The Hi-Voltage Blues

[Tubejunke]

[QUOTE=Raddion;3086687] I only tested the heater circuit - but if I remember right that was supposed to be a pretty good sign for the CRT if it passed? ![/QUOTE

]WOW! What a score on the tube tester! You have come a long way in a very short time from checking a heater with a V.O.M. to being able to do all facets of proper tube testing. Just so you know, the heater check of the tube, or any tube is only the most basic of test. OF course without heater operation with thermionic emission, you have no chance at all of moving electrons, But conditions like shorts and gas must be taken into consideration.

I wouldn't have any hesitation in using that tester as is beyond simply doing a routine inspection and perhaps leaving it powered up and checking a few tubes of different heater voltages to put various circuits to use. The good thing about 70s test equipment is that first off it was never used daily as a TV or radio may be. Also, it was brand new then as opposed to the TVs we love. They were being retired through the 70s and into the 80s even.

Last, by the 70s many devices were either hybrid or completely solid state meaning that tubes were replaced with transistors and PN junction devices which operate at much lower voltages and are much more stable than vacuum tubes. Don't get me wrong; I wouldn't be here if I did not hugely enjoy the operation of vacuum tube equipment. However, I do prefer my test equipment to be a tool and not a project. Not to say that dated solid state equipment does not require service. Anywhere that there are capacitors there is potential failure.

[Raddion]

It's Friday, time for some beer!!!

Ok here's an update on my old '53 Philco. I still haven't plugged her in. I have obtained a Variac via Cragslist, it's an old one but it looks ok. So I'm all set hopefully for a careful power-up (more questions on that another time) when I get a few more issues straightened out.

Last night I hooked up the REM CRT Tester/Rejuvenator box that I scored at the flea market ($4.00) and ran through some tests... as far as I could tell, the picture tube isn't toast. The test meters were right about in the middle, definitely not in the red but not in the like new range either. I did not try the "Rejuvenate" function yet, I think I'll wait until I know more before I go zapping it. I was pretty glad that nothing blew up in my face!

Now.. the selenium rectifiers. There are two of them on the sweep chassis. I know I have to use silicon diodes, and I guess add resistors to the circuit etc etc - the more I read about it, the more the selenium rectifiers in my brain heat up. If anybody out there has already done this on a Golden Grid and could point me on the right path to success, i.e. parts needed, wiring diagrams, pictures, anything - I would be eternally grateful. Everyone here has been just great!


Time for pizza!!!!

[Tubejunke]

Originally Posted by miniman82

You must ground the anode wire to the chassis for several minutes before going near it, just discharging it once and digging in is asking for trouble. Ask me how I know, stray voltage will build up as it sits, then next thing you know you get whacked even though you thought you were being careful!

You are correct and remember this: Even after doing what you mentioned and you are going to handle a C.R.T. for say a swap or even a good cleaning, you can still get hit and drop the tube. A C.R.T. is basically a giant capacitor only a bit harder to fully discharge and have it remain discharged.

Someone once posted about this and it would be a good one to look up to get the details, but the jist of the story was that the tube can be seemingly safe and even handled a number of times and then BAM you get hit. Static charge perhaps making you flinch and drop the tube!?!?!

[Raddion]

I, uh, remembered to try the Search function (DOH!) and came up with a great thread on replacing the seleniums from only a couple months ago..

http://videokarma.org/showthread.php...nium+rectifier

There is a lot of info here I will need to absorb. I guess I should be able to figure out what diodes and resistors to get, I just have to make sure I get everything wired correctly.