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Re: Tektronix 492BP chassis heat.
arthurok
alot of modern equipment either just has a 115/230 vlt switch "like a pc" or a uni
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versal input switching supply. one simple solution for high line voltage is a filament transformer with n its secondary connected as a bucking winding bucking down your high aussie voltage 25 vac down probably wont bother modern equipment most modern equipment will work quite well on even 105 vac thats 210 vac on your settings "experiment using a variac just be carefull about cranking the variac up very high on older equipment" 130 volts is plenty high for checking older stuff my variacs will put out almost 145vac with my high line voltage. that could blow up and older piece of equipment. some old radio buffs suggest using a bucking transformer inside of old radios to keep the input voltage down. alot of very old stuff was designed to work on 110vac. my 123 vac line voltage is a bit high. look at the back of even a tek 547 "115 vac" i think the 547 has internal taps my 7904 just has the 115/230 vlt settings "switching supply ----- Original Message -----
From: JOHN BYERS To: TekScopes@... Sent: Saturday, December 30, 2006 7:31 PM Subject: [TekScopes] Re:Tektronix 492BP chassis heat. Hi, Gerald Dont know in what part of Aussie you be, but over here in the West we are often plagued with higher than normal Line Voltages, specially if u live near an industrial area or near a feeder transformer / substation No doubt u have already checked this , but just in case check yr own line voltage preferable with a true RMS meter or known caiibrated (standard AC) average reading one Test the line waveform too. Generally its a good enough sine wave but I have seen line waveform distortions in some of the places ive been that u woudn't believe! Check out that the 492P is on its max line taps (if it has such a selection) and not just on 220V. Does it get so hot all the time, or only in the evenings? If the latter it coulf be that industrial area shut downs around knock off time leave an uncompensated line voltage too high For these very reasons my own GP bench in Perth is ran from a metered step down auto transformer with selectable taps and my test bench outlets from a number of AC stabilizers to keep RMS line volts to 220v with good AC waveform If all this seems obvious and u are well aware of it all, my apologies, but I have ran into the same issue myself in the past and others with similar problems may benefit Whats the ambient temp in yr shop /room ? Probably an external fan is a good idea anyway in our ever warming climate for those items of lab gear really intended to work in a protected lab environment (not that ime saying the 492P is) Of course,you could have a fault with the 492P that others are better quailfied to comment on but the above seems a good place to start. Hope yr 492P gives u years of trouble free use. Happy new year John (hpxref) |
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Re: Invitation for another exchange of questionably useful information.
--- In TekScopes@..., Lars Ahlstr?m <lea56@...> wrote:
1 ] !!! =)get a square of the sides = 1.Your square of area=1 in the first quadrant of the XY plane, this is correct. And if I pinpoint X= -1 and Y= -1 I get a square with the sides -1,and the area is then -1. foot, inch, yard or whatever.The area of the square in the third quadrant is area=1 as well. Remember that Area = length * height for a square, that being Area = - 1 *-1 = 1, Area is not negative unless it is of a hole or empty space. The root of -9 is -3 !!! (I think¡;)Almost. The root of -1 is "i" for math people, and is "j" for electronics people. i or j being root(-1) i or j squared = -1,remember (root(-1))^2 the root and exponent cancel i or j ^4th power = -1 *-1 = 1 you get the idea. So, root(-9)= 3i or 3j for electronics people. This ordinate in the complex plane is O= 0 + 3j, or simply 3 in the y direction, and 0 in the x direction. There are lots of ways you can play with this to give all kinds of phasors and vectors. Matt F?r arthurokquestionably useful information.questionably useful information.method. after 33 ayears... rumour)±è²õ²â³¦³ó´Ç²õ¾±²õ¡ from agot a anonymously job advertise in his mail for this teacher job teacher,former headmaster. He was totally incompetent as a mathematician instrument techand had one item in his track record only: as a mechanical ownat ASEA. He was totally unable to give me the idea (part from my brainsone. Yourlack of fantasy) of the "root of minus one".Well, it's an abstract concept, I guess it's better treated like only "idea" should be of the properties of this number, and someby just knowing that the number has "otherwise" normal properties, i.e. youtreat it real numbers. And when you square it, it goes away. I did my grad levelmight be) minimal properties are necessary to extract a lot of mathematicalexpression power.
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Re: Invitation for another exchange of questionably useful information.
Lars Ahlstr?m
Yeah, I understand. Its just to accept.
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But the whole brain of mine want to give the result [ sqrt(-1) = -1 ] !!! =) If I draw a carthesian coordinate system and pinpoint X=1 and Y=1 I get a square of the sides = 1. The square is 1. meter, mm, inch, foot or whatever And if I pinpoint X= -1 and Y= -1 I get a square with the sides -1, and the area is then -1. foot, inch, yard or whatever. The root of that square is -1 !!! The root of -9 is -3 !!! (I think¡;) That¡¯s why I cant accept it, I guess. I also see cube root of -1 = -1, no problem! ;) But Im just a fool¡ /Lars -----Ursprungligt meddelande----- Fr?n: TekScopes@... [mailto:TekScopes@...] F?r arthurok Skickat: den 30 december 2006 23:57 Till: tekscopes@...; Kuba Ober ?mne: Re: SV: [TekScopes] Invitation for another exchange of questionably useful information. its a shared "delusion" ----- Original Message -----
From: Kuba Ober To: tekscopes@yahoogrou <mailto:tekscopes%40yahoogroups.com> ps.com Sent: Saturday, December 30, 2006 12:02 PM Subject: Re: SV: [TekScopes] Invitation for another exchange of questionably useful information. On Friday 29 December 2006 05:38, you wrote: That post reminds me of my own high school drama: The j-omega method.brains lack of fantasy) of the ¡°root of minus one¡±.Well, it's an abstract concept, I guess it's better treated like one. Your only "idea" should be of the properties of this number, and some applications that suit your interests. I don't think I have any other "ideas" here. You can go pretty far by just knowing that the number has "otherwise" normal properties, i.e. you treat it like any other number that only doesn't "mix" (in addition) with real numbers. And when you square it, it goes away. I did my grad level vibrations course without using any other "higher" properties (whatever those might be) of sqrt(-1). I guess it shows what a powerful concept it is: only minimal properties are necessary to extract a lot of mathematical expression power. Cheers, Kuba [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] |
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Re: Invitation for another exchange of questionably useful information.
Reactance, Negative Frequency, Imaginary numbers, Inductance,
Capacitence, complex phasors, complex exponentials, Transform math... If you have issues with these concepts then look at your options: 1. Become an EE student (I am one and it has done miracles for my understanding of systems) 2. Get yourself a copy of the ARRL Handbook 3. Get copies of older electronics books 4. Read Wikipedia articles 5. Take an Applied Math class It's all out there all you have to do is read. What I don't understand is why my inbox gets filled up with sillyness that EE students understand at a basic level. P.S. If you don't believe in Negative Frequency, don't debate it with me, just take a Communications Systems class or a DSP class and you will see where the math and concepts are justified. |
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Re: Invitation for another exchange of questionably useful information.
arthurok
its a shared "delusion"
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----- Original Message -----
From: Kuba Ober To: tekscopes@... Sent: Saturday, December 30, 2006 12:02 PM Subject: Re: SV: [TekScopes] Invitation for another exchange of questionably useful information. On Friday 29 December 2006 05:38, you wrote: > That post reminds me of my own high school drama: The j-omega method. > > The root of minus 1? still bugs me. Haven?t yet figured it out after 33 > years... > > For me it was too mind blowing. Had to stop thinking before I got a > psychosis? > > > > And? our teacher back then, was a well known idiot, that (by the rumour) > got a anonymously job advertise in his mail for this teacher job from a > former headmaster. He was totally incompetent as a mathematician teacher, > and had one item in his track record only: as a mechanical instrument tech > at ASEA. He was totally unable to give me the idea (part from my own brains > lack of fantasy) of the ?root of minus one?. Well, it's an abstract concept, I guess it's better treated like one. Your only "idea" should be of the properties of this number, and some applications that suit your interests. I don't think I have any other "ideas" here. You can go pretty far by just knowing that the number has "otherwise" normal properties, i.e. you treat it like any other number that only doesn't "mix" (in addition) with real numbers. And when you square it, it goes away. I did my grad level vibrations course without using any other "higher" properties (whatever those might be) of sqrt(-1). I guess it shows what a powerful concept it is: only minimal properties are necessary to extract a lot of mathematical expression power. Cheers, Kuba |
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Re: Chopper wanted (the electromechanical kind)
Looking for GAP/R (Philbrick) amplifiers might help. Some of those wereYes, I had though of that. I think, though, that I would be just as guilty of a crime doing that as I would be taking the tubes out of an early Tek scope to make an guitar amp. I think that if I got one of those amplifiers, I'd have to build it a little shrine... There's one in that auction place right now, too, taunting me. |
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Re: Bringing up a 555
This is not for filtering. The L manual says:
"Low-frequency peaking for the X10 amplifier is provided mainly by C6002A and C6002B in the plate circuits of V5942 and V6042. With their associated resistors, these capacitors form a low-frequency boost network to compensate for the low-frequency attenuation introduced in the cathode circuits, the screen circuits, and the RC coupling network between the Second amplifier and the Second cathode follower. ... the amount of attenuation can be varied with the LOW FREQ. ADJ. control in the grid of V6132." This technique is discussed in detail in "Typical Oscilloscope Circuitry." Larry Christopher --- In TekScopes@..., "morriso2002" <vilgotch@...> wrote: It certainly has quite comprehensive decoupling of the B+ to the lowout my L to check, but that's almost certainly what it's for. Thatquite a high gain wideband amplifier and keeping such devices stable isnot a trivial design task! |
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Re: 7D15 COUNTER TIMER , FAULTY U688
Lars Ahlstr?m
I have an invaluable book from Fairchild, published 1973. ¡°The TTL
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Application Hanbook¡±. I checked your need, and what I can see, the only thing you need is a divide by 10 counter. The 8292 is very like the old 7490, today probably the 74LS90, in that it can easily divide by 10. The 7490 is two counters, one modulo 2 and one modulo 5. Together they divide by 10. You need to make a pin adapter. In the pdf you need the LS90 B config, I guess, in order to get a symmetrical output. I hope this was a step in rite dir 4 u. /Lars -----Ursprungligt meddelande----- Fr?n: TekScopes@... [mailto:TekScopes@...] F?r arthurok Skickat: den 30 december 2006 12:26 Till: TekScopes@...; Craig Sawyers ?mne: Re: [TekScopes] 7D15 COUNTER TIMER , FAULTY U688 maybe dean kidd has one ----- Original Message -----
From: Craig Sawyers To: TekScopes@yahoogrou <mailto:TekScopes%40yahoogroups.com> ps.com Sent: Saturday, December 30, 2006 1:41 AM Subject: RE: [TekScopes] 7D15 COUNTER TIMER , FAULTY U688 the XTAL osc/divider board. In fact a faulty N8292A (U688) Tek PNOnly thing I could find was a reference to it as a decade counter. Perhaps someone on the list with an old Signetics logic book could confirm the details (IOW why it was chosen compared with 74xx logic). Craig [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] |
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Re: Chopper wanted (the electromechanical kind)
Kuba Ober
There used to be such a thing as an electromechanical chopper (AKALooking for GAP/R (Philbrick) amplifiers might help. Some of those were chopper-stabilized and used IIRC Airpax choppers. Cheers, Kuba |
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Re: Invitation for another exchange of questionably useful information
Kuba Ober
Being myself a remarkably stupid fellow, I have had to unteach myself theHadn't we all :) and now beg to present to my fellow fools the parts that areThat's like with some "advanced" and "seemingly complex" ultra-low-current measurement. If you look for it on-line, there's a Bob Pease EDN article where he explains how he measured femtoampere op-amp input currents using the op amp itself, a capacitor, some teflon standoffs, and some ingeniuity. One could come up with a thousand more complicated methods that wouldn't even work as well. A similar "complex made simple" example is the outstanding L/C Meter IIB (no relationship to the maker, yada yada), at . It gives big bang for the buck, considering the "trivial" circuit it employs. The "triviality" is only a crooked impression -- it took some insight to come up with a device so simple and so powerful. It doesn't measure certain classes of components (large dissipation/slow cores like laminated iron), but for RF work you don't really need much else. One could come up with thousand more such examples which set apart the "enkelt och geniallt" (my favourite Swedish saying: simple and ingenious) from the mundane and complex. Cheers, Kuba |
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Re: Invitation for another exchange of questionably useful information.
Kuba Ober
On Friday 29 December 2006 05:38, you wrote:
That post reminds me of my own high school drama: The j-omega method.Well, it's an abstract concept, I guess it's better treated like one. Your only "idea" should be of the properties of this number, and some applications that suit your interests. I don't think I have any other "ideas" here. You can go pretty far by just knowing that the number has "otherwise" normal properties, i.e. you treat it like any other number that only doesn't "mix" (in addition) with real numbers. And when you square it, it goes away. I did my grad level vibrations course without using any other "higher" properties (whatever those might be) of sqrt(-1). I guess it shows what a powerful concept it is: only minimal properties are necessary to extract a lot of mathematical expression power. Cheers, Kuba |
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Re: Tektronix 492BP chassis heat.
--- In TekScopes@..., Didier Juges <didier@...> wrote:
"... Over here, this is the season where a little bit more heat in the shack is a good thing :-) The 494P is the second best shack heater in my stable, at 170W. The HP 5370A is close behind at 160W. The best is the HP 8673M at 200W. ------------------------------------------------------------------ The clear winner here is the DSA602A at 585 Watts! |
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Re: Tektronix 492BP chassis heat.
Didier Juges
I have both a 492 and a 494P and both run quite hot (measured with my finger). I did not put a thermometer on it, but 56 degrees C sounds about right, I can lightly touch it but would not want to press my finger against it.
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Over here, this is the season where a little bit more heat in the shack is a good thing :-) The 494P is the second best shack heater in my stable, at 170W. The HP 5370A is close behind at 160W. The best is the HP 8673M at 200W. I think the small fan blowing over the heat sink makes sense, I am considering adding one to the rack where the instrument resides. If you have ever opened the instrument, the cooling fan is quite small and it's not clear where the air circulates, but one thing is sure, not much blows over the heat sink. Some air may find its way through the holes, but I have not been able to feel any air flow. On the other hand, the heat sink supports power transistors that can run at 80 degrees or more pretty much forever, so there should not be real concerns for the reliability of the instrument (I think that should be established by now, these instruments have great reliability), but it is a concern for handling it when it has just been powered. Didier KO4BB Gerald wrote: Hi all, |
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Re: 7D15 COUNTER TIMER , FAULTY U688
Chuck Harris
The 8292A is a low power presettable decade counter that can be connected
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as a /2 or /5 counter. In the biquinary mode, it is a /5 followed by a /2, and produces a square wave. The outputs can be set to the D inputs on the transition of the data strobe line. The minimum count rate is 5MHz, and typical 10MHz. The 7490 is a better counter; the only reason to use an 8292A is if you need the presettable characteristic. -Chuck Harris Craig Sawyers wrote: the XTAL osc/divider board. In fact a faulty N8292A (U688) Tek PNOnly thing I could find was a reference to it as a decade counter. Perhaps |
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Re: Invitation for another exchange of questionably
Russ
Just need to remember ELI the ICE man. This is the way I learned it in the early 70s. See . I think you have it reversed.
Russ WQ3X >>>>>>>>>> I'm lost with you going down too deep into details, right hand and left hand rule.... Back from school times I just simple memorized (sometimes it's helping to memorize!) - phase shift between AC current flow vs voltage drop on same element (cap/inductor) , and it is helping all the way till today....If current (of coarse AC) is ahead by 90 deg from voltage -> inductor, then opposite if voltage is ahead by 90 deg from current -> capacitor. Greg __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around |
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Re: 7D15 COUNTER TIMER , FAULTY U688
arthurok
maybe dean kidd has one
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----- Original Message -----
From: Craig Sawyers To: TekScopes@... Sent: Saturday, December 30, 2006 1:41 AM Subject: RE: [TekScopes] 7D15 COUNTER TIMER , FAULTY U688 > the XTAL osc/divider board. In fact a faulty N8292A (U688) Tek PN > 156 0091 00 > it seems to be wired in just as a > simple /10 divider. Only thing I could find was a reference to it as a decade counter. Perhaps someone on the list with an old Signetics logic book could confirm the details (IOW why it was chosen compared with 74xx logic). Craig |
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Re: 7D15 COUNTER TIMER , FAULTY U688
--- In TekScopes@..., "hpxref" <face1941@...> wrote:
gate board , which led me a bit astray as the fault was actually on Ime thinking of making up a plug in DIL header with a 7490 to ------------The 156-0091-00 was replaced by 156-0727-01 in all it's appearances. No reference to any parts repl or mod kits so it should be a direct replacement. According to the databook 156-0727-01 is either: Motorola 74LS196ND National 74LS196N/A+ or Texas 74LS196N3 /Hakan |
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Re: Bringing up a 555
Hi Andy,
I have sent you the 21A/22A manual extract off list. I'm not sure what you mean by the big honking filter cap in the L. It certainly has quite comprehensive decoupling of the B+ to the low level amps which is pretty standard practice. I'm too lazy to get out my L to check, but that's almost certainly what it's for. That quite a high gain wideband amplifier and keeping such devices stable is not a trivial design task! Good luck with your scoposaurus, it's worth the effort Morris --- In TekScopes@..., "faustian.spirit" <faustian.spirit@...> wrote: hints from experience on bringing this up without risking unnecessarydamage? heavy!) be bench-tested separately, or will there be unexpected effectsone horizontal, or one only each...? Don't want to switch on and fryrather avoid turning the scope on its side... oh well...)... BTW, doesanyone of the history buffs here know why a Type L has such a big honkingagain...
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zenith5106
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