Date   
Re: free - tek 453 scope manual printout

Dale H. Cook
 

At 06:48 PM 10/10/2018, Chuck wrote:

just confirmed my scope is pre "a" so the docs would need to be for the vanilla 453.
Chuck -

There is no vanilla 453 - there are two versions, early production (serials under 20,000) with Nuvistors in the front ends and the triggers, and late production (serials over 20,000) with FETs in the front ends and the triggers.

Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcity/radios/index.html

Re: Tek 2467B

tekscopegroup@...
 

In preparation on working on my own 2465B scope which is on the way, I read elsewhere that apparently there have been cases of a still working DS1225 being corrupted while reading is attempted because some programmers may sink some current from ICs pins when trying to read, and so pulling an already frail backup battery too low for the data to be retained. There is even a dedicated PDF out there that shows how to do a "surgical" procedure to connect an external battery to the DS1225 to insure the backup voltage does not droop during the data reading. Search for "Tektronix 2465B repowering the DS1225" to find this PDF.

Maybe a good idea before even disturbing the NVRAM module would be to go through the EXER02 "Calibration RAM Examine" routine and hand copy all the data, or make a video while scrolling through it on screen. This information I understand will be enough to rebuild your cal constants in case they are lost during the programming/replacement process.

As a reference, some programmers I've taken note of that are being said to work with the DS1225 are the GQ-4X, Wellon VP-390, and EasyPro 90B programmers. The TL866 programmer is also mentioned, but apparently some users had trouble reading the NVRAM, while others had no problem. There might be other compatible programmers, I'm sure. But again, I have never done any tinkering on this yet. Maybe also worthwhile to mention the alternative that some people are using a Ramtron FM16W08 instead of the DS1225, it does not even need a battery anymore for data retention. It is a SOIC28 pinout part, so it needs to be mounted on a small adapter board in order to be plugged into a regular DIP28 socket. Neat solution I would think, no more battery worries, ever.

Last but not least, DO NOT buy any NVRAM modules on ebay, there seems to be a lot of counterfeit stuff being offered, mainly from China, but also some US based sellers (suspiciously almost always located in CA). Some are relabeled older chips with falsified date codes, or just plain fakes. Best to buy from Mouser or Digikey to insure you do get a fresh 1225 chip with a recent date code.

Re: 2445A calibration

Max Vlasov
 

Hello Chuck,

Thank you for your explanations!

Regarding the AWG in use, I have an ancient, but well calibrated HP 8175A with 10 bit resolution DAC and the output attenuator. When it works on 50 Ohm load, it adds internally the series 50 Ohm resistance between it's amplifier output and the BNC connector. Also another generator I tried was Agilent 33250a (can't reach 10Vp-p output from 0 to 10V to 50 Ohm). I've borrowed the recently calibrated AFG3102. It has 0.5% of the output accuracy when running full amplitude to 50 Ohms. IMHO, it will be sufficient to do the job as the calibrator too, however I have a doubt about the 2445a DAC.

It seems like the DAC calibration is a complex procedure somehow (saw on youtube: https://youtu.be/m7adJq5xMHE). I don't have the same approach at all (in the video the approach is to align the cursor to the extreme left and right horizontal division).
But in my approach I need no calculus at all since I follow the instruction "rotate the Delta control until DMM reading remains at constant value". So it means that I don't even look at the screen of the scope at all. Only at DMM. So, I use two multimeters in parallel with FREEZE/HOLD function. I turn the knob CCW until the voltage reading is constant (same on both) then I press FREEZE/HOLD on the first one. Then I rotate the knob to the CW all the way until the reading is constant and press FREEZE/HOLD on the second. Then I turn the pot just a bit in the direction (of gradient) of the sum of two voltages to get to 2.5V, unfreeze one of the multimeters, swing the delta knob to another extreme and repeat the iteration again. So, in 2 minutes I get to the point where the full scale swing (again judging DMM readings) is exactly 2.500V without any pre-calculated successive approximation steps. But now I wonder whether I do it correctly and whether I should be looking at the screen rather than at DMM.
Watching again the aforementioned video it seems like the alignment technique required to have a nicely centered full swing (judging visually by matching the 1st and the 11th vertical divisions with the delta cursor line).

Hmm, looks like the manual is a bit ambiguous.....

How does your DAC tuning procedure look like, like in video or by always using the voltage extremes?

Thank you,

Maxim

Re: 7000-series power-hungry plug-ins

Dave Voorhis
 

On 11 Oct 2018, at 15:03, Tim Phillips <timexucl@...> wrote:

It is 'well known' that the 7D20 draws too much power from a standard 7603;
Is it? Does it?

I used a 7D20 in a 7603 for a while, until — notably — what appears to be partial power supply failure. I haven’t got around to diagnosing which rail(s) are off.

What is the typical failure mode?

Re: Tek 2467B

Chuck Harris
 

You might notice that there is a routine to read the calibration
constants, but no routine to write the calibration constants. I seem
to recall that there is a way, but I don't have it in my notes.

I am certain that Tektronix believed, as I do, that the only right
way to write the calibration constants is to do a calibration.

And,

These scopes are made up of components that drift, and they are
not permanently calibrated. The NVRAM doesn't contain any primary
standards. By the time the battery in your NVRAM goes bad, your
scope has been out of calibration for 15 or 20 years.

Each scope is the sum of all of the thousands of different parts
that went into their making. No two scopes are the same, and no
two NVRAMS contain the same data. It is a fool's errand to hunt
up some other 2465B's NVRAM data and put it into your NVRAM, thinking
doing so will calibrate your scope... it won't.

[No good service technician would ever put a new calibration into
a 30 year old NVRAM... That would be like changing the oil in
your car but leaving in the dirty oil filter.]

To further the insult, if you ever replace the caps in the power
supply, or on the A5 board, your calibration is toast.

All those new capacitors will reduce the ripple (a good thing), and
in so doing, will make the feedback loops in the 10V power supply
come up with a slightly different idea of what 10.000V really is.

Similarly, replacing the leaky SMD capacitors on the A5 board, the
10K reference resistors, and then cleaning up the leaked electrolyte
will give the DAC reference a different idea of what's what.

So, you say: "I will just set them to 10.000V and 2.500V swing, and it
will be as good as new!" Except, you have no idea how your DVM compared
to the last guy's, and no idea how careful the last guy was to get the
settings exact.

-Chuck Harris

Claimer: I am most certainly biased. I can't help it, I calibrate 2465's.

tekscopegroup@... wrote:

In preparation on working on my own 2465B scope which is on the way, I read elsewhere that apparently there have been cases of a still working DS1225 being corrupted while reading is attempted because some programmers may sink some current from ICs pins when trying to read, and so pulling an already frail backup battery too low for the data to be retained. There is even a dedicated PDF out there that shows how to do a "surgical" procedure to connect an external battery to the DS1225 to insure the backup voltage does not droop during the data reading. Search for "Tektronix 2465B repowering the DS1225" to find this PDF.

Maybe a good idea before even disturbing the NVRAM module would be to go through the EXER02 "Calibration RAM Examine" routine and hand copy all the data, or make a video while scrolling through it on screen. This information I understand will be enough to rebuild your cal constants in case they are lost during the programming/replacement process.

As a reference, some programmers I've taken note of that are being said to work with the DS1225 are the GQ-4X, Wellon VP-390, and EasyPro 90B programmers. The TL866 programmer is also mentioned, but apparently some users had trouble reading the NVRAM, while others had no problem. There might be other compatible programmers, I'm sure. But again, I have never done any tinkering on this yet. Maybe also worthwhile to mention the alternative that some people are using a Ramtron FM16W08 instead of the DS1225, it does not even need a battery anymore for data retention. It is a SOIC28 pinout part, so it needs to be mounted on a small adapter board in order to be plugged into a regular DIP28 socket. Neat solution I would think, no more battery worries, ever.

Last but not least, DO NOT buy any NVRAM modules on ebay, there seems to be a lot of counterfeit stuff being offered, mainly from China, but also some US based sellers (suspiciously almost always located in CA). Some are relabeled older chips with falsified date codes, or just plain fakes. Best to buy from Mouser or Digikey to insure you do get a fresh 1225 chip with a recent date code.

Re: Tek 2467B

BryanByTheSea
 

I did it and it went bad, not sure what happened, but I believe the voltage got pulled too low when using the programmer to read and it erased/corrupted the DS1225. Possibly the control IC itself relies on the backup battery voltage being above a certain level or it fails to pass the chip select signal through. In hindsight I should have taken screenshots of the memory displayed from the CRT, can't remember what menu option off hand, but at least I would have had some type of backup.

Here is a link to some useful information on the DS1225 and alternatives.

http://www.worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf

Dual-pole power switches

Kurt Rosenfeld
 

Why do some instruments use dual-pole power switches while other instruments use single-pole? For example, the 564 uses a dual-pole power switch (interrupting neutral and hot) while the 547 uses a single-pole power switch (only interrupting hot).

Re: 7000-series power-hungry plug-ins

Craig Sawyers
 

Other power-hungry plugins are the spectrum analyzers.

It is 'well known' that the 7D20 draws too much power from a standard 7603;

Re: 2445A calibration

Chuck Harris
 

I think you are misinterpreting what is going on with the
DAC reference calibration.

The delta control is simply being used as a way of
driving the DAC to its two digital extremes: 0 and 255.

What is shown on the screen is a visual representation
of the DAC's digital input as it is being counted up/down
from 0 to 255.

What is read at the DAC test point is an analog representation
of the digital 0-255 drive to the DAC.

The calculated "successive approximation" is anything
but approximate. If you do what they say, you will get
the correct value with only three steps:

CCW to stop (0) and measure
CW to stop (255) measure, calculate and adjust
CCW to stop (0) confirm measurement... and you're done.

The way you are describing is as likely to diverge as it is
to converge.

As to the generators, use whatever you want... just consider
that the proscribed test equipment, with its impedances, inaccuracies,
and steps is what the internal calibration routing is expecting.

My first time calibrating the 2465, I reasoned, as you are, that
I could make do with the equipment I had on hand. It was a
frustrating experience, rife with "Out of Range" indications.

A large part of the problem was misunderstanding the specifications
of the equipment I was using.

For instance, with a AWG that has a 12 bit DAC, and a 0.5% full scale
accuracy, what is the accuracy at 1/8 of full scale?

With the PG506, when in its voltage reference function, the accuracy
is the same for every output position, not just full scale.

-Chuck Harris


Max Vlasov via Groups.Io wrote:

Hello Chuck,

Thank you for your explanations!

Regarding the AWG in use, I have an ancient, but well calibrated HP 8175A with 10 bit resolution DAC and the output attenuator. When it works on 50 Ohm load, it adds internally the series 50 Ohm resistance between it's amplifier output and the BNC connector. Also another generator I tried was Agilent 33250a (can't reach 10Vp-p output from 0 to 10V to 50 Ohm). I've borrowed the recently calibrated AFG3102. It has 0.5% of the output accuracy when running full amplitude to 50 Ohms. IMHO, it will be sufficient to do the job as the calibrator too, however I have a doubt about the 2445a DAC.

It seems like the DAC calibration is a complex procedure somehow (saw on youtube: https://youtu.be/m7adJq5xMHE). I don't have the same approach at all (in the video the approach is to align the cursor to the extreme left and right horizontal division).
But in my approach I need no calculus at all since I follow the instruction "rotate the Delta control until DMM reading remains at constant value". So it means that I don't even look at the screen of the scope at all. Only at DMM. So, I use two multimeters in parallel with FREEZE/HOLD function. I turn the knob CCW until the voltage reading is constant (same on both) then I press FREEZE/HOLD on the first one. Then I rotate the knob to the CW all the way until the reading is constant and press FREEZE/HOLD on the second. Then I turn the pot just a bit in the direction (of gradient) of the sum of two voltages to get to 2.5V, unfreeze one of the multimeters, swing the delta knob to another extreme and repeat the iteration again. So, in 2 minutes I get to the point where the full scale swing (again judging DMM readings) is exactly 2.500V without any pre-calculated successive approximation steps. But now I wonder whether I do it correctly and whether I should be looking at the screen rather than at DMM.
Watching again the aforementioned video it seems like the alignment technique required to have a nicely centered full swing (judging visually by matching the 1st and the 11th vertical divisions with the delta cursor line).

Hmm, looks like the manual is a bit ambiguous.....

How does your DAC tuning procedure look like, like in video or by always using the voltage extremes?

Thank you,

Maxim



Re: free - tek 453 scope manual printout

Dave Wise
 

Aren't there some high-S/N non-A 453's with the A's large CRT? Or was that a mod?

Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Dale H. Cook <bridgewaterma@...>
Sent: Thursday, October 11, 2018 7:21 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] free - tek 453 scope manual printout

At 06:48 PM 10/10/2018, Chuck wrote:

just confirmed my scope is pre "a" so the docs would need to be for the vanilla 453.
Chuck -

There is no vanilla 453 - there are two versions, early production (serials under 20,000) with Nuvistors in the front ends and the triggers, and late production (serials over 20,000) with FETs in the front ends and the triggers.

Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcity/radios/index.html

Re: free - tek 453 scope manual printout

johncharlesgord
 

Yes, and Yes. The 453 mod 703K has the 8 division high screen. I think it was made for the USAF.
I might still have one around here somewhere.
--John Gord

On Thu, Oct 11, 2018 at 10:36 AM, Dave Wise wrote:


Aren't there some high-S/N non-A 453's with the A's large CRT? Or was that a
mod?

Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Dale H. Cook
<bridgewaterma@...>
Sent: Thursday, October 11, 2018 7:21 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] free - tek 453 scope manual printout

At 06:48 PM 10/10/2018, Chuck wrote:

just confirmed my scope is pre "a" so the docs would need to be for the
vanilla 453.

Chuck -

There is no vanilla 453 - there are two versions, early production (serials
under 20,000) with Nuvistors in the front ends and the triggers, and late
production (serials over 20,000) with FETs in the front ends and the triggers.

Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcity/radios/index.html






Re: Dual-pole power switches

johncharlesgord
 

Kurt,
It may be a safety measure (on the dual-pole units). Not all outlets are wired correctly.
--John Gord

On Thu, Oct 11, 2018 at 08:45 AM, Kurt Rosenfeld wrote:


Why do some instruments use dual-pole power switches while other instruments
use single-pole? For example, the 564 uses a dual-pole power switch
(interrupting neutral and hot) while the 547 uses a single-pole power switch
(only interrupting hot).

Re: 7000-series power-hungry plug-ins

 

Hi Tim,
I have used a 7D20 in several 7603s I have. All of the plugins could not exceed a well-defined set of power supply voltage, current and power specifications the mainframes had available. Meeting these requirements was sometimes the most difficult aspect of a design.

I suggest you calibrate your 7603 power supplies (and take a look at the power supplies in the 7D20 as well) and then try using the 7D20 again.

I would not disagree with you there were many power hungry plugins. Many of those came along in the mid-1970s and they used power hungry digital logic. The power needs of this type of circuitry was not something the designers of the 7K series could anticipate when they were finalizing the basic requirements of the product line.

The 7D20 is power hungry but it should work if the scope is working properly.

Another really good example would be the 7D01 Hardware Logic Analyzer which is almost entirely made of extremely power hungry ECL logic. It was the only way to reach the 100MHz speed necessary to troubleshoot complex digital circuits.

The 7D02 Microprocessor Logic Analyzer is also a power hungry plugin. It is packed full with TTL which is not as bad as ECL but still needs lots of power. None of the more lower power TTL families were available yet in the numerous logical building blocks that plugin needed. The product engineer on the project told me all the things they tried to lower the power requirements so it would meet the mainframe specs. He was disgusted by the entire process.

The triple wide Spectrum Analyzer plugins are also power hungry.

Dennis Tillman W7PF

-----Original Message-----
From: Tim Phillips
Sent: Thursday, October 11, 2018 7:04 AM
Subject: [TekScopes] 7000-series power-hungry plug-ins

From Tim P (UK)
It is 'well known' that the 7D20 draws too much power from a standard
7603; is there a definitive list of power-hungry plug-ins, and which
'scopes they can be used in ?
IIRC this also applies to some of the 7L- SpecAnal plug-ins.
thanks
Tim


--
Dennis Tillman W7PF
TekScopes Moderator

Re: Dual-pole power switches

 

Hi Kurt,
ALL of the 7K and TM mainframes use dual pole switches. This was probably due to changes in the electrical codes and grounding requirements which were becoming more focused on safety in the late 1960s. Also, because most of Europe is 220V-240V, they have much stricter safety requirements and it may be that as Tek sold more products internationally they discovered it was cheaper to meet the strictest standards worldwide and apply those standards to all their instruments going forward regardless of which country the instrument was sold in or would be used in.

Dennis

-----Original Message-----
From: Kurt Rosenfeld
Sent: Thursday, October 11, 2018 8:46 AM
Subject: [TekScopes] Dual-pole power switches

Why do some instruments use dual-pole power switches while other
instruments use single-pole? For example, the 564 uses a dual-pole power
switch (interrupting neutral and hot) while the 547 uses a single-pole
power switch (only interrupting hot).


--
Dennis Tillman W7PF
TekScopes Moderator

Re: 7000-series power-hungry plug-ins

Chuck Harris
 

If I remember correctly, the original 7603 had a
wimpy linear supply, and no fan. Later revisions
used a more robust linear supply, and a quiet little
internal fan.

The 7603 of the later years was the scope intended
for the 7D20, 7L family.... it was the big screen that
made it desirable.

The 7904 (plain) cannot handle the 7L13. It will send
the supply into tick mode. Not the usual tick mode,
but one that was very weird sounding.

The 7904A handles it just fine... but then it has a big
supply and a loud fan.

-Chuck Harris

Dennis Tillman W7PF wrote:

Hi Tim,
I have used a 7D20 in several 7603s I have. All of the plugins could not exceed a well-defined set of power supply voltage, current and power specifications the mainframes had available. Meeting these requirements was sometimes the most difficult aspect of a design.

I suggest you calibrate your 7603 power supplies (and take a look at the power supplies in the 7D20 as well) and then try using the 7D20 again.

I would not disagree with you there were many power hungry plugins. Many of those came along in the mid-1970s and they used power hungry digital logic. The power needs of this type of circuitry was not something the designers of the 7K series could anticipate when they were finalizing the basic requirements of the product line.

The 7D20 is power hungry but it should work if the scope is working properly.

Another really good example would be the 7D01 Hardware Logic Analyzer which is almost entirely made of extremely power hungry ECL logic. It was the only way to reach the 100MHz speed necessary to troubleshoot complex digital circuits.

The 7D02 Microprocessor Logic Analyzer is also a power hungry plugin. It is packed full with TTL which is not as bad as ECL but still needs lots of power. None of the more lower power TTL families were available yet in the numerous logical building blocks that plugin needed. The product engineer on the project told me all the things they tried to lower the power requirements so it would meet the mainframe specs. He was disgusted by the entire process.

The triple wide Spectrum Analyzer plugins are also power hungry.

Dennis Tillman W7PF

Re: 2445A calibration

maxim.vlasov@...
 

Chuck,

Now I understand the DAC calibration routine. The full voltage scale from 0x000 to 0xFFF is 2.500V. My concern is that the DAC reference isn't centered (when I bring the DELTA cursor to the middle graticule division, J119 pin 13 is at 0.006V instead of 0.0V). And it seems that it should be close to the center (the other ppl managed passing CAL02 & CAL03 w/o LIMIT with DAC center around +/-0.001V).
In my 2445a TP2421 measures -0.12424V (very stable in a few hours). TP2420 measures 1.3639V. I wonder what level should be there. In the schematics it's stated -0.125V and +1.36V? At least I see that the negative checkpoint is higher than expected.

I could only assume that the reason of LIMIT is the underperforming DAC and/or demultiplexer and/or sample&hold or repeater...

I'll start from the demultiplexers and opamps, since they could develop some more leakage.

Thank you,

Best regards,

Maxim

Re: Dual-pole power switches

 

On Thu, Oct 11, 2018 at 09:56 PM, Dennis Tillman W7PF wrote:


because most of Europe is 220V-240V, they have much stricter safety requirements
Also our (not counting UK) power plugs aren't keyed i.e. they could be connected either way.
/Håkan

Almost finished 468 and parts needed.

Brendan
 

The 468 I have been working on is almost done. https://groups.io/g/TekScopes/album?id=75300
So far it seems to work really well. I ordered a set of EPROMs from the VIntage Tek museum $40. Way cheaper than a programmer which I doubt I would use all too much. I think I'm going to use the Mostek that are in there until they fail. I'll be ready to pop the new ones in if need be.
I am wondering if anyone here can help me out with a few parts? I need the knob for the cursor adjustment and a set of good feet.

Re: Almost finished 468 and parts needed.

Jim Olson <v_12eng@...>
 

Which feet are you looking for? There are a couple of sellers on ebay that have new repro rear cord wrap feet for the 4xx series scopes and some others and another seller has new rubber cushion feet for the bottom ones.
Is the knob you need a small tapered gray colored one? as I have a few like that from the 475's>

Jim O

On October 11, 2018 at 2:16 PM "lop pol via Groups.Io" <the_infinite_penguin=yahoo.com@groups.io mailto:the_infinite_penguin=yahoo.com@groups.io > wrote:


The 468 I have been working on is almost done. https://groups.io/g/TekScopes/album?id=75300
So far it seems to work really well. I ordered a set of EPROMs from the VIntage Tek museum $40. Way cheaper than a programmer which I doubt I would use all too much. I think I'm going to use the Mostek that are in there until they fail. I'll be ready to pop the new ones in if need be.
I am wondering if anyone here can help me out with a few parts? I need the knob for the cursor adjustment and a set of good feet.


Re: Almost finished 468 and parts needed.

Brendan
 

On Thu, Oct 11, 2018 at 03:33 PM, Jim Olson wrote:


Which feet are you looking for? There are a couple of sellers on ebay that
have new repro rear cord wrap feet for the 4xx series scopes and some others
and another seller has new rubber cushion feet for the bottom ones.
Is the knob you need a small tapered gray colored one? as I have a few like
that from the 475's>

Jim O

On October 11, 2018 at 2:16 PM "lop pol via Groups.Io"
<the_infinite_penguin=yahoo.com@groups.io
mailto:the_infinite_penguin=yahoo.com@groups.io > wrote:


The 468 I have been working on is almost done.
https://groups.io/g/TekScopes/album?id=75300
So far it seems to work really well. I ordered a set of EPROMs from the
VIntage Tek museum $40. Way cheaper than a programmer which I doubt I would
use all too much. I think I'm going to use the Mostek that are in there until
they fail. I'll be ready to pop the new ones in if need be.
I am wondering if anyone here can help me out with a few parts? I need
the knob for the cursor adjustment and a set of good feet.


The knob has a recess for the push button for changing cursors.
I'm looking for the cordwrap feet. I check on evilbay also.
https://groups.io/g/TekScopes/photo/75300/8?p=Name,,,20,1,0,0