Re: What have i here ? (Tek TDS 540 )
URL show two pictures
Pleas let me know, if url doesn't work.
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I quite often have a need to sense small currents (~10-200mA) and have
always wanted a clamp on current probe but even the used ones for a
scope are out of my budget.
A series resister is one solution but it is rather intrusive and
sometimes the circuit cannot tolerate the voltage drop.
Recently, at a garage sale I came across an old RS current clamp
intended to be used with a multimeter, it is a Hall effect device so
it's good for DC too, so just as an experiment I attached it to my scope
with a "banana<--->BNC" adapter and it works a treat :-)
The sensitivity is 1mV for 10mA and the bandwidth seems adequate for my
needs. If I need better sensitivity I just wind the wire 10 times around
the sensor clamp which gets me 1mV per 1mA.
Since I'm trying to get an Arduino and ESP8266 WiFi adapter to run on
batteries it is proving invaluable.
It may not have the bandwidth of a purpose built 'scope current probe
but it seems OK for my needs.
Dave
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Re: 466 Channel 2 problem
Hi Roger,
Thanks for your comments so far.
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-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Roger Evans via Groups.Io
Sent: 09 December 2018 08:27
To: [email protected]
Subject: Re: [TekScopes] 466 Channel 2 problem Colin, If you press the beam finder and then switch Ch 2 to 'invert' does the position of the channel 2 trace move? This is a quick check on whether the channel 2 imbalance is before or after the >invert circuitry (Q220 - Q226). Yes, it does. It starts off at about three main divisions above the graticule centre-line and then drops to about three below the centre-line when "invert"-ed. I am puzzled when you say that you 'mostly cannot see anything untoward' on channel 2 voltages and then say that the voltages on TP11 and TP14 are very different. Are they the only >places where the DC voltages on the two halves of the paraphase amplifier are noticeably out of balance? Since the amplifier is DC coupled throughout a failed transistor or diode tends to >upset the DC levels through other parts of the chain and finding the failed component can take patience. If the transistors are socketed then just pulling them out for testing, or swapping >with the corresponding channel 1 parts if you don't have a transistor tester is an easy route. If they are soldered in then you need to measure Vbe and Vce to check that they are consistent >with a transistor operating in its linear regime. Don't forget that the switching diodes CR314 - CR318 are part of the DC circuitry so a failed diode will also upset the amplifier balance. I understand your puzzlement. I had actually only checked a few voltages, but I had probed with another scope the signals at the various points indicated in the manual and seen the signal going through, though there was a voltage offset. I had only recently decided to check the voltages. My hope was that there was a common failure that someone with more experience would immediately point out to me. Mea culpa. I will check out the other voltages more rigorously. The probablility is that you have a failed semiconductor but it is possible that a resistor has drifted badly over time. Yes, I am inclined to agree that there is a failed semiconductor. Now to find which one... Roger Colin.
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Re: wrenching ( was: Capacitor sniffing) OT
Re: vomit smelling screwdrivers and : ?There were a couple different types of plastic used for tool handles,
and one develops a white film as it decomposes. Cellulose Acetate, and Cellulose Acetate Butyrate. I /think/ both get the white-crud. ? It's the CAB that breaks down and releases butyric acid, which smells like vomit.
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Re: Russian Tunnel Diodes
I don't want my comments to be a source of disparagement of Leo's
work. I haven't spent a great deal of time studying what he has
done, but in all of the scope pictures he has presented, there is
very significant leading edge overshoot and ripple. To my weathered
eyes the peaking and ripple appears to be 20-30% of the pulse
amplitude.
In calibrating high performance scopes, you need a fast risetime,
flat-topped pulse. You take that pulse, and adjust the scope under
test's pulse forming networks for a sharp leading edge with no
overshoot, and a flat top. Usually you can't achieve perfection,
but I always have been able to do much better than what I see in
the scope pictures, using the Tektronix tunnel diode pulser, or
the Tektronix CG5011 calibrator.
Generally what one sees when a pulser, with a nearly ideal shape
(so says a sampling scope with 10x the bandwidth of say a 7104...),
is used for calibration, is a risetime that appears slower than
the sampling scope showed, and a curved leading edge. Not a
30% peak, unless the peak was already there.
In other words, the peaks and ripples get filtered out by the
slower scope's networks, not accentuated. That is the whole point
of the transient calibration.
If Leo's pulser is intended for measurement of the risetime of
wide and varied scope models, as a method of displaying and calculating
the theoretical bandwidth, then it is perfect.
If it is intended as a calibration device, I have worries that it
won't do the job as well as the Tektronix TD pulser, or the CG5011
calibration generator. Probably all it needs is a little better
matching network between the comparator switch and the DUT.
-Chuck Harris
Reginald Beardsley via Groups.Io wrote:
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Consider the time scale on Leo's plots and the response of the scope he's using which is what you are seeing in the calibration plot. I can't find my plot right now as my bench is undergoing at upgrade and everything is a huge mess. But IIRC the entire length of the step response Leo provides is less than the sample rate of anything most of us are likely to own.
I have put the BNC version on a new MSOX3104T. 436 pS rise time and 7% overshoot. I discussed with Keysight support which confirmed what I was seeing. A 750 MHz low pass filter reduced the overshoot to well less than 1%. But I could not inline the filter.
I then had an RTM3104 on demo. It arrived with 350 pS rise time and 3% overshoot. If I applied a 1 GHz LPF I had no visible overshoot. I was ecstatic. But for some legal reason the K18 option is not available in North America and the available FFT was completely useless. It was suggested that I install the 1.300 FW update. After that it had 10% overshoot. Restoring 1.100 did not restore the original response.
I've looked at 4 other scopes with Leo's pulser. I have no doubt that the waveform I saw is the true step response of the instrument. Now if you have one of the new Keysight 256 GSa/S 111 GHz DSOs, you probably need a better signal source. I suspect it would require one to give an accurate picture of the step response of Leo's pulser.
There are a large number of plots of the pulser output made on a wide variety of scopes in this thread.
My big problem at the moment is he's developed a version that produces 100pS wide pulses. I'm trying to come up with a justification for buying one.
I was amused that there were two posts in succession about Leo's pulser.
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Re: Russian Tunnel Diodes
Consider the time scale on Leo's plots and the response of the scope he's using which is what you are seeing in the calibration plot. I can't find my plot right now as my bench is undergoing at upgrade and everything is a huge mess. But IIRC the entire length of the step response Leo provides is less than the sample rate of anything most of us are likely to own.
I have put the BNC version on a new MSOX3104T. 436 pS rise time and 7% overshoot. I discussed with Keysight support which confirmed what I was seeing. A 750 MHz low pass filter reduced the overshoot to well less than 1%. But I could not inline the filter.
I then had an RTM3104 on demo. It arrived with 350 pS rise time and 3% overshoot. If I applied a 1 GHz LPF I had no visible overshoot. I was ecstatic. But for some legal reason the K18 option is not available in North America and the available FFT was completely useless. It was suggested that I install the 1.300 FW update. After that it had 10% overshoot. Restoring 1.100 did not restore the original response.
I've looked at 4 other scopes with Leo's pulser. I have no doubt that the waveform I saw is the true step response of the instrument. Now if you have one of the new Keysight 256 GSa/S 111 GHz DSOs, you probably need a better signal source. I suspect it would require one to give an accurate picture of the step response of Leo's pulser.
There are a large number of plots of the pulser output made on a wide variety of scopes in this thread.
My big problem at the moment is he's developed a version that produces 100pS wide pulses. I'm trying to come up with a justification for buying one.
I was amused that there were two posts in succession about Leo's pulser.
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Re: wrenching ( was: Capacitor sniffing) OT
I think Shakespeare warned us of that Chuck?
"The tongues of mocking wenches are as keen as is the razor's edge"
...oh....sorry........w*R*enching....misread the subject.....
Adrian
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On 12/9/2018 3:42 AM, Chuck Harris wrote: I think that in many
cases if you removed the plastic you would find the handle
was thin and spindly with sharp edges
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Re: Tube test adaptor for Tektroinx 575 was: Re: [TekScopes] FS: miscellaneous Tektronix manuals
That is absolutely true! Should have spotted the potential for confusion since my son is a bass
guitarist :-)
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That can be confused with a type of guitar pickup. :)
Michael A. Terrell The other common term (at least on my side of the pond) was hum bucker.
Craig
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Re: Succession plans and wills - Re: [TekScopes] How Many Scopes?
One of the less bad routes is to a local hackspace/makerspace. My local one has had a Tek 2245 , a Telequipment DM63, and lots of drawers of components.
A problem is that youngsters think digital==good, and analogue=="where's the autoset button?".
Overall I think it is best to dispose of /stuff/ while you can. There's an ebayer in the UK who does that with an accurate description of what does and doesn't work.
I'd love to be let loose in his manshed - two walls of glowing Tek/HP equipment. As it was I picked up a couple of CRTs for ?10 (one worked, one didn't) and a Tek 485 with an entertaining intermittent fault that I eventually traced.
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On 09/12/18 01:16, John Griessen wrote: On 12/8/18 6:36 PM, toby@... wrote:
The "wife seeks to get rid of 97 of husband's instruments by Sunday,
local pickup only", that we see semi-regularly now, is far from the
worst case scenario.
WCS = surviving wife driving tractor over instruments?
WCS = Son calling the "got junk?" company?
WCS = survivors putting craigslist ad for $500 per instrument, and one sells, rest go to estate sale buyer for $75.
WCS = daughter delegates to her daughter, who calls local donations nonprofit that is expert at appraising silverware and furniture and clothing.? Instruments go to Salvation Army and are forwarded to e-waste company.
etc, etc...
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Re: wrenching ( was: Capacitor sniffing) OT
There were a couple different types of plastic used for tool handles, and one develops a white film as it decomposes. I've only seen it in colored handles, but once it starts, it seems to keep eating away the surface and the stink gets worse.
Michael A. Terrell
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-----Original Message----- From: Brad Thompson <brad.thompson@...>
Sent: Dec 8, 2018 10:58 PM
To: [email protected]
Subject: Re: [TekScopes] wrenching ( was: Capacitor sniffing) OT
On 12/8/2018 10:42 PM, Chuck Harris wrote:
If by stink, you mean smell, a lot of plastics start out
benign, and end up really smelly. I have a set of Craftsman
nutdrivers from the 1970's that woke up one day and smelled
like vomit. And, have ever since.
I don't know if it is something the acrylic handles were
exposed to, or perhaps a plasticizer that was put in them
to make them less brittle, but I do know it stinks.
Hello, Chuck--
I have a set of those, too. A set of screwdrivers from that time
don't smell like much of anything.
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Re: wrenching ( was: Capacitor sniffing) OT
That hasn't been my experience, and the same wrench was sold with or without the plastic cover. They have the same weight, since their isn't that much plastic. It was pre 'Cooper Tools' manufactured by Xcelite which was my preferred brand of electronics tools. I still have most of an original Xcelite 99SM roll up tool kit that was given to me by a friend in the Army when I was a short timer. I only wore out a couple tools, since 1974, and the reamers were NLA.
As far as other brands of adjustable wrenches, I have no opinion. Other than some thin open end sets from HF, most of my tools were American made. The HF sets were bought to assemble some connectors, where they didn't need high strength.
Michael A. Terrell
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-----Original Message----- From: Chuck Harris <cfharris@...>
Sent: Dec 8, 2018 10:42 PM
To: [email protected]
Subject: Re: [TekScopes] wrenching ( was: Capacitor sniffing) OT
If by stink, you mean smell, a lot of plastics start out
benign, and end up really smelly. I have a set of Craftsman
nutdrivers from the 1970's that woke up one day and smelled
like vomit. And, have ever since.
I don't know if it is something the acrylic handles were
exposed to, or perhaps a plasticizer that was put in them
to make them less brittle, but I do know it stinks.
As to plastic dipped wrench handles. I think that in many
cases if you removed the plastic you would find the handle
was thin and spindly with sharp edges.... The plastic is
there to hide manufacturing economies.
-Chuck Harris
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Re: wrenching ( was: Capacitor sniffing) OT
I used to have a cheap hammer that someone broke off most of the head, driving a 16 penny nail. It was in the box of 'loaner tools' as a joke. :)
OTOH, someone could have been badly hurt, or killed by that sharp chunk of metal flying across the room.
Michael A. Terrell
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-----Original Message----- From: Jim Ford <james.ford@...>
Sent: Dec 9, 2018 12:56 AM
To: [email protected]
Subject: Re: [TekScopes] wrenching ( was: Capacitor sniffing) OT
Yeah, I had a friend in high school who used to buy cheap tools at the swap meet.? The infamous "lead-head" hammer that got dents in it after pounding in nails and the ratchet extender that twisted at the ratchet end but didn't move at the socket end come to mind.? ?I kept telling him that he was going to get hurt using crappy tools.? Not sure whatever happened to that guy...? Poor quality tools are not only false economy, they can be dangerous.
Jim F
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Re: Mod on horizontal plug-in 7B80
On Sun, Dec 9, 2018 at 04:17 AM, Gary Robert Bosworth wrote: This is a tough one. I have a Tek Plug-In number 7B80. It is mod GB. I see no
mention of this modification in the manuals. It should be quite obvious if compared to an unmodified 7B80. This is what the mod manual insert says: // 7B80 MOD GB This manual insert describes MOD GB as it applies to the Tektronix Time Base plug-in unit. MOD GB increases X2 the horizontal preamplifier gain to extend the top sweep rate to 5 ns/div and to 0.5 ns/div, magnified. Rates slower than 10 us/div have been deleted, limiting the TIME/DIV switch to 11 positions and the front-panel HOLDOFF control has been deleted, and internal circuits wired to provide minimum holdoff for all ranges. // /H?kan
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Re: Tube test adaptor for Tektroinx 575 was: Re: [TekScopes] FS: miscellaneous Tektronix manuals
That can be confused with a type of guitar pickup. :)
Michael A. Terrell
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-----Original Message----- From: Craig Sawyers <c.sawyers@...>
Sent: Dec 9, 2018 4:53 AM
To: [email protected]
Subject: Re: Tube test adaptor for Tektroinx 575 was: Re: [TekScopes] FS: miscellaneous Tektronix manuals
A center tapped filament transformer, or a 'hum balance' circuit to create an artificial center tap
will do
even better. That circuit was often no more than a 200 ohm pot across the winding, with the wiper
connected to ground, and both filament leads floating above ground. A 2W pot was common for this
use.
Michael A. Terrell The other common term (at least on my side of the pond) was hum bucker.
Craig
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Re: Tube test adaptor for Tektroinx 575 was: Re: [TekScopes] FS: miscellaneous Tektronix manuals
A center tapped filament transformer, or a 'hum balance' circuit to create an artificial center tap
will do
even better. That circuit was often no more than a 200 ohm pot across the winding, with the wiper
connected to ground, and both filament leads floating above ground. A 2W pot was common for this
use.
Michael A. Terrell The other common term (at least on my side of the pond) was hum bucker. Craig
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Re: Tube test adaptor for Tektroinx 575 was: Re: [TekScopes] FS: miscellaneous Tektronix manuals
A center tapped filament transformer, or a 'hum balance' circuit to create an artificial center tap will do even better. That circuit was often no more than a 200 ohm pot across the winding, with the wiper connected to ground, and both filament leads floating above ground. A 2W pot was common for this use.
Michael A. Terrell
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-----Original Message----- From: Mike Dinolfo <mdinolfo@...>
Sent: Dec 5, 2018 10:53 PM
To: [email protected]
Subject: Re: Tube test adapter for Tektronix 575 was: Re: [TekScopes] FS: miscellaneous Tektronix manuals
Another thing to consider (if you are feeding tube filaments via AC
power) and want to minimize hum is to use twisted pair wiring to
distribute AC power to the tube filament socket connections (rather than
individual single conductor wires which are haphazardly separated from
each other). Twisted pair tends to minimize inductive (magnetic)
radiation within the equipment/chassis that could otherwise occur with
separated wires supplying AC to the tube socket filament pins; the
magnetic field (at 60 hz) can lead to audio hum. Of course, it's also
OK to use single conductor wires which are twisted together in "paired"
wiring for the filament power distribution.
Mike Dinolfo N4MWP
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Re: 466 Channel 2 problem
Colin,
If you press the beam finder and then switch Ch 2 to 'invert' does the position of the channel 2 trace move? This is a quick check on whether the channel 2 imbalance is before or after the invert circuitry (Q220 - Q226).
I am puzzled when you say that you 'mostly cannot see anything untoward' on channel 2 voltages and then say that the voltages on TP11 and TP14 are very different. Are they the only places where the DC voltages on the two halves of the paraphase amplifier are noticeably out of balance? Since the amplifier is DC coupled throughout a failed transistor or diode tends to upset the DC levels through other parts of the chain and finding the failed component can take patience. If the transistors are socketed then just pulling them out for testing, or swapping with the corresponding channel 1 parts if you don't have a transistor tester is an easy route. If they are soldered in then you need to measure Vbe and Vce to check that they are consistent with a transistor operating in its linear regime. Don't forget that the switching diodes CR314 - CR318 are part of the DC circuitry so a failed diode will also upset the amplifier balance.
The probablility is that you have a failed semiconductor but it is possible that a resistor has drifted badly over time.
Roger
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Re: wrenching ( was: Capacitor sniffing) OT
Yeah, I had a friend in high school who used to buy cheap tools at the swap meet.? The infamous "lead-head" hammer that got dents in it after pounding in nails and the ratchet extender that twisted at the ratchet end but didn't move at the socket end come to mind.? ?I kept telling him that he was going to get hurt using crappy tools.? Not sure whatever happened to that guy...? Poor quality tools are not only false economy, they can be dangerous.
Jim F
Sent from my Verizon, Samsung Galaxy smartphone
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-------- Original message --------From: "Michael A. Terrell" <mike.terrell@...> Date: 12/8/18 7:33 PM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] wrenching ( was: Capacitor sniffing) OT I don't use the same tools for Electronics and automotive work. I do have several large adjustable wrenches, but they are New Britain. The smaller ones for electronics are Xcelite, and they do have plastic coated handles. I've also been told that no real mechanic ever uses an adjustable wrench because he has all the proper tools to work on a vehicle. If that wrench still stinks, it had to stink when he bought it. If so, he should have bought something else. I had someone give me a buncuh of Japanese tools made in the '60s and '70s. They were made of pot metal, and the drill bits were so soft that they unwound while drilling plastic. They were quickly tossed in the scrap for recycling. I agree about throwing out crap tools, or gather them all up, and only loan them to people instead of your good tools. The only cheap tools that I have had were either given as cheap gifts, or will be part of what I clean out of my dad's house as we get it ready to sell. He got them from a neighbor who had passed away. I started buying good quality tools as a teenager, and I still have some of them, 50 years later. The only ones that ever broke, were sold as tools for mechanics. The rest of what is missing were stolen from my truck, or at job sites. -----Original Message-----
On 12/8/18 8:07 PM, Michael A. Terrell wrote:
The plastic is there to reduce the chance of damaging the device awaiting you on your bench. Ummmmm.... I use Crescent wrenches from Jamestown NY mostly and none have plastic
and I have a fine touch at mechanicing.? I'd say a vinyl or other plastic coating
or dip layer is just insulation against fine feel on a wrench.? If it reeks, lose it.
If it wiggles around randomly, lose it.
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Re: wrenching ( was: Capacitor sniffing) OT
On 12/8/2018 10:42 PM, Chuck Harris wrote: If by stink, you mean smell, a lot of plastics start out
benign, and end up really smelly. I have a set of Craftsman
nutdrivers from the 1970's that woke up one day and smelled
like vomit. And, have ever since.
I don't know if it is something the acrylic handles were
exposed to, or perhaps a plasticizer that was put in them
to make them less brittle, but I do know it stinks.
Hello, Chuck-- I have a set of those, too. A set of screwdrivers from that time don't smell like much of anything. 73-- Brad AA1IP
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Re: Mod on horizontal plug-in 7B80
Are you sure you didn't mod it yourself?? Maybe the GB stands for Gary Bosworth?! ;)
Jim F
Sent from my Verizon, Samsung Galaxy smartphone
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-------- Original message --------From: Gary Robert Bosworth <grbosworth@...> Date: 12/8/18 7:17 PM (GMT-08:00) To: [email protected] Subject: [TekScopes] Mod on horizontal plug-in 7B80 This is a tough one. I have a Tek Plug-In number 7B80. It is mod GB. I see no mention of this modification in the manuals. Anyone out there super knowledgeable who can give me the low down on mod GB?
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Michael A. Terrell
zenith5106