What in the name of... - Page 1
Forum section: electronics / beginners

author: Unknown
author_rank: Unknown
timestamp: August 22, 2015, 09:53:55 am
content: So about a year ago I was doing a teardown on a vintage cathode ray tube TV. But some of the things I saw inside looked nothing like what was in "modern day" CRTs. By the way this was not a REALLY old TV, just a dusty wooden cabinet. (with a "cardboard" back.)Sorry, I have no pictures, because I never anticipated I would post this. But I'll describe it as best I can.The first thing was a huge red tube that was really long but not very wide. It looked like some kind of resistor. A huge cable went in one end (high voltage?) and a TINY little cable came out the other end.The second thing was a huge red potted block with several high voltage cables coming out of it. One went to the CRT itself via the cathode, and another to the flyback transformer (mounted on the mainboard). I can't remember where the rest went, but one might have gone to the large resistor-like device.Any ideas mates?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 22, 2015, 10:19:11 am
content: A couple options:- High voltage resistors (often enameled or painted in such colors?)- High voltage diodes (semiconductors of the day, e.g. selenium, copper oxide, weren't very good, but a stack consisting of thousands of layers would be good enough)- Voltage multiplier (with the several wires)- Voltage regulator (Corotron or other gas discharge sort of type?)There's quite a lot of information on vintage sets, available online today; the oldest and most sought-after command a good price by collectors and restorers, and are fairly well documented (both for their original owner's and service manuals and other documentation, and of restorers recording common faults and fixes). The cheaper and more mass-produced sets aren't nearly so attractive, but many representative sets are at least partially documented, so that you'd very likely recognize each and every component you've seen, after looking through a couple service manuals of related sets.Resources e.g.http://www.earlytelevision.org/american_postwar.htmlTim

author: Unknown
author_rank: Unknown
timestamp: August 22, 2015, 11:05:38 am
content: Thanks for the info

author: mzacharias
author_rank: Frequent Contributor
timestamp: August 22, 2015, 11:35:08 am
content: Is it a Sony? They had something called an "H-Stat" which we always joked about and called "the red thing". I truth, I couldn't really tell you what it's function was (I wasn't the TV guy in the shop), but when they developed a visible crack in the body, there was no high voltage.

author: Unknown
author_rank: Unknown
timestamp: August 22, 2015, 11:40:10 am
content: This.https://133fsb.files.wordpress.com/2011/07/hstat_grieta.jpg?w=700Is exactly what I was looking for!Edit: Isn't exactly what I was looking for. But it looks almost exactly the same, just with more wires.But the question is, what does it do?Thanks!

author: SeanB
author_rank: Super Contributor
timestamp: August 22, 2015, 12:20:13 pm
content: Red block is the focus control, basically a very high value pot rated for operation at 30kV. If only 2 leads then it was Sony, as they integrated half the pot in the CRT itself and the pot only had to handle the focus voltage itself. 2kV as opposed to 30, though the wiring to the HV end had 30kV isolation in case of flash over. 2 controls and it is a combined focus and G1 control, which controls both focus and the maximum brightness of the tube by setting the A2 final acceleration voltage on the CRT gun assembly.Big long red tube would be a high voltage diode, with a LOPT that is not split, but which has multiple layers of insulation at the high voltage end and a single lead out of the middle of the big block of resin or wax on the one side leading direct to the diode, the thin wire because it was short and held both ends, and the thick EHT cable to the Focus,G1 controls in a splitter block and then the final anode on the CRT side. Only used on older smaller CRT units, as it could not provide the power required to operate a CRT bigger than about 10 inches. Large screens used a diode split LOPT, where the HV winding was split into many small ( 2kV or so ) sections all in series, with diodes inside the body so the insulation for each section was not stressed and the capacitance of each section to the core provided a reservoir capacitor instead of having to be charged and discharged at line rate. Might only be 200pF total, but at 30kV and 15kHz a fair current to dissipate in the windings.

author: Unknown
author_rank: Unknown
timestamp: August 22, 2015, 12:22:39 pm
content: Ah niceThanks again!