Parts and Safety

First off I'm assuming you have a multimeter, if not you can get one for around $15 that will do. A service manual is handy to help you locate some of the components I'll be talking about. Service manuals can ordered from http://www.servicemanuals.net/

Parts can be ordered from Matt Electronics.com or Electronix.com. Call or e-mail them for a free catalog.

Infared detectors for testing remote controls can be found at MCMElectronics.com.

Some parts are mounted on heatsinks and will have a white grease applied to their backside. This is heat sink grease, and you can buy it from Radio Shack.

For testing electroyltic capacitors I recommend the ESR tester model no. mul-3333, it's very easy to use and lists for $49.95 at Matt Electronics.com.

It's easy to get distracted when working on TVs, someone walks into the room or the phone rings and you walk away and forget the set is plugged in. Later you return and you are so busy thinking about the problem that you don't check the power cord. This is a dangerous thing to do. Don't let this happen to you! ask a friend to help with the repairs and keep watch that the power is always removed before you reach inside your TV set to make repairs.

Caution: Be careful when working around an open TV, should something fall and hit the picture tube it could break and impode. Never leave an open TV sitting on your work bench, if you are leaving for the day replace the cover. Don't get lazy and leave it open. One time I left a TV sitting on the shop floor open and it tipped over and the glass neck of the picture tube broke. The owner of the shop was very unhappy with me that day.

Soldering

I also assume you have good soldering skills if not don't attempt to repair your set.

Here's two sites I found that will help you learn to solder.

• http://www.epemag.wimborne.co.uk/solderpix.htm
• http://www.epemag.wimborne.co.uk/desolderpix.htm

There are two methods of desoldering, one uses copper braid and the other a solder sucker. If you're using copper braid brush a little flux on it before you use it.

Power problems, set won't turn on

First check to be sure your remote control is working. If your set has a power button on the front panel, then try turning on your set that way. Next, test your remote control using a infared detector. If it's not working change the batteries.

If you set is still not working you will need to remove the back cover and start troubleshooting. After removing the screws gently pull the cover off; never pull hard because you could damage something. If it doesn't come off all the way, shine a flashlight down inside to see what's holding it.

Caution: The main fuse carries 110 volts AC and can hurt you so be sure the set is unplugged. If you're not sure what the fuse looks like go to this website: http://www.electronix.com/catalog/default.php/cPath/253

To check the fuse put your meter on diode check and then place the probes across the fuse. A good fuse will cause the meter to beep. Replace the fuse if it's bad and then plug the set back in while watching the fuse. Turn the power switch on. If the new fuse blows you have a short somewhere.

A common part that often fails in the power supply is the regulator. Take a look at the following wesite to see a picture of what a voltage regulator looks like: http://www.electronix.com/catalog/product_info.php/products_id/9598.

Varistors

A shorted varistor can cause the fuse to blow. These are found in Magnavox, Sony and other sets. To locate this part you will probably need a service manual. They usually mounted on the board close to the ac fuse.

Go to the following sites below to see some pictures of varistors and to learn more about them:

• http://en.wikipedia.org/wiki/Varistor
• http://www.electronic-repair-kits.com/Resistors.htm
• http://www.gallawa.com/microtech/varistor.html

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How to Remove the Chassis

1. To remove the chassis you will probably have to remove the large, red high-voltage wire that goes to the picture tube. Follow the instructions carefully, because the tube has a high voltage charge on it.

2. Look closely at the back of the picture tube and you will see a silver metal strap that's fastened to the outside of the picture tube. Next, take a clip cord (a wire with a metal clip on each end) and fasten one clip to the bare metal strap on the tube. The metal strap will be tight because it's held by a spring, so you may have to pull and lift up it up to fasten your clip to it. Next, fasten the other end of your clip cord to the bare metal shaft of a long flat blade screwdriver.

   Caution: in the next step we will discharge the picture tube, so be sure to hold the screwdriver by it's plastic handle and to keep your fingers well away from the metal shaft of the screwdriver.

3. Discharge the tube by gently pushing the blade of the screwdriver under the large rubber cap and touching the metal spring that's inside the center of the cap. If you lift up the cap with the end of the screwdriver you should be able to see it. Touch the end of the screwdriver to the metal clip, remove it, and wait about a minute. Touch it again to be sure the picture tube is fully discharged. After you discharge the tube use the screwdriver to push on the metal spring and pull to remove the cap.
4. When you finish your repairs don't forget to reinstall the cap and make sure it is tight by pulling on it. Should the cap come loose, it could cause some expensive damage to your set.

Inspecting the chassis

First turn the chassis over and look for bad solder connections, as this is a common problem today. Don't skip this part, take you time and carefully look at all solder connections. The first site below shows some bad solder connections.
The second site shows what a good solder connection looks like. I would suggest you use a 25-30 watt iron when soldering on the chassis.

1. http://resnet.uoregon.edu/~gurney_j/kenwoodrepair/img_0462.jpg
2. http://resnet.uoregon.edu/~gurney_j/kenwoodrepair/img_0474.jpg

Electrolytic Capacitors

Go to these two websites below to read about bad electroyltic caps:

1. http://en.wikipedia.org/wiki/Capacitor_plague
2. http://badcaps.net/ (Click on the pictures to enlarge them.)

The (-) markings on the side of these capacitors is the negitive leg, so be sure to mount the new ones the same way. Electrolytic Capacitors often leak, so take a close look at the underside of any caps you remove. If you see black sticky stuff oozing out, then it's bad and should be replaced. Sometimes you will look at a capacitor and think it's leaking, but it might just be glue. Glue is sometimes applied to large capacitors at the factory so if you desolder one and it won't come out you may have to pry on it with a small screwdriver.

You will also notice numbers printed on the capacitors, for example, 33uf 100v. The first number is the value of the cap in farads, and the second is the rated voltage. Make sure your new one is of the same value and voltage rating.

An intresting site I found is at http://www.uoguelph.ca/~antoon/gadgets/caps/caps.html.
Scroll half way down the page to see pictures of different kinds of capacitors.The first one shown is an electroyltic capacitor, and it reminds us that if they are installed backwards they can explode !!

Resistors

Most resistors have color bands on them but the large white ones use the BS 1852 code so go to
http://xtronics.com/kits/rcode.htm to see how to read them. For example 2R2 =2.2 ohms.

Go to the website below to learn about resistors: http://www.circuit-innovations.co.uk/resistors.html

A easy to use resistor color code chart can be found at:
http://www.samengstrom.com/nxl/3660/4_band_resistor_color_code_page.en.html
In the upperleft corner of this web page you will see 4 band, 5 band, etc. If your resistor has 4 bands of color, start by clicking on four band in the upper left corner of the page.
For example, if your resistor is brown, red, orange, gold click on these colors on the chart shown and it will tell you the value. In this example it's value would be 2.3 ohms. For a brown, orange, yellow resistor it's 130,000 ohms, since the letter K=1,000. The letter M=1 million.

To test a resistor use the resistance range of your meter, most resistors found in a TV set will have a tolerance of 5% or 10%. What does this mean? For example, a 1K (1,000 ohm) resistorwith a tolerance of 5% can measure anywhere from 950 - 1,050 ohms with your meter. This is because 5% of 1,000=50.

Check all of the large wirewound resistors and also look for the smaller fusible or flameproof resistors. They are sometimes blue or gray in color and have color bands on them. To learn more about them go to the website: http://www.tokenchina.com/resistor/fusible-resistor.htm. Should you find any open fusible resistors be sure to get an exact replacement for safety reasons.

In part two of my article on TV repair, I'll explain how to fix a problem in the vertical output stage. This is a common problem that many of you have asked about in the forums. I will also talk more about the power supply and high voltage section.

Brian Gay
Los Angeles, California

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