On Saturday 02 May 2015 07:14:14 Mark Wendt wrote: > On Fri, May 1, 2015 at 8:17 PM, Gene Heskett <ghesk...@wdtv.com> wrote: > > On Friday 01 May 2015 15:08:45 Mark Wendt wrote: > > > On Fri, May 1, 2015 at 12:53 PM, Gene Heskett <ghesk...@wdtv.com> > > > > wrote: > > > Our bullfrogs here in MD are bowled over pretty easily too. ;-) > > > > I am glad you said that. If I had, there would have been a contract > > out on me. > > ROFL! > > > [...] > > > > > I'm kinda partial to the Tek 7000 mainframe series. There are > > > tons of plugins besides the horizontal and vertical amps from > > > counters, to curve tracers to spectrum analyzers to you name it. > > > > Yeah, but you can't put it, a probe, and a usb cable to charge it > > with, along with the DSO-1, in your polo shirt pocket. ;-) > > True dat. But your DSO-1, usb cable and probe can't do waveform > calculations, curve tracing, spectrum analyzing or have up to 1 GHz > bandwidth... ;-)
Given the bw limit of about 4mhz, when I started out all those years ago, the scope I inherited for a bench scope was a Hickok 505. Even that trace could be mentally expanded to tell you a lot. Most folks see a rounded top on a waveform at the grid of the tune and take it at face value which to them is meaningless. But that rounded top needs to be compared to the DC bias, something that AC coupled Hickok couldn't do. But I learned early on that it was generally a sign of a tired tube, it was drawing grid current when it wasn't supposed to be. If you know what to expect, even that DSO-1 can tell you much more than the specs would lead you to believe. Thats 100% mental, and thats what I seem to be decent at. > The 7000 series are lab scopes, that's for sure. But they sure are > fun to work with, and for some things, pretty much essential. > Besides, if you have enough of 'em, stick one permanently in the shop. > Nobody sez ya gotta stop at just one! ;-) True, but that "lab" scope is not something you would want to slip a couple pieces of big spaghetti on so you could close a transmitter door on it, and standing on a plastic floor, proceed to use it to determine the screen grid current flowing in a 4CX5000A modulator stage by measuring the voltage drop across a 100 ohm 200 watt power resistor. The scope is going to be sitting at nominally 1500 volts above ground, One hand in pocket is the rule for stuff like this folks, do NOT try it at home. I once did that with a triple insulated 35 mhz dual trace phillips scope, worked right well, and told me the tube was toast as during the sync pulse, it was drawing nearly an amp of screen current, and the drop in screen voltage was what was causing pretty extreme, uncompensatable synch compression. The 4CX5000a is built as a shadow grid construction internally, and because the screens wire is physically wound to be precisely behind the control grid wires, exerting its fixed positive voltage as both an electron accelerant and because its well bypassed at the rf frequency, shields the control grid from the several thousand volts of rf swing on the plate making it quite easy to neutralize. And it all works quite well until something sneezes, causing one or more of those wires to overheat and sag. At that point, it is no longer precisely in the control grids shadow and starts intercepting the edge of the electron stream going by. That self destruction cycle continues until a tube, despite being able to handle the amperage in terms of plate current, is effectively burnt toast. That was a teaching/learning moment for me. A fresh tube, at full power will not draw more than 2.5 to 3 milliamps of screen current. And it can run several thousand hours, but if, in the 2x an hour logging of the meters, you note that this screen current is rising, order a fresh one when the meter says 5 milliamps, you have about a month left because the compression will become un compensatable by the time its showing 10 milliamps. The synch tip time is 4.7 microseconds, out of every 63.xx microseconds. All of that 10 milliamps average is drawn in that 7.4% of the synch pulse time. > That being said, the 2000 series also make some pretty nice shop > scopes, and are pretty portable, though not pocket protector-sized. That they were, once you had put a decent crt in them. But they are loaded with stuff thats now made out of the purest unobtainium made. They also have a 3rd pin grounded power cord, and because the line bypass filtering is so weak in breakdown voltage, such a stunt as I did with that triple insulated Phillips couldn't even be considered with the tek. You would probably, even if the 3rd pin was removed, have used the line cord as a fuse when the whole tx power supply, usually capable of fusing a 16 gauge wire, would be destroyed in a flash of light accompanied by the sound of clearing bullding entrance breakers if the transmitters own breakers aren't fast enough. One such incident on Fisher hill resulted in replacing a 4 ton plate transformer. And a lot of other stuff that damned near included me. The AK-225 breaker was expected to trip off by dropping power to the undervoltage relay. But at nearly 50 years old, it had sat there and buzzed gently until the springs failed & didn't have enough left to pull the trigger on the opener knee. That too was made out of pure unobtainium in 1990 since it was then 40 yo, so, knowing they were doing a major remodel on Mon General Hospital in Morgantown, I drove up & talked to the jobsite super to see what they might have. They had about 20 of them lined up for the recyclers, help yourself. So I came home with 2 and made one good one out of the 4 I then had. And WDTV-5 was back on the air in about 4.5 days, while I was coming down with the shingles from being electrocuted bad enough for 2nd degree burns. But he wasn't ready for me anymore than he was when I had the pulmonary embolism at the end of May last year. Yeah, there is a goodly number of BTDT's in my log book. ;-) > > Cheers, Gene Heskett > > Cheers, > mark > ---------------------------------------------------------------------- >-------- One dashboard for servers and applications across > Physical-Virtual-Cloud Widest out-of-the-box monitoring support with > 50+ applications Performance metrics, stats and reports that give you > Actionable Insights Deep dive visibility with transaction tracing > using APM Insight. > http://ad.doubleclick.net/ddm/clk/290420510;117567292;y > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ One dashboard for servers and applications across Physical-Virtual-Cloud Widest out-of-the-box monitoring support with 50+ applications Performance metrics, stats and reports that give you Actionable Insights Deep dive visibility with transaction tracing using APM Insight. http://ad.doubleclick.net/ddm/clk/290420510;117567292;y _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
