Topics

Tek 571 curve tracer


Bill Higdon
 


Dave Casey
 

Built by Sony-Tektronix. They are fairly handy though not as capable as
more complex designs like the 370 series.
No kelvin fixturing and a limited selection of parameters with software
interlocks preventing the more blunderous combinations.
Parallel printer output.
Memory save and recall of traces for comparisons.
They show up on eBay from time to time; one was on there within the last
month.
I got mine there several years ago.
It's fairly easy to use, but perhaps not as educational to the user as a
more manual unit.
No comments on serviceability as mine has been working fine since I got it.

Dave Casey

On Thu, Aug 20, 2020 at 8:16 PM Bill Higdon via groups.io <willard561=
aol.com@groups.io> wrote:

https://www.publicsurplus.com/sms/auction/view?auc=2614769

I've never seen one of these before




 

On Fri, Aug 21, 2020 at 05:49 AM, Dave Casey wrote:


Built by Sony-Tektronix.
No,not Sony-Tek. It was built by Tek Netherlands (SN begin with H) and as far as I remember it was also designed by them.

/Håkan


Dave Casey
 

I stand corrected; can confirm, my S/N also starts with H. Thanks!

Dave Casey

On Fri, Aug 21, 2020 at 5:12 AM zenith5106 <hahi@...> wrote:

On Fri, Aug 21, 2020 at 05:49 AM, Dave Casey wrote:


Built by Sony-Tektronix.
No,not Sony-Tek. It was built by Tek Netherlands (SN begin with H) and as
far as I remember it was also designed by them.

/Håkan




Dave Casey
 

I spoke so highly of my 571 last month. When I recently went to use it, I
was getting some artifacts in the display so I have set out to investigate.

Unfortunately you can tell this wasn't designed in Beaverton because you
have to remove the CRT to get the main board out. There are some large
Roedenstein electrolytics used for supply smoothing that have a bit of a
dome to the end of them. Not sure if these were flat when new, but they
don't appear to be leaky (neither physically nor electrically). There is
significant noise (100-200mVpp) on the supplies, but it's not line ripple.
It appears to be around 2 MHz and is two similarly disruptive pulses around
200ns out of phase.

In the process of disassembly, I have pulled and saved the three EPROM
images. Two run the 8032 controller, and one runs the NS405 "terminal on a
chip" that is used to draw the display and printer output.
I haven't exhaustively perused the images, but the graphics ROM has some
ASCII easter eggs I noticed. After the usual Tektronix copyright statement
is "Written by: Folkert ten Brummelhuis (started). Sjoerd J. Punter" and
soon after "[Makke yn Fryslân]" which is Frisian for "Made in Friesland",
the province in which Heerenveen is situated. Later in the ROM the phrase
"Joke Mirjam Esther" appears twice, about (but not exactly) 64 bytes apart.
I believe these are three given names commonly used in the region, perhaps
the names of those endeared to one or both programmers.

Dave Casey

On Fri, Aug 21, 2020 at 1:31 PM Dave Casey via groups.io <polara413=
gmail.com@groups.io> wrote:

I stand corrected; can confirm, my S/N also starts with H. Thanks!

Dave Casey

On Fri, Aug 21, 2020 at 5:12 AM zenith5106 <hahi@...> wrote:

On Fri, Aug 21, 2020 at 05:49 AM, Dave Casey wrote:


Built by Sony-Tektronix.
No,not Sony-Tek. It was built by Tek Netherlands (SN begin with H) and as
far as I remember it was also designed by them.

/Håkan






Richard R. Pope
 

Dave,
Those electrolytics are defective. They have been running hot. Time to replace them. I hope that this helps!
GOD Bless and Thanks,
rich!

On 9/23/2020 9:39 PM, Dave Casey wrote:
I spoke so highly of my 571 last month. When I recently went to use it, I
was getting some artifacts in the display so I have set out to investigate.

Unfortunately you can tell this wasn't designed in Beaverton because you
have to remove the CRT to get the main board out. There are some large
Roedenstein electrolytics used for supply smoothing that have a bit of a
dome to the end of them. Not sure if these were flat when new, but they
don't appear to be leaky (neither physically nor electrically). There is
significant noise (100-200mVpp) on the supplies, but it's not line ripple.
It appears to be around 2 MHz and is two similarly disruptive pulses around
200ns out of phase.

In the process of disassembly, I have pulled and saved the three EPROM
images. Two run the 8032 controller, and one runs the NS405 "terminal on a
chip" that is used to draw the display and printer output.
I haven't exhaustively perused the images, but the graphics ROM has some
ASCII easter eggs I noticed. After the usual Tektronix copyright statement
is "Written by: Folkert ten Brummelhuis (started). Sjoerd J. Punter" and
soon after "[Makke yn Fryslân]" which is Frisian for "Made in Friesland",
the province in which Heerenveen is situated. Later in the ROM the phrase
"Joke Mirjam Esther" appears twice, about (but not exactly) 64 bytes apart.
I believe these are three given names commonly used in the region, perhaps
the names of those endeared to one or both programmers.

Dave Casey

On Fri, Aug 21, 2020 at 1:31 PM Dave Casey via groups.io <polara413=
gmail.com@groups.io> wrote:

I stand corrected; can confirm, my S/N also starts with H. Thanks!

Dave Casey

On Fri, Aug 21, 2020 at 5:12 AM zenith5106 <hahi@...> wrote:

On Fri, Aug 21, 2020 at 05:49 AM, Dave Casey wrote:

Built by Sony-Tektronix.
No,not Sony-Tek. It was built by Tek Netherlands (SN begin with H) and as
far as I remember it was also designed by them.

/Håkan







Dave Casey
 

I'm not so sure they are. DC leakage current is well below 100uA at 20V.
I'll check them again at 40.
When I say the cans are domed, they may have been made that way as these
are sealed at the bottom and don't have the usual "fault lines" in the
domed end.
I will also check ESR. Replacements are standing by, but I'm not convinced
these were the source of the noise, especially since it's not line noise.
These are all pre-regulator caps, so I'll check the smaller ones after the
linear regulators to see if anything is suspicious there. Low capacitance
on the output and some fast switching in the video circuits could be to
blame. I should also see if the noise is in sync with the video.

Dave Casey

On Wed, Sep 23, 2020 at 9:43 PM Richard R. Pope <mechanic_2@...>
wrote:

Dave,
Those electrolytics are defective. They have been running hot. Time
to replace them. I hope that this helps!
GOD Bless and Thanks,
rich!

On 9/23/2020 9:39 PM, Dave Casey wrote:
I spoke so highly of my 571 last month. When I recently went to use it, I
was getting some artifacts in the display so I have set out to
investigate.

Unfortunately you can tell this wasn't designed in Beaverton because you
have to remove the CRT to get the main board out. There are some large
Roedenstein electrolytics used for supply smoothing that have a bit of a
dome to the end of them. Not sure if these were flat when new, but they
don't appear to be leaky (neither physically nor electrically). There is
significant noise (100-200mVpp) on the supplies, but it's not line
ripple.
It appears to be around 2 MHz and is two similarly disruptive pulses
around
200ns out of phase.

In the process of disassembly, I have pulled and saved the three EPROM
images. Two run the 8032 controller, and one runs the NS405 "terminal on
a
chip" that is used to draw the display and printer output.
I haven't exhaustively perused the images, but the graphics ROM has some
ASCII easter eggs I noticed. After the usual Tektronix copyright
statement
is "Written by: Folkert ten Brummelhuis (started). Sjoerd J. Punter" and
soon after "[Makke yn Fryslân]" which is Frisian for "Made in Friesland",
the province in which Heerenveen is situated. Later in the ROM the phrase
"Joke Mirjam Esther" appears twice, about (but not exactly) 64 bytes
apart.
I believe these are three given names commonly used in the region,
perhaps
the names of those endeared to one or both programmers.

Dave Casey

On Fri, Aug 21, 2020 at 1:31 PM Dave Casey via groups.io <polara413=
gmail.com@groups.io> wrote:

I stand corrected; can confirm, my S/N also starts with H. Thanks!

Dave Casey

On Fri, Aug 21, 2020 at 5:12 AM zenith5106 <hahi@...> wrote:

On Fri, Aug 21, 2020 at 05:49 AM, Dave Casey wrote:

Built by Sony-Tektronix.
No,not Sony-Tek. It was built by Tek Netherlands (SN begin with H) and
as
far as I remember it was also designed by them.

/Håkan













Dave Casey
 

An update:

My initial indication of a problem was glitches in the display, such as "_"
characters showing up on parts of the screen where they didn't belong.
These glitches were stored in video RAM and were thus visible until the
screen image in RAM was updated.
My guess for the most likely culprit was power supply noise, and indeed
there is a LOT of noise on the supplies, but it is not line noise. In fact,
it is nearly all switching noise from the digital circuitry. If I hold the
microcontrollers in reset, the supplies get very quiet. When the
microcontrollers are running, there is significant noise on all the
supplies:
-15V rail: 1.2Vpp
+5V rail: 1.1Vpp
+12V rail: 0.5Vpp
+15V rail: 0.7Vpp
The noise on each of the supplies is all the same noise (triggering on one
channel produces a solid lock on the others). It is asynchronous to the
14.xxx MHz pixel clock of the NS405, so I believe it is all from the 8032
(12 MHz XTAL). The lowest observable frequency in the noise is around 2 MHz
(only looking in the time domain at the moment).
I've isolated this down to just the main board; the CRT, front panel, and
collector supply are out of the picture.
The main board contains the 8032, NS405, base/gate drive circuit (DAC), and
emitter test circuit (ADC).
Supplies are all linear, using 78xx and 79xx regulators.
At this high of frequency, electrolytics aren't contributing much to the
bypass, right? Each rail only has 220uF after the regulator. I've checked
half of them, and while they've aged they aren't trash yet. Anybody seen a
ceramic bypass cap go bad?

Dave Casey


On Thu, Sep 24, 2020 at 1:11 AM Dave Casey via groups.io <polara413=
gmail.com@groups.io> wrote:

I'm not so sure they are. DC leakage current is well below 100uA at 20V.
I'll check them again at 40.
When I say the cans are domed, they may have been made that way as these
are sealed at the bottom and don't have the usual "fault lines" in the
domed end.
I will also check ESR. Replacements are standing by, but I'm not convinced
these were the source of the noise, especially since it's not line noise.
These are all pre-regulator caps, so I'll check the smaller ones after the
linear regulators to see if anything is suspicious there. Low capacitance
on the output and some fast switching in the video circuits could be to
blame. I should also see if the noise is in sync with the video.

Dave Casey

On Wed, Sep 23, 2020 at 9:43 PM Richard R. Pope <mechanic_2@...>
wrote:

Dave,
Those electrolytics are defective. They have been running hot. Time
to replace them. I hope that this helps!
GOD Bless and Thanks,
rich!

On 9/23/2020 9:39 PM, Dave Casey wrote:
I spoke so highly of my 571 last month. When I recently went to use
it, I
was getting some artifacts in the display so I have set out to
investigate.

Unfortunately you can tell this wasn't designed in Beaverton because
you
have to remove the CRT to get the main board out. There are some large
Roedenstein electrolytics used for supply smoothing that have a bit of
a
dome to the end of them. Not sure if these were flat when new, but they
don't appear to be leaky (neither physically nor electrically). There
is
significant noise (100-200mVpp) on the supplies, but it's not line
ripple.
It appears to be around 2 MHz and is two similarly disruptive pulses
around
200ns out of phase.

In the process of disassembly, I have pulled and saved the three EPROM
images. Two run the 8032 controller, and one runs the NS405 "terminal
on
a
chip" that is used to draw the display and printer output.
I haven't exhaustively perused the images, but the graphics ROM has
some
ASCII easter eggs I noticed. After the usual Tektronix copyright
statement
is "Written by: Folkert ten Brummelhuis (started). Sjoerd J. Punter"
and
soon after "[Makke yn Fryslân]" which is Frisian for "Made in
Friesland",
the province in which Heerenveen is situated. Later in the ROM the
phrase
"Joke Mirjam Esther" appears twice, about (but not exactly) 64 bytes
apart.
I believe these are three given names commonly used in the region,
perhaps
the names of those endeared to one or both programmers.

Dave Casey

On Fri, Aug 21, 2020 at 1:31 PM Dave Casey via groups.io <polara413=
gmail.com@groups.io> wrote:

I stand corrected; can confirm, my S/N also starts with H. Thanks!

Dave Casey

On Fri, Aug 21, 2020 at 5:12 AM zenith5106 <hahi@...> wrote:

On Fri, Aug 21, 2020 at 05:49 AM, Dave Casey wrote:

Built by Sony-Tektronix.
No,not Sony-Tek. It was built by Tek Netherlands (SN begin with H)
and
as
far as I remember it was also designed by them.

/Håkan

















 

Anybody seen a ceramic bypass cap go bad?
Yes, but that was a very high leakage failure (almost a short) on a 7K series logic board.

I've known them to crack and fail open as well.

Anyone have some other cases to add?

David


Dave Casey
 

Well so far I have found two cracked bypass caps. They were not visually
cracked, but when I removed them they came off in two pieces. In both
cases, the lead made a clean break from the plate under the epoxy. So the
epoxy was holding them together until removal stressed it enough to crack
and let go of the leg. These are axial leads, and the caps were installed
pretty snug to a rather large board that can flex a bit, so I could see
mechanical stress contributing to the failures.
I chose the caps to remove based on where the noise was worst on the board.
Since this is just a 2-layer board with no planes, the noise is measurably
different closer to the source.
One especially noisy spot was near one of the two video RAMs. This noise
went away when I pulled the NS405's EPROM (so it quit using the RAM).
The bypass capacitor for that RAM was one of the two that ended up being
broken.

Another especially noisy spot was near the 8032's EPROMs, EEROM, PALs, and
reset supervisor. The bypass cap for the reset supervisor came apart upon
removal as well.

Both of these were on the 5V rail, so that has yet to explain how the noise
is so bad on the -15V rail; I probably have more to find yet. I've removed
a few more. A lot of the caps (0.1uF) measure a little low at 85-90nF on my
uncalibrated 4274A, but if I bias them with 5V they come up to 100-105.
They are all Murata M5E (20%, 50V, Z5U dielectric).
I keep a pile of X7Rs on hand and will use them as replacements. They have
radial leads, so there's some built in strain relief when put them in place
of the axials. I am tempted to shotgun the lot of them. A new X7R does not
change capacitance with bias, but neither does a 100pF Murata I pulled from
the 571 for testing.

So tomorrow I'll put X7Rs in place of the 8-10 caps I've pulled so far and
see how quiet things run before I go hunting for more.

Dave Casey

On Fri, Sep 25, 2020 at 4:40 AM David C. Partridge <
@perdrix> wrote:

Anybody seen a ceramic bypass cap go bad?
Yes, but that was a very high leakage failure (almost a short) on a 7K
series logic board.

I've known them to crack and fail open as well.

Anyone have some other cases to add?

David