Restoring a Vintage Tube Television

So you’ve stumbled across an old tube television at an estate sale or Facebook Marketplace and think, “I’d love to watch old horror movies on this bad boy.” Well, fortunately, you can! Old televisions that used vacuum tubes were built like tanks and most can be restored to their former glory. This article will act as a primer for tube television restoration. This process will be easier if you have a general understanding of how electronics work. It will not be a quick and easy restoration but you will be able to get the television working again if you know what you are doing.

            The first thing I want to mention is the safety aspect of messing with vacuum tube electronics, especially cathode-ray tubes (CRTs). These are not like electronics built today. Vacuum tubes can require a lot of voltage to operate properly. The CRT, depending on the size, can require upwards of 27,000 volts. Please take proper precautions and don’t mess around with any wiring when power is applied.

tv repair man examining a tube televison

Things You Will Need

Let’s go over some of the items you will need to get started with your restoration and reasons for needing them. Most of these items can either be found on Amazon or eBay for the older electronics.

  • Soldering Iron & Solder
    • You will be replacing a good amount of components inside the television so be prepared to do a lot of soldering.
  • CRT Tester
    • These aren’t necessarily required but are important to know if your picture tube is still good. Without a good picture tube, there will be either a very dim picture, or no picture at all. A CRT tester will be able to tell you if your picture tube is still in good condition and will be able to work for many years to come.

CRT tester

  • Vacuum Tube Tester
    • This is a different tester than the CRT tester. Old televisions use a good amount of vacuum tubes. Vacuum tubes were designed to be easily replaceable since they will eventually fail. A vacuum tube tester will tell you if your tubes still have good emissions and if there are any shorts in them.
      vaccum tube tester
  • Replacement Components
    • Old electronics would use “bumblebee” or wax-coated capacitors. These capacitors have paper inside of them and over time, the paper becomes acidic which diminishes how they operate. Capacitors are supposed to block DC and only allow AC through them. These old capacitors have the ability to leak DC to other parts of the chassis and can do all sorts of damage to transformers which we don’t want. Websites such as Mouser and Antique Electronic Supply provide replacement components for your project.
      compacitors
  • Voltage Multimeter & LCR Multimeter
    • During this restoration, you will need to check voltages and components. A voltage multimeter will be used to measure AC and DC. An LCR multimeter will be used to measure the inductance, capacitance, and resistance of components to determine if they are still within the value.
      LCR multimeter
  • General Tools
    • Screwdriver, needle-nose pliers, socket wrench are a few items you will need to disassemble the television and help replace components. Also, having electronic cleaner spray is great for cleaning old potentiometers and tube sockets to reduce problems down the road.

STEP 1: FIND THE SCHEMATIC

            The schematic is your best friend. Find the schematic for your television model. You can usually find the television model number on the back of the set, or on the back of the chassis. Having the schematic is very important to see what components go where and how your television is supposed to operate. Samswebsite.com has a huge library of old schematics for televisions and radios. Most schematics also include a troubleshooting section for your model set. This will come in handy if a certain aspect of the television isn’t working properly.

television schematics

STEP 2: REMOVE THE CHASSIS

            Remove the chassis from the television shell. Most televisions from the 1950s were designed to be serviceable for repairmen. This is good news for us. The chassis should be able to be removed from the television shell after unscrewing a few screws. Many tabletop models have the picture tube attached to the chassis as well.

television chassis

STEP 3: STUDY YOUR TELEVISION

            Look over the chassis. I mean really take a good look and familiarize yourself with where everything is. Take many photos of the chassis and how everything is hooked up. Under the chassis is where you will find all the wiring and old components that will need to be replaced. Take photos of how everything is wired too. It could be helpful to look back later if you hooked something is wrong. Make sure all the vacuum tubes are still in the set and in the correct sockets.

STEP 4: TEST PICTURE TUBE & VACUUM TUBES

            Here is where you would test the picture tube to see how it tests. If emissions are good and there are no shorts, your restoration can continue. You will notice a cable that plugs into the side of the picture tube with a rubber cap on it. That is your anode cap. High voltage travels to the picture tube through that cable from the flyback transformer. You can unplug it from the picture tube if the set has been off for more than 24 hours because high voltage can still be present in the tube. You can also make a discharging tool to discharge the CRT to the chassis if you can’t wait. Just make sure that the anode cap is put back before applying power to the set.

            Having a vacuum tube tester is also nice but not essential for restoration. If you suspect a tube is the culprit to a problem and you do not have a tube tester, you can find replacements readily available on eBay.

 STEP 5: CHECK COMPONENTS

            This is where the LCR multimeter comes into play. You do not need to check the paper/wax capacitors since you need to replace those no matter what. Check the capacitance of the electrolytic capacitors and see if it’s close to its original value. If it’s above or below 20%, replace it. I personally replace all electrolytic capacitors if it’s a set I plan to use regularly, just so I don’t have to take out the chassis again in the near future.

STEP 6: REPLACE WAX CAPACITORS & ELECTROLYTICS

            We’ve talked briefly about replacing the wax and paper capacitors. Electrolytics are a different type of capacitor that needs to be replaced as well. They are polarized capacitors that have positive and negative sides. MAKE SURE not to solder them in the wrong way. They can be found under the chassis or in can-like shapes on top of the chassis. They will have values on their side. The “can” capacitors will have anywhere from 1-4 electrolytes inside of them. Some may test fine on a meter, but after applying power to them, they can reform and either short or reform to a new capacitance rating. Electrolytics usually put negative to chassis ground but be sure to read the schematic because that’s not always the case.

            Take a look under the chassis and start replacing the paper/wax capacitors. These capacitors are non-polarized so it will not matter what direction they are facing. You will most likely deal with caps that are (.001uf, .0033uf .0047uf, .0068uf, .01uf, .022uf, .033uf, .047uf, .1uf, .22uf, .33uf, .47uf). These are capacitance ratings measured in microfarads (uf). Some old capacitors have values that are close to these but are hard to find exact replacements for. You have some tolerance for putting in a proper substitute. Here are the replacement values I follow if a capacitor has an odd value:

.0015uf = .001uf

.002uf = .0022uf

.003uf = .0033uf

.004uf = .0047uf

.015uf = .01uf

.02uf = .022uf

.03uf = .033uf

.04uf = .047uf

.15uf = .1uf or .22uf

.2uf = .22uf

.5uf = .47uf

4uf = 4.7uf

8uf = 10uf

20uf = 22uf

30uf = 33uf

40uf = 47uf

60uf = 47uf+10uf in parallel

            These values will work fine as replacements for odd values. Another thing you need to look out for is the voltage rating on the capacitor. The voltage rating shows the max amount of voltage the capacitor can handle. Most old wax capacitors have a rating of 200v or 400v. Replacement capacitors will usually be 600v or 630v. Those are fine to use. As long as the voltage is not less than the original rating, you will be okay. Always better to use a higher voltage rating, especially with electrolytes.

racap

STEP 7: CHECK RESISTORS

            Resistors are usually fine to leave in, as they don’t typically drift as far as capacitors. I usually replace the ones that have over a 100k rating. You can find replacement resistor packs relatively cheap on eBay or Amazon rated at 1/2W or 1W. Also, check the resistance of the larger watt resistors to make sure they are close to the original value in the schematic.

STEP 8: REPLACE SELENIUM RECTIFIER

            Selenium rectifiers are rectifiers that convert AC to DC. If your set has a power transformer, this step will not apply to you since the set will not have a selenium rectifier. They are usually orange-colored metal blocks and are located near where power is applied to the chassis. In some television sets, there is no transformer, so the set needs a rectifier. The problem with selenium rectifiers is that over time, there is a progressive increase in forwarding resistance, and increased forward voltage drop which reduces the rectifier’s efficiency. If a selenium rectifier goes bad, it can produce toxic fumes. Replace them with a 1N4007 silicon diode. Be aware of polarity when replacing. If they are put in backward, you will see lots of smoke the instant you turn on the set.

selenium rectifierdiode

STEP 9: APPLY POWER

            Now that the tubes are tested and in their correct sockets, capacitors are replaced, resistors are checked, and selenium rectifiers are replaced, you can now apply power to your set. Some use a variac transformer to slowly add voltage to their set, but since you have replaced most components with modern components, you should be okay to plug it into a surge protector. Power is usually derived from the volume potentiometer so go ahead and turn it on. If you hear any loud popping or electrical arcing, turn it off immediately. If you don’t hear anything at first, that’s a good sign. You should see the vacuum tubes start to light up. It takes around 10-15 seconds to start to hear the high pitch whine of the high voltage which goes to the picture tube. Once you start to hear high voltage, an image should appear on the picture tube. If not, check to make sure your brightness knob is turned up. If all is correct, you should get a raster up on the screen. There’s a high chance you will need to adjust some knobs to get a steady picture (vertical hold, horizontal hold, width, height, vertical linearity, AGC). I will include troubleshooting photos to show you what some problems look like on the picture tube and what to adjust or replace.

            Try turning the channel knob and see how all the channels look. Since analog no longer exists in the United States, you won’t be able to pick up a signal for channels. You should see a raster on every channel though.

STEP 10: HOOK UP A MEDIA PLAYER

            If you have a DVD player or VCR you’d like to hook up to the television, there’s a very easy way to do so. On the back of the set, you should see an external antenna hook up. If you connect a 75 to 300 ohm matching UHF/VHF matching transformer, you can hook up a coax cable to the set. The signal will most likely appear on channel 3 or 4. Most DVD players have an RF modulator in them and you can choose whether the signal will be on channel 3 or 4. There’s a fine-tuning knob on the channel selector where you can fine-tune into the incoming signal to get a better picture. There are also pattern generators that you can get for fine-tuning your image.

color bar pattern generatorpattern generatorzenith television

CONCLUSION:

            If all went well, you should be able to get some type of image on the picture tube. If not, go back through your photos and check to make sure everything is hooked back up properly. If you’re still having problems, reach out to me on Instagram at @televisionforever and hopefully, I’ll be able to help you out. Most tube televisions from the 50s were built to last and most of them can be restored. Don’t let it go into the garbage. We must preserve what history is left and how it shaped our future.

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