Date   

Re: Timebase and CRT Issues on Tektronix Type 545A

 

Dave at Artek Manuals is very much correct regarding getting the proper manual for your 'scope. As he stated, whenever Tektronix made a change in a 'scope that resulted in a new designation, i.e.: 545 to 545A, there were usually some pretty big differences.

The 545B oscilloscope is partially solid state state, uses a helically wound differential shielded delay line, and employs one of Tek's first ceramic envelope CRTs.


The 545 and 545A were very similar circuit wise, were all-tube construction, and used the lumped L-C type of delay line.


You really must download the proper manual. One can be found at w140.com, the TekWiki. There are also other manuals available on the site that may prove quite useful for diagnosing your issue. You may want to also download the Navair manual listed, as many military manuals carried pretty detailed diagnostic sections that the factory manuals didn't.


J.D>


Looking for a Broadband (>1GHz) Noise Source

 

I am looking for a broadband noise source to use to test my Tek spectrum
analyzers with.



Ideally it should be flat to 1GHz and roll off above that would be
acceptable.

This one on Ebay (eBay item number:251953200778) caught my eye initially
until I saw it was not flat.

http://www.ebay.com/itm/251953200778?_trksid=p2060353.m1438.l2649
<http://www.ebay.com/itm/251953200778?_trksid=p2060353.m1438.l2649&ssPageNam
e=STRK%3AMEBIDX%3AIT> &ssPageName=STRK%3AMEBIDX%3AIT



Does anyone have a recommendation or suggestion for what I should look for?



Thanks, Dennis Tillman W7PF


Re: Timebase and CRT Issues on Tektronix Type 545A

Alex Brinister
 

Sorry, here is a link for the images.

545A Pics http://imgur.com/a/OxwlC

http://imgur.com/a/OxwlC

545A Pics http://imgur.com/a/OxwlC Imgur: The most awesome images on the Internet.



View on imgur.com http://imgur.com/a/OxwlC
Preview by Yahoo



Alex Brinister


Re: Shootout of Substitute SG504 heads = a better head.

 

Hi Ancel,
Very impressive results.

I would like to see how the original Tek head designed by George Steen compares to both yours and David's heads. Of course the Tek head was designed 40 years ago but it would be informative to know how they all compare. I have both.

When you finally produce boards for sale I would like to buy one and repeat the tests I did on George's head and David's head and include your head in the tests. My test method using a slow continuous sweep through the entire SG504 output range would catch any anomalies in between the x100MHz marker frequencies you selected for your tests. I may not be able to measure the dB levels to 2 decimal places but I will be able to spot any unusual or sudden variation in flatness in those regions between the markers.

Dennis Tillman W7PF

-----Original Message-----
Sent: Sunday, March 20, 2016 2:01 AM
Subject: [TekScopes] Shootout of Substitute SG504 heads = a better head.

Hi all:

I finally got around to doing a precision shootout between the David Partridge substitute head and my own 'upgraded' design. Had to calibrate my SA to do it.

Having done the measurements of both heads at the same time on the same calibrated instruments, the result shows my new head demonstrates improvement past 600Mhz consistently and repeatably. Around 0.1dB to 0.2dB better.

Improvements:
1) Better VHF performance from 600Mhz up. Due to reduced inductance/resonance in the design.
2) Replaceable input and lemo cabling for custom test setups (e.g. longer or shorter cabling).
3) Small size (laser cut housing is 1" x 1.8" long x 0.4" thick) permits direct connection to DUT.
4) BNC male output launcher and 90° female input facilitates 360° rotation for strain free connection to DUT.
5) DIY build, using stock 0.8mm FR4 and toner transfer etching! Epoxy sealed housing.
6) Direct connection (no cable or adapters) to a BNC DUT like a scope permits even better precision than shown in the shootout via lower insertion losses.

I will be making this an open source design for all and I will place a few fully built and tested on Ebay for sale as I have some excess parts inventory.

Here is the comparison with pics and an Excel file detailing the test setup, calibrations and results.

https://www.dropbox.com/sh/jtl5xnxaw6yqstn/AADPDb4MVoZ8lbUESyORTWR6a?dl=0
Ancel
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Re: Timebase and CRT Issues on Tektronix Type 545A

ArtekManuals
 

On 3/20/2016 3:20 PM, alex_brinister@... [TekScopes] wrote:
Hello,

I have an old Tektronix Type 545A that was just given to me by a friend.
I've been having some issues getting it to operate properly.

First, Timebase A does not show a signal on the CRT. The oscilloscope
recognizes that there is a signal there (the position lights change when
changing the Vertical and Horizontal position dials) but the CRT remains
blank. This is the first attached picture.

The second issue is that in Timebase B (the signal shows up in this
one), the signal only shows on half of the CRT monitor. This is the
second attached picture. Has anyone ever seen this? The oscilloscope is
old and had been sitting in the basement for awhile. I haven't had the
time to properly clean the inside so there is a considerable amount of
dust. Perhaps something burnt out? I have a a physical manual for the
545B and a PDF from BAMA but those haven't been much help. I was
thinking it could be a calibration issue but the calibration
instructions call for a lot of materials that I don't have on hand...
like a 117 V automatic transformer.

All help appreciated. Thanks,

Alex Brinister
Alex

Getting a manual is essential and I think there is a free copy out there, just gotta do some more Google. If you dont find a free one contact me off list at manuals@... I have one I can scan for a reasonable cost. I havent scanned it yet because it is marked on my list as "free copy available" which is our short hand for "dont waste my time scanning"

NExt you start with the all the main power supply voltages. The 117V auto Transformer is not needed for your purposes in the context of servicing these units it was used to test the "power supply regulation". mostly and you are a ways from that

The autotransformer is useful when powering up an old tube type scope which has been in storage for a along time to hold the voltage down while the electrolytics "reform" . Sounds like you have had the unit on at full line for a bit so this application is mute now and not something you would find in the service manual anyway

I am not intimate with 545A or 545B so cant comment on the differences, Typically Tek did not change the letter suffix unless the changes were significant so I would guess the 545B manual is of marginal value for detailed troubleshooting


Dave


--
Dave
Manuals@...
www.ArtekManuals.com


Re: OT: underground pipe locating

Peter Gottlieb
 

I've been involved in a bunch of large system installations where we needed to put in various sorts of piles. We first call Dig Safe (for liability reasons) then have a specialized firm come in. They use a combination of electrical (live) detection, induced current and GPR (ground penetrating radar). In two recent cases they located concrete encased medium voltage (4160 and 13.8k volt) duct banks which were nowhere near where the "as built" plans indicated. The GPR did pick up the PVC drain pipes although they were pretty close to the surface. Not sure how deep they could be detected. Point here is that a single method won't detect everything. See if Dig Safe will come out for you. They won't always for stuff on private property but they have been known to as a courtesy if they're not too busy.

Peter

On 3/20/2016 3:22 PM, Stefan Trethan stefan_trethan@... [TekScopes] wrote:

Up to 4 feet is probably quite the challenge for a metal detector.
Also a farmyard might be a nightmare for false positives.

But they often complain of interference from electric fences and such,
so perhaps the metal detector could be used as a sensitive receiver
for an injected signal?

I wouldn't be surprised if "what would I have done" turns out to be
your best friend in locating the runs.

ST

On Sun, Mar 20, 2016 at 7:53 PM, David @DWH
[TekScopes] <TekScopes@...> wrote:
Except for the PVC water pipes, it seems like an ideal job for an
inexpensive or even home made metal detector.


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Posted by: David <@DWH>
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Yahoo Groups Links



Re: OT: underground pipe locating

stefan_trethan
 

Or if that won't go in, perhaps salt water or some vinegar?

Was it this list where someone linked the article about finding a
central heating leak with radioactivity? Back when the atom still had
a bright future they made a proof of concept experiment where they
introduced some radioactive substance with a short half life into the
central heating system to locate a leak with a geiger counter. It
worked, but was somewhat hazardous compared to just looking for the
wet spot.

ST

On Sun, Mar 20, 2016 at 8:22 PM, n2lym n2lym@... [TekScopes]
<TekScopes@...> wrote:
To find pvc pipes run a snake thru them first!
Mike


Re: OT: underground pipe locating

stefan_trethan
 

Up to 4 feet is probably quite the challenge for a metal detector.
Also a farmyard might be a nightmare for false positives.

But they often complain of interference from electric fences and such,
so perhaps the metal detector could be used as a sensitive receiver
for an injected signal?

I wouldn't be surprised if "what would I have done" turns out to be
your best friend in locating the runs.


ST

On Sun, Mar 20, 2016 at 7:53 PM, David @DWH
[TekScopes] <TekScopes@...> wrote:
Except for the PVC water pipes, it seems like an ideal job for an
inexpensive or even home made metal detector.


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Posted by: David <@DWH>
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------------------------------------

Yahoo Groups Links



Re: OT: underground pipe locating

Mike Santas
 

To find pvc pipes run a snake thru them first!
Mike

On Sun, Mar 20, 2016 at 02:53 PM, David @DWH [TekScopes]
wrote:

 













Except for the PVC water pipes, it seems like an ideal job for an

inexpensive or even home made metal detector.
















[Non-text portions of this message have been removed]


Timebase and CRT Issues on Tektronix Type 545A

Alex Brinister
 

Hello,

I have an old Tektronix Type 545A that was just given to me by a friend. I've been having some issues getting it to operate properly.

First, Timebase A does not show a signal on the CRT. The oscilloscope recognizes that there is a signal there (the position lights change when changing the Vertical and Horizontal position dials) but the CRT remains blank. This is the first attached picture.

The second issue is that in Timebase B (the signal shows up in this one), the signal only shows on half of the CRT monitor. This is the second attached picture. Has anyone ever seen this? The oscilloscope is old and had been sitting in the basement for awhile. I haven't had the time to properly clean the inside so there is a considerable amount of dust. Perhaps something burnt out? I have a a physical manual for the 545B and a PDF from BAMA but those haven't been much help. I was thinking it could be a calibration issue but the calibration instructions call for a lot of materials that I don't have on hand... like a 117 V automatic transformer.

All help appreciated. Thanks,

Alex Brinister


Re: FET leakage question

 

My phone does not have a camera but I got my flatbed scanner working
and had a backup plan in any case.

It should work fine for a transimpedance amplifier although it does
nothing for capacitance at the inverting input of the operational
amplifier which will cause peaking if the bandwidth is not limited. I
will draw up the general idea and try to apply it to a transimpedance
configuration.

On 20 Mar 2016 06:42:50 -0700, you wrote:

Do you think this would work for a low leakage switch? For example, switching in different gain resistors in a low current transimpedance amplifier? If your scanner is not working, perhaps your cell phone camera would suffice? Very interested in this idea.

Dave


Re: OT: underground pipe locating

 

Except for the PVC water pipes, it seems like an ideal job for an
inexpensive or even home made metal detector.


Re: 7A22 Differential Amplifier Calibration

 

On Sun, 20 Mar 2016 17:38:15 -0000, you wrote:

...

Steps 11 and 12 both refer to Fig. 5-2. But for step 11 it shows overshoot
and for step 12 undershoot!

Fig 5.2states that (A) is correctly adjusted and that (B) is incorrect. (A)
is, to me, flat-topped and as square a leading corner as possible, but (B)
shows overshoot - there is no figure showing corner rounding, unless I am
missing something, but that is what shows on my 7A22.

BTW It seems that 50R feed-thru terminations are not prescribed in steps 11
and 12.
The 7A22 instructions for calibration strike me as more nebulous than
usual. I often end up studying the schematics in detail to figure out
what they are trying to do and then altering the calibration
instructions to match.

Yes, I think that is correct and that I wasn't using them. I merely
mentioned some of the calibration kit so that people could see that I am
doing the best I can with what seems to be reliable gear. Unfortunately, you
haven't really solved my quandary. Would fiddling with these capacitors put
me deeper in trouble, or should I go ahead when I have the normalizer and
can adjust the other presets?

Albert
If the neutralization is that far off then I do not think you can get
into any more trouble; something is broken or misadjusted or your
measurement was bad. The neutralization adjustments alter the
response of the two sides of the differential amplifier independently
but this is masked by the 1 MHz bandwidth limit which is trimmed by
C425 shown in the middle of schematic 2. I think they should be
adjusted for maximum *matching* bandwidth with clean response using
either input.


Re: OT: underground pipe locating

stefan_trethan
 

If you want to google translate it, here is a german website with some
information about building a cable locator:
<http://sbwd.de/seiten/rahmen.php?nav=kabelsuch>

Forget the guy with the dowsing rod, there isn't a single double blind
study that shows it working.

ST


On Sun, Mar 20, 2016 at 7:05 PM, edbreya@... [TekScopes]
<TekScopes@...> wrote:
I need to locate a bunch of underground wiring and piping up at the farm, and thinking about setting up a simple DIY system using an audio power amplifier to drive a fixed low frequency into the underground items, and detect it with an electromagnetic pickup coil, amplifier, and headphones (or a scope for a more quantitative view, and to be more on-topic). I know there are lots of commercial units for this, using various methods, but would rather make my own setup for basically a one-time use.

I think the wiring stuff should be easy since I have access to each end of the runs, and can shut down the power and use the conductors temporarily to pass the test current. A lot of the piping probably shares the same trench pathways with wiring, so that should narrow it down a bit. The big problem I think will be the pipe lines with no wiring nearby. These include galvanized steel and PVC water lines, and steel propane lines (that likely are tape-wrapped). The spring water here is very hard, so should have enough conductivity to get some decent current through the PVC pipes (I hope).

Except for one set of PVC lines, all the run lengths are probably less than 200 feet between access points, at depths probably ranging from about one to four feet, in clay soil that's pretty well saturated from the rains. I likely won't get around to it until spring/summer anyway, when it will be dried out more. I'm now gathering up the main parts and thinking about the design.

I'd like to use audio frequency for simple direct human interface, no more than 3 kHz or so. I can make very high gain and narrow filters to get high sensitivity if needed. For the power amp I've got and old stereo receiver good for up to 100 Wrms/channel that I can pump through a series protection R and a transformer to Z-match into the various loads.

Does anyone here have knowledge/experience with this sort of thing, particularly the best frequency range to use? One of my neighbors insists that he can find all this stuff with dowsing, so maybe I'll see what he can do, but backed up with technology that's understood.

Ed




[Non-text portions of this message have been removed]



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Yahoo Groups Links



Re: 7A22 Differential Amplifier Calibration

 

I have not had to make the adjustments on my 7A22 but I did do the
performance check which showed everything working well enough.

You can use a x10 probe in place of a normalizer. It is just not as
convenient since it attenuates the input by 10 instead of by 2
requiring a larger input signal.

The cross neutralization procedure uses a direct connection to the
signal source without a normalizer at a vertical sensitivity of
10mV/div to 10uV/div where none of the input attenuators are used so
they have no effect. 10mV/div is what the manual recommends but I
think it could be clearer about this.

Since adjusting C141 and C241 changes the input capacitance, they
affect the input attenuator time constants which do need a normalizer
to calibrate. The cross neutralization really should be checked
before doing any of the input adjustments.

If the cross neutralization is that far off, then either someone
adjusted it poorly or something is wrong.

On 20 Mar 2016 09:14:09 -0700, you wrote:

I have run into a quandary while going through the calibration procedure with my 7A22. I have been using a PG506 and a couple of 50-ohm feed-through terminators and I have got to the section on "Cross Neutralization". This involves possibly adjusting a capacitor in each of the two differential inputs. There are warnings that adjustment of these capacitors may require adjustment of other presets concerning attenuator time-constants, differential balance and attenuator compensation. One input seems to be fine, but the other shows some "rounding" of the 1KHz square-wave. The figures showing how the waveform might appear show a nice square corner or overshoot, but no rounding of the corner. While I am expecting a 47pF normalizer to be delivered any time soon and this item is needed for the further tests and adjustments, I don't want to fiddle with these capacitors unless it is really a good idea.
I am aware that the bandwidth of the 7A22 is 1MHz at maximum and I might expect to see rounding of the leading corners of a 1KHz square-wave under normal circumstances.
Has anyone carried out this calibration of a 7A22 and, if so, could I have some advice? My gut feeling is to leave well alone, but the perfectionist within me wants to see this 7A22 be as good as it can be.
Colin.


OT: underground pipe locating

Ed Breya
 

I need to locate a bunch of underground wiring and piping up at the farm, and thinking about setting up a simple DIY system using an audio power amplifier to drive a fixed low frequency into the underground items, and detect it with an electromagnetic pickup coil, amplifier, and headphones (or a scope for a more quantitative view, and to be more on-topic). I know there are lots of commercial units for this, using various methods, but would rather make my own setup for basically a one-time use.

I think the wiring stuff should be easy since I have access to each end of the runs, and can shut down the power and use the conductors temporarily to pass the test current. A lot of the piping probably shares the same trench pathways with wiring, so that should narrow it down a bit. The big problem I think will be the pipe lines with no wiring nearby. These include galvanized steel and PVC water lines, and steel propane lines (that likely are tape-wrapped). The spring water here is very hard, so should have enough conductivity to get some decent current through the PVC pipes (I hope).

Except for one set of PVC lines, all the run lengths are probably less than 200 feet between access points, at depths probably ranging from about one to four feet, in clay soil that's pretty well saturated from the rains. I likely won't get around to it until spring/summer anyway, when it will be dried out more. I'm now gathering up the main parts and thinking about the design.

I'd like to use audio frequency for simple direct human interface, no more than 3 kHz or so. I can make very high gain and narrow filters to get high sensitivity if needed. For the power amp I've got and old stereo receiver good for up to 100 Wrms/channel that I can pump through a series protection R and a transformer to Z-match into the various loads.

Does anyone here have knowledge/experience with this sort of thing, particularly the best frequency range to use? One of my neighbors insists that he can find all this stuff with dowsing, so maybe I'll see what he can do, but backed up with technology that's understood.

Ed


Re: 7A22 Differential Amplifier Calibration

Colin Herbert
 

Hi Albert,

From: TekScopes@... [mailto:TekScopes@...]
Sent: 20 March 2016 17:13
To: TekScopes@...
Subject: [TekScopes] Re: 7A22 Differential Amplifier Calibration





A compensation of this type almost necessarily is one where you can go from
"not far enough" to "too far", with the optimal position somewhere in the
middle.

I agree with you on this.

Steps 11 and 12 both refer to Fig. 5-2. But for step 11 it shows overshoot
and for step 12 undershoot!

Fig 5.2states that (A) is correctly adjusted and that (B) is incorrect. (A)
is, to me, flat-topped and as square a leading corner as possible, but (B)
shows overshoot - there is no figure showing corner rounding, unless I am
missing something, but that is what shows on my 7A22.

BTW It seems that 50R feed-thru terminations are not prescribed in steps 11
and 12.

Yes, I think that is correct and that I wasn't using them. I merely
mentioned some of the calibration kit so that people could see that I am
doing the best I can with what seems to be reliable gear. Unfortunately, you
haven't really solved my quandary. Would fiddling with these capacitors put
me deeper in trouble, or should I go ahead when I have the normalizer and
can adjust the other presets?

Albert


Re: 7A22 Differential Amplifier Calibration

Albert Otten
 

A compensation of this type almost necessarily is one where you can go from "not far enough" to "too far", with the optimal position somewhere in the middle. Steps 11 and 12 both refer to Fig. 5-2. But for step 11 it shows overshoot and for step 12 undershoot!
BTW It seems that 50R feed-thru terminations are not prescribed in steps 11 and 12.

Albert


7A22 Differential Amplifier Calibration

Colin Herbert
 

I have run into a quandary while going through the calibration procedure with my 7A22. I have been using a PG506 and a couple of 50-ohm feed-through terminators and I have got to the section on "Cross Neutralization". This involves possibly adjusting a capacitor in each of the two differential inputs. There are warnings that adjustment of these capacitors may require adjustment of other presets concerning attenuator time-constants, differential balance and attenuator compensation. One input seems to be fine, but the other shows some "rounding" of the 1KHz square-wave. The figures showing how the waveform might appear show a nice square corner or overshoot, but no rounding of the corner. While I am expecting a 47pF normalizer to be delivered any time soon and this item is needed for the further tests and adjustments, I don't want to fiddle with these capacitors unless it is really a good idea.
I am aware that the bandwidth of the 7A22 is 1MHz at maximum and I might expect to see rounding of the leading corners of a 1KHz square-wave under normal circumstances.
Has anyone carried out this calibration of a 7A22 and, if so, could I have some advice? My gut feeling is to leave well alone, but the perfectionist within me wants to see this 7A22 be as good as it can be.
Colin.


Re: FET leakage question

 

Do you think this would work for a low leakage switch? For example, switching in different gain resistors in a low current transimpedance amplifier? If your scanner is not working, perhaps your cell phone camera would suffice? Very interested in this idea.

Dave

---In TekScopes@..., <davidwhess@...> wrote :

On 17 Mar 2016 16:55:38 -0700, you wrote:

>---In TekScopes@... mailto:TekScopes@..., <davidwhess@...> wrote :
>
>>There is a trick I have used in the past to make super low leakage
>>switches using power MOSFETs. If you cascode two of the same MOSFET
>>in series, then you can bias their midpoint such that one of them
>>operates with a Vgs of 0 and Vds of 0 when switched off. Under these
>>conditions, leakage will be minimized.
>
> I would be interested in more detail on this. Are you talking about minimizing Vds leakage of a switch, or Vgs leakage of an amplifier? Any chance of a schematic?
>
>Dave

The idea is simple and reduces leakage from the drain to source and
drain to gate. I originally used it when replacing a discontinued
relay used in a low leakage (50 picoamps at 25C doubling every 10C)
application. Biasing the exposed transistor to minimize leakage
requires some other source so it will not help in John's application
because he wants the total leakage to be reduced to prevent discharge
of the battery back through the power source.

I am in the middle of struggling to get my scanner to work with
Windows 7 or I would make a drawing available of how it can be done.