Date   
Re: Tek 2465B Calibrator issues

Siggi
 

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

Phillip Potter
 

Hi John,

I suspect that it's just a matter of what's going at the moment. I have seen a number of older scopes being worked on and written about here, over time.

I have a 575 that I intend to use, but it's not on my near horizon... LOL!

Phil

On 3/27/2019 6:07 PM, John Williams wrote:
Has all interest in the restoration and repair of these old “boat anchors” gone somewhere else, or has it died altogether?

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

Dave Seiter
 

It's probably just temporary; at least I hope it is.  I've limited myself to the 7K series and earlier, omitting the portables.  Have to draw the line somewhere!
-Dave

On Wednesday, March 27, 2019, 6:08:22 PM PDT, 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 am just wondering if this is a temporary trend or is it too late. Has all interest in the restoration and repair of these old “boat anchors” gone somewhere else, or has it died altogether? I am still working on several projects bringing new life to the ‘50s and ‘60s units. I hope I am not the last of a dying breed. Regards, John

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

toby@...
 

On 2019-03-27 9:07 PM, John Williams 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 am just wondering if this is a temporary trend or is it too late. Has all interest in the restoration and repair of these old “boat anchors” gone somewhere else, or has it died altogether? I am still working on several projects bringing new life to the ‘50s and ‘60s units. I hope I am not the last of a dying breed. Regards, John
Hi,

As a relatively recent member, I'm unlikely to ever own or have space
for a tube Tek, but I'm thrilled to know that people are keeping them
alive. As many as possible, I hope.

Please keep discussing them on the list!

--Toby





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

Brad Thompson
 

Phillip Potter wrote on 3/27/2019 9:46 PM:

Hi John,

I suspect that it's just a matter of what's going at the moment. I have seen a number of older scopes being worked on and written about here, over time.

I have a 575 that I intend to use, but it's not on my near horizon... LOL!
Hello--

Next question: is anyone out there building an oscilloscope from scratch? (*)

If so, I have one only used/RFE cast-aluminumfront-panel  bezel for a 5-inch CRT.
Manufactured by JAN Hardware of Brooklyn, NY (AKA Cylex), the casting
is their part number C-JAN-1358; the finish is a tasteful matte black and
has some scuffs.

I'm offering it free for postage plus another buck for a cuppa coffee.

Questions welcomed, PayPal honored
Thanks, and 73--

Brad  AA1IP

(*) I did this, sort of, as a teenager in the late 1950s when I was given a used
and nonworking Heathkit oscilloscope model O-something in lieu of a week's
wages at a TV-repair shop.

The scope's performance was dismal in all respects, so I undertook improvements.
What an education-- I learned about power supplies, triggered-sweep circuits, and
amplifier bandwidth compensation-- all tubed, BTW. The Radio Amateur's handbook and  a
copy of USAF Manual 52-8 (RADAR Circuit Analysis) were my texts.

I lacked tools for cutting holes in the scope's steel chassis. One of the first items to go
was the original cabinet, which was in the way of various aluminum subchassis
hung on the sides. At one point, I acquired a flat-face CRT which replaced the
original 5BP1 and greatly improved trace resolution.

All told, I learned a lot from that project!

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

Harvey White
 

On Wed, 27 Mar 2019 18:07:51 -0700, you 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.
Well, there's the 400 series, of which I had some, and still have
468s. I have a Telequipment D75 which was well loved at one time (and
put aside for other, more sophisticated equipment).

I am just wondering if this is a temporary trend or is it too late. Has all interest in the restoration and repair of these old “boat anchors” gone somewhere else, or has it died altogether? I am still working on several projects bringing new life to the ‘50s and ‘60s units. I hope I am not the last of a dying breed. Regards, John
I'm not equipped any more to do tube scope restoration. I have no
more tube equipment other than an old Drake R4-B receiver.

For lab scopes, I'm likely to stay at the 7000 series for now. Other
than a 7854 (which I don't need..........) there's nothing much in the
7000 series that I could make use of.... maybe a 7912A or the like...
but I don't need any of them.

For portable, I can go to 150 Mhz, digital or analog, up to 4 channels
depending....

For really portable, I'd kinda like a 225 or so, but not only are they
hard to come by, but also expensive. A 222 would be neat, but again,
while less expensive, not something I *have* to have.

Newer than that I have a TDS-540A and a TDS-640A. The only thing I'd
like in that kind of thing would be a color display....

So seriously enough, the older scopes (535, 545, 585) aren't
attractive, I've used them in the past. The even older ones (512,
513D), I've had and just don't need any more (and those were passed on
to someone else many years ago).

For what I do, and what I need, the 7000 series is pretty good.

Harvey




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

John Williams
 

It seems like most people here would actually use a scope. The other side would be those of us that don’t have scopes to use, but to restore and preserve. I only use a scope to fix a different scope, or some associated equipment. And for that I use the 475 or 2213. So I won’t try to guess which is the dark side. But there is a distinct difference. And never acquire anything you can’t fix. Probably that is.

Re: Advice sought on 7934 vs 7904A mainframe

David DiGiacomo
 

On Wed, Mar 27, 2019 at 5:01 PM John <@VK2DLP> wrote:
I have an opportunity to buy a 7934 mainframe. I would have preferred a 7904A but the 7934 has come up. I am not all that impressed with storage tube scopes but ignoring the storage function how do the 2 mainframes compare? They are both 500 MHz units so the question becomes are there any real or effective differences in their performance? Are there any weak spots in either of these two mainframes? On the surface ignoring the storage capability of the 7934 it and the 7904A look fairly similar. Can I get some feedback on these two units from the group.
The 7934 is the best Tek storage mainframe. It's quite usable as a
general purpose scope in non-storage mode, but obviously it is not as
bright as a 7904 or 7904A.

Both the 7934 and 7904A have fans that are loud enough to be annoying
in a quiet lab.

Re: 577 Curve tracer ringing CRT and noisy step generator

DW
 

I have found that moving the horizontal volts division selector around significantly affects the trace artifact with the step generator on. Some horizontal volts / division causes a aggravated trace artifact while other selections completely eliminate it. When selecting the lowest horizontal / division the trace artifact is almost eliminated.

When I have the horizontal / volts selection at the selection that causes the worst aggravated artifacts 0.5V / div, moving the step amplitude to a higher value causes the artifact to get worse while lower values incrementally decrease the artifact until it is not noticeable at or near the lowest step amplitude setting.

Re: Advice sought on 7934 vs 7904A mainframe

Craig Sawyers
 

I have an opportunity to buy a 7934 mainframe. I would have preferred a 7904A but the 7934 has come
up. I am not all that impressed with storage tube scopes but ignoring the storage function how do
the
2 mainframes compare? They are both 500 MHz units so the question becomes are there any real or
effective differences in their performance? Are there any weak spots in either of these two
mainframes? On the surface ignoring the storage capability of the 7934 it and the 7904A look fairly
similar. Can I get some feedback on these two units from the group.
The 7934 is somewhat rare (much rarer than the 7834), and is a fine storage scope. Like all Tek's
"multimode" storage scopes, bistable is useless (ridiculously low contrast), but in variable
persistence and fast variable persistence it has astonishing performance.

The other main difference is that driving a storage scope is an acquired art; it is quite easy to
damage the storage meshes, particularly where the readout is. If you get the chance to try before you
buy, check that out.

Also the 7934, and the 7834 before it, has a relatively low acceleration voltage (8kV) as compared
with 21kV on the 7904A. That makes the 7934 trace appear somewhat dim as compared with any non-storage
scope, like the 7904A. The 7934 uses a much lower acceleration voltage because it is optimised for
storage.

But if you want to store a single shot (or even repetitive waveform) for photography or visual
inspection, that is the way to go. And it is very impressive to see a single shot with a
sub-nanosecond rise stored.

If it was available to buy, I'd buy it in a heartbeat. And then look for a 7904A.

I suppose it goes without saying that I have a 7834 and 7934, and 7904 and 7904A. But then again I'm
almost certifiable.

Craig

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

Leanna L Erickson
 

I have a bunch of 500 series working scopes.

Real room heaters.

Keith

Wayzata, mn.

On Mar 27, 2019, at 9:52 PM, John Williams <books4you@...> wrote:

It seems like most people here would actually use a scope. The other side would be those of us that don’t have scopes to use, but to restore and preserve. I only use a scope to fix a different scope, or some associated equipment. And for that I use the 475 or 2213. So I won’t try to guess which is the dark side. But there is a distinct difference. And never acquire anything you can’t fix. Probably that is.


Re: TEK 475 voltage issues.

Tony G4NGV
 

On mine, I had a fault where the 104 was dragging down the 110v
The 104v was shorting/arcing to the ground plane of the pcb as it was
touching and over the years the paint on the R wore off?. I monitored the
104V while lifting parts of the cct to eliminate them. Hope this helps.
Tony UK

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On Wed, Mar 27, 2019 at 11:01 PM Glen Layne <gelayne@...> wrote:

Hey all. I'm new to the group and trying to restore 475 scope. when I
got it, 2 of the voltages were way off. The +110 was about +19 and the
+105/160 was coming in at +10.7. The other voltages were fine. So, I
ordered and replaced the 6 main caps. Q1497 was bad and I replaced it.
Now the +110 is coming at 86.1 and the +105/160 is still at 10.7.

So, the scope appears to work. Surprisingly well considering the voltage
issues I still have. I can't find what's bringing down the +110 and the
+105/160 at 10.7 can't be good. Q1456 (darlington) runs pretty hot and
it's on the +105 rail.

On occasion, the trace will shrink to postage stamp size. I can usually
adjust the Horizontal position all the way to the right and it will come
out of the postage stamp mode even though it may not be a stable trace.
Sometimes, I double push the 10x Mag and fiddle with the Horiz position to
get things back working.

Any ideas what to do next?





--
*From November 2013 I am using @Tonyvirago
<@Tonyvirago> as my email address.*
*My o2 email is going soon.*

Re: TEK 475 voltage issues.

Tony G4NGV
 

Sorry, there was a resistor with 104V on it and this resistor was touching
the groundplane of the PCB.

On Thu, Mar 28, 2019 at 6:46 AM Tony G4NGV via Groups.Io <tonyvirago2=
gmail.com@groups.io> wrote:

On mine, I had a fault where the 104 was dragging down the 110v
The 104v was shorting/arcing to the ground plane of the pcb as it was
touching and over the years the paint on the R wore off?. I monitored the
104V while lifting parts of the cct to eliminate them. Hope this helps.
Tony UK

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On Wed, Mar 27, 2019 at 11:01 PM Glen Layne <gelayne@...> wrote:

Hey all. I'm new to the group and trying to restore 475 scope. when I
got it, 2 of the voltages were way off. The +110 was about +19 and the
+105/160 was coming in at +10.7. The other voltages were fine. So, I
ordered and replaced the 6 main caps. Q1497 was bad and I replaced it.
Now the +110 is coming at 86.1 and the +105/160 is still at 10.7.

So, the scope appears to work. Surprisingly well considering the voltage
issues I still have. I can't find what's bringing down the +110 and the
+105/160 at 10.7 can't be good. Q1456 (darlington) runs pretty hot and
it's on the +105 rail.

On occasion, the trace will shrink to postage stamp size. I can usually
adjust the Horizontal position all the way to the right and it will come
out of the postage stamp mode even though it may not be a stable trace.
Sometimes, I double push the 10x Mag and fiddle with the Horiz position
to
get things back working.

Any ideas what to do next?





--
*From November 2013 I am using @Tonyvirago
<@Tonyvirago> as my email address.*
*My o2 email is going soon.*



--
*From November 2013 I am using @Tonyvirago
<@Tonyvirago> as my email address.*
*My o2 email is going soon.*

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.