Date   

Re: 'Improved' Mystery Switch on the 576 and 577 Curve Tracers

Kevin Oconnor
 

It is interesting to hear of the "hobby" interest in safely using the high voltage ranges on tracers who the DUT safety cover. It is commendable since the current is lethal. Professionally, in 25 years at a well known US industrial R&D laboratory now based in Italy, I encountered many Tek tracers. Seldom would there be a cover. But I could generally count on finding a wooden Q-tip jammed into the little micro switch hole! That permanently solved the ambiguity.
I always assumed there could be lethal voltages present on curve tracers till I determined otherwise. I also learned early in my education and from an old GM welding electrician, keep one hand in pocket until you deactivate the lethal voltage.


Re: 7S11/7T11 advice

Roger Evans
 

I would certainly try using the AD4350 board, that gives excellent results with my 7T11, 7S11, S4 and I see edges around 80psec but with a little overshoot. I found that the lowest jitter was using the AD4350 oscillator output into the 7T11 external trigger input but this may vary with different oscillator modules and different slew rates. Certainly the 2.5V swing from the oscillator out connector made the trigger settings very uncritical.

The AD4350 is also invaluable to check the 7T11 sweep speeds, my 100psec/div is actually close to 80psec.

Have fun, I certainly have,

Roger


Re: 7S11/7T11 advice

Siggi
 

On Sun, 18 Dec 2016 at 10:24 Sigurður Ásgeirsson <siggi@undo.com> wrote:

I've attempted the trigger adjustment, but it looks like the unit has some
problems. The 10X trigger amplifier can't be zero adjusted with R80 as a
case in point. The indicated measurement point is resting against one of
the clamping diodes at -0.7V. After my first attempt at adjustment, the
(random sampling) trigger jitter is still >100ps.
Oops, this was a PEBKAC - I must have been measuring the wrong point. Still
doesn't adjust right - I was trying the procedure in <
http://w140.com/tekwiki/images/7/75/Tekscope_1973_V5_N2_Mar_1973.pdf>. At
step 6, I can't stop the sweep from free-running without a trigger. It
doesn't matter where I set the stability control or R135, the sweep runs
regardless.


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


Re: Tek 464 - Correct transistor for Sync Generator Matched FETs 151-1042-00

 

On Wed, 14 Dec 2016 16:37:17 -0200, you wrote:

...

At various sites (Sphere, sellers at e-pay and others) those FETs are said
to be 2N5454, but on Tektronics Semiconductor Device Catalog (available
here at TekWiki: http://w140.com/Tektronix_Xref_sm.pdf), part number
151-1042-00 is listed as being from 2N4416 "family", for which there is
this one plus 4 other tek part numbers, selected (or matched) to different
parameter values.
The Tektronix Semiconductor Device Catalog also says 2N5454 in the
Tektronix part number to vendor number cross reference.

Initially I thought that 2N5454 could be just a different code to refer to
the matched pair, but what is confusing is that there is an actual a
2N5454: (datasheet here:
http://www.alldatasheet.com/datasheet-pdf/pdf/86408/INTERSIL/2N5454.html)
and besides it's a DUAL FET (in a single casing) and not a matched pair,
its specs are quite different than the 2N4416.
I have weakly assumed that the 2N5454 is a dual part made with 2N4416
dies but you are right, even the Intersil 2N4416 is not a match for
the Intersil 2N5454 and the Intersil 2N4416 matches the Tektronix
2N4416. Further, the Ft of the 2N4416 is 250 MHz as shown in the
Tektronix book but the Ft of the 2N5454 is not even close at about 90
MHz. The 2N5454 however *is* a pretty close match for the Tektronix
2N3684 family shown on page 7-6.

So, there's a mismatch between Tektronix Catalog, which tells they're a
selected 2N4416 and the general wisdom, that tells this part is 2N5454.

I tend to believe the Tek Catalog is right... but then, from where did it
come the information that those transistors are 2N5454?

Which is right?
So I think the original error was in the Tektronix transistor cross
reference index and others copied it.

I checked National's data and the transistors are not built on the
same process and do not even look the same.

Any experiences with this one?

Rgrds,

Fabio
The characteristics of the replacements are not critical as long as
the transistors are matched for Vgs or Idds and they do not oscillate.
The 2N5454 would work (if it fit) but limit bandwidth which probably
would not be noticed without specific testing.

I do not think there is any reason to try on find a 2N5454 though. It
would be cheaper to find a few of some other single part and grade
them for Vgs or Idds or an already matched set. Even a pair of not so
well matched JFETs would at least work or could be made to work if the
source resistors are adjusted.


Re: 7S11/7T11 advice

Siggi
 

Thanks everyone for hints and tips. It was certainly very confusing the
first time I tried to look at the scope's calibrator with the sampler. It
really does seem to be necessary to read through the manual to understand
which buttons to press and which to twiddle which way for which effect :).

I've attempted the trigger adjustment, but it looks like the unit has some
problems. The 10X trigger amplifier can't be zero adjusted with R80 as a
case in point. The indicated measurement point is resting against one of
the clamping diodes at -0.7V. After my first attempt at adjustment, the
(random sampling) trigger jitter is still >100ps.

It seems it'll be hard to check the trigger jitter without a delay line and
a sharp rise pulse. Apparently the QuickStart 8 test board has fairly high
jitter on the fast-rise output, and so the second edge can't really be used
to assess the jitter. I do have an ADF4350 demo board with differential
50Ohm outputs - maybe I can use that...

I may also end up looking for another 7T11 that's mechanically whole.


Re: Tek 464 - Correct transistor for Sync Generator Matched FETs 151-1042-00

 

I have probably noticed this before but I quickly studied the circuit
and found another reason to use this configuration of two JFETs
besides temperature tracking and improved linearity.

The designer wanted zero, or at least controlled, voltage offset
between the input at the JFET gate and the output. That will only be
true at one drain current for a given JFET and JFET Vgs is not well
controlled. By using a pair of JFETs matched for Vgs with the gate of
the lower JFET shorted to the output, the lower JFET sets the current
for the upper JFET such that its offset is also zero. Besides the
advantage of temperature tracking, this removes an adjustment and the
birthday paradox makes it relatively easy to find JFET pairs with
matched Vgs.

As long as the source resistors, 15 ohms in this case, are the same
value, they have no effect other than to alter the drain current of
both JFETs because the bottom JFET's gate connection includes its
source resistor. If a bipolar emitter follower was used after the top
JFET to lower the buffer's output impedance, then the same type of
bipolar emitter follower (or a diode) could be used on the bottom one
to compensate the Vbe drop and I have occasionally seen this done in
Tektronix designs.

So what does this mean for us? The JFET characteristics are not
critical as long as they have a matching Vgs. If replacements have a
drain current which is too high, then the source resistors can be
increased to lower it.

Later oscilloscope designs use a bipolar constant current source
controlled by an operational amplifier in place of the lower JFET and
this is common today. This removes the requirement for matched JFETs
but overload recovery will suffer unless the input is held within the
operating range of the operational amplifier. I think this explains
why these designs use an attenuator before the operational amplifier
to increase its input voltage range.

On 14 Dec 2016 18:48:38 -0800, you wrote:

I don't know what the part numbers should be, but I do know that Tek often used pairs of JFETs that were matched to some degree, and also sometimes linked them together with spring clips for better thermal tracking. In a trigger circuit the balance isn't as critical as in say a vertical amplifier, so two reasonably close ones should work OK.

Ed


Re: 7S11/7T11 advice

Siggi
 

Hey Sergey,

that's very kind. The seller refunded me the unit, and as I think it may
have other problems, I'm probably going to try and look for another one.
Hopefully that one will be in better mechanical shape.
I appreciate your offer very much, and I may still take you up on it,
though...

Thanks,
Siggi

On Sat, 17 Dec 2016 at 00:25 Sergey Kubushyn ksi@koi8.net [TekScopes] <
TekScopes@yahoogroups.com> wrote:

On Sat, 17 Dec 2016, Sigurður Ásgeirsson siggi@undo.com [TekScopes] wrote:

I do have a dead 7T11. Although it is kinda beaten up the time base knob
is in good, no cracks or whatever. Can send the complete knob (there are
3 of them there in that assembly) to you if you pay for shipping.

Hey y'all,

as I'm coming of a certain age, I've been feeling the urgent need to set
up
a sampling system. So, from a guy's garage came a couple of 7834
mainframes, from another direction came a 7S11/S-4 and off evilbay came a
7T11. Amazing what a few Canadian pesos can buy you.
So, I now have a somewhat functioning sampling system that'll give me a
look into the time domain at N GHz, where N > 1, or even N >> 1. It
currently has all the usual & endearing quirks of the vintage, so
de-glitching pots and contacts is a given.

Unfortunately the 7T11 was shipped in a padded envelope(!!!) and took
some
mechanical damage en-route. If anyone has the time base knob to share
from
a dead'un, that'd be awesome, and I'm also looking to fix or replace the
trig level pot and knobs.

Like I said above, everything sorta works, except not quite right.
One thing is that at high speeds (maybe the fastest timebase?) the
sampling
isn't uniform in the horizontal. There are bright patches and dark
patches,
which aren't affected by the scan pot, not much at least. I'm thinking
this
has to be some kind of crosstalk, as it seems to be stable in the trigger
point. Could also be that one of the ramps isn't so rampy? Seems to
happen
more in random than sequential sampling, though I'll have to look harder
in
the light of day and sobriety.
The trigger jitter also seems awfully high - I've been looking at one of
those QuickStart 8 boards, which reputedly has ~150ns rise, as well as a
homebrew tunnel pulser that ought to be inside 200ns. In both cases I get
pretty severe drift and what looks like at least 100ps trigger jitter.
Not much use to have 10ps/DIV precision when the jitter smears across the
whole screen :).

I've yet to read through the 7T11 adjustments section with both eyes
open,
but if you have hints, tips or tricks, I'm all ears.

Siggi


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



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Re: 7S11/7T11 advice

Albert Otten
 

Hi Siggi,
I would stay away from random sampling until sequential sampling works flawless. Random is much more tricky, Those varying intensities along the trace are inherent to the random sampling technique in the 7T11 I think, especially when the signal source periods are jittery in length. Also one of the adjustments is to minimize a slowly repeating combination of drift in one direction and jump in the other direction. Very temperature sensitive in my experience.
Turn off the Readout when you look at intensities, sometimes the readout interrupts are almost synchronous with the trace repetition rate.
Albert


Re: TDS430A attenuator replacement

brian l
 

In my case all the measurement tools and other menu options were working as well prior to replacing the caps but the attenuator board was not passing any signals through. Turning the vertical sensitivity to maximum would show some random noise waveforms on one channel but other channels were essentially deaf.


New file uploaded to TekScopes

TekScopes@...
 

Hello,


This email message is a notification to let you know that
a file has been uploaded to the Files area of the TekScopes
group.


File : /RDBKPRTS.pdf
Uploaded by : ikerooney <ikerooney@gmail.com>
Description : Repl Assys mostly TDS but includes a few Rhode&Swartz and Television measurement instruments. Prices, I'm guessing from about 1995.


You can access this file at the URL:
https://groups.yahoo.com/neo/groups/TekScopes/files/RDBKPRTS.pdf


To learn more about file sharing for your group, please visit:
https://help.yahoo.com/kb/index?page=content&y=PROD_GRPS&locale=en_US&id=SLN15398


Regards,


ikerooney <ikerooney@gmail.com>


Re: introduction, issues with 2335

 

U43 is in stock at Qservice as is U54. U54 is two power transistors and some hybrid resistors that you should be able to buzz out with you DMM to rule that part out.

I guess you made the measurements with the position control centered and no input signal? Also, are the readings the same for both channels?

http://www.tek-parts.com/shopexd.asp?id=14187 u43

http://www.tek-parts.com/shopexd.asp?id=14088&bc=no u54

BTW, on Tektronix schematics the reference to the schematic is in the lower RH corner and is in a diamond. This is all on schematic 3. Just a FYI.


Regards
tom

----- Original Message -----
From: ajecq6dgz6kfqotq7wtbntwdjsn7nrnkkaun3uoy@yahoo.com [TekScopes]
To: TekScopes@yahoogroups.com
Sent: Saturday, December 17, 2016 5:19 PM
Subject: Re: [TekScopes] introduction, issues with 2335



thanks for the reply, I guess I wasn't all that clear the 9.1 volt requirement is on u43 pin 2, schematic a15, vertical output, yes before I change anything I will try and define the problem a lot better
greg


Re: 2215A repair advice needed

 

That is too bad and I am not surprised that the CRT is broken which
the rattling confirms. Given the costs involved, maybe the seller
will just issue a refund and let you keep the rest.

On Sun, 18 Dec 2016 01:45:15 +0000 (UTC), you wrote:

Just wanted to thank everyone that replied. I've decided to send the scope back though I have yet to hear from the seller. I guess EBAY has a resolution process even if the seller does not accept returns. I did double check the pictures on the listing with what I received and it is the same scope. The serial number shows in the picture. The CRT is broken, you can hear the pieces moving around inside the tube. I'm sending it back, because I don't think I should pay for the sellers carelessness. A few dollars worth of padding could have prevented all this trouble.
So I'll keep reading and learning for now and try again after the holidays.

Thanks to all,Michael


Re: introduction, issues with 2335

 

On 17 Dec 2016 14:21:43 -0800, you wrote:

supply voltages are right on at 40, 10, -10, 5 and -5. Pins 8 and 13 are both 4.5 mv

greg
So for U54 (155-0219-00):

Pin 1: +40 Volts
Pin 7: +10 Volts

Pin 4: ?
Pin 10: ?

Pin 6: +9 Volts
Pin 8: +6 Volts (!)

And for U43 (155-0218-00):

Pin 8: +4.5mV (roughly zero)
Pin 13: +4.5mV (roughly zero)

It seems that u43 may not be functioning properly. there is only 6 volts on pin 2 when there should be 9.1. The other pin voltages seem to be ok, although are out be about 1 volt on others. Have others experienced similar problems and is there a chance of finding a NOS U43 or a used working IC.

greg
I think it more likely that U54 is the problem but I agree with Jon
Batters; double check the DC and AC values of the power supply
outputs.

What are the voltages on pins 4 and 10 of U54?

With the power off, what is the resistance between pins 4 and 10 (the
outputs) and pin 1 (the +40 volt input)? Make this measurement with a
low voltage ohms meter if possible. Reverse the test leads and take
the highest resistance reading.

Based on other designs, the resistance should be roughly 450 ohms. In
any event, the values should be equal and represent the collector load
resistors between the collector outputs and positive high voltage
supply which is +40 volts from pin 1 in this case.

If U54 works the way I think it does, then pins 6 and 8 of U54 should
always be roughly 9 volts. If pin 8 is 6 volts, then a likely fault
is that the collector load resistor between pins 10 and 1 is open.

It would also be helpful to know the voltages at pins 3, 4, 17, 18,
and 20 of U43. The control the last stage of U43.

We have the datasheet for U43 (155-0218-00) if anybody is interested
and its brief description of U54 (155-0219-00).


Re: 2215A repair advice needed

Michael Wyatt
 

Just wanted to thank everyone that replied. I've decided to send the scope back though I have yet to hear from the seller. I guess EBAY has a resolution process even if the seller does not accept returns. I did double check the pictures on the listing with what I received and it is the same scope. The serial number shows in the picture. The CRT is broken, you can hear the pieces moving around inside the tube. I'm sending it back, because I don't think I should pay for the sellers carelessness. A few dollars worth of padding could have prevented all this trouble.
So I'll keep reading and learning for now and try again after the holidays.

Thanks to all,Michael


Re: 7S11/7T11 advice

 

Hi Siggi,
As far as triggering goes I struggled with it like everyone else until I
figured out to improve my chances. Several other members do the same thing.
File this suggestion under 'tricks of the trade'.

I put the 7S11/7Tll in the middle two slots of a 4 slot mainframe. In the
left most slot I put a 7A24 50 ohm amplifier. In the right slot I put a fast
timebase (7B80, 7B92 etc).
When I have a signal I want to look at on the sampler I first plug it into
the 7A24. I work the controls and the trigger levels, etc. on the 7A24 and
the 7B92 timebase until I get a stable waveform. Now I know what my trigger
levels, V/Div, and time /Div settings should be to display the waveform.
At that point I set up the sampling plugins precisely the same way and
transfer the signal over to the 7S11. That gives me a fighting chance at
getting a sampling display without too much fuss.
Once I get a display of any kind on the sampling system it is usually pretty
easy to refine the settings until its stable and then I start to increase
the sampling speed.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com]
Sent: Friday, December 16, 2016 6:24 PM
To: TekScopes@yahoogroups.com
Subject: [TekScopes] 7S11/7T11 advice

Hey y'all,

as I'm coming of a certain age, I've been feeling the urgent need to set up
a sampling system. So, from a guy's garage came a couple of 7834 mainframes,
from another direction came a 7S11/S-4 and off evilbay came a 7T11. Amazing
what a few Canadian pesos can buy you.
So, I now have a somewhat functioning sampling system that'll give me a look
into the time domain at N GHz, where N > 1, or even N >> 1. It currently has
all the usual & endearing quirks of the vintage, so de-glitching pots and
contacts is a given.

Unfortunately the 7T11 was shipped in a padded envelope(!!!) and took some
mechanical damage en-route. If anyone has the time base knob to share from a
dead'un, that'd be awesome, and I'm also looking to fix or replace the trig
level pot and knobs.

Like I said above, everything sorta works, except not quite right.
One thing is that at high speeds (maybe the fastest timebase?) the sampling
isn't uniform in the horizontal. There are bright patches and dark patches,
which aren't affected by the scan pot, not much at least. I'm thinking this
has to be some kind of crosstalk, as it seems to be stable in the trigger
point. Could also be that one of the ramps isn't so rampy? Seems to happen
more in random than sequential sampling, though I'll have to look harder in
the light of day and sobriety.
The trigger jitter also seems awfully high - I've been looking at one of
those QuickStart 8 boards, which reputedly has ~150ns rise, as well as a
homebrew tunnel pulser that ought to be inside 200ns. In both cases I get
pretty severe drift and what looks like at least 100ps trigger jitter.
Not much use to have 10ps/DIV precision when the jitter smears across the
whole screen :).

I've yet to read through the 7T11 adjustments section with both eyes open,
but if you have hints, tips or tricks, I'm all ears.

Siggi






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Re: Odd looking 453... Schematic needed

Daniel Olguin
 

It was indeed epoxied in red, but it was manufactured by ERIE. It was also flopping around inside it's little plastic tomb (like the bottom screw wasn't completely tightened), so I don't know if this had anything to do with it's demise or not. I'll know better when I install the new part.

The capacitor also had a dark (black) spot on one side, but no discoloration of the plastic tomb that it lived (and died) in, which tells me that the part failed internally.


Re: introduction, issues with 2335

Jon Batters
 

Sent from Mail for Windows 10

Hi Greg,

First,….Get the S/M and O/M for the 2335. This ain’t horseshoes and close with a 2336 doesn’t count

Don’t be lookin’ for a u43 yet. Print out the P/S list and notate the ave/peak and ac of the values and repair as needed. Close values on the ic’s doesn’t work. They’re in spec or not. U43 may work when you get the scope normalized.

Write Tekscope back when you get more and clarified info and we’ll help.

Jon Batters, Grants Pass, Or.


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


Re: introduction, issues with 2335

ajecq6dgz6kfqotq7wtbntwdjsn7nrnkkaun3uoy@...
 

supply voltages are right on at 40, 10, -10, 5 and -5. Pins 8 and 13 are both 4.5 mv
greg


Re: introduction, issues with 2335

ajecq6dgz6kfqotq7wtbntwdjsn7nrnkkaun3uoy@...
 

thanks for the reply, I guess I wasn't all that clear the 9.1 volt requirement is on u43 pin 2, schematic a15, vertical output, yes before I change anything I will try and define the problem a lot better
greg


Re: introduction, issues with 2335

ajecq6dgz6kfqotq7wtbntwdjsn7nrnkkaun3uoy@...
 

u43 is on schematic a15, vertical output
greg

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