Beginners guide to Vintage TV Restoration?

[Tube TV]

Originally Posted by cdmarion

No i don't, although I've been considering buying a Picture Tube (CRT) Restorer/Analyzer/ Rejuvenator. Is there any other way to test the crt's?

The Beltron is the best and also does a better job of rejuvenating the CRT , they sell on ebay for 120 bucks ???? if I am correct . But just for general the B&K model 400 is a great unit , it's self contained in a carring case , and does emmision and short tests and also rejuvenates CRT's , the rejuvenation is course compaired to the Beltron .
But the B&K 400 is common and usually sells for $20.00 or less .
This thread was started a few months back , it might be of interest to you .
http://www.audiokarma.org/forums/sho...d.php?t=130048

[Chad Hauris]

Originally Posted by andy

Before you do anything, you need to replace all the paper and electrolytic capacitors. Then you can at least safely turn it on and see what you have to work with. A lot of 50's TVs work fine after replacing the caps, cleaning the tuner and other controls, and making a few minor adjustments. Be prepared to find other problems though.

This is one thing I have learned is very important...if there are any old capacitors still in there it can cause all kinds of hard to track down problems and make it impossible to repair.
I always start with all new capacitors and check the tubes and then troubleshoot any problems which may be due to resistors, etc.

I also highly recommend the photofact. This comes in very handy on sets which use the old color band caps...it helps to confirm which cap is what value. Also you will need the voltage test readings to help you if you have any problems after the capacitors are replaced.

Also just looking at different photofact schematics and tracing how the signal flows from one part of the set to the next is very helpful in understanding it. The schematics are always layed out so you can see how the signal starts from the antenna terminals and flows through the tuner, to the IF, where the sync signals come off, etc. Also you can see things like how a vertical output tube or audio detector can rely on boost voltage from the horizontal output section, or how an audio output tube can act as a voltage divider and supply plate supply voltage to the IF tubes...things that might not be immediately obvious but can help with tough troubleshooting problems.

[RetroHacker]

That set you have for your first TV project actually looks like it will be a very good set to start on. It's a 50's set with a large all glass tube and a big metal chassis. The all glass tube is nice, because those have much better odds of still having their vacuum. The large metal chassis is a big plus, because it will be pretty easy to work on, comparitively, to some other sets. It will be cramped in places, but still, not too bad to work on. This set uses a power transformer, which is another nice thing - hot chassis sets are scary.

Now, I'm still reccomending you start with a radio first. But that should take a day or two. Then you can start on the TV.

First thing, you need to pull the chassis out of the set. To do this, remove the knobs on the front. If this set has a flip down door (doesn't appear to, but might), check in there for knobs too. They should just pull off, but check for setscrews first. Then, from inside, disconnect the yoke plug. The yoke is the big coil on the back of the picture tube - it deflects the electron beam magnetically to scan across the face of the tube. It's attached to the chassis with four wires, that should terminate in a plug. Some of the later, cheaper sets omitted this plug, requiring that you remove the yoke to take out the chassis. This one seems to have a plug. Disconnect the connector at the back of the picture tube. Do this CAREFULLY. The base of the picture tube might not be still attached to the glass, the glue dries out over time. Hold onto the base with one hand and gently pull the connector off with the other. Disconnect the high voltage lead from the side of the tube. Since this set has sat unplugged for decades, there's no danger. But to be on the safe side, get in the habit of discharging the tube any time you disconnect this wire. It's the big scary one that attaches to the right side of the tube with a suction cup. High voltage can be stored here because the tube acts like a big capacitor.

To discharge a picture tube, you should make a discharge tool. Get an inexpensive large flathead screwdriver with a long shaft and a fairly narrow driver end, and a good plastic handle. Then, take a length of lamp cord and bare both conductors on one end. You'll want to expose a few inches of copper. Twist the wires together and wrap them around the lower part of the screwdriver shaft tightly, making sure to get good electrical connection. You want to finish your wrap at the bottom of the shaft with a turn or two of the still insulated lamp cord. Wrap the shaft of the screwdriver in electrical tape, from top to bottom, leaving two inches or so on the driver end bare. Use a couple coats of tape. On the other end of the lamp cord, bare a short amount of wire (both conductors), and twist them togehter.

Now, a lot of people prefer to use a resistor to discharge tubes, and they're probably right. I never did, simply because I didn't know any better. Also, it's hard to find a suitable resistor, from what I hear. I still do it without a resistor, but I'm sure others will chime in with a proper value and type to use. I think a large power resistor of one meg or larger is what's good to use. I don't use the resistor... If you want to use a resistor, connect it here, to the end of the lamp cord.

Connect the other end of the lamp cord (or the other end of the resistor, if you used one) to a large alligator clip. Be sure to make good connections (solder, if possible). And wrap any exposed metal in plenty of tape.

To use the discharge tool, clip the alligator clip onto the metal chassis of the TV, and carefully slide the screwdriver under the suction cup until you feel the metal spring clip in the center. If you didn't use a resistor, you'll hear a nice loud SNAP if there was any high voltage stored. Without it, I don't think you will. Do this again, just to be sure.

To disconnect the anode lead, once it's discharged, squeeze the suction cup together at the top, and rock it free. You might need to peel it up to see the connection, but it's two little bits of springy metal that stick down into a hole in the tube, and clip in (kinda like the top of a christmas ornament). You just need to gently press these clips together and work them out.

Disconnect the speaker, noting the polarity if it doesn't have a convenient connector. (You are making notes here, right?). Check to make sure there isn't anything else connected, some cabinets have a built in antenna, etc. Under the wooden shelf that the chassis is resting on, there will be several bolts (probably 4). Remove these.

Now, you should be able to slide the chassis out the back of the set. Do it slowly, to be sure that nothing else is still connected, and that the mice haven't started to regroup. You're stealing their home, after all. Careful, it's heavier than it looks most of the time.

Once you've got the chassis out, you can clean the inside of the cabinet. Check for signs of leaked tar or wax under where the chassis was, and any signs of burning in the past.

Take the chassis and start cleaning it. Make a chart of all the tubes, and remove them. Watch out for the rectifier tube in the back, it's often held in with a springy clip that will constrict on the base when you pull it out. Hold this spring down to pull the tube out. Vacuum all the crud out of tube sockets, corners, etc, and clean everything real good. Careful not to damage coils, or get water into them. Don't polish the tubes with Windex. I know it'll make them shiny, but it will also take the numbers off. I've found that the best way to clean them is to run them under warm water for a bit, and gently wipe them on a cloth, like an old sock. You'll want to note the tube number first, in case it does wipe off. Depending on the tube manufacturer, the other non-number markings may come off. (GE tubes particularly). The number on GE tubes is put on with another kind of paint, and doesn't rub off as easily. If the number comes off, feel free to scrub and polish the tube all you want, then write the number back on with a sharpie. Avoid cleaning tubes unless it really needs it.

If you have a tube tester, test the tubes. Note any that are weak - but remember that in a TV, a weak tube might not actually cause problems. It's best to try the first test with the original tubes, provided that they're not broken, open, or totally dead. But put the tubes away for now, you need to turn your attention to the rest of the innerworkings.

Turn the chassis on it's side and look carefully for signs of damage, mouse-eating, burnt wires, missing parts, or Jimmy Hoffa. Carefully clean away any crud you find, compressed air and a clean paintbrush work well, and you can vacuum provided you're careful not to disturb anything. Figure out a way to get the chassis to stay up on it's side. Metal L brackets bolted to the original holes, clamping it to your workbench, whatever. You just don't want it to fall over when you're working on it.

Look at all those wax capacitors! You need to replace them all. Before you start, take digital pictures of the underside of the chassis. Close up ones too. You want to have a reference point just in case. Using the schematic as a guide, start replacing capacitors. Go slowly, take notes, and don't be sloppy. Clipping the old capacitor leads, bending the ends into hooks, and soldering new ones onto that is sloppy. You'll actually want to, wherever possible, actually desolder the leads of the old capacitor, properly attach the new one to the terminal strip, and resolder it. Clipping and tacking works, and you might get away with it in a radio, but it looks sloppy, creates more connections, is more prone to shorting, and ultimately makes the new capacitor rely on a 50 year old solder connection that may not have been that great, and an old oxidized capacitor lead.

To desolder, I like to use a desoldering pump. The blue one from Rat Shack (about 8 bucks) works well. Heat the connection with the iron, and flow new solder into it. This gets the solder melted and supplies it with fresh flux. Then, put the desoldering pump next to it and press the button. This takes practice - another reason to start on a small radio. You might have to do it a couple times, and even then you won't get everything perfectly clear. But once you can see the way the old capacitor lead was folded around, you can use your little needle nose pliers to gently unfold it, and straighten it enough to remove. Once you've gotten the old capacitor lead out of the terminal strip, clean the terminal up with the desoldering pump. Install the new capacitor like the old one was, use 'spaghetti tubing' or stripped off solid core wire insulation to insulate the leads if necessary, since the new one is smaller than the old one, there will be a large area of exposed wire - more prone to shorting in some areas. Try to only remove one cap at a time, but many times you'll need to take off three or four at a time in a TV, since there will be a couple tight together, or on the same lug of a terminal strip. This is another reason to start simple. But take notes, and you'll get it back together. Also, don't push or pull too much on a terminal strip, tube socket, whatever. Terminal strips are just bits of phenolic with metal tabs, and it's easy to break them if you're not careful. Be extra careful around coils - the open type are just wax dipped cardboard with wire, and the soldering iron can melt them. You might have to tack onto old leads here if you're not comfortable removing the old lead from the original tab. When resoldering the connection, always heat the terminal, not the solder - and flow the solder in, making sure it makes good electrical connection. Don't wiggle anything as the solder cools, this will create a cold solder joint. Wiggleing as the joint cools is, however, a great way to create a bad solder joint to make it easier to remove the old capacitor, however. A good connection will be shiny. Once again, you MUST use rosin core, lead/tin solder. Lead free solder is unsuitable for electronics, and acid core plumber's solder is a bad idea, for obvious reasons.

The electrolytics are another story. Here you have to get creative. The electrolytics are the big cans on the top of the chassis. New electrolytics are smaller, and look much different. Common practice is to disconnect the original electroltyics, and connect new ones under the chassis. You might have to install a terminal strip to mount them on. Make sure the electrolytics are installed the proper direction! They have polarity. The cans are multi-section electroltyics. That means that the can's outer casing (or outer terminal) is negative, and the inner pins are the positive sides of the capacitors in the can. The side of the can will list symbols (circle, triangle, etc) that correspond to the symbols stamped on the bottom of the can near the pins. The schematic will help a lot here.

Remember, replace only the paper capacitors, and the electrolytics. Leave ceramic disc capacitors and mica capacitors alone. See http://www.antiqueradio.org/recap.htm for more information on capacitors.

Any time you have a terminal strip cleared out and have a resistor that's only connected on one end, check it with your meter. If it's out of spec (+/- 10% of the printed value) replace it. You can't really check resistors that are in circuit at both ends, because the rest of the stuff in the set will interfere with your readings. But don't go unsoldering every resistor - just do the ones that you run accross. Pay special attention to any resistors that are supposed to be 1meg or higher. They drift the most. Use proper rated replacement resistors. Most common resistors are 1/2 watt. The big suckers vary - check the schematic.

Have fun, and if you have any questions, don't hesitate to ask!

-Ian

[bkharris]

Originally Posted by cdmarion

No i don't, although I've been considering buying a Picture Tube (CRT) Restorer/Analyzer/ Rejuvenator. Is there any other way to test the crt's?

Not really...You may be able to find another akr in the vicinity that has one that will let you borrow or test your crts for you....That is how I did it before I had one of my own.

[bgadow]

I've read instructions for testing a crt with a multimeter (or maybe VTVM) but it was kinda complicated.

I'd agree that this Admiral would be a great one to start with. Straightforward.

This set probably uses a lot of black beauty caps. Often called bumble bees-they are marked with colored stripes, similiar to resistors, instead of having the values printed on them. For the longest time I mistook them for big resistors, and I don't think I'm the only one! Helpful to have the Sams when replacing them since they're not always easy to decode. You should save the old bb caps-people have been known to pay good money for them on ebay!

[Chad Hauris]

We have never had any problems with using the old capacitor leads to attach the new one to. I always file the end of the old lead so a good connection is made, and add heat shrink tubing or spaghetti to the lead if needed for insulation. This method avoids the heat/physical stress on old terminal strips, tube sockets or coils that can be caused by completely desoldering all the old leads.

Also always make sure you put a fuse in the AC power circuit if there is not one already. You can put an in-line fuse holder or mount a fuse clip under the chassis.
If a short occurs in an un-fused set, serious damage to the set can occur...the house circuit breaker will likely not trip on the overload and the current can flow until the 5U4 tube literally melts or the power transformer is charred. A 3 to 4 amp fuse is probably good for an old TV.

[nasadowsk]

I try to keep the leads dressed as original, if possible.

Another tool that's super useful when you have the tricky problems, is the oscilloscope. I find it right behind the multimeter as the most useful thing - it'll help you find problems - fast - once you know how to use it (not hard!).

For TV circuit theory and repair, look for a book written in the late 40's or early 50's - they were written for radio folks looking to get into TV, so they were simple and covered circuits in detail. Admirals were pretty simple and straightforward sets.

Another thing - be careful with the CRT. They break easy and they're pretty nasty when they do. NEVER hold one by the neck, or place it face down on a hard surface. I like to have an old bath towel folded up as a surface, and put it in a safe place. Not only does glass go everywhere when they break, but they're harder and harder to find these days.

And remember, a TV isn't magic! And the set you had worked at one time - so, if something's not going, sleep on it, ask questions, etc. You'll get it eventually.

I like to get the sweep going then the picture and tuner circuits. Often, you need the sweep for B+ boost anyway. Once you've confirmed the CRT 'lights' don't worry about yoke and ion trap adjustments too much, just enough to get a raster. You'll have to fine tune them in the set anyway.

Don't turn screws on transformers and coils unless you know what they do and you're 100% sure that's the right thing. Re aligning a TV set's tuner and IF is a royal pain and requires a bit of equipment...

Tubes 101: Plate higher voltage than cathode, grid lower voltage than cathode, screen almost voltage of plate, supressor same as the cathode. Blue glow ok, purple glow bad (unless it's an OA2), red plates bad, sparks really bad. Silver = vacuum, white haze = no vacuum.

Oh yeah, and stay out of the HV box while the set's on (and watch for the horizontal output plate cap!)

[cdmarion]

Another tool that's super useful when you have the tricky problems, is the oscilloscope

I have an oscilloscope, that i have never used. What leads do i need for TV restoration?

[cdmarion]

Thanks to everyone for the information, it's incredible the amount of information everyone has given me so far.

Retrohacker, your awesome!!! Just what i was looking for. I appreciate the detail. It would be great to see your name on a modern "How to restore you vintage TV" book (Yes that’s a hint)

[kbmuri]

I agree with most of what has been said. If you don't start with a few radios first, then this set is a fair "beginner's" TV. The CRT stays in the cabinet so you don't have to lug it around with the chassis. The chassis is big, so you have room to work. It's not a super-early set that can have completely unobtanium parts if you break something.

I photographed a lot of said details on this thread:
http://www.audiokarma.org/forums/showthread.php?t=76517

It's more than a year old, perhaps some of the newcomers haven't seen it.

I also have done a hundred radios and a half-dozen TV sets and have used the clipped-leads-of-the-original-capacitor trick and never had a problem. I've found that the terminal strips can be fragile, the leads are usually wrapped several times and crimped before soldering (which makes it a BEAR to desolder), and you have to put a LOT of heat into them to get the solder off. If you clip the old capacitors out as close to the cap body as possible, sand the remaining leads bright with wet-or-dry fine sandpaper (the kind that doesn't "shed" sand), 200 or 400 grit, you can tack onto them with 100% results. And you keep the heat requirements light, no melting nearby coils or other unobtanium.

I don't like to bend the leads into hooks, but rather leave the original leads straight, bend the new cap's leads into tight spirals, then slide the spirals over the straight original lead. Flow solder into the whole works and you have a tidy joint that comes apart next time with just heat (no more clipping or sanding).

I use a 500K, 2-Watt carbon resistor for discharging CRTs. Same method otherwise (flat-blade screwdriver and electrical tape).

The tube numbers on GE, RCA, etc (American) tubes are sandblast-etched into the glass and won't wash off (even when the painted labels wash off). European tubes, the tube number usually washes off too. Good way to turn a 100-dollar Telefunken or Bugle-Boy ECC83 into a 5-dollar anonymous one. So leave the foreign tubes alone. I windex my US tubes usually, to no complaints. Really helps the motivation to have some sparkling glass to look at.

Most of all, have fun, take your time, post pics, and enjoy the hobby.

[Chimes]

Speaking of ctr tester/rejuvenators, will these things work on the smaller tubes like the 7JP4?

[kbmuri]

Originally Posted by Tube TV

The Beltron is the best and also does a better job of rejuvenating the CRT , they sell on ebay for 120 bucks ???? ...

The last 3 or 5 Beltron restorers on eBay sold for around $35-$50.

The consensus around here is that the Beltron is the best. Mine has restored two zero-emission tubes to full strength, removed a strange arcing from the neck of another, and tested and verified the "Good" status of my remaining working sets. Based on how each tube performs vs. what the Beltron tests them at leads me to believe the Beltron's test readings are accurate enough.

I've been told that the Beltron will do 7JP4s and 3KP4s by a very good authority. Another AKer here made an adaptor to fit them, it doesn't originally come with that socket size. He posted the plans, a search of the forum should find it easily.

[radiotvnut]

Originally Posted by bgadow

I've read instructions for testing a crt with a multimeter (or maybe VTVM) but it was kinda complicated.

I'd agree that this Admiral would be a great one to start with. Straightforward.

This set probably uses a lot of black beauty caps. Often called bumble bees-they are marked with colored stripes, similiar to resistors, instead of having the values printed on them. For the longest time I mistook them for big resistors, and I don't think I'm the only one! Helpful to have the Sams when replacing them since they're not always easy to decode. You should save the old bb caps-people have been known to pay good money for them on ebay!

Yes, I was once one of those that thought bumblebee caps were resistors. When I was about 12, I found one of these caps blown apart in a radio. I took the cap to the local parts house and told the older man working there that I needed this resistor. He explained to me that the part was a capacitor and pointed out the foil.

As far as CRT testers, I use a B&K 480 from the '90's. With the right adapters, it will test most CRT's from the late '40's to the present. If you can't find a Beltron, look for a B&K 467, 470, 480, or 490. Try to stay away from anything before the 467. They will check the older tubes OK; but, their rejuvenate function often does more harm than good. My first CRT tester was a B&K 465 and I ruined more tubes (especially the color tubes) than I helped with that model.

[cdmarion]

I thought i'd give a quick update.

I've started on the Dim Bulb Tester and will be finished tomorrow, i ran out of parts and need to hit the hardware store in the morning. Easy to make and i'll have maybe $10 after i'm done. Can't wait to try it out. I'll post a pic when its done.

I've also started on my radio project, i chose a 5 tube RCA. It's really simple and looks like a good first re-cap radio. I have no caps on hand so again tomorrow i'll have to hit the local Radio Shack in the morning for parts.

I'm hoping to have this done tomorrow also. I may do a couple while i'm waiting on the TV schematics and caps.

I'll keep posting updates

[cdmarion]

Be careful. TV's can be dangerous. Radios too. Especially "hot chassis" sets. Learn how to properly discharge a picture tube. That thing can store a nasty jolt long after poweroff.

How can i tell if i have a hot chassis? Is it as simple as checking voltage from chassis to ground?