A good hot air solder rework station costs well upwards of $100. If you have just a few parts you need to reflow, you can use a common heat gun available at most hardware stores for around $30. These guns have all kinds of uses and are commonly used in construction to strip paint. They are usually around 1000W and some have temperature control. I use a Wagner HT1000, which has selectable 750F and 1000F modes.

How

Common solder melts around 500 degrees F, no problem for most of these guns. These guns push a lot of air and can blow away smaller components if they aren’t held down, so be careful! For hobbyists building boards with lots of small surface mount components, I’ve heard wonderful things about toasters converted into reflow ovens. The hot air gun trick is more for fixing bad connections or mounting or removing single components on an already populated board.

For mounting a single component, put a little solder paste on each of its PCB pads (assuming a surface mount component) and lay the component on the board. Hold the component down with a pair of tweezers or something else that won’t catch fire. Turn on your hot air gun and blow on the component until you see the solder paste get shiny. If the component is large, be sure to keep the stream of hot air moving to distribute the heat evenly. The hot air gun should not be on for more than a minute. Semiconductors are sensitive to heat and being too hot for too long will damage them.

Hot Air Saves The Day

A client recently came in with an HP laptop (HP Pavilion DV2700, PN: KQ654AV) behaving badly. He said that for the past few weeks it had been throwing up errors and bluescreening relating to the integrated graphics. Now the unit would not boot or post. A little research revealed an occasional problem with this model was a poorly soldered GPU chip on the motherboard. The chip was a ball grid array, making the pins difficult to get to and check. I disassembled the laptop down to the bare motherboard. With nothing to lose, I broke out my hot air gun, set it to 750 degrees F and waved it over the chip in question for roughly a minute. I let it cool for 10 minutes and reassembled it.

Presto, the unit booted without a hitch and our client was saved having to spend $300 on a new motherboard!

~James

This is the cloud you may have heard about, and while most of the things I just mentioned used to require bulky servers, noisy computer rooms and expensive software, they’re now just a few clicks away in your web browser.  Some will say this has eliminated a lot of the work that companies like ours used to thrive on, which is probably true, but for most small businesses these services might be otherwise unobtainable.

Point of Sale

We use MerchantOS, and could not be more impressed.  It tracks service tickets, customer information, processes credit cards, works with barcode scanners, receipt printers, and cash drawers (so we are told… we don’t accept cash).  Best of all, it runs on any computer with a web browser.  With a very small investment in hardware (a $100 used Dell Optiplex with Windows XP, a USB receipt printer, Barcode reader, and Credit card swiper) we have a fully functional point of sale system.  An equivalent standalone system would have cost thousands of dollars, and probably come with a fat service contract or lease.  We’ve already run through a real-world disaster recovery on this system.  The drive failed on the $100 used Dell (go figure!) while ringing up a customer.  We took two steps to the left to a workbench computer, fired up merchantOS, entered the card manually, and printed the receipt on our main network printer.  Downtime: 30 seconds.

E-Mail

Google Apps is the hosted email solution of choice, and it includes all the coolness of google docs, google wave, and everything else you can use your google account for.  Best of all, it’s free!  The biggest challenge for the average person would be the initial steps of verifying your domain by uploading a file and changing MX records (that’s where a good I.T. services company comes in)

I’ve mentioned in other posts how I still encounter a surprisingly high number of professionals that have verizon.net or yahoo.com email addresses on their business cards. Google Apps may be the easiest way to establish email addresses with your domain name.  Most hosts or registrars will bundle them in with your web hosting agreement, and then make you use some clunky web email client (usually inefficient) or pop your mail to a local mail client (very inefficient, very 5 years ago).

Again, disaster recovery instructions.

1. Curse the mortal remains of dead computer.

2. Load google apps on living computer.

3. No more disaster.

Backups

Hosted backups may not be the way to go if your company is processing massive architectural drawings, or generating tens of gigabytes of new data per day.  For most small businesses, we are saving email archives, proposals, agreements, pdf brochures, advertisements, etc.  Hosted backup is dirt cheap these days, and it works like a charm.  Mozy and Carbonite are two of the better known brands.  You sign up, install their software, tell it what to back up, then sit back and relax.  It will constantly backup new files as they appear in the selected folders, and send them off to the cloud.  Recovering them is just as easy, with an intuitive graphical interface, you just drag the file back to where it used to be (before your meddling coworkers accidentally overwrote it!) and all is well.

This is one hosted solution that we haven’t gone through the whole disaster recovery scenario for, but I am told it’s a snap…  Things to remember: The backup is being done over the internet, so it’s not going to be as fast as moving files locally.  If you have a lot to back up, the initial backup can take days.  After that, it’s just one or two at a time as you change them. Some people don’t like the notion that their precious data is out in the cloud… to me, better in the hands of a trusted company than on a hard-disk-turned-paperweight making scratchy-clicky noises.

We advise clients to run a hosted backup solution on their server, and emphasize that employees keep file storage to a minimum on their workstations.

That’s it for now… there’s a few more hosted solutions we’ll be talking about soon.

-Chris

To be continued…

We have the expertise to provide the highest quality tech services to businesses of all sizes.  Please contact us for more information about service agreements.

We recently found ourselves in a fight with SURBL.org to get a client’s domain off of one of their blacklists. This is a little bit of information about SURBLs and some resources to help others who have been wrongfully blacklisted.

What is a SURBL and How Does it Work?

A SURBL is a list of domains that appear in spam emails. When a user of some email client flags a message as spam, that message is sent off to a central service for analysis. The message’s originating server is noted and the contents are analyzed. If the same domain appears in enough spam emails, it is considered for addition to a SURBL blacklist.

Spam filters then reference the SURBL blacklists when deciding what to filter. If a domain that appears on a SURBL list appears in the body of an email, it might be flagged as spam or rejected entirely depending on the filter.

Personal Experience: Limited Recourse for Victims of a False Positive Listing

No algorithm is perfect and false positives can happen. What then?

Recently we had a client land on a SURBL blacklist. This client is an online business that runs the majority of its marketing through email. No notification was given to the client, their mass emails simply started bouncing, rejected as spam.

Needless to say, this was a huge problem.

SURBL has a web form available on their website at http://george.surbl.org/lookup.html through which you can request blacklist removal. Note about the form: There is a limit on the size of your entry in the ‘message body’ field, and though it is written on the form, if you submit with too much data in that field it will throw up a vague error:

Error in: sample message body entry! Please wait 20 seconds, go back
and correct it!

In our case, the listing was seriously damaging our client’s revenue and we decided to email whitelist@surbl.org as well. The listing was in clear violation of SURBL’s own published policy for many reasons and I was sure the listing was an error and could be quickly corrected.

SURBL’s listing policy was available at surbl.org/policy.html until very recently. I am posting a copy that I downloaded a few days ago here. I will also link to a version in web.archive.org as a loose corroboration. Link.

Though the response I received from the email address provided by surbl.org was timely, it was anonymous and its content revealed that either surbl.org had no regard for its published listing policy or they were not reading my emails. All the while our client was losing business.

This is a list of the most relevant quotes from their listing policy document that could help you if you’ve been wrongfully blacklisted (emphasis theirs):

• “Add domains that appear only in spam. Do not add any domains that appear in ham.”
• “Visit the site or at least check the google summary of it. If the site looks like a mostly legitimate site do not add it.“
• “Don’t add domains or IPs that are mentioned in legitimate newsletters, mailing lists or other similar mailings.”
• “Do not add domains of otherwise legitimate sites that have open (unconfirmed) subscriptions.”
• “Don’t list any mostly legitimate domains or IP addresses. The goal is not to “catch every spam.” The goal is to catch only domains that only appear in spams.”

After a long email thread of me repeating these points of their policy back at them, the client’s domain was removed from the blacklist and the policy document at surbl.org/policy.html was removed. These two events happened within 24 hours of each other. Maybe this was a coincidence, maybe not.

This is the entirety of surbl.org’s final response in our email thread, after the domain in question was removed from the blacklist. At no point did they acknowledge my references to their published policy, and in their final response they cede nothing.

“The domain has been automatically removed from the blacklist since the
unsolicited messages appear to have stopped. Please note that it can
be listed again in future if it appears in unsolicited messages.
Therefore it is urged that best practices be followed by all senders.”

We clearly cannot enforce the email practices of everyone on the internet. Which means the threat of blacklist lingers should any random spammer include our client’s domain in their email. This is unacceptable.

I am disturbed by SURBL for several reasons:

• Surbl.org is incredibly powerful. They themselves will deny having any power, since they just make blacklists publicly available, these blacklists are used by spam filters all across the internet. Being listed by surbl.org can seriously damage a business that relies on email.
• Surbl.org’s automatic tools for blacklist removal provide very little feedback. We received a confirmation that our web form was submitted, but nothing after that.
• Surbl.org’s blacklist removal request email address is anonymous. The replies I got from it were unhelpful. I don’t know if I was talking to one person or multiple. I was provided with no recourse beyond the email stonewalls.

The bottom line is SURBL.org has a lot of power and very little accountability. It is unlikely to become any more accountable as it is not legally responsible for the emails it blocks, it is simply a maintainer of the lists. It is powerful only because mail administrators across the internet use it to filter their emails.

A Plea to Mail Administrators Everywhere

Mail administrators should not reject messages outright because they are listed on a SURBL. Flag it as spam and deliver it, but don’t block it entirely. SURBL.org is not a transparent and accountable enough organization be given the de facto power to crush businesses.

99+% of the time, SURBLs are right to list a site, but the false positives do real damage to legitimate businesses. Now that they’re removed their published listing policy, victims of false positives are even more in the dark.

A Plea to SURBL.org

With great power comes great responsibility. You didn’t ask for it (in fact you recommend against it on your front page), but many mail servers block based on your lists. You have a lot of power, and the writer of your original listing policy (now removed from your site) seemed to realize that.

At the very least, inform domain owners when their sites are blacklisted and give them reasons. Supplying the domain owner with a copy of an unsolicited message that triggered the blacklisting would be incredibly helpful (when legal). Publish a listing policy and follow it. When answering emails, use your name or a consistent alias if you’re not comfortable with that, just don’t be completely anonymous. I couldn’t even tell if it was the same person responding every time.

Surbl.org is a black box full of black lists. A few simple changes would make a world of difference to the owners of domains falsely listed.

~James

This is a circuit I designed to generate a PWM signal for an RC servo given an analog voltage or high frequency PWM.  It has no microcontroller and can be built with one quad op-amp and passive components.

The op-amp I used in my implementation is a NJU7034D-ND, available from digikey, but any rail-to-rail quad op-amp will do.

Since the input stage has a low pass filter built in this circuit will accept a high frequency (>~5kHz) PWM as an input in addition to analog voltages.

PARTS:

• 1 Quad  Op-amp (I used NJU7034D-ND)
• 1 10K resistor
• 1 50K resistor (or 2 100K resistors in parallel)
• 7 100K resistors
• 1 0.47 uF capacitor
• 1 0.047 uF capacitor
• 1 10K potentiometer (can be subbed with 100K pot, makes calibration trickier)
• 1 100K potentiometer

HOW IT WORKS:

Linear Ramp Generator:

This is the beating heart of the system, literally.  This is an integrator and a hysteretic comparator hooked into a feedback loop that produces an oscillator with a linear ramp as output.

Low Pass Filter and Buffer:

This is simply a stiff RC low pass and an op-amp follower.  The RC low pass removes high frequency noise from the input.  The follower drives current to the calibration stage, which requires current that the RC low pass can’t deliver.

Calibration:

Every servo is a little different.  These two potentiometers map the full swing of the input voltage to a small range of voltages feeding into the comparator stage.  These have to be set properly for the servo to swing through its full range of motion.  For calibration instructions, see the CALIBRATION INSTRUCTIONS section.

Comparator:

This generates the PWM that is sent to the servo by holding its output high when the input from the calibration stage is higher than the linear ramp from the oscillator and vice versa.  The width of the pulse is directly related to the voltage coming in from the calibration stage.

CALIBRATION INSTRUCTIONS:

1. Connect power and ground.  Connect the servo you want to use to the output.  Connect the input of the circuit and set it to Vcc/2.  The servo should swing to a position, probably one of its physical stops.
2. Adjust the pot labeled ‘Amp Adjust’ all the way to one side so that its output is directly connected to the output of the ‘Bias Adjust’ pot.
3. Rotating the ‘Bias Adjust’ pot should rotate the servo.  Position the servo in the center of its range of motion.  The closer to the center the better.
4. Set the input of the circuit to 0V.  Now adjust the ‘Amp Adjust’ pot until the servo is hitting one of its hard stops.
5. Your circuit is calibrated.  The full range of input voltages from 0V-Vcc should now map linearly to the position of the servo from one hard stop to the other.

NOTES:

• If your PWM frequency to the servo is too low or too high, decrease or increase (respectively) the value of the capacitor labeled ‘freq adjust’.
• You can use 2 100K resistors in parallel as the 50K resistor, reducing the number of different resistor values you need from 3 to 2.
• You can use a 100K pot instead of a 10K pot, reducing the number of different pot values you need from 2 to 1.  This does make calibration trickier, just play with the pots until the range of motion is right.

Good luck!

~James

]]> http://www.charmcitynetworks.com/techblog/drive-an-rc-servo-from-analog-voltage/feed/ 0 http://www.charmcitynetworks.com/news/new-weekend-hours-11am-4pm/ http://www.charmcitynetworks.com/news/new-weekend-hours-11am-4pm/#comments Tue, 02 Mar 2010 16:45:07 +0000 Chris http://www.charmcitynetworks.com/?p=378 We are experimenting with weekend hours at our 1414 Key Highway shop, to provide better service to our residential customers.

We’ll be open this weekend from 11am to 4pm Saturday and Sunday.  These hours are subject to change as determine customer response.

Let us take a look at your computer!  Most repairs are just $99.

The Hard Disk password is stored not only on the logic controller, but also on the disk itself, and make the drive unusable without entering the password.

Under normal circumstances, people will password protect their windows logon, but their data is easily obtainable just by removing the hard drive and accessing it from another computer.  If you set the Hard Disk Password, this is not the case.

This customer happened to know their Hard Disk password, though they had inadvertently set it while going through tech support with someone else (I don’t know how it came to this, but we don’t ask questions, we just fix what people want us to fix.

The hard disk password was just an extra step to go through at startup… it wasn’t really a problem, just a nuisance.  She asked if we could remove it, which is usually an easy process by entering the BIOS.  To our delight, when we attempted to enter the BIOS, there was a password on that as well.

Again, the system started up just fine, so being locked out of the bios only becomes a problem when you need to get into the BIOS.  Most people never do, but it’s a fairly common thing around a computer shop.  The customer didn’t know her BIOS password, or that it had even been set.

If you start your googlehunt for BIOS password recovery, you will find everything from default backdoor passwords for various BIOS vendors, methods for resetting EEPROM memory by shorting out pins, removing the CMOS battery, and a hundred other “proven methods”, but not one thread that ends with “thanks, that worked!”

The bottom line is that the BIOS password is a security measure that is meant to protect your computer in the event that it is stolen.  Most never enable theirs at all, but if you do, make sure you put it somewhere secure and remember it.

In the case of our customer, after a few hundred tries we were able to guess the password, which was derived from the other passwords of hers that we already knew.  (That’s lesson number 2, don’t make your passwords to similar or people like us can guess them!)

-Chris

Some other reasons to do a clean install are:

• When transferring a computer from one owner to another.  This is to delete any personal data and make the computer “new again”.  This is a great option for parents who want to “hand-me-down” their computers to kids.
• When buying a new computer.  It’s a stretch, but some new computers are so bogged down with crapware from the manufacturer that customers just want a clean copy of Windows without popups from HP and Dell appearing every 5 minutes.  (It’s usually simple enough to disable or remove these programs individually, but some people just feel better with a clean install)
• When moving a computer to another user in an office.  Many employees like to make the computer “their own” and add every toolbar known to man, icon and sound tweaks, weatherbug, ding!, and a hundred other background apps.  Sometimes it’s easier and faster to do a clean install then to manually remove lots of programs.

The biggest causes for concern when doing a clean install are personal data and programs.  After the installation is complete, you’ll have a pristine copy of Windows with NO PROGRAMS, and NO DATA in the user’s My Documents, Desktop, and other personal folders.

Moving data from one installation of Windows to another is pretty straightforward.  When we do a clean install, we will generally backup the Documents and Settings folder in its entirety, storing it on one of our temporary file shares, and then restoring everything to the clean install.

The original inspiration for this blog entry was to emphasize that a clean install means you will lose ALL of your programs.  If all you use is Firefox, AIM, and BitTorrent, then your reinstallations are just a download away.  However, that expensive Microsoft Office Suite, Quickbooks, Games, and anything else that is not a part of Windows will NOT be there waiting for you after a clean install.  You will need the installation media and license keys that came with these applications, and you will need to run each installer separately.

We like to remind people that however their computer is running, it’s just a period between clean installs (like a warm period between ice ages).  You should always have installation media and get yourself int he mindset that you might have to rebuild your system tomorrow.

-Chris

This post will show you how to put a nearly dead laptop to good use: Make it a digital sign! You will need the following:

• A dying, old, or otherwise neglected laptop.
• A spare LCD display.
• Display cable, power cables, network cables.

First, we gut the laptop.  The screen was failing, the case was cracked, and it’s lugging around a dead battery, CD drive, and other parts we won’t need anymore.  We carefully remove the motherboard and discard the pile of screws, connectors, and plastic that’s leftover.

Next, re-seat the memory, the hard drive, and keyboard (normally we wouldn’t need a keyboard, but in this situation the power button is integrated into the keyboard).  Connect it to power and an external VGA display, and see if it boots.

Now we want to “wipe” the computer, or perform a clean installation of the operating system. This is a measure to make sure that the system doesn’t have any lingering junk from the previous user, and makes sure their data is GONE.

Once the new OS is up and running with all updates, assign the computer a static IP address, and make sure it can receive remote connections.  This computer has a licensed copy of Windows XP home, which does not support incoming remote desktop connections, so we went with RealVNC instead.

This Laptop also had wireless capabilities through a PC card, which eliminated the need for a network cable at the installation location.

After securing the LCD in our front window, we hooked everything up, powered on the computer, and VNC into it!  Now we can run a powerpoint slideshow, show a website , or cycle through images.

-Chris

Download the source here.

Download the windows executable here.

About:

One of the things I love about Gmail and Gchat is the logging. Every chat I make using Gchat is stored in my archives just like an email.

Unfortunately, though you can download and archive all your regular emails through Gmail’s POP interface using regular email backup tools, for some reason they don’t allow access to the chat logs this way.

Another thing I love about Gmail is the powerful search feature. Google writes search software well, ’nuff said. Unfortunately, you can’t really download emails through a standard POP-based program based on a Gmail search query (if there’s a tool that does this let me know!).

So I hacked together a small program that addresses all of these issues. GmailDownloader is a command line program through which you can:

• Log into your Gmail account
• Run a Gmail search
• Download the results (including chat logs!)

It runs on the Gmail web interface, so it bypasses the restrictions of POP access.  There are limitations to this program:

• If you download too many messages in too short a time, Gmail could detect this as unusual activity and lock you out of your account. I’ve successfully downloaded 1100 messages in one query without being locked out.  I’ve been locked out several times though when trying to download much more all at once.  The lock was released several hours after filling out the unlock captcha each time.
• Since the Gmail web interface is not a standard like POP, it could change at any time and make this program stop working.  Let me know if that happens and I’ll try to update it.

This program uses python, libgmail, a hack to libgmail from this awesome guy, mechanize, ClientForm and ClientCookie.  It is based on the libgmail example program ‘archive.py’.  The Windows executable was generated using py2exe.

Howto:

1. Download and unzip the executable (or the source code… it should run out of box if you satisfy its dependencies)
2. Run the executable.
   
   
   
3. Enter your login credentials.
   
   
   
4. Enter the search term for which you want to download the results.  You may want to experiment with searches in the Gmail web interface to get your search right, searches with many results take longer through the program take longer because the program runs through every page of the results before displaying anything.
5. The program will tell you the number of hits the search term brought and show you the first few results.  Confirm that this is what you want and hit ‘y’ and enter.  If it’s not what you want hit ‘n’ and enter and return to step 4.
   
   
   
6. Sit back and watch the emails roll in.  They will be dumped in a timestamped file in the same directory as the executable.
   
   
   

Enjoy!