Date   
Re: Tek 2465B Calibrator issues

Brian Cockburn
 

Hi Marcial,

Have a look at W2AEW's YouTube channel here: https://www.youtube.com/channel/UCiqd3GLTluk2s_IBt7p_LjA search there for 'compensation' and watch the probe compensation videos. This might help.

Also check out EEVblog's https://www.youtube.com/watch?v=OiAmER1OJh4

Cheers, Brian.

Re: Tek 2465B Calibrator issues

Tom Gardner
 

I'm unconvinced it could check the measurement accuracy in one sense, since I assume the cursors and calibration signal are derived from the same source.

It could be used to check the X linearity and the X magnification, but personally I'd just use other independent equipment for that.

On 28/03/19 01:18, Siggi wrote:
The point of this on the 2465s is that it allows the user to validate the
time base accuracy on the spot. For this purpose, the poor rise and fall of
the calibrator are unimportant, as you just line some part of the rise or
fall up to the graticule for a check.

It sure looks ugly at fast sweeps though :).

On Wed, Mar 27, 2019 at 20:43 Tom Gardner <tggzzz@...> wrote:

I don't like the "calibrator" output on the 24x5 series: the period
changes
according to the timebase so that there is always 5 cycles on the display.
At
high sweep speeds (i.e. much faster than1ms/div) the poor risetime of the
calibrator signal is evident.

The only practical use for a calibrator output is to calibrate the low
frequency
frequency response of a *10 "high" impedance probe. For that, all you need
is a
couple of cycles of a 1kHz waveform with a flat top - and you just tweak
the
scope probe so that its response looks flat. There are many descriptions
of how
to do that.

Summary: if you have fast sweep speeds (say <1us/div) and the waveform is
distorted, don't worry because that is normal. If, OTOH, the waveform is
distorted at 200us/div, then tweak the probe. If a problem remains, post a
picture.


On 26/03/19 13:29, Marcial Gomez Varas wrote:
Hi everyone,

I bought some time ago (2017) a TEK 2465B that I didn't have too much
time to play with (having 2 kids and a travelling job doesn't help!)
I have been toying with it lately, and I've discovered that the
calibrator is showing some really awful square signal.
It's clearly NOT square ! It has quite a bit of slope in the rise and
fall lines, and bouncing on the high level.
I have checked and both the output levels and frequency seem to be OK,
but somehow the signal is distorted.
Could it be some capacitor? Looking at the service manual it shows to be
in the A1 board, section 5 (That should be in the middle left side, am I
right?)
Any help would be appreciated !

Re: I wonder if there is much interest in vacuum tube oscilloscopes such as the 500 series

Morris Odell
 

I still use a 547 as my main bench scope and a 575 to test semiconductors.
Fortunately I have the skills to maintain them. I have several 7000 series
and a DSO but don't need their facilities very often. Later model Tek curve
tracers are very rare and expensive down here in Australia.



The 547 is a wonderful scope, and works perfectly even though it's over 45
years old.



Morris

Re: Need Help repairing a 7104 oscilloscope

Nenad Filipovic
 

Hi,

7104 is a very special instrument with a MCP CRT, which is very susceptible
to damage from excessive brightness and static images. You can easily
destroy it if careless, or if the instrument is faulty and generates static
images (like your in case). Given the state of your instrument, I'd turn
the brightness down so that the image is barely visible. Readout on 7104
should be off unless you need it, to avoid MCP burn in. Before attempting
any repair, thoroughly read the documentation on tekWiki, and search for
posts on this group discussing MCP CRT and 7104 in general.

Based on your video, I'd say that something may be wrong with the high
voltage circuit driving the CRT, therefore the focus issue. This CRT
contains a complex internal electrostatic lens that expands the image after
deflection, and is fed by numerous voltages (those black potentiometers
under the clear protective shield on the right side of the instrument). But
I would not touch any of these before I did the following:

- get thorough familiarity with this special instrument from documentation
and group posts
- check each plugin in a known to work mainframe
- check the PSU voltages for ripple and value
- check internal connectors for bad contacts, including plugin slot
connectors
- give knobs and buttons some exercise, patina and corrosion from old age
are a major nuisance for instruments which haven't been used for a while

7104 is worthy of care and attention, don't rush things (touch adjustments)
if unsure, equip and prepare properly before going in.

Best Regards,
Nenad

On Thu, Mar 28, 2019 at 1:01 AM Fast Hardware <@Armando49> wrote:

Hello all

I just got a 7104 for 30 dollars. With all 4 plugins. Including the 1ghz
one.

I need help fixing it. It powers on but the trace is wide and choppy . I
created a video. Please see it and let me know. I will start with
checking the volts on the different rails.


https://youtu.be/wMGDOzYwLys


Thx in advance for your help

Re: I wonder if there is much interest in vacuum tube oscilloscopes such as the 500 series

Brian
 

Hi everyone , I also have 500 series scopes , 547 , 2 x 549 and a 564 . I even have a 661 that still works . I like all these scopes and will hang on to them as long as I have the space as they are all reminders of my early working life as they (547,549 and 564) were all new and state of the art when I started work
Despite my liking of these I also have a number of 7000 series scopes and even a couple of TDS scopes , one of which I am attempting to repair as for me buying broken ones and fixing them is the only way I can afford any of them having retired now .

Brian

Re: TEK 475 voltage issues.

Roger Evans
 

Hi,

I am struggling to understand your measurements. The +105/160 is the unregulated supply to Q1496 which regulates the +110V line, so it is hard to understand why the output voltage from the series regulator (86.1V) is higher than the input voltage (10.7V). Q1456 is the series regulator for the +5V line, and yes it does run quite hot. I can't find Q1497 in the parts list. Are we talking about the 1970 ish 200MHz analogue scope? There is also a 475A model.

Roger

Re: Tek 2465B Calibrator issues

Chuck Harris
 

That is not what the OP is talking about!

The 2465 family has a variable frequency calibrator, which
always shows a couple cycles of the calibrator signal,
regardless of the sweep speed.

The purpose of this fancy calibrator is threefold:

1) scope probe calibration
2) sweep speed and cursor/graticule verification
3) it was nifty, and made the scope look special compared
to all scopes that came before.

[The calibrator's frequency is derived from the crystal
oscillator that is the microprocessor's reference on the
A5 controller card. The calibrator's amplitude is derived
by the DAC, and its reference, and a digital constant that
is determined and stored during scope calibration.

The sweep's frequency (rate) is derived by the Miller
integrator's precision capacitors, and some digital calibration
constants stored during scope calibration.

The cursor's relationship to the graticule is determined
by the DAC and the trimmer pots that adjust horizontal and
vertical size and centering... all adjusted during calibration.

It is good to be able to relate all three to each other, and
gives a nice indication of the calibration state of the
scope.]

When you make a calibrator whose frequency rises in lock
step with the sweep speed, you will eventually reach a point
where the scope's bandwidth is too low to show the calibrator's
wave form as a square wave.

Remember, Fourier Transforms: a square wave is a sum of an
infinite series of sine waves all harmonically related,
something like:

f + 1/3 f3 + 1/5 f5 + 1/7 f7 + ... + 1/inf finf

Where f is the frequency, f3 is the third harmonic, f5 is
the fifth harmonic...

Well, to see something that resembles a square waveform,
the vertical amplifier has to be able to pass up to about
the 7th harmonic without distorting its amplitude. Even
then the wave you see will have ripple on its top and bottom.

The operator's guide doesn't adequately inform the user about
this fact, so many a new 2465 user eventually runs into this
on his own, and thinks his scope is broken. For me, that
happened in 1985 after I brought my brand new 2565 home and
ran it through its paces.

I'm not sure which is the worst marketing: showing your flagship
scope does something ugly, or letting your user think his new
scope's broken because it is doing something ugly.

It's all water over the bridge at this point.

-Chuck Harris

Brian Cockburn wrote:

Hi Marcial,

Have a look at W2AEW's YouTube channel here: https://www.youtube.com/channel/UCiqd3GLTluk2s_IBt7p_LjA search there for 'compensation' and watch the probe compensation videos. This might help.

Also check out EEVblog's https://www.youtube.com/watch?v=OiAmER1OJh4

Cheers, Brian.



Re: Advice sought on 7934 vs 7904A mainframe

Chuck Harris
 

David DiGiacomo wrote:
....
Both the 7934 and 7904A have fans that are loud enough to be annoying
in a quiet lab.
Ok, when I read the above line, I immediately snorted! Then I realized
he was talking about the cooling fan, and not scope aficionados.

-Chuck Harris

Re: I wonder if there is much interest in vacuum tube oscilloscopes such as the 500 series

Daniel Koller
 

There's still an interest!    I have a 575 (used irregularly) and a 545 (used OFTEN).   but it just works every time I turn it on.   I haven't needed to fix it in a few years.    I completely disagree that the 500 series are useless "boat anchors" or "room heaters" .   Yes, they are bigger than a modern scope, but if you have the bench space, they are every bit as useful.   Mine are on carts.  More so, for general experimenting, there are a lot input and out put connections on the 545 made by banana jacks (on my older version).   that makes it very easy to set up an experimental setup, rather than to just monitor a signal.   It's a great scope to *use*!
  Dan

On Thursday, March 28, 2019, 7:07:02 AM EDT, Brian via Groups.Io <brianas1948=yahoo.co.uk@groups.io> wrote:

Hi everyone , I also have 500 series scopes , 547 , 2 x 549 and a 564 . I even have a 661 that still works . I like all these scopes and will hang on to them as long as I have the space as they are all reminders of my early working life as they (547,549 and 564) were all new and state of the art when I started work
Despite my liking of these I also have a number of 7000 series scopes and even a couple of TDS scopes , one of which I am attempting to repair as for me buying broken ones and fixing them is the only way I can afford any of them having retired now .

Brian

Re: I wonder if there is much interest in vacuum tube oscilloscopes such as the 500 series

Dave Voorhis
 

On 28 Mar 2019, at 01:07, John Williams <books4you@...> wrote:

Hi folks. I have been observing the topics of interest here for a few weeks, and I am not seeing much on older scopes ie before the 7000 series.
I have a 549 with Type Z, 1A2 and 1A4 plugins. I love it and it just works, though I need to do some mechanical restoration work on one of the 1A4 channels.

I also have a 564 which produces a trace and the storage works, but I need to fix the plugins.

I haven’t posted about them much because so far I haven’t encountered anything on them I felt the need to ask questions about.

I’d like to get my hands on a 575, but here in the UK they’re relatively rare.

Re: TEK 475 voltage issues.

Glen Layne
 

I'm trying to measure the +105/160 from the labeled trace. This trace with +105/160 printed on it ends on the + of C1452. So, basically, I was trying to find +105/160 on C1452. Maybe I'm trying measuring in an incorrect spot. There is an unlabeled measurement pin near Q1496 that has +142 v. The metal top of Q1497 (2n2907a) has +142v. The metal top of Q1496 is where I think I should find +110 but right not I just got 87.4 and the same at the +110 pin.

Q1497 from the parts list. My serial number is > 275000
tek part no Serial/Model
151-0301-00 XB080000

Re: TEK 475 voltage issues.

Roger Evans
 

OK, I understand the +105/+160V measurement problem! There is some screen printing on the 475 PCB near Q1490 that says '+105/160V' and it is printed on one of the PCB traces but that trace does NOT connect to the +105/160V line (and it measures about 10V!). The schematic shows a +105/160V test point but I can't find it. You can measure the real +105/160V on R1423, mine measures around 125V.

Roger

Re: TEK 475 voltage issues.

Glen Layne
 

Many thanks Roger. At R1423, I find +141.7. Now, my issue is something dragging down the +110. It's currently sitting at 87.3. If I leave the unit on, it will slowly drop even more.

Glen

Re: I wonder if there is much interest in vacuum tube oscilloscopes such as the 500 series

bill koski
 

I still have a 556 which I built my own cart for. I have it next to my test bench and use it often. I bought it with the manual for $25 at a HAM fest about 15 years ago. Other than needing a vertical driver tube (which cost me 30 bucks at the time) it has worked great. I have a bunch of plugins for it including a 1L5 Spectrum analyzer (a subject for another day that I'll have to pick the brains of the people here!) and a 1A4 4 channel plug in. Friends are impressed when I use a 2 channel in the other bay and can put 6 different traces up on the screen! Though it's only rated 50MHz I've displayed a stable 100MHz on it.
Amazing scope for its time and still quite a performer today. Plus it keeps me warm in my office on cold winter nights!!!
I also have a single bay scope that I acquired with some other equipment. I believe it's a 545B? I've not even attempted to plug it in yet. It's sitting in the wings waiting for some much needed TLC.
While we're on the subject does anyone have an extension cable for the plugins that they would like to sell so I can work on a couple sick ones?

Electromyograph EDX-1 - Based on Tektronix 5000 Series Mainframe

Wolfgang Schraml
 

Hello,
Acquired an interesting device at a recent swap meet - an Electromyograph ("EDX-1") based on what appears to be a 5000 series mainframe. I posted a few pictures in the photos section under "Electromyograph EDX-1". I did some googling but couldn't find a whole lot (other than another one of these that sold on eBay Canada not too long ago).
Haven't done any detailed assessment yet.

Just wondering if anyone has any information about this. Trying to decide whether it is worthwhile restoring.

Thank you,
wschraml, KI7PFX

Re: TEK 475 voltage issues.

Roger Evans
 

I guess it is obvious out last posts crossed and also I seem to have a different board revision from you.(serial 708886, Holland, no Q1497). For some reason the series regulator Q1496 (on my schematic at least) is a PNP so the output is from the collector not the emitter, hence the 87.4V. On my 475 almost all the transistors are socketed so can you pull Q1496, Q1490 and Q1494 and check them? If they all check OK then measure the voltage at the junction of R1486 and R1487, if it measures at 50V then the regulator is working and one or other resistor has drifted. If it measures at 87.4 *(50/110) then the resistors are OK and you either have excessive load current or something else around Q1494 is at fault.

If the scope is basically working then measure the ripple on the 105/160V line. The calibration may be out but it is just a go/no go measurement.

Roger

Re: TEK 475 voltage issues.

Roger Evans
 

Posts crossed again!

It sounds very much like you have an excessive current load on the +110V line. If you look at the power distribution diagram, schematic <11>, then the horizontal amplifier would be a good starting point, there are two loads via the 100R resistor R1267 so try measuring the voltage drop across R1267 and also check C1267 and VR1267. Also check the value of R1267, it may have overheated.

Roger

Re: TEK 475 voltage issues.

Chuck Harris
 

If there hasn't been a ripple measurement on the 110V line,
now would be a good time.

If a diode is open circuit, or a filter is very high ESR, the
ripple could be such that the regulator is dropping out of
regulation during the valleys between the peaks. This will
show up as a lower than normal average voltage from the supply.

The scope may even work fairly well under that circumstance.

-Chuck Harris

Roger Evans via Groups.Io wrote:

Posts crossed again!

It sounds very much like you have an excessive current load on the +110V line. If you look at the power distribution diagram, schematic <11>, then the horizontal amplifier would be a good starting point, there are two loads via the 100R resistor R1267 so try measuring the voltage drop across R1267 and also check C1267 and VR1267. Also check the value of R1267, it may have overheated.

Roger



Re: 11801 question

Albert Otten
 

Hi Reg,

In another thread you say:
"Watching the clock period vary by 100 femtoseconds over the course of 15-30 seconds with a 1 s gate time is rather interesting.".
I'm not sure whether I read this correctly. Does the 5 ns period vary 0.1 ps in 15-20 s (I hope not!)?
I measured the 200 MHz clock of a CSA803A using the DC510 as counter. Counter already warmed up.
Frequency dropped from 200,000.62 MHZ at startup of the CSA to 200,000.26 MHz after 30 minutes. In those last 10 minutes the drop was 0.02 MHz or 0.1 ppm. That means 0.5 fs increase in period.

I don't know how the time base delays are created. Long delays could be obtained as multiples of the 5 ns period. But somehow the dot steps as short as 0.1 fs (!) need a classical ramp and comparator circuit I guess.

You seem to forget that you are in the lucky circumstance of having internal triggering so far. The delay from trigger event to strobe event will likely be less jittery than from external trigger event to strobe event. In your applications you probably need external triggering with a pretrigger signal generated by the DUT. That introduces extra jitter and might even be the main source of jitter. (I am a layman w.r.t. to the intended use you mention.)
In my opinion the internal channel drift cannot be caused by the time base. The schematics suggest that one and the same time base event starts the strobe action for both heads.

Albert

On Thu, Mar 28, 2019 at 12:52 AM, Reginald Beardsley wrote:


I've got the unit running with a pair of SD-22s fed by a 2 port splitter from
the calibrator into ports 5 & 7. I was finally able to figure out how to
manually adjust the skew so the two traces overlaid. The cables are about 1/2
mm different lengths

I'm seeing the displacement between the two traces vary from 0 to about 10 ps
over the course of a few minutes. Is this normal or is there a fault? I've
read the user manual once, but it's not great. Certainly no match for a 465
or 485 manual.

Does anyone know why this is happening? I've got the internal clock output
connected to an HP 8356A and I can see the period varying. I don't have the
8356A connected to a GPSDO at the moment, but it has the OXCO option and is
very stable.

Is there any reason to think that replacing the 200 MHz master oscillator with
one of Leo Bodnar's GPSDOs would eliminate the interchannel drift?

I discovered this shortly after making an offer for four SD-26 heads. My
intended use is to measure actual FPGA word skew of a DSP stream, so this
would be a serious problem.

Thanks,
Reg

Re: I wonder if there is much interest in vacuum tube oscilloscopes such as the 500 series

Nenad Filipovic
 

My 536 serves as a lab power supply for occasional tube experiments.
Otherwise is in excellent condition, complete and functional, and will keep
it as such. On winter evenings I sometimes fire it up with covers off, when
some of my vintage-fan friends drop by for a visit. 536 is an X-Y
instrument, so with 2 CA plugins we once played stuff like
https://www.youtube.com/user/jerobeamfenderson1

A year ago I rescued a 555 about to be ripped apart by audiophools.
Restored it to a quite decent condition, but alas I do not have its power
supply, only the mainframe. Still looking for one.