Date   
Re: Tek 576 noise and looping

 

Hi Peter,
TekScopes couldn't find your photos when I asked it to search on the file name you gave. It took me 8 or 9 search queries before TekScopes finally found it.
In the future it would be very helpful to include the actual URL in addition to the name of the file so people could immediately see what you need help with.
Dennis Tillman W7PF

-----Original Message-----
From: peter bunge
Sent: Monday, November 11, 2019 12:58 PM

I suspected that I could not attach photos.
Any one interested please see the file I uploaded with examples of looping on pages 5 and 6.
File is: Tektronix 576 Curve Tracer Repair Log 1.pdf
It also covers several repairs and my current attempt to find out about the noise.
PeterB

On Mon, Nov 11, 2019 at 12:19 PM Mlynch001 <@mlynch001> wrote:

"I'm not sure if pictures show up, let me know.
[image: 2N3568 low current.jpg]"

Peter,

Attachments are not allowed within our posts. However, you can post
your
picture(s) in the "PHOTOS" section. Make a File and share the
filename in a post. Then anyone can see the photos. Please edit and
reduce the size of the files to save our limited storage space on the forum.

--
Michael Lynch
Dardanelle, AR







--
Dennis Tillman W7PF
TekScopes Moderator

Re: 577 D1 storage & brightness control

 

Hi Siggi,
Congratulations! You have found an excellent curve tracer.
There is a circuit in all 577s to prevent the CRT from being burned when you turn the collector voltage down so low that it essentially becomes a dot on the lower left corner of the screen when you are testing NPN transistors or on the upper right corner when testing PNP transistors. That bright spot would eventually burn the phosphor at that spot.

The brightness control should work regardless of how long the collector voltage trace looks like when it is sweeping across the screen. You should be able to adjust the brightness when the beam is anywhere.
The only time the trace is automatically dimmed is when the trace is reduced to the size of a dot or when it is so very short that it might burn the phosphor.
Some perceptive Tek engineer realized the problem and solved it by dimming the trace in those two locations.

Dennis Tillman W7PF

-----Original Message-----
From: Siggi
Sent: Monday, November 11, 2019 9:37 AM
Subject: [TekScopes] 577 D1 storage & brightness control

Hey y'all,

a 577/177 D1 in pristine condition just popped up locally and followed me home this weekend. After cleaning the pots and the test fixture connector, everything seems to be working just fine. I'll need to walk through the calibration process and jiggle all the trimmers though.

I found it curious and initially confusing that the brightness control only works when the collector supply is set to zero. Is the intended usage for this to erase the display, then sweep the collector supply up and down to get a set of curves?

So far I've fried only one transistor, turns out a to-92 is no match for the power the 577 can deliver when the operator fumble-fingers the controls :).

Siggi




--
Dennis Tillman W7PF
TekScopes Moderator

Re: anyone have 310 or 360 parts machine?

 

Hi Oliver,
I don't have a 310 or 360. I MAY have access to some parts, that's all. I can't help you with wiring. HOWEVER, the wiring information should be in the service manual schematics.
Search for 310 and for 360 on TekWiki's main page for the service manuals. They are there.
http://w140.com/tekwiki/wiki/Main_Page

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of oliver johnson via Groups.Io
Sent: Sunday, November 10, 2019 4:27 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] anyone have 310 or 360 parts machine?

I have the same scope that i will repair some time in the future, can you send me a diagram of each interconnect cable , i have the ends but not sure is its a one to one connection.
On Sun, Nov 10, 2019 at 11:00 AM, Dennis Tillman W7PF<@Dennis_Tillman_W7PF> wrote: Hi Phil,
I MAY have one. I am on the road until Friday so you will have to wait until then.

Next Saturday send me an email off list to dennis at ridesoft dot com to remind me and I will take a look.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Phil Cirocco
Sent: Saturday, November 09, 2019 9:40 PM
To: TekScopes@groups.io
Subject: [TekScopes] anyone have 310 or 360 parts machine?

I am looking for a graticule lens for my Tektronix 360 indicator module. This is the old scope module for the 160 series with the round CRT.The 310 scope used the same part. Tektronix part #331-0027-00. I will gladly pay for it and shipping. Any help would be appreciated.

Thanks

Phil Cirocco





--
Dennis Tillman W7PF
TekScopes Moderator








--
Dennis Tillman W7PF
TekScopes Moderator

Re: 7S14 7S11 SAMPLER bias QUESTION

Miguel Work
 

Raymond, complicated does not mean that it is impossible to understand. Yes I understand the basics, now is time to know why engineers put batteries in this design.
Thanks!
Best regards

Re: Early 2456 power supply ripple on 87V...

tek_547
 

Good to know Chuck and a good find!
René

Re: 2465 Fan Collet Thingy

n4buq
 

That's exactly where mine broke but since it broke so cleanly, it provided a relatively smooth, flat surface to which the CA glue could adhere.

Being a little picky, but the other end of that stud is 40 t.p.i. so an even finer pitch (#4-40 on one end and #8-32 on the other).

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Siggi" <siggi@...>
To: TekScopes@groups.io
Sent: Monday, November 11, 2019 5:18:10 PM
Subject: Re: [TekScopes] 2465 Fan Collet Thingy

On Mon, Nov 11, 2019 at 4:55 PM n4buq <n4buq@...> wrote:

When the stud is turned CCW, provided the collet doesn't break first, the
threads in the collet itself would push the flanged part of the stud
against the inside surface of the impeller.
I don't have much experience with this other than my own scope and
machining some replacement collets, but when I inspected my own scope, I
figured this is exactly what the stud is for. This is a very gentle way to
separate the two, as the thread's quite fine (32TPI). I can't see any
reason why Tek would have gone to the trouble of using this
double-threaded, collared stud, if not for this very purpose. It would have
been less expensive and simpler for sure to mold the collet around a
threaded stud that protruded out through the impeller.
On my scope, the collet was fractured all around the insert, while the
tapered end looked just fine. This commonly happens with parts molded
around inserts, over time the plastic wants to shrink, while the metal
insert is unyielding.



Re: Tek 576 noise and looping

peter bunge
 

Kevin; I found the looping capacitor broken probably from dropping the 576
during shipping. I repaired it with epoxy and used a different shaft
coupling that can be seen in a photo in my notes. Have you looked at them?
Why do you ask? It does nothing to the noise or looping I'm seeing. I have
the parts unit working, with the help of epoxy, so I can compare both
units. I will try to get thru the adjustments to the noise check on the
parts unit and see if there is a difference.
Peter.

On Mon, Nov 11, 2019 at 5:53 PM Kevin Oconnor <@KO3Y> wrote:

Peter,
I had forgot about that looping compensation capacitor Ed mentioned. Do
look into it since it sounds like you are digging inside. Let us know what
you fine.
KJO KO3Y



Re: 2465 Fan Collet Thingy

Siggi
 

On Mon, Nov 11, 2019 at 4:55 PM n4buq <n4buq@...> wrote:

When the stud is turned CCW, provided the collet doesn't break first, the
threads in the collet itself would push the flanged part of the stud
against the inside surface of the impeller.
I don't have much experience with this other than my own scope and
machining some replacement collets, but when I inspected my own scope, I
figured this is exactly what the stud is for. This is a very gentle way to
separate the two, as the thread's quite fine (32TPI). I can't see any
reason why Tek would have gone to the trouble of using this
double-threaded, collared stud, if not for this very purpose. It would have
been less expensive and simpler for sure to mold the collet around a
threaded stud that protruded out through the impeller.
On my scope, the collet was fractured all around the insert, while the
tapered end looked just fine. This commonly happens with parts molded
around inserts, over time the plastic wants to shrink, while the metal
insert is unyielding.

Re: Tek 576 noise and looping

Kevin Oconnor
 

Peter,
I had forgot about that looping compensation capacitor Ed mentioned. Do look into it since it sounds like you are digging inside. Let us know what you fine.
KJO KO3Y

Re: 2465 Fan Collet Thingy

Chuck Harris
 

Milling the surface flat after several layers of metal
are deposited, and suddenly this is becoming very
complicated and expensive...

Though it would take care of the warpage.

-Chuck Harris

Bruce Griffiths wrote:

Hybrid laser sintering and machining:
https://www.lumex-matsuura.com/english/about
N.B. for Titanium powder an inert atmosphere is required to avoid catastrophic fires.

Bruce
On 12 November 2019 at 10:46 Chuck Harris <cfharris@...> wrote:


Looks like a MIG welder without the argon.

The vacuum would certainly reduce the power requirements for
the melt.

I wonder how warpage is managed?

-Chuck Harris

Re: 2465 Fan Collet Thingy

Chuck Harris
 

Hi Barry,

Ok, I see what you are saying.

What we don't know is how the average person
will respond when they see a tiny shaft going in,
and a screw slotted thread coming out.

I think most folks are not used to seeing a collet
in that context... but are pretty familiar with how
a screw works.

I suspect that most would observe the threads, and
intuit that the skinny shaft grows to be a threaded
shaft somehow inside of the hub of the impeller.

Since the threads of the slotted shaft are clockwise,
you would then need to turn the threaded shaft in the
clockwise (tighten) direction to move the shaft out of
the back of the impeller.. which will only serve to
further tighten the threaded stud into the threaded
insert, and break the collet.

If they were to turn the threaded shaft in the CCW
direction, it would likely do what you suggest, and
push the collet out.

But as you also say, 9 times out of 10, the plastic
is already full of small cracks from the stress risers
caused by the extreme diamond knurling on the brass insert,
and will simply shatter before the steel stud will break
free in the threads of the brass insert.

Of course a combination of tightening the threaded
shaft (and finding it didn't help), and then loosening
the threaded shaft would be fatal to the decades old
plastic.

-Chuck Harris

n4buq wrote:

Hi Chuck,

That's not what I meant. When the stud is turned CCW, provided the collet doesn't break first, the threads in the collet itself would push the flanged part of the stud against the inside surface of the impeller. Of course, 10 times out of 9, the collet breaks before the threads allow the stud to turn because the stud is locked somewhat tightly against the back face of the collet.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Chuck Harris" <cfharris@...>
To: TekScopes@groups.io
Sent: Monday, November 11, 2019 2:16:22 PM
Subject: Re: [TekScopes] 2465 Fan Collet Thingy

Hi Barry,

The screw threads do NOT engage the impeller body. It is
a tight through hole. So, if you turned the screw slot,
all you would be doing is torquing the screw free of the
collet body. Which breaks the head of the collet, freeing
the collet's jaws.

When the collet is new, simply loosening the nut will allow
it to relax enough to be pulled off of the shaft... especially
given that pulling moves the collet in the direction of
release.

When the collet has been tightened for 2 or 3 decades, the
plastic of the impeller stretches out a little bit and
relaxes, leaving a pit for the collet to get stuck into.

That is why you need to loosen the nut, and give it a tap.

-Chuck Harris

n4buq wrote:
It's strange to me how the stud that holds the collet tight appears to have
been designed so that reversing the screw (with the screwdriver slot)
would naturally push the collar on the stud against the impeller and push
the collet open. The instructions don't say to do that and to simply grab
the impeller and pull it but that doesn't seem to work (at least it didn't
for me and, supposedly, that could easily break the impeller or strain the
motor bearing surfaces, etc).

Fun stuff...

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Chuck Harris" <cfharris@...>
To: TekScopes@groups.io
Sent: Monday, November 11, 2019 12:19:01 PM
Subject: Re: [TekScopes] 2465 Fan Collet Thingy

It should be pretty clear that even plastic works very
well.




Re: 2465 Fan Collet Thingy

Bruce Griffiths
 

Hybrid laser sintering and machining:
https://www.lumex-matsuura.com/english/about
N.B. for Titanium powder an inert atmosphere is required to avoid catastrophic fires.

Bruce

On 12 November 2019 at 10:46 Chuck Harris <cfharris@...> wrote:


Looks like a MIG welder without the argon.

The vacuum would certainly reduce the power requirements for
the melt.

I wonder how warpage is managed?

-Chuck Harris

Bruce Griffiths wrote:
You mean something like this?:
https://www.sciaky.com/additive-manufacturing/electron-beam-additive-manufacturing-technology

Bruce
On 12 November 2019 at 04:34 Chuck Harris <cfharris@...> wrote:


I have a CD stud welder that can weld a 3/8" threaded stud onto
a piece of heavy sheet metal without burning the paint on the
other side... takes about 5ms to do the weld. Clearly a much
smaller "weld" would take less time and less energy.

I have thought that using a CD method to fuse the stock metal onto
the part being made might be effective. The big problem is avoiding
fusing the feedstock metal to the electrode.

A pulsed laser to a bed of powdered metal granules is probably
an ideal way of avoiding that issue... and avoiding metal distortion
due to the heat of fusion.

-Chuck Harris

Re: 7S14 7S11 SAMPLER bias QUESTION

 

On Mon, Nov 11, 2019 at 09:35 PM, Miguel Work wrote:


Thanks Raymond, for that I´m studying and asking what I don´t understand.
I'm not sure that understand the following:
- All sampling (the sampling that is the direct subject of our discussion) is done inside the front-end of the 7S14 and a sampler head plugged into a 7S11. It is *never* done inside the 7S11
- The 7S11 *only sees* the low-frequency signal that the sampler produced
- The 7S11 is meant for sampling plug-ins. These are made for HF and fast edges. DC is not important.
- The 7S14 OTOH is meant for DC to 1 GHz, being positioned by Tek as a general purpose LF and HF vertical and horizontal unit

The sampling bridges we're talking about here (either in the sampler plugin or in the 7S14) all use very fast, low capacitance diodes. These are switched "on and off" while sampling (conducting or not). In this process, the diodes see a continuously applied reverse (blocking) voltage, called the bias voltage, to make them stay off. Strobe pulses are applied periodically via capacitive coupling to switch them into conduction, where they'll conduct and transfer the input signal for a very short time. This is all in the documentation available (SM's and other docs).
The bias voltage (DC) may be applied by circuits directly coupled with the 'scope's power supply system or floating, depending on design decisions and technology available. 7S11 plug-ins all use direct power supply coupling for their reverse bias, the 7S14's inbuilt sampling circuits use the battery solution. There is no simple way of converting the 7S14 to the 7S11-way. Tek engineers had their reasons to do it this way in the 7S14, we discussed this before and there's no simple "now I understand, so now I can change it".


The goal is to understand in detail why 7S14 needs floating bias, to be able to modify it.
From the above it should be clear that the straightforward way to go when replacing the Hg cells is to supply another floating bias circuit. That's not difficult: 4 leds per channel, a few resistors, a few capacitors. Ed Breya has written a very good document which you've seen on Tekwiki.

If OTOH you're prepared to risk your 7S14 (especially the sampler diodes), by all means emulate the constant-current circuits in the samplers, keeping currents, DC levels and impedances in mind.

Raymond

Re: 2465 Fan Collet Thingy

n4buq
 

Hi Chuck,

That's not what I meant. When the stud is turned CCW, provided the collet doesn't break first, the threads in the collet itself would push the flanged part of the stud against the inside surface of the impeller. Of course, 10 times out of 9, the collet breaks before the threads allow the stud to turn because the stud is locked somewhat tightly against the back face of the collet.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Chuck Harris" <cfharris@...>
To: TekScopes@groups.io
Sent: Monday, November 11, 2019 2:16:22 PM
Subject: Re: [TekScopes] 2465 Fan Collet Thingy

Hi Barry,

The screw threads do NOT engage the impeller body. It is
a tight through hole. So, if you turned the screw slot,
all you would be doing is torquing the screw free of the
collet body. Which breaks the head of the collet, freeing
the collet's jaws.

When the collet is new, simply loosening the nut will allow
it to relax enough to be pulled off of the shaft... especially
given that pulling moves the collet in the direction of
release.

When the collet has been tightened for 2 or 3 decades, the
plastic of the impeller stretches out a little bit and
relaxes, leaving a pit for the collet to get stuck into.

That is why you need to loosen the nut, and give it a tap.

-Chuck Harris

n4buq wrote:
It's strange to me how the stud that holds the collet tight appears to have
been designed so that reversing the screw (with the screwdriver slot)
would naturally push the collar on the stud against the impeller and push
the collet open. The instructions don't say to do that and to simply grab
the impeller and pull it but that doesn't seem to work (at least it didn't
for me and, supposedly, that could easily break the impeller or strain the
motor bearing surfaces, etc).

Fun stuff...

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Chuck Harris" <cfharris@...>
To: TekScopes@groups.io
Sent: Monday, November 11, 2019 12:19:01 PM
Subject: Re: [TekScopes] 2465 Fan Collet Thingy

It should be pretty clear that even plastic works very
well.


Re: 2465 Fan Collet Thingy

Chuck Harris
 

Looks like a MIG welder without the argon.

The vacuum would certainly reduce the power requirements for
the melt.

I wonder how warpage is managed?

-Chuck Harris

Bruce Griffiths wrote:

You mean something like this?:
https://www.sciaky.com/additive-manufacturing/electron-beam-additive-manufacturing-technology

Bruce
On 12 November 2019 at 04:34 Chuck Harris <cfharris@...> wrote:


I have a CD stud welder that can weld a 3/8" threaded stud onto
a piece of heavy sheet metal without burning the paint on the
other side... takes about 5ms to do the weld. Clearly a much
smaller "weld" would take less time and less energy.

I have thought that using a CD method to fuse the stock metal onto
the part being made might be effective. The big problem is avoiding
fusing the feedstock metal to the electrode.

A pulsed laser to a bed of powdered metal granules is probably
an ideal way of avoiding that issue... and avoiding metal distortion
due to the heat of fusion.

-Chuck Harris

Early 2456 power supply ripple on 87V...

Chuck Harris
 

I remember a thread a few years back where there was excess ripple
on the 87V supply in a 2465.

I just fixed such a problem on a properly recapped 2465.

The issue was there was 80mVpp ripple on the 87V test pin, that was
discovered during calibration. 80mvpp happens to be the max value
of ripple allowed, but more typically the ripple at that point is
1/10th that amount.

The ripple looked like an oscillation that was all over the place in
frequency, but steady in amplitude. It went away when the supply was
hot, but came back when the opamp U1281 was given a squirt of
freeze spray.

The scope was a pre B020000 unit, and was built without any feedback
stabilization in the feedback loop. A stabilization cap was added
in all scopes B020000 and later.

Adding in the missing C1222, a 0.1uf cap, to slows down Q1222 fixing
the problem.

-Chuck Harris

Re: 2465 Fan Collet Thingy

Bruce Griffiths
 

On 12 November 2019 at 04:34 Chuck Harris <cfharris@...> wrote:


I have a CD stud welder that can weld a 3/8" threaded stud onto
a piece of heavy sheet metal without burning the paint on the
other side... takes about 5ms to do the weld. Clearly a much
smaller "weld" would take less time and less energy.

I have thought that using a CD method to fuse the stock metal onto
the part being made might be effective. The big problem is avoiding
fusing the feedstock metal to the electrode.

A pulsed laser to a bed of powdered metal granules is probably
an ideal way of avoiding that issue... and avoiding metal distortion
due to the heat of fusion.

-Chuck Harris

EricJ via Groups.Io wrote:
It's out there now, but it's not trickled down to the hobbyist level yet. May be a while.

https://gpiprototype.com/metal-3d-printing

--Eric

On Nov 11, 2019 8:09 AM, Chuck Harris <cfharris@...> wrote:




Very cool, but not useful as the strength of these composite
filaments is entirely in the plastic binder.

-Chuck Harris

Re: 7S14 7S11 SAMPLER bias QUESTION

Miguel Work
 

Thanks Raymond, for that I´m studying and asking what I don´t understand.

Yes, S3 head DC coupled, but the preamplifier is AC coupled, it samples the DC level.
There is no blowby circuit in S3 head?

The goal is to understand in detail why 7S14 needs floating bias, to be able to modify it.

Regards

Miguel

-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de Raymond Domp Frank
Enviado el: lunes, 11 de noviembre de 2019 20:19
Para: TekScopes@groups.io
Asunto: Re: [TekScopes] 7S14 7S11 SAMPLER bias QUESTION

On Mon, Nov 11, 2019 at 07:37 PM, Miguel Work wrote:


I´m looking S1 diagrams, preamp board seems to be AC coupled, Q45, C49.
Even earlier in the circuit *the signal* is AC coupled at C40, directly after the "sample-and-hold FET"


I´m not an expert, but it seems that S1 is ac coupled, and 7s14 is DC coupled,
Yes, signal-wise. Apart from the fact that the S1 is just a sampler and the 7S14 is a complete "general purpose" 'scope plugin, including sampler.
The 7S14 has DC to 1 GHz BW, whereas the S1 is a specialized sampler for fast edges and high frequencies, AC only, not meant to view DC.


DC coupling could explain the need to use floating bias in 7S14?
No, not in and by itself: The S3(A) sampler plugin for the 7S11 goes from DC to 1 GHz and uses the same non-floating bias.


But, looking 7s14 diagrams and like S1 head, the difference is in R45,
8M2 resistor feedback?
No. There are more (significant) differences. R45 and C52/62 are part of the blowby (LF feed-through compensating) circuit, not general feedback.

You really need to read more about the workings of this kind of samplers...

Raymond

Re: Tek 576 Curve Tracer, 3 mechanical parts wanted; Does anyone have a parts unit ?

Dave Brown
 

Where are you located? We have one or possibly two 576 parts units at the museum. If local, stop by and we can see what we have. If not, send us an email at contactus@.... We can likely look this weekend when the museum is open.

Dave

Re: 2465 Fan Collet Thingy

Chuck Harris
 

Hi Barry,

The screw threads do NOT engage the impeller body. It is
a tight through hole. So, if you turned the screw slot,
all you would be doing is torquing the screw free of the
collet body. Which breaks the head of the collet, freeing
the collet's jaws.

When the collet is new, simply loosening the nut will allow
it to relax enough to be pulled off of the shaft... especially
given that pulling moves the collet in the direction of
release.

When the collet has been tightened for 2 or 3 decades, the
plastic of the impeller stretches out a little bit and
relaxes, leaving a pit for the collet to get stuck into.

That is why you need to loosen the nut, and give it a tap.

-Chuck Harris

n4buq wrote:

It's strange to me how the stud that holds the collet tight appears to have been designed so that reversing the screw (with the screwdriver slot) would naturally push the collar on the stud against the impeller and push the collet open. The instructions don't say to do that and to simply grab the impeller and pull it but that doesn't seem to work (at least it didn't for me and, supposedly, that could easily break the impeller or strain the motor bearing surfaces, etc).

Fun stuff...

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Chuck Harris" <cfharris@...>
To: TekScopes@groups.io
Sent: Monday, November 11, 2019 12:19:01 PM
Subject: Re: [TekScopes] 2465 Fan Collet Thingy

It should be pretty clear that even plastic works very
well.