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Re: Who's up to some remote troubleshooting?
Lynn Lewis
I'm ashamed to admit I have not checked that. Will do so in the A.M.
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Thanks. Lynn -----Original Message-----
From: Miroslav Pokorni [mailto:mpokorni2000@...] Sent: Tuesday, January 22, 2002 4:56 PM To: TekScopes@... Subject: Re: [TekScopes] Who's up to some remote troubleshooting? Hello Lynn, How about Trigger Source Selector (or whatever is name of that mux controlled by a rotary switch) being stuck to Channel A. I think that the selector proper are two ICs that get alternatively disabled by a voltage input; that might be even broken wire (or trace) coming from the rotary switch, so select input is in default position. Regards Miroslav Pokorni |
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Re: On screen display and other CRT items....
I was initially surprised by the 40-80Kh number also. The difference I think
is that in a scope the tube is not driven as often (duty factor) or as hard (especially white background applications) as a CRT is in a raster scan application. Therefore I would expect digital scopes using raster CRT displays to have shorter lives than analog scopes or, say, 2400 series digital scopes which vector write an analog scope type CRT. In CRT raster scan applications, I would agree with 10Kh though they seem to last a lot longer now than 10-15 years ago. Remember those old 12" monochrome CRT monitors for PC use in the early 1980's (e.g. for HP80 series desktop computers)? If we left those greenscreens on 24/7 on our burn-in systems, they'd be toast in a year. After the first wave had to be replaced, the production operators would turn them down at night before they went home, and left them down whenever they did not have to see the display. In later years (the systems ran 17 years I'm proud to say), we couldn't even find replacement "NTSC sorta" analog input monitors. And how about those EGA color displays from around 1990?--tubes went fuzzy fast with Windows applications. We had a whole room of the things with bad tubes (and also broken electronics). Of course it didn't help that people ran, ahem, "screen saver" pictures on them when not in use. If the scope CRT number is truly closer to 10Kh there would be a lot more junk scopes around our operation, as most are left on in production, through two shifts, 5+ days a week, in auto sweep mode (with the brightness turned up too high to boot). To the best of my knowledge, we've never pulled a CRT in any of the scopes, and most of those go back more than 10 years (including a couple Tek 465Bs, Leader 100Mhz dual trace, a couple Tek 2200 series). Any more we would junk them for whatever cause if they failed--I have two I got that way. One (465B) I restored and the other (TAS465) I haven't found a service manual for yet. Both have good CRTs though. The only dim scope tube is in our trusty 571 (bought from Tucker many moons ago) which exhibits the double peaking on the intensity control that others have mentioned. The trace is pretty dim when cold, though improves with a good warmup. I watch it closely to make sure nobody just leaves it running. Quite frankly, I don't think there is anyone left besides me that can run it anyway so it is in a way "out to pasture". I've wondered if a replacement CRT is available for them from anybody.... Don |
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Re: Digitizer on eBay
Gaston,
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The EMP is a very wild beast. One of the first tests where effects were to be measured was a test named Starfish. It fired a bomb about 200 miles above Johnson Island (do not know how far on the side). As result, parts of Hawaii lost electricity and no one expected that. A nuclear caused EMP is always associated with high altitude shots. I am not sure, but it looks like lack of atmosphere is important, possibly not to attenuate charged particle flux. I do not think that any of Nevada tests had significant EMP, most of them were underground. My understanding was that instruments were physically destroyed, through shock. I guess, thumper in the hole bought time to transmit out data. Regards Miroslav Pokorni ----- Original Message -----
From: "ghpicard" <ghpicard@...> To: <TekScopes@...> Sent: Tuesday, January 22, 2002 6:52 AM Subject: [TekScopes] Re: Digitizer on eBay --- In TekScopes@y..., "Miroslav Pokorni" <mpokorni2000@y...> wrote:I believe that those digitizers were used to measure all sorts ofparametersduring test, so a number of them was consumed for a single test. Myremember |
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Re: I found a nice 7CT1N :-)!
Jose and Richard,
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When you start working on those 7D01, do not forget that cheap IC sockets were used in them. Reseating ICs does wanders for these plugs. I was burned by trying to find which IC is failing and replacing it to make it work. Then, when original IC was restored plug still worked. The character generator in DF1(2) uses ASCII for input code (that might help when finding which memory chip is not operating). If you need listing for Signetic's IC, used in DF1, I should still have it. Regards Miroslav Pokorni ----- Original Message -----
From: "Richard W. Solomon" <w1ksz@...> To: <TekScopes@...> Sent: Monday, January 21, 2002 3:07 PM Subject: RE: [TekScopes] I found a nice 7CT1N :-)! I also have one of these Plug-Ins. Now I also need to figure out how tomake it work !!am able to look at late at night listed auction items (specially those atwas not too cheap, I must admit (US$180), but it seems in perfect cosmeticCustoms to Spain and shipping is not expensive :-) |
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Re: 7603 lights, and more about transient protection
Hello Dave,
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If those gas filled tubes were high voltage indicators, as Walter thinks, they would not indicate for very long. There are no serial resistors to limit current, once 'indication' takes place, current would go sky high and burn them up. I do not think that gas is neon, either. Neon is fine for indicators, but does not seem capable to support high current density. The indicator that Walter read about in manual is hung across two caps in voltage doubler. Although Tektronix was known to run some caps at the knife edge of voltage ratings, this setup would be a real stretch. The 'high voltage warning indicators' were called 230V and caps after rectifier were rated 200V. I would guess that spark gaps that you are talking about are part of the caps, so they do not show in schematic, I could not find them. A name 'Capacitor with Sparker' seems to be what cap manufacturers used for them (another case of foggy memory). The caps which I saw were discs with an elongation opposite from leads and a radial cut of various width, probably depending on rating. My guess is that disc cap was leaded with continuos wire, making a short across the cap. Then, cap was dipped in coating and a saw cat made desired spark gap width. I have not seen one of those in a long time. I am quite sure that sparkers were to protect scope from outside world. I do not think that to this day there is a requirement to protect line from load. Someone in this group is in power business, maybe he can tell us if 500 hp motor would require protection of the line. Just in case, we should keep quite about that requirement for protecting line from small loads. If European Union hears about it they might add it to EC requirements; those boys have been on a regulation binge forever. Regards Miroslav Pokorni ----- Original Message -----
From: <david@...> To: <TekScopes@...> Sent: Monday, January 21, 2002 8:13 PM Subject: Re: [TekScopes] 7603 lights, and more about transient protection disaster.Miroslav's comments about neon lamps in the older supplies asSome of the supplies have spark gaps as well as neon lamps - an example is |
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Re: On screen display and other CRT items....
Don,
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I like single shot mode for scope standby, too. A number of times I forgot that scope was in single shot and spent some time trying to find out 'what is wrong with my scope', but I still think that is a better way, because you do not have to mess up any settings. It did surprise me that life of a CRT was in the range of 40 k to 80 k hours; my gut feel was that it was around 10 k. I never had a CRT to die on me, it was only passives, mostly electrolytics. While I was still working with tube scopes never had any tube to die on me, though that was a matter of luck, and at that company there was security guard who would come around and turn everything off and write you up even for soldering iron that was left on. When I was talking about keeping a scope on all the time, I did say 'working ' (as opposed to scope from collection used for hobby work). When paid to do work one should not spend too much time trying to save pennies and skip over dollars. Regards Miroslav Pokorni ----- Original Message -----
From: <donlcramer@...> To: <TekScopes@...> Sent: Monday, January 21, 2002 9:48 PM Subject: Re: [TekScopes] On screen display and other CRT items.... The company I work for has sold custom flat panel displays to anothermajor US test equipment manufacturer (use your imagination here). About 5 yearsget in a situation of having to replace backlights mulitiple times during theCRTs, but I digress.one would burn up a tube in roughly 4 to 8 years if the instrument was left on(something not all that abundant as was shown this last summer) and life of otherparts like electrolytic caps, I tend to shut everything off when not in use, orat work for 13 years now, and even when it's on, if I'm not using it for ashort bit, I will put the scope in single shot mode to shutoff the beam andrental instrument. Hopefully, when used only when needed, the instrument willlast a lifetime :>) |
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Re: Who's up to some remote troubleshooting?
Hello Lynn,
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How about Trigger Source Selector (or whatever is name of that mux controlled by a rotary switch) being stuck to Channel A. I think that the selector proper are two ICs that get alternatively disabled by a voltage input; that might be even broken wire (or trace) coming from the rotary switch, so select input is in default position. Regards Miroslav Pokorni ----- Original Message -----
From: "Lynn Lewis" <mrzuzu@...> To: "TekScopes@yahoogroups. com" <TekScopes@...> Sent: Tuesday, January 22, 2002 1:52 AM Subject: [TekScopes] Who's up to some remote troubleshooting? I plan to get back to this after lunch today. Any suggestions would beto see the waveforms. The 7B53A is set to use the internal trigger.receiving square wave, it syncs. If channel B only is receiving square wave, it willthe scope and it's not the 7B53A.scope and follow it right up to U2750. The input pins to U2750 have the squareIf I feed the square wave only into channel A, I can see it on both the input |
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Re: Digitizer on eBay
ghpicard
--- In TekScopes@y..., "Miroslav Pokorni" <mpokorni2000@y...> wrote:
I believe that those digitizers were used to measure all sorts ofparameters during test, so a number of them was consumed for a single test. Myremember I think it's more probable that the units could reliabily withstand just one EMP, so why to risk a second EMP with a total data loss when you could buy a new one... If the unit become damaged *during* the test, the data, if you could recover anything at all, would be either garbage or unreliable at all. Memory circuits (except perhaps ferrite cores) are most sensitive to gamma rad. Anyway, if using ferrite cores, the M part of the EMP could make a nice mess with the contents... Regards Gaston |
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Re: Digitizer on eBay
ghpicard
--- In TekScopes@y..., "Miroslav Pokorni" <mpokorni2000@y...> wrote:
I believe that those digitizers were used to measure all sorts ofparameters during test, so a number of them was consumed for a single test. Myremember I think it's more probable that the units could reliabily withstand just one EMP, so why to risk a second EMP with a total data loss when you could buy a new one... If the unit become damaged *during* the test, the data, if you could recover anything at all, would be either garbage or unreliable at all. Memory circuits (except perhaps ferrite cores) are most sensitive to gamma rad. Anyway, if using ferrite cores, the M part of the EMP could make a nice mess with the contents... Regards Gaston |
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Re: Who's up to some remote troubleshooting?
Craig Sawyers
I don't have a copy of the 7A26 schematic, so this is a *real* stab in the
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dark. How long are the triggering events that you're looking for? I fooled myself for a day recently while trying to fix my HP counter when I was convinced that the input section wasn't working I was feeding it with a 1kHz square wave, and could see nothing at all on the bus lines coming from the differetial line driver on that card. The reason? The output was a 5ns duration ECL pulse at the trigger transitions of the input wave (as set up by the trigger level controls). Once I triggered on the event, and then sped the scope sweep up - there it was! Interestingly (and very tackily) this is generated by using three ECL NORs in a loop, and the output pulse duration is generated by the differential pulse delay of two gates - or about 5ns for 10xxx series ECL. Now since many of the y-amp 7000 series plug ins use custom silicon (as well as the timebase), and much of this fast custom silicon is ECL-based, are you sure that there isn't a triggering event there but of a non-intuitive time duration? Cheers Craig -----Original Message----- |
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Who's up to some remote troubleshooting?
Lynn Lewis
I plan to get back to this after lunch today. Any suggestions would be
appreciated. It's not life or death, just my idea of fun. Item: 7A26 with serial number B2.... Setup: This 7A26 is in a 7704 with a known good 7B53A. I am feeding both channels, not necessarily at the same time, from the 1KHz square wave calibrator. I started at .04V but have worked up to 4V. I'm using a 7904 to see the waveforms. The 7B53A is set to use the internal trigger. Symptom: Can not sync through channel B using internal trigger. If both channels are receiving square wave, it syncs. If channel A only is receiving square wave, it syncs. If channel B only is receiving square wave, it will not sync. Knowns: 1. I have another 7A26 that works perfectly in that same bay so it's not the scope and it's not the 7B53A. 2. If I feed the square wave only into channel B, I can use the other scope and follow it right up to U2750. The input pins to U2750 have the square wave (fuzzy but square). The output pins do not (fuzzy and flat). (Note: If I feed the square wave only into channel A, I can see it on both the input and output of U1750.) The DC voltages around U2750 are very close to those indicated on the schematic and appear to me to be reasonable. I did resistance checks on the resistors in the input network to U2750. 3. I have tried: a. replacing U2750 twice b. replacing U1750 c. replacing Q920, Q940, Q960, and Q980. Suggestions: |
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Re: On screen display and other CRT items....
I also recall, vaguely, something about some adjustments in some 7K mainframesUnfortunately, the IC vertical designs don't have a thermal compensation adjustment. Again, the 7904 is an example, and my 7904s do suffer from swimming readouts. |
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Re: 7603 lights, and more about transient protection
Miroslav's comments about neon lamps in the older supplies asSome of the supplies have spark gaps as well as neon lamps - an example is the 7904. I'm not sure if they are to protect the scope from the power line, or to protect the power line from the scope's HV in case of disaster. |
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Re: Question about 7603
Stan or Patricia Griffiths
The 040-0686-01 mod kit for 7600 series plugin lamps uses an LM309K between +8
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volts in the mainframe and +5 delivered to the plugin compartments for lamp power. Derating of the range of acceptable line voltages and operating temperature of the scope are required if the total plugin lamp current exceeds 1.5 amps. You just add up the lamp current requirements of each plugin to see if it exceeds 1.5 amps to know if you have to derate line voltage or temperature specs. The total kit instructions are on 7 pages of microfiche and installation instructions and a parts list are included along with a derating chart. I can provide hard copies of the instructions for 50 cents per page plus $1 for postage (total = $4.50). Stan w7ni@... david@... wrote: Is the 7603 supposed to light up the buttons on the plug-ins? Some of myThere is a listing in the catalog for the 040-0686-01 "lights power supply |
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Re: On screen display and other CRT items....
The company I work for has sold custom flat panel displays to another major
US test equipment manufacturer (use your imagination here). About 5 years ago, their info said their analog scope CRT life historically was between 40-80K hours typical. This discussion was in the context of concern regarding CFL backlight life of AMLCD flat panel displays, which was about 10K hours back then (to 50% of initial brightness). They did not want to get in a situation of having to replace backlights mulitiple times during the life of the instrument, when this wasn't an expectation for the analog CRTs, but I digress. Assuming Tek tube life is similar to the stated CRT life mentioned above, one would burn up a tube in roughly 4 to 8 years if the instrument was left on all the time. For that reason, plus the benefit of saving power (something not all that abundant as was shown this last summer) and life of other parts like electrolytic caps, I tend to shut everything off when not in use, or when I won't be back to it for more than a couple hours. I've had a 2465A at work for 13 years now, and even when it's on, if I'm not using it for a short bit, I will put the scope in single shot mode to shutoff the beam and readout. It still has a very healthy CRT despite starting life as a rental instrument. Hopefully, when used only when needed, the instrument will last a lifetime :>) My Heathkit 25" TV, with brightness and contrast used in moderation, has lasted so far 19 years. Perhaps too long according to my wife.... Don |
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Miroslav: re ESR meter [via 7D01 discussion]
Ashton Brown
Miroslav Pokorni wrote:
Your point noted.. as I haven't gotten around to using the meter - can't say how many caps are marginal. There's a good discussion of the subtleties in following links, incl. limits of mere ohms or capacitance 'checks': ESR meter info: Some more comments about usage: I ordered from Vancouver BC: A different (analog) meter - w/schematic refs As to the Dick Smith kit - I concluded it was cheaper and a lot handier to not reinvent the wheel. Good qual. parts and it worked precisely as described. Anyone with Heathkit experience would achieve same, of course. I haven't tried the hints re small batteries - mentioned in a link below, but it might be useful on odd PS problems in micro-sized devices (hearing aids?) My problem is making the time to troubleshoot a variety of Teks (incl. a few 485s and one 'chirping'!) - whereas I spent my time mostly using scopes.. not in their more subtle repair. Some of the arcane problems which say, the Z-axis board can cause.. stress my more Boolean effforts :( And if a 335 is clockmaking - a 2xx is watchmaking! See what you think of the Dick Smith Special. IIRC schematic is on one or more of these sites. Cheers, Ashton Brown (ex-LBL - particle accelerators. Tons of Tek everywhere!) |
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Re: I found a nice 7CT1N :-)!
Richard W. Solomon
I also have one of these Plug-Ins. Now I also need to figure out how to make
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it work !! BTW, I have a 7D01 plug-in, but condition unknown. Someday I'll plug it in and see if it works. (I had the manual, but sold it.) 73, Dick, W1KSZ -----Original Message-----
From: JOSE V. GAVILA (EB5AGV/EC5AAU) [mailto:eb5agv@...] Sent: Monday, January 21, 2002 1:57 AM To: TekScopes@... Subject: [TekScopes] I found a nice 7CT1N :-)! Hello my friends, As saying says, 'early bird gets the worm'! I start working at 7:00AM... yes, I know it is early in the morning. But it has its advantages: I stop working at 3:05PM (so I have lots of time for other things, including family, hobbies :-), extra works, ...). Also, I am able to look at late at night listed auction items (specially those at eBay Germany and eBay UK) very early. This time, there was a 'Buy It Now!' Tektronix 7CT1N curver tracer. It was not too cheap, I must admit (US$180), but it seems in perfect cosmetic shape and comes with manual. And it is in Germany, so there is no Customs to Spain and shipping is not expensive :-) I have been looking for that curve tracer for a while so I am very happy to have located one. Now I 'just' need to explain it to my wife... but this is another story ;-) I would appreciate any hints about operating that plug-in. Regards, JOSE ---------------------------------------------------------------------- 73 EB5AGV / EC5AAU - JOSE V. GAVILA La Canyada - Valencia (SPAIN) EB5AGV Vintage Radio Site: European Boatanchors List: To unsubscribe from this group, send an email to: TekScopes-unsubscribe@... Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. |
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7603 lights, and more about transient protection
wshawlee2
No, the plug in lights to NOT light in a 7603 frame, this was
intentional, but I don't know the orignal thinking that led to it. 7A26 and similar format vertical plug ins don't need it, and the 7B53A (the intended sweep plug in) has white indicator rings around the pushbuttons, and NO internal lights. so, if yours doesn't light, that's just what it's supposed to do, but the rationale is now lost to history. Miroslav's comments about neon lamps in the older supplies as transient protection are not correct, they were warning indicators for lethal voltage, nothing more. This is even explained in the service manuals. Older unit have no AC transient protection. Tek really should have incorporated transient protection with it's switchers, as many were designed before rugged high voltage FETs existed, and they are easily damaged by transients. I was not suggesting you buy a crappy $4.95 trasient protector, as I use some very high end ones here, but it's up to you. Tek (after many field failures) added this protection to later 2200 series units, and it seemed to help significantly, they were just single ordinary GE varistors. If you are really in love with your gear, by an autocorrecting Liebert UPS, the ultimate in line conditioning. Leaving it on vs. turning it off. well, this argument has raged for decades, but I think you need to consider some simple math: the 7K series runs VERY hot, and it has some definite MTBF limits associated with capacitor and semiconductor failures caused by this, not to mention consuming the CRT. if you leave it on, you are wasting 2/3 of that MTBF at night, and when no one is around. I get the thermal shock argument, but my own long standing experience is that this is an order of magnitude less of a problem than burning the equipment for endless hours. It makes no difference to me what other people do, but to me, the wasting of so much equipment life is silly, and serves no purpose whatsoever. When the tube is gone, you can't exactly whittle one from a block of wood, so think it over carefully. I have often thought of putting a small NTC or other surge limiter in series with the filament to reduce thermal shock, but interestingly, the overwhelming failure mode I have seen from Tek CRTs is going weak or gassy, NOT filament failure. What do you suppose that means? Not good statistical support for leaving it on, that's for sure. all the best, walter |
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Re: On screen display and other CRT items....
Stan or Patricia Griffiths
The only two Tek scopes that I can remember having more than one power switch
are the 507 and 517 and I don't really recall what the real story was on those. I think they were separate switches for filament and DC power. I don't recall anything like a "standby switch". One other reason you might not want to keep your scope turned on all of the time is that tubes in distributed amplifiers develop cathode interface over long hours of on time. The only answer to cathode interface is to retube the amplifier. In order the "save the CRT" it has also been suggested to simply turn down the intensity to cut off the CRT beam current. In the case of some of the 560 series, I understand that even if there is no visible display on screen, the CRT cathode may be emitting anyway. This is because some scopes used a scheme of driving the beam off screen during retrace time so it was not visible, rather than actually shutting down the CRT gun. I can't be more specific about model numbers because this is all from my weak, 63 year old, memory . . . I also recall, vaguely, something about some adjustments in some 7K mainframes to minimize things like readout jitter due to thermal heating of the vertical position stages when the vertical has to make large and rapid changes in beam position due to going from displaying readouts on screen to switching way off screen to a trace way above or way below the screen. This is another "weak" memory of mine. Maybe Dean has more on this . . . Stan w7ni@... |
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Re: Question about 7603
Michael
Is the 7603 supposed to light up the buttons on the plug-ins? Some of mybut no light emerges....I remember reading somewhere that the 7000 plugins were designed to be lit, but the poor reliability of the bulbs and the difficulty in changing them caused Tek a rethink and the idea was scrapped. Dunno if this is correct. (mine don't light either). :-( Michael |
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