primary
>> side has
>> failed, replacement fuses will open immediately despite the secondary
>> being
>> disconnected.
>>
>>
>>
>> ...Phil
>>
>>
>> Hmm,
> This isunthinkab;e crazy idea but is the x-former being put in backward?
> Rgwew i a such thing as current limiting x-formers. One thig I'd try
> then I'd put in proper Wattage low value resister to lower the primary
> voltage.

My word, you need sleep or something. Backwards would, oh never mind
you just proved you have no electronics knowledge.

== 4 of 5 ==
Date: Fri, Apr 15 2011 6:37 pm
From: "Phil Allison"

"Tony Miklos"

** FFS - learn to TRIM !!!!!!!!!!

== 5 of 5 ==
Date: Fri, Apr 15 2011 8:04 pm
From: Tony Miklos

OK ;-)

==============================================================================
TOPIC: Electric mower battery
http://groups.google.com/group/sci.electronics.repair/t/a079faa9f877be2f?hl=en
==============================================================================

== 1 of 7 ==
Date: Fri, Apr 15 2011 2:21 pm
From: "Guv Bob"

Got a dumb question.... I have an electric mower that uses two 12V lead acid batteries wired in series to give 24V. The batteries are marked 18Ah. Cost is around $100 for one 12v, or $140 for 2 in series, including shipping.

For the same money or less, I can get two std 12v car batteries and end up with more amp hours to boot, which would be good for a mower. Heavier to push around, but that's not a problem.

I don't know nuthin about how amp-hours work - reckon this would be a good idea? Anyone had experience with this kind of thing before?

Bob

== 2 of 7 ==
Date: Fri, Apr 15 2011 2:37 pm
From: Sjouke Burry

Guv Bob wrote:
> Got a dumb question.... I have an electric mower that uses two 12V lead acid batteries wired in series to give 24V. The batteries are marked 18Ah. Cost is around $100 for one 12v, or $140 for 2 in series, including shipping.
>
> For the same money or less, I can get two std 12v car batteries and end up with more amp hours to boot, which would be good for a mower. Heavier to push around, but that's not a problem.
>
> I don't know nuthin about how amp-hours work - reckon this would be a good idea? Anyone had experience with this kind of thing before?
>
> Bob
>
Car start batteries are not meant for repeated deep discharge.
It will damage them.
Google for deep discharge batteries.

== 3 of 7 ==
Date: Fri, Apr 15 2011 2:40 pm
From: news@jecarter.us

The batteries i your mower are sealed, so they don't leak acid when
the mower is tilted. Is there a sealed car battery that will fit the
space?

John

On Fri, 15 Apr 2011 13:21:33 -0800, "Guv Bob"
<guvbob2003@YAHOOOOOOOOEY.com> wrote:

>Got a dumb question.... I have an electric mower that uses two 12V lead acid batteries wired in series to give 24V. The batteries are marked 18Ah. Cost is around $100 for one 12v, or $140 for 2 in series, including shipping.
>
>For the same money or less, I can get two std 12v car batteries and end up with more amp hours to boot, which would be good for a mower. Heavier to push around, but that's not a problem.
>
>I don't know nuthin about how amp-hours work - reckon this would be a good idea? Anyone had experience with this kind of thing before?
>
>Bob

== 4 of 7 ==
Date: Fri, Apr 15 2011 4:24 pm
From: Archon

On 4/15/2011 5:21 PM, Guv Bob wrote:
> Got a dumb question.... I have an electric mower that uses two 12V lead acid batteries wired in series to give 24V. The batteries are marked 18Ah. Cost is around $100 for one 12v, or $140 for 2 in series, including shipping.
>
> For the same money or less, I can get two std 12v car batteries and end up with more amp hours to boot, which would be good for a mower. Heavier to push around, but that's not a problem.
>
> I don't know nuthin about how amp-hours work - reckon this would be a good idea? Anyone had experience with this kind of thing before?
>
> Bob
>
12v 18Ah SLA Ebay 300539898701 about $35 each inc s/h
not my auction, no affiliation with the seller.
JC

== 5 of 7 ==
Date: Fri, Apr 15 2011 5:18 pm
From: Jim Yanik

news@jecarter.us wrote in
news:jnehq6pvlutdnm1gui2087j4gf2vifdra7@4ax.com:

> The batteries i your mower are sealed, so they don't leak acid when
> the mower is tilted. Is there a sealed car battery that will fit the
> space?
>
> John
>
>
> On Fri, 15 Apr 2011 13:21:33 -0800, "Guv Bob"
><guvbob2003@YAHOOOOOOOOEY.com> wrote:
>
>>Got a dumb question.... I have an electric mower that uses two 12V
>>lead acid batteries wired in series to give 24V. The batteries are
>>marked 18Ah. Cost is around $100 for one 12v, or $140 for 2 in
>>series, including shipping.

from GOOGLE;
Amazon has UB12180 12/18AH SLA batteries for $30.Don't know how much for
shipping.
another place has the same for $50 including shipping.

you can probably get similar pricing from local battery supplies,since
those are common in mowers,"Jump starters",and kids scooters.But you will
pay sales tax.
>>
>>For the same money or less, I can get two std 12v car batteries and
>>end up with more amp hours to boot, which would be good for a mower.
>>Heavier to push around, but that's not a problem.
>>
>>I don't know nuthin about how amp-hours work - reckon this would be a
>>good idea? Anyone had experience with this kind of thing before?
>>
>>Bob
>

car batteries are not designed for the type of discharge that lawn mowers
perform.Car batteries give high currents for a brief period,then get
recharged immediately,while the deep discharge batteries in mowers output a
moderate current for a long period.

Use the same replacement batteries.

--
Jim Yanik
jyanik
at
localnet
dot com

== 6 of 7 ==
Date: Fri, Apr 15 2011 6:28 pm
From: LSMFT

It should work fine. If car batteries are too big, try ATV/Lawn tractor
batteries although the bigger the better. Try not to drain them
completely flat and they should recharge just fine. The plug in
lawnmower might be better for you. I prefer gasoline.

--
If your doctor isn't taking new patients,
he ain't curing any of them.

== 7 of 7 ==
Date: Fri, Apr 15 2011 8:08 pm
From: "Michael A. Terrell"

Guv Bob wrote:
>
> Got a dumb question.... I have an electric mower that uses two 12V lead acid batteries wired in series to give 24V. The batteries are marked 18Ah. Cost is around $100 for one 12v, or $140 for 2 in series, including shipping.
>
> For the same money or less, I can get two std 12v car batteries and end up with more amp hours to boot, which would be good for a mower. Heavier to push around, but that's not a problem.
>
> I don't know nuthin about how amp-hours work - reckon this would be a good idea? Anyone had experience with this kind of thing before?

Harbor freight sells their jump packs for about $40 when they are on
sale. (Most of the time)

<http://www.harborfreight.com/automotive-motorcycle/battery/12-volt-jump-start-and-power-supply-38391.html>

I bought several for the batteries, since that was cheaper than the
batteries + shipping.

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

==============================================================================
TOPIC: SEXY HOT GIRLS
http://groups.google.com/group/sci.electronics.repair/t/87d23ed6b04c5fa7?hl=en
==============================================================================

== 1 of 1 ==
Date: Fri, Apr 15 2011 9:12 pm
From: SAILAJA LOVES U

==============================================================================
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 1 ==
Date: Sat, Apr 16 2011 12:48 am
From: "N_Cook"

Downloaded the datasheet and that IRS is for pwm/D class operation. Input
,pin3, goes back via Q9 to 74C04 buffer so digital.
That large L , in a 53x53x24mm case is connected between the common points
of both FET pairs and across the speaker (with an ohm or so somewhere not
ascertained). That L1 measures 4K ohms , inductance not possible on LCR
meter as a yellow block HV polyprop? cap , label obscured by L1, is also
across it but measures 1.15uF apparently on LCR meter.

Speaker lead has a 4 pole connector for disassembly , 2 poles per wire, but
same size connector on the pcb only 1 pole each. Worse than that the commons
traces going to L1 are 3mm wide with solder run thickening for the current
but the 2 output traces going to the speaker are 1.5 mm wide and plain
tinned. So assuming 300 watt for a second into 4 ohm then about 9 amps.
From the Enumber in ul.com, it is 1 oz board and using
http://www.pcbco.com.au/tracecalc.html
for 60 mil track and 9 amps for plain copper then 100 deg C rise , don't
know how much the tinning coat would change things , say an unlikely
doubling to 2 oz in effect, then 32 deg C rise , unacceptable ?

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