The PHILCO Phorum

Hey all, I have a question about this type of picture tube (16AP4). This is a 16" round tube with a metal bell. The 12kv high voltage connects to the metal bell of this tube and is supported by 4 insulated grips screwed to the inside of the cabinet. One has a contact that feeds the HV into the tube. Im not really fond of this, but since this tube very low, almost flat, I wondered of anyone knew if this could be replaced with an all glass tube or had any experiance/ advice about this type of tube? Never dealt with one of these before.

Many thanks!

You can use an all glass tube. As long as you keep it clean, the metal tube will work as designed. With metal tubes, for troubleshooting, I use a 5AXP4 test tube.

Thanks for the advice. I had wondered how I could service the chassis since the tube was mounted to the cabinet, and the deflection yoke to the chassis. I had thought of using some 2x4's to support the tube, but one mistake, and there goes the neck of the tube or 12kv worth of fun! Or both!

Look for a little 5AXP4 or 8XP4 test CRT on ebay. They were designed for just this situation

Thanks Bob for the info and posting the pictures! Most of the tvs I have worked on have the picture tube mounted to the cabinet and yoke mounted on the neck of the tube. I could usually pull the chassis and flip to where I could service. Most of the older sets have the tube mounted to the chassis, making removal and service simple, but heavy. I really didnt know how I was going to deal with this set. On a good note, I had read somewhere an article about how companies were "recycling" tubes back in the 50's I think, and would cook the filaments to rejuvinate. This tube would barely move the needle on the tester/rejuvinator when I first tested it. I think the set has been idle since the 1960's. I left the tester on the heater (6.3v), then turned up to 8v for about 1hr. When I returned it to 6.3v, let it sit for several minutes, the reading had raised to the high side of 'bad', to just under the '?'. I may do this again and see what I get. Should be enough to run the set now. I dont know long this will last, but I doubt I will ever use the set enough (after recapping/repairs) to pull the tube down. I am reluctant to do a 'rejuvinate', as I have seen some tubes lose focus and sharpness. I think I read it also strips some of the emission coating from the cathode, and enlarges the hole in the end of the gun.

I will start searching for one of those test tubes.

Thanks again Bob

Since my last post, I have been patiently waiting for one of those tubes to show up on ebay. I found one and it arrived a couple days ago. It tested perfect. Wow, finally something from ebay that IS as described! It was well pack and survived the USPS abuse! Had to thank that seller! Anyways, it is an 8XP4. Before I try this, I need advice if I can use the ION trap magnet from the 16" tube, or what you may recommend. I doubt this is an aluminized tube.

 I am still 'aways' off from getting my bench set up. Seems when I started this about a month ago by cleaning out a room in my attic - then, somehow, it took the detour of becoming my sons room, which meant more cleaning to the very back room in the attic, in which I discovered "mouse central". Soooo - now, I am remodeling that room to mouse-proof, the next room for my son, then finally, his old room will become will become 'my tv/radio' shop, man cave - eh' ya get the picture... whole other story here... gonna be a while before I can warm my soldering iron.

8XP4 does not need an ion trap. It also is self focusing so do not use a focus magnet with the test tube. It only needs the yoke, CRT socket and high voltage.

Don

Agree, can't recall ever having used an ion trap with a testing CRT, but it's been many moons.