Date   
Re: 11801 diagnostic help

Bob Koller
 

I have been following this thread with some interest, as I have a 11801A that had dead TB NVRAM, and a 11801B with all (still) good OEM NVRAM and batteries.
I don't think there are factory only cal constants stored in any NVRAM, here's why: The service manual for all these instruments describe how to diagnose and replace these batteries and NVRAM devices, without caveat about calibration after replacement.
Also, all these boards were FRU, or Field Replaceable Units, so that repair could be made via board swap.
I think all relevant calibrations take place from the menu items.

Re: Repairability of SD-24, SD-30 & SD-32 sampling heads

Bob Koller
 

These are thin film hybrid microcircuit assemblies. Easy enough to repair IF you have a well equipped hybrid lab and access to the right chips. Figuring out the correct parts, and then finding the die, could be a major problem, as hybrids are bit of thing of the past.
I was a hybrid microcircuit manufacturing engineer in a past life.

Re: Repairability of SD-24, SD-30 & SD-32 sampling heads

Reginald Beardsley
 

I rather feared that was the case. So "For parts" units are a significant gamble. I was very lucky that the two SD-22s I got for $150 delivered both turned out to be good. That seller mostly dealt in electrical power parts, boxes, breakers, etc.

And one never knows if the claim "untested" is true or not. It's very easy for someone to have two eBay accounts. One selling tested kit and the other selling "untested" which are actually known to be unrepairable and for which they have a "no returns" policy.

I have verified that the NVRAM does *not* store the last instrument settings and it does not store the RTC values. But what they store is still a mystery.

I'll summarize my adventures once I replace the NVRAM.

--------------------------------------------

On Mon, 3/25/19, Bob Koller via Groups.Io <testtech=yahoo.com@groups.io> wrote:

Subject: Re: [TekScopes] Repairability of SD-24, SD-30 & SD-32 sampling heads
To: TekScopes@groups.io
Date: Monday, March 25, 2019, 10:07 AM

These are thin film hybrid
microcircuit assemblies. Easy enough to repair IF you have a
well equipped hybrid lab and access to the right chips.
Figuring out the correct parts, and then finding the die,
could be a major problem, as hybrids are bit of thing of the
past.
I was a hybrid microcircuit
manufacturing engineer in a past life.

Re: 11801 diagnostic help

Jack2015
 

Bob,

I think you are right,
According to Tektronix_11801_Factory_Diagnosis_Manual,page 2,
about "Clearing NVRAM:":
the NVRAM is initialized by filling all but a few locations with default value.
the following are left intact after the NVRAM is reset:

numbers of instrument power-ons(poweron?)
instrument power-on time(uptime?)
mainfram serial number(uid?main)

Re: 11801 diagnostic help

Reginald Beardsley
 

Despite having removed all power from the D432656 SRAM to get it to function, it still remembered all of that information, so it is stored in multiple locations.

My replacement NVRAM came today, so I should have everything fixed and buttoned up before bed.

I was just reading the 11801 service manual and the Enhanced Accuracy calibration has to be done for all channels *every* time the instrument is power cycled. Which may explain the large on time hours vs power cycles that seem to be typical. It also leaves me amazed there is no screen burn.

Sampling scopes are very much a niche item, but if you need accurate timing information they are the most economical option.

In my case, I am working on FOSS DSO FW for Zynq and Cyclone V based COTS DSOs. Having LeCroy style stackable filters and math are an essential requirement. I'm not yet clear on how I'm going to get time accurate signals off the FPGA board, but my intent is to examine the timing of variable word length multiplier and adder chains for FIR and IIR filters to verify that the simulation timings are actually correct. The price point of the 8/12/14 bit AD HMCAD1520 ADCs makes limiting the FW to 8 bits foolish.

More later and thanks to all for their help.

Reg


--------------------------------------------

On Mon, 3/25/19, Jack2015 <tolkien@...> wrote:

Subject: Re: [TekScopes] 11801 diagnostic help
To: TekScopes@groups.io
Date: Monday, March 25, 2019, 11:48 AM

Bob,

I think you are right,
According to
Tektronix_11801_Factory_Diagnosis_Manual,page 2,
about "Clearing NVRAM:":
the NVRAM is initialized by filling all but a
few locations with default value.
the
following are left intact after the NVRAM is reset:

numbers of instrument
power-ons(poweron?)
instrument power-on
time(uptime?)
mainfram serial
number(uid?main)

Re: Repairability of SD-24, SD-30 & SD-32 sampling heads

Craig Sawyers
 

hybrids are bit of thing of the past.
I was a hybrid microcircuit manufacturing engineer in a past life.
Not in the space industry. Hermetically sealed thin film hybrids are still the only way frequently.
Not cheap for space qualified parts though ;-)

Craig

vintageTEK photo of the month

Dave Brown
 

Once a month I post a unique or humorous photo we run across at the museum. This is only the third month so there are only three so far. This month's is kind of unique. We ran across the picture but didn't know really what it was or why until we ran into someone who worked in that group and knew firsthand. Photos are at https://vintagetek.org/photo-of-the-month/

Re: vintageTEK photo of the month

ROLYNN PRECHTL K7DFW
 

Photos are at https://vintagetek.org/photo-of-the-month/


===============================================================

I used to work for/with Jim on the T4002 in Building 50. His amateur radio call was K7ZIR.


Rolynn

Re: Repairability of SD-24, SD-30 & SD-32 sampling heads

Bob Koller
 

How well I know. My last job in the hybrid business was at Teledyne Microelectronics. Space Qual parts had reams of paperwork, x-rays, PIND test,photographs, etc...
Tek, Keysight, and many other still , out of necessity, use hybrid technology with custom parts, in the front ends, and other places, of very high frequency instruments. But, commercial hybrid production has, I think, largely been supplanted by ASIC, FPGA, and more modern, more reliable, less expensive technology.

11801 is reassembled, up and running :-)

Reginald Beardsley
 

My ST NVRAM came today. As previously reported it took 3 boots to clear the T1331 error.

I now have both the 11810 User Manual and Service Manual in original Tek hardcopy.

I experienced a good bit of operator confusion after performing the Enhanced Accuracy procedure from the service manual. In particular it seemed to be aliasing the calibrator output. But now I'm getting 26-32 ps rise times which seems about right for an SD-20 head.

I tried to copy the A5-U300 ROM but I'm not sure that succeeded. The TNM5000 said it failed to identify it. Can anyone tell me what type of EPROMs are used in the scope?

As much as I hate to take it apart again, I would like to archive the ROMs in case I or anyone else needs them. I'll also scan the User Manual.

I'd like to thank all who helped but especially Tom for the tip about removing the DS1213s, Adrian for procuring the NVRAM replacements, Albert for general guidance and the person who sent me a link to a PDF scan of the 11801 manual. I've tried in vain to find out the name, but I may not be looking in the correct place.

BTW the upper knob has a crack where it pushes over the encoder shaft which resulted in it slipping a lot. I put a piece of heat shrink over it and it seems to be working fine now. But if anyone has a replacement, please contact me off list.

Have Fun!
Reg

Re: Repairability of SD-24, SD-30 & SD-32 sampling heads

Jose Luu
 

https://www.qsl.net/ct1dmk/wbond_ex.html

This guy seem to have made a home hybrid lab and repairs. Could former
professionals comment ?

Best
Jose


On Mon, Mar 25, 2019 at 9:30 PM Bob Koller via Groups.Io <testtech=
yahoo.com@groups.io> wrote:

How well I know. My last job in the hybrid business was at Teledyne
Microelectronics. Space Qual parts had reams of paperwork, x-rays, PIND
test,photographs, etc...
Tek, Keysight, and many other still , out of necessity, use hybrid
technology with custom parts, in the front ends, and other places, of very
high frequency instruments. But, commercial hybrid production has, I think,
largely been supplanted by ASIC, FPGA, and more modern, more reliable, less
expensive technology.



Impedance matching question

David Berlind
 

I was watching a video on impedance matching experiments and, supposing you
had a 75 ohm signal generator connected to a 1 M-ohm oscilloscope input, one
option that was suggested was to add a 75 ohm terminator at the scope input. The
only diagram I can find of this shows a physical connection of the BNC terminator
(mounted on a BNC T connector) to ground.

is that physical connection from the back of the terminator necessary to successfully terminate and if so, to what ground
do you connect? Or, do the terminators by themselves take care of the connection to ground through the BNC
connection?

Re: Impedance matching question

Reginald Beardsley
 

A through teminator will give better performance at high frequencies. You can get away with a Tee and terminator up to a few MHz, but things go downhill very quickly after that.

A thru terminator is a 50 ohm load with an inline connection to the output which is expected to be 1 Meg or more. Surprisingly, none of the Chinese eBay thru terminators landed in the junk bin when I was testing devices using one of Leo Bodnar's 100 ps pulse units.

If you're using a 75 ohm signal generator, make sure you're using 75 ohm cable and BNCs in addition to the 75 ohm thru.


--------------------------------------------

On Mon, 3/25/19, David Berlind <david@...> wrote:

Subject: [TekScopes] Impedance matching question
To: TekScopes@groups.io
Date: Monday, March 25, 2019, 6:36 PM

I was watching a video on impedance matching
experiments and, supposing you
had a 75 ohm signal generator connected
to a 1 M-ohm oscilloscope input, one
option that was suggested was to add a
75 ohm terminator at the scope input. The
only diagram I can find of this shows a
physical connection of the BNC terminator
(mounted on a BNC T connector) to
ground.

is that physical connection from the
back of the terminator necessary to successfully terminate
and if so, to what ground
do you connect? Or, do the terminators
by themselves take care of the connection to ground through
the BNC
connection?

Re: Impedance matching question

Jim Ford
 

Usually the terminator contains the ground connection.  Going for your description rather than a drawing or photo. Jim FSent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: David Berlind <david@...> Date: 3/25/19 4:36 PM (GMT-08:00) To: TekScopes@groups.io Subject: [TekScopes] Impedance matching question I was watching a video on impedance matching experiments and, supposing you had a 75 ohm signal generator connected to a 1 M-ohm oscilloscope input, one option that was suggested was to add a 75 ohm terminator at the scope input. The only diagram I can find of this shows a physical connection of the BNC terminator(mounted on a BNC T connector) to ground. is that physical connection from the back of the terminator necessary to successfully terminate and if so, to what grounddo you connect? Or, do the terminators by themselves take care of the connection to ground through the BNC connection?

Re: Repairability of SD-24, SD-30 & SD-32 sampling heads

Bob Koller
 

Yes, Luis has done great work! He is in South America I think. Ascertaining and sourcing the correct parts can be difficult.

Re: Repairability of SD-24, SD-30 & SD-32 sampling heads

Craig Sawyers
 

He clearly knows what he is doing. You don't knock up something with an Altera FPGA unless you have a
major development lab at your disposal https://www.qsl.net/ct1dmk/gw_04.jpg

Craig

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jose Luu
Sent: 25 March 2019 23:29
To: TekScopes@groups.io
Subject: Re: [TekScopes] Repairability of SD-24, SD-30 & SD-32 sampling heads

https://www.qsl.net/ct1dmk/wbond_ex.html

This guy seem to have made a home hybrid lab and repairs. Could former professionals comment ?

Best
Jose


On Mon, Mar 25, 2019 at 9:30 PM Bob Koller via Groups.Io <testtech= yahoo.com@groups.io> wrote:

How well I know. My last job in the hybrid business was at Teledyne
Microelectronics. Space Qual parts had reams of paperwork, x-rays,
PIND test,photographs, etc...
Tek, Keysight, and many other still , out of necessity, use hybrid
technology with custom parts, in the front ends, and other places, of
very high frequency instruments. But, commercial hybrid production
has, I think, largely been supplanted by ASIC, FPGA, and more modern,
more reliable, less expensive technology.



Re: 11801 is reassembled, up and running :-)

Bob Koller
 

Great!

Calibrator risetime? Isn't the cal output specified at about 250ps? Both of my instrument measure it about 300ps.

Re: Impedance matching question

Roy Thistle
 

Hi:
If you haven't watched EEVblog #652, he demonstrates a couple of problems that can arise when using coax, terminators, and Ts, to connect a sig gen to a scope.
Cheers.

Re: 11801 is reassembled, up and running :-)

Reginald Beardsley
 

11801 User manual p 42.

"The signal from the calibrator output us a 250 mV square wave with a rise time of approximately 20 ps and a period of approximately 10 microseconds."

After I did the Enhanced Accuracy cal process I got results similar to yours. I eventually got it to do something sensible after a bunch of semi-random button pushing. Pulse amplitude was not stable on the display among other weirdness. It is now behaving as one would expect.

Someone else has stated that the calibrator is the same as the pulse generator in the SD-24.

I am now getting the same results I got before I replaced the NVRAM.


--------------------------------------------

On Mon, 3/25/19, Bob Koller via Groups.Io <testtech=yahoo.com@groups.io> wrote:

Subject: Re: [TekScopes] 11801 is reassembled, up and running :-)
To: TekScopes@groups.io
Date: Monday, March 25, 2019, 7:08 PM

Great!

Calibrator risetime? Isn't the cal output
specified at about 250ps? Both of my instrument measure it
about 300ps.

Re: Repairability of SD-24, SD-30 & SD-32 sampling heads

Dave Brown
 

Far as I know he still works at a university in Portugal -he's been there for some years and is well known in scientific and amateur (especially EME) circles.
73
Dave, ZL3FJ

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Bob Koller via Groups.Io
Sent: Tuesday, March 26, 2019 13:05
To: TekScopes@groups.io
Subject: Re: [TekScopes] Repairability of SD-24, SD-30 & SD-32 sampling heads

Yes, Luis has done great work! He is in South America I think. Ascertaining and sourcing the correct parts can be difficult.