Thursday, April 30, 2009

VP181 Viewsonic LCD monitor repair

Here are some Viewsonic VP181 LCD monitor repair tips. I picked up a lot of LCD screens on EBay a while back and one of the last ones to be fixed is a VP181. It did not work because it would not light up the screen. The problem was most likely the inverter. However this monitor takes a 6 output inverter that lists for around $100. After some digging around I found a universal 6 output inverter that sells for less than 1/3 of that price.

Also here is a strange point about the VP181. It will not work without the base. So if you apply power to the screen and expect it to work, it will not. Also it has an unusually large AC adapter jack. I cut into the power cable between the base and the screen and spliced in power from a universal 12 volt 5 amp AC adapter. The universal adapters are available for about $10 each on EBay.

Universal 6 output inverter to Viewsonic VG 181 LCD Screen adapter.
Wire colors are from the cable from the control board to the inverter board.

Purple - Enable to middle wire to inverter
Blue - Unknown
Green - Gnd to Blue striped wire to inverter
Yellow - Gnd
Orange - Gnd
Red - +12V to wire furthest from ground to inverter
Brown - +12V
Black - +12V

The replacement inverter only lines up with one of the mounting screws, the one in the middle. The ends of the inverter are held in place by rubber stoppers. The wires to the CCFL tubes need to be unhooked and stretched a little. The order they plug into the inverter may have to be changed as well.

Friday, April 24, 2009

2400 Volt Can Crusher

The promised and much awaited 2400 volt power supply went through its first test run. The video is up on YouTube. It was a little disappointing it takes 4 firings to get the can into the hourglass shape. One of the capacitors might be bad. Anyway a Microwave Oven Transformer charges six 400 volt capacitors through a 500 ohm 250 watt resistor. The idea is to electronically crush the soda can into an hourglass shape.

The switch to connect the capacitors to the coil is made of two 1/2 inch bolts meeting head to head. They need to be filed off after every 5 to 10 operations as they will melt together if not cleaned up. A piece of plastic holds them apart and is removed by pulling on a string.

There are 6 turns of 10 gage wire wrapped around the soda can. The last time I tried this was at 800 volts and I used about 10 turns of 14 gage wire. The wire was turned into a jumbled mess and every solder connection melted. So this time everything is connected with two 10 gage wires in parallel and fastened together with bolts. The coil has been rewound into 2 layers totaling 5 turns and is now more effective at crushing the soda can.

Below is the updated schematic. The resistors are matched with a volt ohm meter for 10:1 correspondence so that the built in volt meter will read exactly 1/10 of the output voltage. The meter runs on a 9 volt battery, I could have used the filament winding of the MOT but the 9 volt battery was easier.

There are 2 Youtube videos;
Then it was improved with better results;
I have been thinking about the future of can crushing. It is hard to balance this many electrolytic capacitors when they are wired up in series. Some do not completely discharge and some reverse charge. The solution would be to use higher voltage capacitors. One easy source is microwave oven capacitors but they are only 1 uF each. So now I am searching for some capacitors in the range of 10 to 100 uF at 5 to 6 KV. I hope to find something at the Ham fests this summer.

Thursday, April 23, 2009

Dodge Caravan air deflector repair

Sometimes it just makes sense to fix things yourself. The air deflector on my van was scraping on the road whenever I hit a bump. It would really catch on parking lot blocks and curbs. So I parked it on some bricks and crawled under there to see what was the matter. First there is a plastic piece that is missing. Second the bolts that are there do not line up to catch the holes in the plastic. To fix it I used two large three inch washers, two about six inch pieces of strap, and two 1/4 inch bolts with nuts and washers.
In the first picture you can see the over all view with the two white metal straps. Notice how rusty the oil pan is. It could have used something to hold up the center of the air deflector as well. I had used a plastic wire tie there at one point to hold it up and it has ripped a slot through the plastic over time.

In this close up picture you can see one of the straps and one of the 3 inch washers. To be honest the washer should have been made of a heavier metal and it should have had a smaller center hole. I was just using whatever I had already sitting around.

Tuesday, April 14, 2009

VE170 LCD monitor repair of inverter

If you would like to donate your old LCD monitor and see how it was fixed here on my blog, please contact me. The same goes for P3 or newer laptops. I love to recycle these and donate them to pastors and missionaries.

Two of the LCD monitors that I purchased really cheaply on EBay had bad inverters. I had never successfully fixed a bad inverter before, even after trying to fix them a lot. But this time I was in luck, every one of the bad inverters had a little silver 22 uF capacitor that was bad. Replace that capacitor and the inverter works! You can optionally replace the power supply filter cap, it was bad but did not appear to affect the monitor. Below is a picture of the inverters with the capacitors replaced. You can use a 10 uF at 25 volts to replace the bad capacitor.

Next I needed some 12 volt 4 or 5 amp power supplies for these monitors. They sell for around $25 on EBay. That is unless you look for universal LCD monitor AC adapters. They sell for $10, and the text says they support the VE170 screens!

Monday, April 13, 2009

Intro to the Basic Stamp - 7 segment displays

Interfacing the Basic Stamp to dual 7 Segment Displays
This requires two seven segment common anode displays and 16 x 470 ohm resistors.

Connections to the LA-6460 - Looking Down at the display from Above.

G F + A B

E D + C DP

It is wired up so that D0 goes to A, D1 goes to B, D2 goes to Dp, D3 goes to C, etc. Each segment connection is made with a 470 ohm resistor. The + goes to 5 volts to power up the display.

The first problem is to output the 8 bits to the I/O pins to light up the LED segments. For this we use the lookup command to find and then output a set of binary bits that set a 1 or 0 to each associated bit or segment position. A 0 will light up a segment a 1 will leave it unlit. However this outputs bit 7 first, on the left, and bit 0 last, on the right. So the 1's and 0's have to be encoded in the reverse of their segment order.

The 'OUT' command reverses the order so the segments order in software is;
F G E D C Dp B A - Segment order.
It could also be that I have them wired backwards?

Bit Segment
7 - F
6 - G
5 - E
4 - D
3 - C
2 - Dp
1 - B
0 - A

See it working on YouTube;
Here is the code to make it all work. Note that percent, zero, zero is missing from some of the lines of code. Somehow blogger takes it out every time.
' {$STAMP BS2e}
delay CON 1000
upnum VAR Nib
lownum VAR Nib
DIRH = %11111111
DIRL = %11111111
n0 CON %01000100
n1 CON %11110101
n2 CON %10001100
n3 CON %10100100
n4 CON 110101
n5 CON 100110
n6 CON 000110
n7 CON %11110100
n8 CON 000100
n9 CON 100100

FOR upnum = 0 TO 9
LOOKUP upnum, [n0,n1,n2,n3,n4,n5,n6,n7,n8,n9], OUTL
FOR lownum = 0 TO 9
LOOKUP lownum, [n0,n1,n2,n3,n4,n5,n6,n7,n8,n9], OUTH
PAUSE delay

Saturday, April 11, 2009

Intro to the Basic Stamp

My interest in the Basic Stamp started as an upgrade for several of my inventions. Many years ago I designed several devices and several of them were published in electronics magazines. They included things like an LED sign, an O'Scope, an Audio analyzer, a video grabber, an energy management system, and even a heart monitor. The problem is that all of them used the printer port to connect to the computer and all of them used GW Basic as their programming language. However finding a laptop that has a printer port or that could run the old version of GW Basic is nearly impossible these days.

I had played with an 8052 Basic processor as a possible solution but even that processor is out of date. I also had some 68HC11's laying around but they are programmed in Assembler and I wanted this to be something an average person could work with. So I concluded that the best option available is the Basic Stamp.

Once I decided on the Basic Stamp I went on EBay and started looking for a simple proto board and processor that is cheap. On eBay I found a cheap circuit board from called the Proto 24. I bought the blank version because I have lots of parts around to populate it with and I like to solder things together. I did not have a right angle 9 pin serial plug so I cut the plug off a serial cable and glued it onto the board. Then I soldered the wires into the correct holes.

When I first started working with the Proto 24 board and a Basic Stamp 2e processor I could not even do something as simple as getting an LED to turn on and off. It turns out that this circuit board has the pins labeled in reverse order! Output 0 is on the left where it says C7 and output 15 is on the right where it says A0.

Proto 24 board web site -

Steps to get the Basic Stamp up and running;
1. Download and Install the Basic Stamp Editor program.
2. Plug in the AC adapter, the LED should light.
3. Connect the serial cable, must be a 1:1 cable not a null modem.
4. Start the 'Basic Stamp Editor' communication program.
5. Hit F6 to find the Basic Stamps serial port.
(It should say 'COM1 Basic Stamp 2e')
6. Select 'directive' 'stamp' and 'BS2e' to identify the stamp chip.
7. Press enter and then type 'debug "I am here"'
8. Select 'Run', 'Run'
A window should pop up and say 'I am here'
That's it, you are now up and running!

In the next article I will tell you how to set up a 2 digit counter using 7 segment LED displays. Then I hope to show you how to set up an 8 x 8 LED array.

Friday, April 10, 2009

VE175 LCD monitor repair

I sold something on eBay and had some money to spare. I also needed a LCD monitor for a friend so I placed a minimum bid on some LCD screens that needed repair. To my surprise I won several auctions! So hopefully I will be posting repair tips for several of these monitors over the next few days.

Up first is a Viewsonic VE175. The picture comes on for a second and then goes out. I opened up the monitor expecting that the power supply had bad caps in it but that was not the case. The bad caps were on the control board. There are 5 of them that needed to be replaced. They are the bigger ones that are bulging at the top. One of them even has stuff oozing out of it. Most of them can be replaced with 1000 uF 16 volt capacitors, you will need some 470 uF 25 volt caps too. You can almost always use a slightly larger value or higher voltage capacitor.

If you have never replaced motherboard or power supply capacitors before you will need to know some tricks. First you need to add fresh solder to get the heat to travel through the board to remove the old capacitor. Second use a tiny screwdriver to clean out the holes for the new capacitor.

Saturday, April 4, 2009

Write protecting USB memory sticks

Have you ever plugged in your USB memory stick and then get a warning message saying that a virus has been found on it? The anti virus program will remove the virus but how did it get there to begin with? The signs that your memory stick is infected may include an executable found in each directory on the memory stick. For instance a utilities directory might have a file called utilities.exe that is the virus. Also look for a hidden system directory in the root directory called zpharaoh. The problem with virus' on memory sticks is so serious that the Pentagon recently banned all USB memory sticks.

After a while I found the infected computer that had put the virus onto my memory stick. Every time I plug in the memory stick the virus infected it and disabled the anti virus program on the memory stick from being installed in order to fix the computer. There are two possible solutions, one is to boot from a CD and then reformat the hard drive, just reinstalling Windows will not remove the virus. The other solution is to remove the hard drive and set it up as an external USB drive with an IDE to USB adapter. Then you can either scan the drive and remove the virus or you can at least copy all of your important files off the drive before you reformat it. Below is a picture from scanning the hard drive as an external USB device. Make sure your anti virus software is up to date before doing this or your computer will be instantly infected.

If you remove the virus from the drive with an anti virus program make sure that the virus infected files are actually deleted. Some anti virus programs will see that they are critical system files and will not remove them unless you tell it to remove them. Once the hard drive is cleaned you can reinstall it into the computer and then you will need to reinstall Windows, but be sure to do a clean install of Windows or there will still be several programs that will not work such as notepad, paint, etc.

Another solution would be to write protect the USB memory stick, right? Well doing that is not as simple as you might think. The computer has to be able to send things to the memory stick in order for the memory stick to know what you are looking for on it. So you would have to write protect the memory on the memory stick but you can not disable writing to the memory sticks controller.

My brother suggested that I try using camera memory sticks, because some of them have write protection built into them. First I tried using a SD memory card and a USB adapter. However thought matter what position the write protect switch was in the memory can always be written to. As it turns out the SD card depends on the device it is plugged into to prevent writing to the memory. No USB adapter bothers to read the status of the SD cards write protect switch and so they allow you to write to the SD cards memory either way. Most of the newer SD cards do not even have the write protection switch on them.

Next I tried using a Sony memory stick. I happened to have one of them in my older Sony camera. It worked perfectly allowing you to read from the memory stick but when you try to write to it a message comes up saying that it is write protected. However like the newer SD cards the newer Sony memory cards no longer have a write protection switch on them. The older memory sticks are called 'Memory stick' and 'memory stick pro' and they have the write protect switch but not the newer ones that are called 'memory stick pro duo'.

The size of the ones with the write protect switch goes up to 512 MB and there are some 1GB memory sticks with a write protect switch but not all of them. Many of the imitation Sony memory sticks also have the write protect switch as well. However 512 MB is usually enough memory to put all of the necessary utilities on it. The older Sony memory sticks do not fit inside of the USB adapter, they stick out of the end and prevent putting the cover back on.

I would recommend that you have the following programs on the protected memory stick;
AVG - Free anti virus program
Startup - Removes programs that are starting automatically
MRT - Microsoft malicious software removal tool program
Stinger - McAfee's free program to scan and remove virus's

Friday, April 3, 2009

Dodge Caravan/Voyager Strut tower repair

I know that I do not blog much about car problems. There was a day when I fixed most of my own car problems. However this repair was a bit over my head. My drivers side strut mount had rotted out as you can see in the picture below. If it is not fixed the strut can come up through and the car will then fall down and be totally disabled.

This problem would send most cars to the junk yard. But I thought I would research the problem first. It turns out that most places will charge you around $1000 and they will weld in a replacement strut mount from another car.

Well it turns out that if you will go to the car dealer, they have what is essentially an upgrade to the strut mount. I got it done on my van for $450 and taxes. There is a place in Ohio that says they will do it for $300. However I did not think my car could be driven that far.

This is what the repair looks like. They did both sides. As I understand it, the repair piece is also glued in place besides the several bolts that you can see.
Here is a link to the guy who fixes them in Ohio for $300. He uses rivets instead of bolts and that should be a better fix IMO.