Date   
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.

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

 

On Mon, Mar 25, 2019 at 10:52 PM, Reginald Beardsley wrote:

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?
27C010 and 27C512

/Håkan

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

 

On Tue, Mar 26, 2019 at 10:49 AM, zenith5106 wrote:



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?
27C010 and 27C512
I may have to take part of that back.
In my F/W EPROM collection I don't have 11801 but there is a note saying that 11801 can also use 11801A F/W
which I have and it uses both types. I now begin to think that is wrong and if so 11801, just like 11802 no letter,
use only 27C512.

/Håkan

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

Reginald Beardsley
 

Thanks. It will be a while before I take it apart again, but I'll make a note in my service manual.

Fortunately, most of my HP gear lists the parts in the manuals, so those will be easier to do.

I've attached a photo showing the calibrator output trace. The measured rise time is shown in the lower left at 32 ps. I've got smoothing on.



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

On Tue, 3/26/19, zenith5106 <hahi@...> wrote:

Subject: Re: [TekScopes] 11801 is reassembled, up and running :-)
To: TekScopes@groups.io
Date: Tuesday, March 26, 2019, 7:01 AM

On Tue, Mar 26, 2019 at 10:49 AM,
zenith5106 wrote:

>
> >
> > 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?
>

> 27C010 and 27C512
>
I may have to take part of
that back.
In my F/W EPROM collection I
don't have 11801 but there is a note saying that 11801
can also use 11801A F/W
which I have and it
uses both types. I now begin to think that is wrong and if
so 11801, just like 11802 no letter,
use
only 27C512.

/Håkan

Re: Impedance matching question

David Berlind
 

That was a decent video, thank you. It doesn't seem like he had problems
with the terminators themselves. In fact, he uses them to address
mismatches. I'd be curious to know (from anyone who knows) why maximum
power (matched impedance) is ideal in some situations, but a low-Z to
high-Z arrangement is the ideal in other situations (ie: guitar to
amplifier or microphone to PA). I realize the outcome in the latter
situation; you preserve the audio highs and lows. But need some schooling
on why to maximize voltage at the load (vs. maximizing transfer power) in
those situations and why the mismatch isn't destructive to the signal. And
correspondingly, why the same isn't true of the impedance match between
output tubes and the primary of an output transformer since its a similar
audio application. Again, I understand the requirements and outcomes... but
am confused about the underlying physics.

Thanks in advance for this help.

On Mon, Mar 25, 2019 at 8:09 PM Roy Thistle <roy.thistle@...>
wrote:

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 :-)

Albert Otten
 

Attachments are not allowed here Reg. Via the website you can create a new Album in the Photos section and put your picture(s) there. If you do so, it's handy for "us" if you insert a link to the album in your messages.
Albert

On Tue, Mar 26, 2019 at 02:06 PM, Reginald Beardsley wrote:


I've attached a photo showing the calibrator output trace. The measured rise
time is shown in the lower left at 32 ps. I've got smoothing on.

Re: Impedance matching question

Craig Sawyers
 

That was a decent video, thank you. It doesn't seem like he had problems with the terminators
themselves. In fact, he uses them to address mismatches. I'd be curious to know (from anyone who
knows) why maximum power (matched impedance) is ideal in some situations, but a low-Z to high-Z
arrangement is the ideal in other situations (ie: guitar to amplifier or microphone to PA). I
realize the
outcome in the latter situation; you preserve the audio highs and lows. But need some schooling on
why to maximize voltage at the load (vs. maximizing transfer power) in those situations and why the
mismatch isn't destructive to the signal. And correspondingly, why the same isn't true of the
impedance match between output tubes and the primary of an output transformer since its a similar
audio application. Again, I understand the requirements and outcomes... but am confused about the
underlying physics.
It is to do with the frequency range. As soon as the length of the cable becomes a significant
fraction of the electrical wavelength in the cable, you need to impedance match. That is because
energy is reflected at an impedance discontinuity, so you end up with standing waves along the length
of the cable. For a 1 metre long coax the wavelength becomes a significant fraction of the cable
length by about 10MHz, so you need to impedance match.

With audio, the wavelength is so long (at 20kHz it is about 10km in a typical coax cable) you
absolutely do not need to match. Hence you guitar example.

Going way back long distance telegraph and telephone lines were significant fractions of an audio
wavelength in the cables, and they needed to impedance match.

Craig

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

Bob Koller
 

They must have changed the cal output circuitry on the later models.

Re: Impedance matching question

David Berlind
 

Thanks Craig... so, if I were to summarize what you wrote, at such short
distances, there's really no opportunity for a reflected signal to go out
of phase with the incident signal?

In watching the EEVblog videos, he's clearly using pretty high frequencies
(well out of the audio spectrum). So, your explanation is consistent with
that.

So, two questions remain.

1. why is an impedance match between output tubes and the output
transformer primary so important given the short physical differences. Or,
maybe the tube specs are not showing the actual impedance, but rather the
recommend Hi-Z on the load end to offer the optimal Low-Z to Hi-Z ratio?

2. Why is a Low-Z to Hi-Z ratio desired in audio applications vs. an
impedance match? I understand your point that it doesn't matter at low
distances, but Low-Z to Hi-Z appears to be an objective (iow, the objective
is to avoid a match, by orders of magnitude). Does the higher resultant
voltage (amplitude) at the load spread the signal out in a way that give
the amp more to work with from a fidelity POV?

On Tue, Mar 26, 2019 at 9:59 AM Craig Sawyers <c.sawyers@...>
wrote:

That was a decent video, thank you. It doesn't seem like he had problems
with the terminators
themselves. In fact, he uses them to address mismatches. I'd be curious
to know (from anyone who
knows) why maximum power (matched impedance) is ideal in some
situations, but a low-Z to high-Z
arrangement is the ideal in other situations (ie: guitar to amplifier or
microphone to PA). I
realize the
outcome in the latter situation; you preserve the audio highs and lows.
But need some schooling on
why to maximize voltage at the load (vs. maximizing transfer power) in
those situations and why the
mismatch isn't destructive to the signal. And correspondingly, why the
same isn't true of the
impedance match between output tubes and the primary of an output
transformer since its a similar
audio application. Again, I understand the requirements and outcomes...
but am confused about the
underlying physics.
It is to do with the frequency range. As soon as the length of the cable
becomes a significant
fraction of the electrical wavelength in the cable, you need to impedance
match. That is because
energy is reflected at an impedance discontinuity, so you end up with
standing waves along the length
of the cable. For a 1 metre long coax the wavelength becomes a significant
fraction of the cable
length by about 10MHz, so you need to impedance match.

With audio, the wavelength is so long (at 20kHz it is about 10km in a
typical coax cable) you
absolutely do not need to match. Hence you guitar example.

Going way back long distance telegraph and telephone lines were
significant fractions of an audio
wavelength in the cables, and they needed to impedance match.

Craig