The Set: Pete Deksnis's Site about the CT-100
Restoring a Vintage Color Television Set
9-26-99 The CT-100 was so heavy that it was hard to move across the carpet to work on, etc. So, I got a piece of plywood cut to the exact inside dimensions of the bottom of the cabinet. I mounted four wheels on it and then added a 2X2 block of wood in the corner of the cabinet so that the height of the wheels was just enough when they sank into the carpet that the legs of the cabinet look like they are touching the top of the carpet. This way, it rolls around nicely, but the legs don't carry any weight, yet it isn't obvious that it is really on wheels. I painted the plywood and blocks flat black to match the flat black on the inside of the cabinet. This is easily reversible if someone wanted to remove it.
After conferring with people who used to fix these early sets, I also added 6 fuses for additional protection: AC line, Filaments, Filaments, +275, +285, and the cathode of the horizontal output. The two filament fuses were actually replacements for the #26 guage wire fuses on terminal strips. Five of the fuses were mounted in a row just below the bracket that the antenna and ac line are attached to. Looks very neat and professional. Yes, it isn't original, but now I can feel safe powering up the chassis. The cathode fuse became standard practice beginning with about CTC-4 or so. I was satisfied that most of the +375 and +380 lines were adequately protected, so I did not add more fusing there.
9-27-99 Last week I turned my attention to the chassis. My philosophy here differs from yours. I have had lots of experience with paper caps and there is no way I will leave them in a set I am restoring. There is too much risk that they will short out and wipe out a critical component that can no longer be easily replaced. These sets had a history of fires in them and the paper caps were usually to fault. The flyback is particularly vulnerable in this set. By the time you realize something is wrong and reach up to turn it off, it is too late. So, I have replaced every single paper cap and all of the electrolytics, except C1 through C-5, which I plan to reform and only replace if necessary. I used 630 volt metalized mylars throughout. My objective is to have an extremely reliable and safe chassis when I am finished. Also, when I finish the alighment, I want it to last. With those paper caps in there, it could be useless in another week.
10-1-99 I have wired the fuse sockets into the circuits, but I haven't fired up the chassis yet, so I have no idea what the current drain will be. I plan to measure this so the fuses can be sized as accurrately as possible. The fuse in the cathode of the horizontal output was a block mount type, and I used "Goop" to glue it to the bottom of the chassis right near the horizontal tube. The other 5 fuses were mounted in a row right under the metal bracket that holds the tv antenna screws and the AC plug. This way, everything looks relatively neat and unobtrusive. Yes, I know it doesn't leave it as original, but there are just too many irreplaceable parts in that set to take chances anymore. Just try to find a replacement flyback or vertical output transformer!
Since the set draws 475 watts and I am using a current inrush limiter, the fuse can be sized for the steady state current instead of the inrush current, so it will offer better protection. I would bet 5 amps for the AC fuse. The others will all have to be measured. [ Click here for fuse info input from Steve. ]
There is a caution you should observe. The RCA folder warns against using the CTC2 under brownout conditions of less than 100 Vac. This is because the horizontal output tube begins to draw substantially more current as the voltage goes down. This means that when the horizontal output tube is in place you shouldn't bring the power supply voltages up slowly, or you risk damaging the flyback and the horizontal output tube (and god knows what else). I have a graph of it at home and I will try to email it to you from there. The current peaks at about 80 to 90 Vac. As I recall, it had something to do with the bias on the horizontal output tube dropping faster than the self-bias, which increases plate current. This is one of the reasons they began adding a fuse to the cathode of the horizontal output tube.
4-7-00 The 6BD4 h-v shunt regulator tube was replaced shortly after it came out with a better, more rugged version -- the 6BK4. The 6BK4 was used for many, many years in nearly every color tv made and they are available realatively cheap. I bought several for a buck a piece brand new at our local electronics swap meet.
Still haven't had time to get back to checking out my CT-100 chassis. --Tom K6AD
9-4-00 It has been awhile since I've worked on my TVs. I have some time now, so I am getting back to it.
Do you know the source for getting the vacuum sealant to properly reseal the glass-metal bond on the 15GP22 tubes? EVERYONE who has a good tube should use the stuff to protect their valuable investment. Unfortunately, it seems like everyone has heard of the stuff but no one has posted it. [ Click here for info. --Pete ]
9-25-00 I haven't goten to my CT-100 yet, but somehow I got going on the CTC-5 and a Zenith 16" porthole. What got me going was that the Porthole TV developed a problema and I thought I would just go in and replace a bad tube or two. WRONG, Batman! It wasn't a tube so I ended up replacing all of the paper and electrolytic capacitors. Then I noticed that the "getters" in the pix tube were turning white, which means that the tube was taking on some air. Shat! This is the usual problem with the metal/glass type of pix tube. The gun still checked good on my tube tester, so I figured all was not lost as long as I got the tube sealed up in a hurry.
I found the VACSeal stuff on the Internet and ordered some and am now waiting for the stuff to cure on the tube (it takes a very long time at room temperature). I hope there is not too much residual air in the tube. In the next couple of weeks I need to do the same thing to the 21AXP22 so it doesn't get destroyed just sitting there. So, all this stuff is putting off work on my CT-100 for now.