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Re: Scope grounding and generators
Robert Simpson
Getting back to a Tektronix question, I have P6009 probes. Wouldn't using those be safe from over voltage outputs (If there are any) of a generator to the 465M oscilloscope?
Bob
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Re: Desoldering Iron, was Re: [TekScopes] 466-464 stray wire
Brian Symons
One quick comment about air compressors.
The connector that you use can be a major limiting factor. I had a box of odds & sods that I had obtained over the years & went through them recently when doing a clean up. Some of the connectors may appear identical but they can have a centre hole half or even one third of the size as the better brands which really limits the air flow. When I realised the connector difference I did a few tests & couldn't believe the difference in performance. I went & purchased a number of Japanese made connectors - original manufacturer - & redid my tools & hoses & it is much better now. I also found a couple of air hoses that I had been given had been contaminated internally with oil so you may wish to check that when doing your clean up & tests. Cleaning something off with a blast of air & then having to clean off the film of oil is no fun. a couple of last comments of compressed air. Be very careful when using compressed air to clean out bearings etc. It is possible to cause a bearing to literally explode if you have "fun" & speed the bearing up with the air flow. An instructor showed as a safety report once when someone made a siren using the airflow through a bearing. You also need to be careful of airflow on fans. It is possible to drive the fan so fast that it generates an excessively high voltage int the PCB. I saw an incident report about a motherboard damaged due to this. I wouldn't have thought about it myself. Lastly, I saw an incident report of a person with an air embolism due to using an air hose to clean their clothes while wearing them, so another little precaution, keep it clean of body parts. I am sure we have all broken this rule, cleaning or drying off parts :-) Regards, Brian.
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Switched Mode Power Supplies (was: Scope Grounding and Generators)
Roy Thistle
As requested by the moderator.
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Re: Scope grounding and generators
Roy Thistle
And yet, I do.
If anyone chooses to ignore, then I'll have less to read, less to ponder, and less to write about. Go ahead make your day, if that's what makes it a better day for you. My day has certainly been better for participating in TekScopes.
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Re: refurbishing TM500 and TM5000 hardware
Richard R. Pope
Chuck,
toggle quoted messageShow quoted text
In actuality the TM5000 has both a Linear supply and a Switching supply. GOD Bless and Thanks, rich!
On 10/28/2020 9:28 PM, Chuck Harris wrote:
TM500 has a mains transformer powered linear supply.
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Re: refurbishing TM500 and TM5000 hardware
Chuck Harris
TM500 has a mains transformer powered linear supply.
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TM5000 has an inverter powered switching power supply. -Chuck Harris Richard Erlacher wrote:
I’ve not looked inside one of these frames, of which I have several, to see what sort of power supply they have, but I don’t remember anything that looked like a switch-mode supply. They have electrolytic caps, and that’s what I’m worrying about. Also, the function generators have poorly formed waveforms at the higher end of their frequency range, and that may, in fact be due to aging electrolytics as well. I’ve seen a number of cases, albeit in CRT’s and not these particular units, wherein an aged cap caused failure of a power-transistor, and I had several of those CRT’s so I could remove and replace the cap rather than the transistor, whereupon I found that the transistor was still perfectly good. Subsequent fooling around showed that the cap was in need of reforming, at which point it worked just fine.
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Re: refurbishing TM500 and TM5000 hardware
Richard Erlacher
I’ve not looked inside one of these frames, of which I have several, to see what sort of power supply they have, but I don’t remember anything that looked like a switch-mode supply. They have electrolytic caps, and that’s what I’m worrying about. Also, the function generators have poorly formed waveforms at the higher end of their frequency range, and that may, in fact be due to aging electrolytics as well. I’ve seen a number of cases, albeit in CRT’s and not these particular units, wherein an aged cap caused failure of a power-transistor, and I had several of those CRT’s so I could remove and replace the cap rather than the transistor, whereupon I found that the transistor was still perfectly good. Subsequent fooling around showed that the cap was in need of reforming, at which point it worked just fine.
I’m still having trouble figuring out just how to operate within this environment. I’ll catch on eventually. Regards, Uli Sent from Mail for Windows 10
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Re: Scope grounding and generators
May I suggest that the subject of many of these posts should be changed to Switching Mode Power Supplies
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-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Greg Muir via groups.io Sent: Wednesday, October 28, 2020 12:21 PM To: TekScopes@groups.io Subject: Re: [TekScopes] Scope grounding and generators Chuck, In days of yore when power supplies were basically linear it was a simple approach to use any type of AC supply available. Switchers sort of changed that scenario to a certain degree. There are people out there who aren’t aware that most of the early UPS units (and still some from today’s production) have square wave outputs. I have not seen any equipment that disliked that waveform but mostly worry about the high risetimes, overshoot and the stress on power supply components. It is obvious that computers and peripherals seemed to have tolerated that Draconian waveform over the years. Simulated sine wave UPS units was a more progressive step in the right direction until “pure” sine wave units came along. But I place quotes around “pure” since those, too aren’t so precise with regards to distortion. I guess if one tricked a UPS unit by modifying it into running constantly or procured an online unit and placing either one between the generator and the load they would have a happier arrangement given any distortion produced from the generator itself. But those pure sine wave output UPSs do carry a significant quiescent current draw. There was one instance several years ago when I was called on to do some RF field testing whereby I connected my spectrum analyzer to a small square wave 12/115V inverter for power. It worked well with no problems but I felt uncomfortable with the 60 Hz noise emanating from the analyzer’s power supply having to deal with the nasty waveform. So I picked up a true sine wave inverter before the next trip out. When on my next outing I connected my new inverter to the spectrum analyzer and things sounded a whole lot better. But much to my surprise the entire RF spectrum of interest was filled with inverter noise!! The problem was eventually rectified by placing the inverter in a shielded enclosure with heavy high frequency filtration on both the 12V input & 115V output leads. There was one time I was doing engineering for a scientific organization where we were modifying cargotainers to house scientific equipment and living quarters for the scientific staff to drop on the decks of research ships for their use. It was known that the AC power provided by the ship’s supply was rather horrid with regards to noise, transients and other anomalies (something akin to the power found on railroad locomotives). So we procured several large AC-AC converters where the incoming power was rectified to DC (linear-wise) then applied to crystal controlled DC-AC sine wave converters to provide pure power for the instrumentation and other facilities. The system was a real power hog and occupied a lot of space but everything worked well. Besides, the ships have boundless amounts of power to keep things going anyway. As I mentioned previously I cannot speak of any experiences where the quality of the incoming AC power has jeopardized the operation of my equipment but I am always cautious when coming up against unusual circumstances and will take measurements where necessary to guarantee satisfactory operation. A few simple measurements takes far less time that repairing broken equipment. Greg -- Dennis Tillman W7pF TekScopes Moderator
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Re: refurbishing TM500 and TM5000 hardware
Ed Breya
Regarding the OP, in the case of TM500/5000 stuff, I'd tend to go with Chuck's recommendation and just plug it in, and turn it on. It would be good to first fire up the empty mainframe, then check the supplies to see if they look about right. If OK, then do the plug-ins, separately and one at a time, so if anything does go wrong, it's easier to figure out. If it makes you feel more comfortable, you can go ahead and bring up the AC line gradually to soften the initial stress on the caps and such. I know the mainframes won't have any problem with that, but I'm not so sure if all the plug-in circuits would be happy with brownout conditions, considering there are so many different kinds. I think they should be OK.
For TM5000 stuff, you can do the same - the SMPS DC supply has UVLO, and a good amount of hysteresis, so it can sit indefinitely at any line voltage from zero to maximum rating. If line is too low, it will just sit there until it returns to in-range, then activate the DC for the plug-ins. However, this is a dual system - the big AC transformer floating secondaries still supply the reduced voltages to any plug-ins that use them. Regarding reforming, I think ideally it would be good for maximizing service life of caps, but it's a matter of practicality. You wouldn't want to have to do each cap in each piece of equipment individually, with limited current and monitoring of leakage. For very large, expensive caps like in heavy industrial gear, this sort of thing is commonly done or at least recommended. I've seen spec sheets for large inverter bulk supply caps, where reforming is considered necessary if it's been out of service more than a year, and even doing so with brand new replacement parts, if more than a year has passed since leaving the factory (where they were formed in the first place). This kind of treatment is justified for a critical, very big expensive part, that may be worth more than a whole bench full of old obsolete test gear, loaded with the piddly little caps we commonly encounter. So, what do we do with our large collections of piddly little caps, stored neatly and wired inside gear that may sit for years or even decades unused? As always, it depends. If you have rather large, expensive caps in some gear, that are few in number, and accessible, then individual reforming may be the way to go. For most other situations, you'll likely have lots of caps, in-circuit, and not easy to get at, so you can choose to just plug it in and go, and see what happens, or try to determine if it's safe to run it up gradually, and hope for some amount of bulk reforming of the caps. You won't be able to readily monitor any leakage and such, but any gross failures will show. I almost always use the plug it in and go method, even though I have plenty of variacs. I'm confident that most "modern" caps that aren't applied too close to their original voltage rating should be just fine after juicing back up. The initial leakage may be high, but it should recover to a reasonable level after some use, as it reforms. What happens to electrolytic caps when they are unused, is the dielectric that was formed when they were made, gradually gets thinner, so the capacitance goes up, and the breakdown voltage goes down. Even a cap that is in service self-adjusts to the applied voltage - its breakdown voltage diminishes, and capacitance goes up as if it was idle, but the applied voltage keeps it formed to at least that level. Actually, I just today did a little reforming of a couple "computer grade" caps I plan to use in a project. They are (were) 34,000 uF, 75 V, and about fifty years old. I put one on the curve tracer to check the condition, and found it quickly went from maybe 10 mA leakage (after charging current settled) down to way less than 1 mA, at 35 V, in a few minutes. It had no problem welding a couple rusty nails together when shorted, limited mostly by the clip/test leads. Same for the other. The application voltage here will be around 25-35 V, so I don't need to get anywhere near the rated voltage, but I'm sure I could by upping it some more - but gradually, in this case. I'll talk some about SMPSs later maybe. Ed
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Re: Tektronix TAS 465 two channel Oscilloscope
stevenhorii
The photo of the back of the TAS 465 shows what looks to me to have slots
(covered) for PC cards. I looked at photos of the TDS 784 and the rear of the case is different, so I don't think Tek used this case for at least the TDS 780 series. However, since the TAS 465 is not a digital scope, I thought they might have used that case for a later scope that used PC form factor cards for options in a digital scope. On Wed, Oct 28, 2020 at 6:19 PM Ken Wright via groups.io <kenwright309= yahoo.co.uk@groups.io> wrote: Thank you John
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Re: Tektronix TAS 465 two channel Oscilloscope
Ken Wright
Thank you John
toggle quoted messageShow quoted text
73Ken
On Tuesday, 27 October 2020, 21:03:05 GMT, John Gord via groups.io <johngord=verizon.net@groups.io> wrote:
Ken, Take a look at the TekWiki: http://w140.com/tekwiki/wiki/TAS465 --John Gord On Tue, Oct 27, 2020 at 01:57 PM, Ken Wright wrote:
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Tektronix TAS 465 two channel Oscilloscope,
Ken Wright
Hello All.Could someone enlighten me with details of a Tektronix TAS 465 two channel Oscilloscope, I have just seen one advertised, and from its picture it looks like e modern digital scope.
73Ken Wright M0KHW - - - -
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Re: Scope grounding and generators
Chuck Harris
And yet, still nobody cares.
toggle quoted messageShow quoted text
More and more I come to realize that ignoring you completely is a very good policy. -Chuck Harris Roy Thistle wrote:
On Wed, Oct 28, 2020 at 10:59 AM, Chuck Harris wrote:Well in the parlance, the claim that: "There is not one person ("body"), such that that person("body") cares (your vernacular) that that person ("body") is a colonial."... that claim is false. Proof: I care.
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Re: Carry-on adventures (was: Re: [TekScopes] Tek R453 - a rack version of a portable scope!)
-
I was in Kansas City about 25 years ago and found a rare Apple II
prototype. I made the mistake of trying to hand carry it back on an airline the next day. I literally spent about 4 hours in the head of security's office talking to him about everything *except* what I was carrying. After all that time he finally announced that he was going to send me over to one of the maintenance departments so that they could open the computer to be sure that there was nothing inside. I said "Oh, you want to see the inside of this" as I popped open the lid. Luckily I had gotten to the airport about 6 hours early so this episode provided an entertaining diversion. On Wed, Oct 28, 2020 at 3:58 PM Brad Thompson <brad.thompsonaa1ip@gmail.com> wrote: Chuck Harris wrote on 10/28/2020 2:14 PM:I used to take my brand new 2465 on a lot of plane flights<snip>
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Re: Scope grounding and generators
Roy Thistle
On Wed, Oct 28, 2020 at 10:59 AM, Chuck Harris wrote:
Well in the parlance, the claim that: "There is not one person ("body"), such that that person("body") cares (your vernacular) that that person ("body") is a colonial."... that claim is false. Proof: I care. If you limit your universe of discourse to the Tekscopes forum, the claim is still false. (Same proof.) If you interpret your claim within the vernacular, the claim is in-consistent... as given. As for ants... Peng Lei style at most... well... one person may wax metaphorical, even poorly so... yet deny the legitimacy of others to do so. As for UPS et. al., under-cover, or by the label...yes, they come and go out of the computer center(s)/server-room... and more than a few have been scrapped.
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Carry-on adventures (was: Re: [TekScopes] Tek R453 - a rack version of a portable scope!)
Brad Thompson
Chuck Harris wrote on 10/28/2020 2:14 PM:
I used to take my brand new 2465 on a lot of plane flights<snip> Hello-- During the mid-1970s hijacking wave, I was working for a corporate research lab that was supporting the company's agricultural division based in Pennsylvania. Returning home from a one-day business trip, I boarded a Philadelphia-to-Boston flight carrying the following: --One steel shaft measuring 3 feet by one inch (gun barrel) --One prototype machine controller in a steel enclosure the size of a shoebox (bomb) --One complimentary (from Avis car rental) manual razor contained in a sealed steel can (hand grenade) --One boxed shoo-fly pie (bacteriological weapon) --A briefcase containing small tools At the time, airports had installed various companies' metal sensors for weapons detection at boarding gates. I walked through without tripping an alarm and was pleased to see that the detector wasn't one of our company's products<g>. 73-- Brad AA1IP
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Re: Scope grounding and generators
Greg Muir
Chuck,
In days of yore when power supplies were basically linear it was a simple approach to use any type of AC supply available. Switchers sort of changed that scenario to a certain degree. There are people out there who aren’t aware that most of the early UPS units (and still some from today’s production) have square wave outputs. I have not seen any equipment that disliked that waveform but mostly worry about the high risetimes, overshoot and the stress on power supply components. It is obvious that computers and peripherals seemed to have tolerated that Draconian waveform over the years. Simulated sine wave UPS units was a more progressive step in the right direction until “pure” sine wave units came along. But I place quotes around “pure” since those, too aren’t so precise with regards to distortion. I guess if one tricked a UPS unit by modifying it into running constantly or procured an online unit and placing either one between the generator and the load they would have a happier arrangement given any distortion produced from the generator itself. But those pure sine wave output UPSs do carry a significant quiescent current draw. There was one instance several years ago when I was called on to do some RF field testing whereby I connected my spectrum analyzer to a small square wave 12/115V inverter for power. It worked well with no problems but I felt uncomfortable with the 60 Hz noise emanating from the analyzer’s power supply having to deal with the nasty waveform. So I picked up a true sine wave inverter before the next trip out. When on my next outing I connected my new inverter to the spectrum analyzer and things sounded a whole lot better. But much to my surprise the entire RF spectrum of interest was filled with inverter noise!! The problem was eventually rectified by placing the inverter in a shielded enclosure with heavy high frequency filtration on both the 12V input & 115V output leads. There was one time I was doing engineering for a scientific organization where we were modifying cargotainers to house scientific equipment and living quarters for the scientific staff to drop on the decks of research ships for their use. It was known that the AC power provided by the ship’s supply was rather horrid with regards to noise, transients and other anomalies (something akin to the power found on railroad locomotives). So we procured several large AC-AC converters where the incoming power was rectified to DC (linear-wise) then applied to crystal controlled DC-AC sine wave converters to provide pure power for the instrumentation and other facilities. The system was a real power hog and occupied a lot of space but everything worked well. Besides, the ships have boundless amounts of power to keep things going anyway. As I mentioned previously I cannot speak of any experiences where the quality of the incoming AC power has jeopardized the operation of my equipment but I am always cautious when coming up against unusual circumstances and will take measurements where necessary to guarantee satisfactory operation. A few simple measurements takes far less time that repairing broken equipment. Greg
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Re: Tek R453 - a rack version of a portable scope!
Chuck Harris
I used to take my brand new 2465 on a lot of plane flights
toggle quoted messageShow quoted text
as carry-on luggage. Typically I carried my attache case tool kit (stuffed to the gills) and my scope. The tool kit went in the overhead, and the scope was nestled under the seat in front of me. I put a cardboard sleeve around the scope to protect it from getting bunged up. It was brand new, and it was mine. I probably wouldn't have if it had belonged to an employer. Today, I would never be able to carry either on a plane. TSA simply won't allow you to carry tools. The last time I carried my tool kit, the airline screener (pre TSA) wanted to see what was in this case that caught her eye on the x-ray scanner. She saw my little OK Tools spring actuated solder sucker and wanted to know what it was. So, I grabbed it, cocked it, and pressed the button. She about jumped out of her socks! Chuck had a lot of 'splaining to do to a lot of folks with guns. They made me take the solder sucker apart, and explain what it does, and they made a lot of drug jokes about the pair of hemostats I always carried in my kit... They didn't have a thing to say about my box cutter, or Swiss Army knife... Good times... -Chuck Harris Dennis Tillman W7pF wrote:
Hi Dave,
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Re: Scope grounding and generators
Roy Thistle
On Wed, Oct 28, 2020 at 10:13 AM, Paul Amaranth wrote:
Yes, they will do that. Some are more fussy than others. As you pointed out, for a non-inverter generator, you need to spec. a nominal load. A generator and a battery bank, in the context of this discussion is not meant for long term continuous duty... however you spec that. Nothing wrong with batteries, if you spec it right, and realistically. Here in the colonies, the local power provider specs +- 0.5 % from 60Hz nominal... as per the NPPC Directory 12. That's as bad as line power frequency variation could get? Maybe not. But in the long run for power grid interoperability that's the standard they are quoting. 1% would be good?... good enough for me (I don't use/recommend power line frequency as a frequency standard.) 2% is okay? I think some UPS will still operate within 1%; but, maybe not... the newer ones are better. And just to point it out (which I sure you already know; but others might be missing?)... inverter generators are... well they are just a DC power source, running a kind of UPS.
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Re: Scope grounding and generators
Chuck Harris
I have been in involved in the scrapping of thousands of
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commercial grade UPS's from a lot of different manufacturers. There are two general varieties. The Standby UPS, and the True UPS. The standby UPS comes on when the power quality reaches a certain level of degradation. The true UPS supplies the load's power continuously from its inverter. True UPS's can produce power continuously, as that is what they are designed to do. Standby UPS's are generally designed with only enough cooling to supply power until the internal battery is exhausted. The True UPS is typically very heavy, has a strong fan that runs all the time. They also generates a lot of heat. The Standby UPS only makes noise and generates heat when the power is bad. I would guess that we get 100 Standby UPS's for every True UPS. Which makes sense. Why would anybody want a machine under their desk that gets hot, wastes power, and sounds like a vacuum cleaner? -Chuck Harris OBTW Roy, I am pretty sure that nobody cares that you are a colonial. I asked some ants that invaded a scrap UPS, and they said, "Isn't everybody?" Roy Thistle wrote:
On Wed, Oct 28, 2020 at 06:40 AM, Chuck Harris wrote:Nope, unless you buy it from Wally's.
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