Date   

Re: 465B strange ripple

Stephen
 

I cleaned everything the best I could, but the problem is still the same....
The ripple is still there, and the amplitude flickers up and down quite often, at random, on several VOLTS/DIV settings.
Sometimes I have the impression that some capacitors, C30 to C37 are not seated properly. Because when I press on them down a tiny bit, most of the time all comes back to normal. At least for a while.
It’s very weird....


Re: 2467B problems? Sparkles and flashing LED's

 

On Sun, Jan 31, 2021 at 06:02 PM, Jared Cabot wrote:


Here is a video showing the sparkles.
One half is with a shroud, the other is with normal room lighting.
Hopefully you can see what's happening.
The scintillation I've seen from too much MCP bias (in a 7104) looks like a night sky overcrowded with sparkling stars. Maybe the 2467 is different.
Maybe a slight reduction in MCP bias will corrrect your phenomenon in a 2467. You may want to check the adjustment according to the SM.
Otherwise, it looks like jitter, either in the MCP bias voltage or its DC level offset from GND, or even jumps in the trace brightness (Z-axis).

Raymond


Re: 2467B problems? Sparkles and flashing LED's

Craig Cramb
 

On Sun, Jan 31, 2021 at 09:02 AM, Jared Cabot wrote:


Here is a video showing the sparkles.
Jared,
My thought is the CRT Grid Bias calibration needs to be done.

Craig


Re: 549 transformer question

Dave Wise
 

??

I can feel the drive to create a perfect product, but primary loss is only a few percent of the total. In my case (low-tech hand winding), I was unwilling to task myself with the extra complication. I haven't regretted it.

Remember, "perfect" is the enemy of "good enough".


Dave Wise

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Chuck Harris via groups.io <cfharris=erols.com@groups.io>
Sent: Sunday, January 31, 2021 7:12 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 549 transformer question

Both the primary and secondary will still work, but the loss is
a per turn sort of thing. Why keep a lossy primary on a good
secondary? Especially when the primary is only 60T, and can be
wound any way you want.

-Chuck Harris

greenboxmaven via groups.io wrote:
Does the primary winding survive, can a new secondary be wound over it, or is it also
unusable?


On 1/29/21 17:17, Tom Lee wrote:
Chuck has done more extensive research into this than anyone I know. It appears
that it is a chemical change, not simple moisture absorption/adsorption. Must
replace or rewind.



Bruce Gentry, KA2IVY


Re: 7854 revived with a new CRT - how to correctly calibrate Z circuit (was: #157693 - https://groups.io/g/TekScopes/message/157693)

unclebanjoman
 

After careful study I decided to touch and adjust only the Digitizer Horizontal Gain, step H11, R42 on board A9 (very difficult to reach the trimpot, augh!).

Now the horizontal scale is in agreement with the real signal scale, and the two waveforms (real and digitized) superimposes almost perfectly.
So I prefer do not touch all other various calibration points, since the digitized waveforms shows no gross and obvious aberrations.

The 7854 is a splendid scope but calibrating it gives me a headache!

Max


Re: 2467B problems? Sparkles and flashing LED's

Jared Cabot
 

Hi,

Here is a video showing the sparkles.
One half is with a shroud, the other is with normal room lighting.
Hopefully you can see what's happening.

https://youtu.be/uMQoABN77nk


Re: User Experience of Sampling Scopes

Carl Hallberg
 

Jeff,
I had posted still pictures of the conversion of a 7s14 and recommended 3 Watt red LEDs because of the larger surface area that gives more current capability for the receiver (pickup side) with a capacitor to provide stability and, as some had concerns, keep noise (rf or otherwise) from the diodes and fets.  I misstated the physical size as 20 mm, but are about 8 mm LEDs.  I don't recall, but credit to the person who did SPICE (PSPICE on my computer) .  I did a series of empirical data of voltages out for different color LEDs  and posted in earlier Email.
Carl Hallberg (W9CJH)

On Saturday, January 30, 2021, 09:07:35 PM CST, Jeff Dutky <jeff.dutky@gmail.com> wrote:





Miguel,

Thank you for the explanation. I had noticed the tunnel diode in the photos at the beginning, but couldn't make out what else you were doing.

I'm curious what sorts of things you use the sampling scope to do. My hobbies involve 80s vintage computers, and occasionally even older items going back to the 60s, and I think that I understand how I would use a scope like the 475 or 2465 with those systems, but I'm not at all clear what sorts of things one uses a a multi-GHz sampling scope for.

I think I looked at some of those photos while following another discussion (not sure if it was recent, or if I found it in a search) about replacing mercury batteries in a sampling plugin with two LEDs, and I've been meaning to play around with that ever since (the other part of my hobby is just seeing interesting physical effects in electronic devices, and lashing two diodes together to get a constant voltage source qualifies).

I would be interested in a video 7S14 in action, thank you.

-- Jeff Dutky


Re: 2467B problems? Sparkles and flashing LED's

Chuck Harris <cfharris@...>
 

By "sparkles" you have to be more specific in what you
are describing.

There are two types of 2465 family sparkles that I know of:

The first is common to all scopes of the 2465 family, and
is caused by timesharing the CRT beam between the readout,
and the multiple traces. It is how you get all of those
seemingly simultaneously displayed things on the screen.

The second is a 2467 only phenomenon, and is a form of
scintillation.

The 2467 scopes have an image intensifier built into the
CRT, called a Micro Channel Plate, or MCP. It is related
to the third generation night vision scopes, or starlight
scopes, used by the military. When the voltage applied to
the MCP (bias) is increased, the MCP's sensitivity increases,
making the screen's image brighter. If you adjust the bias
high enough, the MCP will start amplifying electron noise,
of its own making, into a sparkles you can see on the screen.
If you set the MCP bias way too high, you can get a full
bright screen, with no waveform display.

Your 2467's MCP bias is supposed to be adjusted to be right
on the edge of visible scintillation in a normally lit room.

Over zealous technicians will sometimes adjust a weak CRT
high enough so that you can see a faint field of grass all
of the time. Doing so reduces the contrast, but may allow
them to make a sale of a "bright-eye" scope with a weal CRT.

-Chuck Harris

Jared Cabot via groups.io wrote:

On Sun, Jan 31, 2021 at 11:40 AM, Ozan wrote:


I've noticed when I press any button on the front panel, the LED's briefly
flash, is this normal?
It has the same behavior on my 2467B too. I believe it is because of how
keys/LEDs are scanned and normal.

Also, I occasionally get little 'sparkles' on the CRT here and there and the
This doesn't sound right. If you turn off readout intensity (turn the
intensity knob counter-clockwise past half-way) do you still see them?

intensity is just a tiny bit unstable.
If this is the trace flickering it could be because of "AUTO LVL". Does
switching to "AUTO" make it go away?

Ozan

Cool, so my panel led's aren't possessed by a gremlin of some sort (or we both have the same one... :D ) I'll mark this as solved.

For the sparkles, it still occurs even with all intensity controls turned all the way down, seems to decrease as the unit warms up too.

With the unit set to 'AUTO' instead of 'AUTO LVL' the brightness problem goes away, it's rock solid in 'AUTO' mode, so I think that is solved.



On Sun, Jan 31, 2021 at 11:49 AM, Gary Robert Bosworth wrote:


Mine have always flashed when I pushed any button. It annoyed me but I just
ignored this phenomenon. At least it let's you know the LEDs work OK.
Great, good to know it's just how it it rather than a ghost I will no longer chase. :)


So now it's just down to finding out where the sparkles are coming from.....






Re: 549 transformer question

Chuck Harris <cfharris@...>
 

Both the primary and secondary will still work, but the loss is
a per turn sort of thing. Why keep a lossy primary on a good
secondary? Especially when the primary is only 60T, and can be
wound any way you want.

-Chuck Harris

greenboxmaven via groups.io wrote:

Does the primary winding survive, can a new secondary be wound over it, or is it also
unusable?


On 1/29/21 17:17, Tom Lee wrote:
Chuck has done more extensive research into this than anyone I know. It appears
that it is a chemical change, not simple moisture absorption/adsorption.  Must
replace or rewind.



       Bruce Gentry, KA2IVY




























Re: NEW TOPIC: Outstanding Rockland Instruments 7000 Plugin; WAS: Slightly OT- Wavetek 7530B?

nonIonizing EMF
 

OK, updated for now the following:
https://w140.com/tekwiki/wiki/Rockland_7530A
https://w140.com/tekwiki/wiki/Rockland_7530B

Thinking there is more good information to place in this message thread also, along with specs from the manuals to add.

I'll wait a few days for feedback, or edits others might make to the above wiki's, before I add any additional information.

Please reply if you have any comments, suggestions, etc.

On Sat, Jan 30, 2021 at 04:35 PM, Dennis Tillman W7pF wrote:


I think TekWiki is the best place for it.


Re: User Experience of Sampling Scopes

 

On Sat, Jan 30, 2021 at 05:41 PM, Jean-Paul wrote:


Many on epay have issues eg burned out and hard to find tunnel diodes.
Most burned out diodes are the sampling diodes. Those aren't tunnel diodes.

Raymond


Re: bandwidth

 

On Sat, Jan 30, 2021 at 11:53 PM, Bob Albert wrote:


I set up the scope to measure the amplitude in rms volts.
You're not measuring BW but observing numbers put out by the 'scope (parametric calcs in 2440), or did you calculate Vrms from observed amplitude? If the latter, why not use observed waveforms directly?
The 2440 has problems showing a reasonable waveform at higher frequencies and I wouldn't trust its calculation results at these frequencies.
AFAIR, the 2445 (non-A/B) didn't have parametric measurements, so did you convert Vpp or amplitude to Vrms yourself or did you use a non-plain 2445?
A BW of 160 MHz (observed as sine wave) is lower than I remember for any of my (long sold) 2445's.

Raymond


Re: Blue Ribbon connectors for 500 letter series plugins

shalopt
 

I have used that type in the past may still have a few in the attic
don't remember the pin count. Could be like the Jones connectors.
When I retired I dumped 50-60 pounds in a recycle bin at the land fill.
I always called them flag connectors.
gary g


Re: NEW TOPIC: Outstanding Rockland Instruments 7000 Plugin; WAS: Slightly OT- Wavetek 7530B?

santa0123456
 

Hello,

I followed this discussion and had a look at the 7530A schematic. My job as a physicist deeply involved in electronics is very high resolution spectroscopy of the atmosphere to follow the evolution of its constituents. Since we are using Fourier transform spectrometers with about up to 8 Million points resolution and I am developing these instruments for 3600m altitude observatory, you will understand why I opened this funny schematic.

When I was finishing what is now called my 'Master', my work (=challenge) was to develop a digital filter that was inserted between the then crazy 16bit @ 100Ks/S ADCs to keep only the frequency band of interest and undersample the data to reduce the computation work for the big FFT. At that time, on a 1000F HP mainframe, a one Megapoint FFT took 45 minutes mostly due to heavy hard disk swaps. Memory was small and very very expensive... My digital filter used a specialized computing hardware like TRW 16x16 bit MACs, ECL RAMs, etc... All this under the slower supervision of a Z80 that would prepare the sequencing of the filtering process (convolution) and the necessary operator vector coefficients.

My school friend and now married with my cousin worked on a similar project for making much faster FFTs because 64Kbit RAMs had emerged. He moved to JPL where he is still doing kind of the same job now before the FFT project could find its end. I still have a pile of 64Kbit RAMs and ALUs at hand.

All this to say that I recognize in the Rockland schematic an architecture like the one I devised in 1981. The 'slice processor' looks mostly like an ALU whose control signals come from the sequencer. Sine/Cosine coefficients come from roms and a processor with its attached usual logic prepares all the controls (ALU sequencing, acquisition, display) for the chosen analysis parameters. So, in a sense, the slice bit stuff is not up to the level of a CPU but of a tweaked and specialized ALU. There is therefore probably no assembly language to analyze here but only digital controls for counters, latches, etc. A state machine preprogrammed by the 8080 will provide this bunch of words which is equivalent in a sense to a raw cpu internal microcode but not decoded from higher level instructions.

For the story, when I was making the dgital filter, our experimental Fourier-transform spectrometer used two Rockland 8MHz digital synthesizers to generate
movement control frequencies millihertz apart. This was also an exceptional device for 1980 and is what we now call a DDS that we can buy for one buck or build in seconds in an FPGA with standard IP building blocks.

I remain however doubtful that, at that time with a 12 bit composite ADC and limited memory, the digital approach was giving a real advantage over a 7L5. A few years ago, I had to search for the source of a ghost in our spectra. I tried to use the 7L5 because it is not tied to any of my interferometer controls and works in (slow) real time. I could, just hardly but I could, find this elusive signal when the 'patient' under scrutiny was itself an FFT spectrum analyzer with the usual 2M points @ 18 bits data set. So, a 7L5 remains for me quite a nice and respectable beast at low frequency.

For those interested : http://labos.ulg.ac.be/girpas/en/


Re: An informative web site for test equipment repairs

tek_547
 

Thanx for the link Brad. Good in these times for hours of reading :-)
René


Re: Tek 576 possible power supply failure

 

Hi all,

I fixed this one... a faulty transistor.

I noted all voltages in the -100V and +12,5V supply, as they seem to depend on each other. With a little try-and-error (easy, as transistors are all socketed) I found the culprit.

I put the schematic of those 2 supplies together with the voltages (hopefully readable) in failure mode in the files section. See if anyone finds the faulty transistor from that information alone...

https://groups.io/g/TekScopes/files/2021.01.31%20-%20Tek%20576%20power%20supply%20failure%20mode.pdf

Later on I checked the small capacitors on the regulator board, they are all fine. When the unit is running I merely get some millivolts of ripple on any of the supplies, so I guess theres not much that can be improved.

Next its the step generator that needs some attention. Some steps are missing or skipped, looks like a problem in the counter / converter area. When that is done there are at least 2 bulbs in the readout that must be replaced. And the "invert" switch array cleaned, maybe.

cheers
Martin


File /2021.01.31 - Tek 576 power supply failure mode.pdf uploaded #file-notice

TekScopes@groups.io Notification <noreply@...>
 

The following files have been uploaded to the Files area of the TekScopes@groups.io group.

By: Martin

Description:
Voltages in a faulty -100V and +12,5V power supply of a Tektronix 576 curve tracer. Since the -100V supply uses the +12,5V and vice versa its not easy to tell which supply is actually at fault... Info: 75V was the only supply working


Re: bandwidth

Bob Albert
 

Okay Tom I figured out which manual.  That has got to be the most involved adjustment procedure I have ever seen.  I must study it a few times before picking up my golden screwdriver.
Bob

On Saturday, January 30, 2021, 10:17:59 PM PST, Bob Albert via groups.io <bob91343=yahoo.com@groups.io> wrote:

Tom, which manual are you looking at?  I have a few that came with the scope.
Bob
    On Saturday, January 30, 2021, 04:57:51 PM PST, Tom Lee <tomlee@ee.stanford.edu> wrote:

Yes, I assumed that you had the termination set properly, or you would
have noticed wild shifts in amplitude as you cranked up the frequency.

Looking through the manual, section 5 (around 5-18, give or take a page
or two) is where you want to focus. You should be able to get above
315MHz routinely with the tweaks available. Without a fast pulser you
won't be able to check transient response directly, though. The 485's
fast pulser is good enough to exercise the 2440 over its spec'd
bandwidth, so that's an additional option.

--Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 1/30/2021 16:28, Bob Albert via groups.io wrote:
  First of all, I set the scope's internal 50 Ohm so that isn't an issue.  I also tried a few different cables with identical results.
I don't have a fast pulse generator so I can't measure rise time.  I could cobble one up, as I once did for TDR but that's been torn apart.  I don't know if it's fast enough anyway.
The thing is, the other scopes were within spec, including the HP which is nearly twice as fast.
Bob
      On Saturday, January 30, 2021, 03:27:16 PM PST, Nenad Filipovic <ilmuerte@gmail.com> wrote:
 
  Hi Bob,

My procedure was identical for the three scopes.  I connected my HP 8657B to
each scope in turn with a short piece of RG-58.
You did not mention using any termination in your setup. Your HP 8657B performance is specified only if terminated with 50Ohm.
Even if you did use an external 50Ohm terminator with your Tek 2440, the scope's input capacitance would be enough to throw the terminator off its fully resistive impedance and make room for considerable errors. 15pF is approx. 35Ohm at 300MHz.
Funny thing is that measurement errors in such setup may be somewhat less if you use a long length of coax (a few times the wavelengths of the frequency of interest), but it would still be a gamble.

Nenad Filipovic










Re: bandwidth

Bob Albert
 

Tom, which manual are you looking at?  I have a few that came with the scope.
Bob

On Saturday, January 30, 2021, 04:57:51 PM PST, Tom Lee <tomlee@ee.stanford.edu> wrote:

Yes, I assumed that you had the termination set properly, or you would
have noticed wild shifts in amplitude as you cranked up the frequency.

Looking through the manual, section 5 (around 5-18, give or take a page
or two) is where you want to focus. You should be able to get above
315MHz routinely with the tweaks available. Without a fast pulser you
won't be able to check transient response directly, though. The 485's
fast pulser is good enough to exercise the 2440 over its spec'd
bandwidth, so that's an additional option.

--Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 1/30/2021 16:28, Bob Albert via groups.io wrote:
  First of all, I set the scope's internal 50 Ohm so that isn't an issue.  I also tried a few different cables with identical results.
I don't have a fast pulse generator so I can't measure rise time.  I could cobble one up, as I once did for TDR but that's been torn apart.  I don't know if it's fast enough anyway.
The thing is, the other scopes were within spec, including the HP which is nearly twice as fast.
Bob
      On Saturday, January 30, 2021, 03:27:16 PM PST, Nenad Filipovic <ilmuerte@gmail.com> wrote:
 
  Hi Bob,

My procedure was identical for the three scopes.  I connected my HP 8657B to
each scope in turn with a short piece of RG-58.
You did not mention using any termination in your setup. Your HP 8657B performance is specified only if terminated with 50Ohm.
Even if you did use an external 50Ohm terminator with your Tek 2440, the scope's input capacitance would be enough to throw the terminator off its fully resistive impedance and make room for considerable errors. 15pF is approx. 35Ohm at 300MHz.
Funny thing is that measurement errors in such setup may be somewhat less if you use a long length of coax (a few times the wavelengths of the frequency of interest), but it would still be a gamble.

Nenad Filipovic










Re: Making your own TM500 containers, some surprises!

Ed Pavlovic
 

Walter,
You’re correct on the 5000 series scope plug in shells, I picked one up last week on eBay for under $10 plus shipping. And the best part about it will be that a knob or two and some of the plastic button frames will be used to fix up my 465 as well, so it some of the parts I’m not needing for the mainframe tester are still being re-used as well.

Ed
KC9MMM

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