Date   

Re: 465 bad rise time

Brendan
 

Im using a 50ohm cable with a 50ohm through terminator.

https://groups.io/g/TekScopes/photo/59361/2?p=Name,,,20,1,0,0

On Sun, Jun 17, 2018 at 08:50 pm, tmillermdems wrote:


You are looking at the waveform with a scope probe that presents a 10 meg
ohm load to the pulse generator. What you need to do is use a 50 ohm cable
to go from the generator to the scope input and include a 50 ohm through
termination right at the scope. A real simple solution would be to use a BNC
T with the center loaded with a 49.9 ohm resistor. Or just look for a 50 ohm
through termination on ebay.

Regards




----- Original Message -----
From: "lop pol via Groups.Io" <the_infinite_penguin=yahoo.com@groups.io>
To: <TekScopes@groups.io>
Sent: Sunday, June 17, 2018 9:47 PM
Subject: [TekScopes] 465 bad rise time


Hey guys. I have done a lot of work to this 465. I had initially planned on
selling it to help me buy some plugins for my 7633. I decided I don't want
to sell it and am keeping it. Today I checked its rise time with a pg506
fast rise. Both channel 1 and 2 closely resemble each other and they are not
close to right. Before I start trying to calibrate this thing, does it look
like there is some type of component issue left to fix? I am thinking since
both channels are so alike there is something wrong besides just out of
calibration. Thanks guys.

here are some pictures

https://groups.io/g/TekScopes/photo/59361/0?p=Name,,,20,1,0,0

https://groups.io/g/TekScopes/photo/59361/1?p=Name,,,20,1,0,0





Re: My 422

 

Clutter ? You gotta see this place. We moved out of 3 houses.

Anyway, I got a couple pictures uploaded here you could look at. It's on AC so I didn't have all day, and my camera batteries are lunch to that thing, something I am going to do something about unless I get hit by a bus of some shit. So all I got are 2 pics, but they are alright. I can't seem to get this camera in the right color mode so I have to use software to get it to look right. But it's no big deal. I kinda like doing it and really, anyone out there who has pictures of poor quality, I will fix them. I got some decent software and know how to use it. If you have alot of them I want some beer or something, but one or two I'll just do. Almost for the fun of it but also for practice and get even more used to the software. It's old and I'll need to always have an older PC to rune it but I ain't giving it up. Not because Bill and Melinda want to feed every kid in Africa and vaccinate them while our vets die in the street out of poverty. I run XP. I will always run XP. (unless I could make 98SE work) If I can't get online with it I'll have something that does, but for everything else old Betsy here is great. Tell me to shut up once in a while OK ? Here are the pics :

https://groups.io/g/TekScopes/photo/59366/0?p=Name,,,20,1,0,0

That is channel one on noise and two on the calibrate, it is in free run. Note the 3 meter P-6105 !

https://groups.io/g/TekScopes/photo/59366/1?p=Name,,,20,1,0,0

That is the collector of Q 1714, one of the choppers. the probe is not calibrated to that scope so it is not all that accurate, but I guess you can do it and I didn't even hook up the ground. I thought you could, but never actually tried it.

I might leave it up and play around a bit. Waveforms in the horizontal, they are not likely to display well. But what about in chop or alternate, the vertical CRT plates ? that sounds i interesting.

I very much doubt this could hurt the scope. It is not like plugging the speaker out to an input on an amp, unless you try to scope channel 1 with channel 1. Anyway, it depends on what comes up. I got a wiring job to do soon and I think I need at least a good box for this.

I will never abandon it, but like frozen peas, it goes on the back burner. (that just popped up in my head as a sort of analogy) But it belongs there right now. Back burner. (actually I am out of ideas right now)


Re: 465 bad rise time

 

You are looking at the waveform with a scope probe that presents a 10 meg ohm load to the pulse generator. What you need to do is use a 50 ohm cable to go from the generator to the scope input and include a 50 ohm through termination right at the scope. A real simple solution would be to use a BNC T with the center loaded with a 49.9 ohm resistor. Or just look for a 50 ohm through termination on ebay.

Regards

----- Original Message -----
From: "lop pol via Groups.Io" <the_infinite_penguin=yahoo.com@groups.io>
To: <TekScopes@groups.io>
Sent: Sunday, June 17, 2018 9:47 PM
Subject: [TekScopes] 465 bad rise time


Hey guys. I have done a lot of work to this 465. I had initially planned on selling it to help me buy some plugins for my 7633. I decided I don't want to sell it and am keeping it. Today I checked its rise time with a pg506 fast rise. Both channel 1 and 2 closely resemble each other and they are not close to right. Before I start trying to calibrate this thing, does it look like there is some type of component issue left to fix? I am thinking since both channels are so alike there is something wrong besides just out of calibration. Thanks guys.

here are some pictures

https://groups.io/g/TekScopes/photo/59361/0?p=Name,,,20,1,0,0

https://groups.io/g/TekScopes/photo/59361/1?p=Name,,,20,1,0,0


Re: 465 bad rise time

Brendan
 

On Sun, Jun 17, 2018 at 07:03 pm, Harvey White wrote:


On Sun, 17 Jun 2018 18:47:37 -0700, you wrote:

Hey guys. I have done a lot of work to this 465. I had initially planned on
selling it to help me buy some plugins for my 7633. I decided I don't want to
sell it and am keeping it. Today I checked its rise time with a pg506 fast
rise. Both channel 1 and 2 closely resemble each other and they are not close
to right. Before I start trying to calibrate this thing, does it look like
there is some type of component issue left to fix? I am thinking since both
channels are so alike there is something wrong besides just out of
calibration. Thanks guys.

This may not be exactly what you think. Rise time is measured from
10% to 90%. I'd have to look at the manual for that scope, but I
remember that the dotted lines on the graticule are supposed to
measure the 10% to 90% parts of the waveform. I think one problem is
that you have too little vertical gain at the moment. Bear in mind
that the risetime also varies with the vertical gain control.

I'd check the manual and see exactly how you are supposed to measure
risetime before thinking that the risetime is bad.

Harvey




here are some pictures

https://groups.io/g/TekScopes/photo/59361/0?p=Name,,,20,1,0,0

https://groups.io/g/TekScopes/photo/59361/1?p=Name,,,20,1,0,0


In the manual it says to set .05us and remove and add attenuators to keep the 5 divisions and to check for 3.5ns rise time. I used a 50ohm through termination with .2V/div. with the pg506 all most maxed out. I did set 10x mag because I dont know how to see 3.5ns while setting the time at .05us/50ns the trace is wider than 3.5ns. Duplicating the exact setup on my 468 shows the correct 3.5ns rise time without that giant round shoulder. Thanks for your help :)


Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)- SMPS caps.

mosaicmerc
 

Regarding ripple current specifications, I have designed a high ripple application, indeed it is akin to KHz frequency spot welding given the currents pulsing to 800A or so. I have found that the Illinois Capacitor PJ series do handle the duty which runs them at up to 60 C continuous (25C ambient). They do better than Rubycon etc.

They are in parallel banks of 3 @ 2200uF with solder braid augmented PCB traces spec'd to sub 2 mΩ per trace. I pre-qualify the capacitors with an ESR meter to sub milliohm  grading and binning for bank balancing.

As I look at the data sheet again, I note they are specified for SMPS duty.

http://www.farnell.com/datasheets/2364654.pdf?_ga=2.158207226.1706536182.1529287061-97959724.1511408215

These capacitors are hammered continuously for 100s of hours per month. I have not had one fail, except when I put in one backward which then pops it in about 30 seconds.

Here is an O'scope 'blue' trace of a pulse event using a 50 Ω impedance @ 40A/V  Ion Physics (purpose built) current transformer monitor:

https://hackaday.io/project/25741/gallery#ee89f2f53ebe882b6909e8e3953adc7b

I have systems running in Africa where the ambient temperature in the shade is 45C.

Ancel


Re: 465 bad rise time

Harvey White
 

On Sun, 17 Jun 2018 18:47:37 -0700, you wrote:

Hey guys. I have done a lot of work to this 465. I had initially planned on selling it to help me buy some plugins for my 7633. I decided I don't want to sell it and am keeping it. Today I checked its rise time with a pg506 fast rise. Both channel 1 and 2 closely resemble each other and they are not close to right. Before I start trying to calibrate this thing, does it look like there is some type of component issue left to fix? I am thinking since both channels are so alike there is something wrong besides just out of calibration. Thanks guys.
This may not be exactly what you think. Rise time is measured from
10% to 90%. I'd have to look at the manual for that scope, but I
remember that the dotted lines on the graticule are supposed to
measure the 10% to 90% parts of the waveform. I think one problem is
that you have too little vertical gain at the moment. Bear in mind
that the risetime also varies with the vertical gain control.

I'd check the manual and see exactly how you are supposed to measure
risetime before thinking that the risetime is bad.

Harvey




here are some pictures

https://groups.io/g/TekScopes/photo/59361/0?p=Name,,,20,1,0,0

https://groups.io/g/TekScopes/photo/59361/1?p=Name,,,20,1,0,0



Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)

Dave Daniel
 

One of them, Mouser or Digikey, will ship for free or at a reduced rate if you place your order by mail with a check. This is useful if one needs a small number of parts.

DaveD

Sent from a small flat thingy

On Jun 17, 2018, at 16:34, Harvey White <madyn@...> wrote:

On Sun, 17 Jun 2018 17:04:07 -0400, you wrote:

On 2018-06-17 2:21 PM, machineguy59 via Groups.Io wrote:
...
Finally, I use Digikey for parts. I have no disdain for Mouser but Digikey is more convenient to me. They are less than 200 miles from my home, shipping is fast (typically two days from order to arrival here), and cheap (as low as 3.95 US for a complete set of caps). So my list does not include Mouser part numbers.
About Digikey (Canada). They are FAST: Once I had parts in hand about 12
hours after ordering on the web. Next day is usual.

For me they also have much cheaper shipping than Mouser.
To avoid blanket statements: I've found that some Mouser prices are
cheaper than Digikey prices. I've also found that Mouser does not
carry some parts that I need (they went Altera rather than Xilinx, and
apparently carry NO Xilinx parts. Didn't check Digikey for Altera).

I'm in the southeast, so Mouser is closer for me and a bit faster.

As in any buy, consider how many you need and what the economies of a
bulk buy happen to be. SMT resistor may be 15 cents in unit
quantities, in lots of 100, you may be paying 0.5 cents.

Once you start ordering that kind of stuff, as long as you don't order
too many, the shipping is the killer. You tend to want to spend
enough that the shipping is not more than the parts total.

Harvey



--Toby





465 bad rise time

Brendan
 

Hey guys. I have done a lot of work to this 465. I had initially planned on selling it to help me buy some plugins for my 7633. I decided I don't want to sell it and am keeping it. Today I checked its rise time with a pg506 fast rise. Both channel 1 and 2 closely resemble each other and they are not close to right. Before I start trying to calibrate this thing, does it look like there is some type of component issue left to fix? I am thinking since both channels are so alike there is something wrong besides just out of calibration. Thanks guys.

here are some pictures

https://groups.io/g/TekScopes/photo/59361/0?p=Name,,,20,1,0,0

https://groups.io/g/TekScopes/photo/59361/1?p=Name,,,20,1,0,0


Self Governance of TekScopes.

 

Members of Tekscopes,



The TekScopes Group Description on our home page says: "All about classic
Tektronix test equipment, its use, repair, and collecting."



I hope everyone understands I do not have the time to read every post to
TekScopes. So I am unaware of the majority of the content posted to
TekScopes.



On occasion, the content strays beyond our Group Description. I have always
been impressed that eventually someone will suggest that the conversation is
not consistent with our group description. This is an important stabilizing
force that keeps TekScopes relevant.



When this happens it would be a big help to me and the other members if one
of our "TekScopes Elders" (you know who you are) intervenes as soon as they
see this occur and suggests to the offending member that their current
conversation is more appropriate elsewhere.



In the spirit of "See Something, Say Something", I would appreciate the
TekScopes Elders making it their responsibly to gently guide any stray
conversation back to Tektronix.



I hope it will only take one reminder from a TekScopes Elder to bring the
stray conversation back to Tektronix. If that doesn't happen then please
send me an email so I can intervene and stop it.



Thank you in advance,

Dennis Tillman W7PF



PS: I would greatly appreciate it if we could keep any follow-up comments to
an absolute minimum so first take a look at these three categories to
determine your next move:

1) If you understand what I am proposing and you are one of the TekScopes
Elders then there is no need to tell me. Please start now to "See Something,
Say Something".

2) If you are someone who feels the need to say you approve of what I
proposed above please refrain from posting at all.

3) If you disagree with what I am proposing pleasing contact me directly
OFF LINE at @Dennis_Tillman_W7pF <mailto:@Dennis_Tillman_W7pF> and explain
how I can do this better.


Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)

Harvey White
 

On Sun, 17 Jun 2018 17:04:07 -0400, you wrote:

On 2018-06-17 2:21 PM, machineguy59 via Groups.Io wrote:
...
Finally, I use Digikey for parts.  I have no disdain for Mouser but Digikey is more convenient to me.  They are less than 200 miles from my home, shipping is fast (typically two days from order to arrival here), and cheap (as low as 3.95 US for a complete set of caps).  So my list does not include Mouser part numbers.  
About Digikey (Canada). They are FAST: Once I had parts in hand about 12
hours after ordering on the web. Next day is usual.

For me they also have much cheaper shipping than Mouser.
To avoid blanket statements: I've found that some Mouser prices are
cheaper than Digikey prices. I've also found that Mouser does not
carry some parts that I need (they went Altera rather than Xilinx, and
apparently carry NO Xilinx parts. Didn't check Digikey for Altera).

I'm in the southeast, so Mouser is closer for me and a bit faster.

As in any buy, consider how many you need and what the economies of a
bulk buy happen to be. SMT resistor may be 15 cents in unit
quantities, in lots of 100, you may be paying 0.5 cents.

Once you start ordering that kind of stuff, as long as you don't order
too many, the shipping is the killer. You tend to want to spend
enough that the shipping is not more than the parts total.

Harvey



--Toby



Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)

toby@...
 

On 2018-06-17 2:21 PM, machineguy59 via Groups.Io wrote:
...
Finally, I use Digikey for parts.  I have no disdain for Mouser but Digikey is more convenient to me.  They are less than 200 miles from my home, shipping is fast (typically two days from order to arrival here), and cheap (as low as 3.95 US for a complete set of caps).  So my list does not include Mouser part numbers.  
About Digikey (Canada). They are FAST: Once I had parts in hand about 12
hours after ordering on the web. Next day is usual.

For me they also have much cheaper shipping than Mouser.

--Toby


Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)

 

Menahem, You may address me as Ron, or Mac (for machineguy).  I usually use Mac on the net and Ron in the "real world".  As a brief introduction, I am 78 years old, retired electronics engineer, now hobbyist, living in Iowa, USA.  Its hot here too (94 degrees F on many days), but air conditioning keeps it at a nice 73 degrees.  I got into repairing Tek scopes because they were everywhere during my working years but unaffordable.  I read the report on your 2465B scope restoration and decided I could do that too.  I now have six 24x5 scopes sitting in my lab, three work, one is being "built" and two are donors.  My wife wants me to "thin the herd" but we have an agreement: She wont throw out my scopes and I wont throw out her dishwasher.  My technical abilities are competent but not expert, too many years in management.  My repair objectives are equal or better than OEM (which in the case of Tek equipment is world class performance).  My three fully working scopes seem to achieve that goal.

Honestly, I was surprised and a bit offended when you first deprecated my updated list.  I had posted it to help someone who was creating a new list "from scratch".  He had asked for help and received little response.  So I offered the list I use.  I was embarrassed that it had two errors but I do think it helped him.  You might do better for him and I encourage you to post a list.  But this one is the best I have.  I use it and it works.

I agree with you, Nichicon is a better choice than Panasonic.  This is evident in their specifications.  Panasonic lists an ESR that is 30% or more worse in ESR than Nichicon.  This may account for the difference you measured in ripple reduction between the two.  (BTW, you may want to check your photos in the file section.  There are only two photos, not four and I believe the key photos are missing.)  But I used Panasonic in six locations.  Based on my agreement with your advice, I have changed my list to use the Nichicon equivalent in these locations.  For what its worth, I have preferred Nichicon to Panasonic for some time, just had not updated my list.

Like you, I give little weight to forecast life expectancy over 5000 hours.  But if all important parameters are equal, I use life expectancy as a factor.

Also like you, I used to avoid "over voltage" specifications in electrolytic capacitors.  But my research showed that higher voltage rated caps often had lower ESR and manufacturers often suggested de-rating their caps in hard stress applications by as much as 50%.  I reasoned then that if it was good for high stress applications, it was acceptable for moderate stress applications.  This discussion and my recent research has given me confidence in that decision.

Finally, I use Digikey for parts.  I have no disdain for Mouser but Digikey is more convenient to me.  They are less than 200 miles from my home, shipping is fast (typically two days from order to arrival here), and cheap (as low as 3.95 US for a complete set of caps).  So my list does not include Mouser part numbers.  

Again, thank you for your explanations.  I hope mine are useful to you.
Ron

On ‎Sunday‎, ‎June‎ ‎17‎, ‎2018‎ ‎02‎:‎46‎:‎49‎ ‎AM‎ ‎CDT, M Yachad <@yachadm> wrote:

MachineGuy
(I’d really like to address you by your real name!)

Thanks for that info from the tin-man.
I can certainly relate to the manufacturer’s published data.
I will take this into consideration the next time I have to select caps.

To address certain points:
1.    I am not at all biased against Panasonic caps. They are superb, and I use the EB in Linear audio applications all the time. They are my go-to for that specific application.
2.    I also use the Panasonic TSHA and ED/EE Snap-ins as my go-to PSU filter capacitors, with Nichicon GU as my second choice.
3.    So, the question arises, WHY do I NOT recommend the EB in THIS Tek PSU application?
4.    It is important to understand the function of a cap in each particular place in the circuit. In any PSU application, the AC ripple BETWEEN the Bridge rectifier and the Regulators is enormous. AFTER the regulators, the AC ripple is negligible.
5.    A few years ago, to quieten my curiosity, I did a test on an older amplifier using 4 new apparently identical 4700uF 25V and 50V capacitors mounted BETWEEN the Bridge and the bank of Regulators (some 78xx, 79xx, 317, 319). The Nichicon HE caps reduced the residual AC ripple to approx 1V p-p (with no discernible difference between the 25V and 50V cap). The other caps reduced the residual ripple to 2V p-p. See attached pictures. This is a test which any of you can easily do, any time.

https://groups.io/g/TekScopes/album?id=59343


6.    That proved to me that the HE has a significant advantage in reducing AC ripple, over another respected brand-name cap. On the datasheets, all the numbers pretty much matched up, but in the real world of flowing voltage and current, my scope waveform showed a substantially significant advantage to the HE.
7.    However, AFTER the regulators, where ripple is negligible, an EB is an excellent choice. The superior capability of the HE regarding ripple damping is of no advantage here.

On this Tek PSU, has anyone actually done any research to specify each cap’s function? From the postings here, I don’t think so. I haven’t. So, unless someone is willing to go and locate each cap on the circuit, and determine whether it is in a low-ripple part of the circuit (where an EB would be acceptable), or it is in a high-ripple part,  I think that we need to globally specify HE or PW (functionally equivalent), in order to be on the safe side for ALL applications. That’s what I did, with full confidence that my choice would give me the lowest ACTUAL ripple on all circuits.

If a user installs EB in a high-ripple area BEFORE the regulators, will the machine work? Of course it will.
But will it work as well, if an HE or PW is installed? My test states not.
After all, a SMPS with loads of AC ripple in all parts of the circuit, is NOT like a linear PSU, at all.

It’s the difference in being able to tune a high-performance engine, to get the last ounce of available HP out of it.

The posters who are asking these questions are people who do NOT have any substantial electronics background, theory or practice. I think it is incumbent on us (the techs with long experience) to point them in a direction which will give them an optimal and safe solution, so that they don’t have to tear their hair out, buying parts which don’t fit, or worrying whether what they choose will last or not.

Regarding the Lifetime numbers of the data provided by MachineGuy:

A 5000Hr lifetime is provided for a (boiling) CONSTANT temperature of 105°C. If the caps in my Tek scope are reaching that temperature, then my scope is on the way to the garbage dump, very quickly, and the 5000hr lifetime is functionally irrelevant.

I have measured the temperature of my HE caps in my A2A1/A3 PSU block, and the hottest individual cap temperature which I measured was 38°C. The average temp of the caps was room temperature.
And it IS hot here in Israel – I’m not just talking about the fires from the Gazan terrorists.

https://www.eetimes.com/author.asp?section_id=183&doc_id=1279791

“For every 10 degree Centigrade decrease in operating temperature, the capacitor life is extended by a factor of two.”

So, if my HE caps are running at a constant 40°C, then their expected lifetime is 5000 x 2 to the power of 6 (=64, check my math) = 320,000 hrs = more than 36 years; scope on all the time, never being switched off.

Given that the data supplied above stated that cap’s casing would breakdown after about 15 years, then there is no apparent benefit HERE of choosing a 10000 hr cap over a 5000 hr, except for the status.

So, IMO what we should be concerned about, is WHAT does the waveform look like at all the HIGH-RIPPLE positions in this Tek SMPS PSU circuit, and then select the cap which dampens that ripple most effectively. To my experience, the Nichicon HE fits the bill most effectively.

Menahem


Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)

Chuck Harris
 

Then you should have seen it in my last post, but here
it is again:
------------------------------------------------------
Ok, we are all engineers here, so, we know that ripple
voltage is pretty directly related to frequency, current,
and capacitance by the equation:

i(t) = -CdV/dt

[We can drop the "-" sign if we remember to get our dV
in the right direction so that we don't get a negative
capacitance.]

Looking at the oscilloscope traces, we see that in:

case 1) C = ?, dV = 2V, and dt = 5ms, and in
case 2) C = 4700uF, dV = 1.2V, and dt = 5ms.

Solving for i, we get 1.13A

Rearranging the equation and substituting the mystery
cap's ripple voltage:

C = idt/dV = 1.13A x 5ms/2V = 2820uF

Hold the phone there Menahem!

If that really is a 4700uf Brand X cap, it is either short
2000uf, or has about an ohm of ESR...

[EIA guidlines show a 4700uf, 25V, has to be less than 0.099
ohm ESR, and a 4700uf, 50V, has to be less than 0.071 ohm ESR.]

So, which is it:

A 2800uf capacitor marked as 4700uf?
A less than 0.1 ohm ESR cap with 1 ohm ESR?
A fib about the capacitance value?
--------------------------------------------------------

Do you have an answer?

-Chuck Harris

M Yachad wrote:

Talk, I'm listening.


Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)

 

Talk, I'm listening.


Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)

Chuck Harris
 

Well, consider me chastised.

I'm guessing that you and I have a different idea
of what constitutes an attack.

The math is simple, tried and true, and leads to
the inescapable conclusion that if everything is
as you said, the capacitor you are comparing to the
HE can't be 4700uf.

Let's talk about that.

-Chuck Harris

M Yachad wrote:

Chuck
Your cynicism stinks.

You have a habit of attacking people when you don't agree with them, and I'm calling you out on this now.
This wasn't the first time.

I'm not even going to dignify your posting with a reply.

Menahem


Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)

 

Chuck
Your cynicism stinks.

You have a habit of attacking people when you don't agree with them, and I'm calling you out on this now.
This wasn't the first time.

I'm not even going to dignify your posting with a reply.

Menahem


Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)

Chuck Harris
 

So, let see if I got this straight:

You did a comparison between brand X and Nichicon HE
caps, and you found that the Nichicon HE outperformed
the brand X capacitor 2 to 1.

Even gave us some pretty pictures.

Ok, wait, there is some fine print:

The brand X cap is old, and apparently to avoid
embarrassing the manufacturer, you won't tell their name.

[Wait! 3:40AM, and the text just changed! Now the other
cap is 4700uf 25V and 50V, not just an old cap... I hate it
when that happens...]

Ok, we are all engineers here, so, we know that ripple
voltage is pretty directly related to frequency, current,
and capacitance by the equation:

i(t) = -CdV/dt

[We can drop the "-" sign if we remember to get our dV
in the right direction so that we don't get a negative
capacitance.]

Looking at the oscilloscope traces, we see that in:

case 1) C = ?, dV = 2V, and dt = 5ms, and in
case 2) C = 4700uF, dV = 1.2V, and dt = 5ms.

Solving for i, we get 1.13A

Rearranging the equation and substituting the mystery
cap's ripple voltage:

C = idt/dV = 1.13 x 5ms/2V = 2820uF

Hold the phone there Menahem!

If that really is a 4700uf Brand X cap, it is either short
2000uf, or has about an ohm of ESR...

[EIA guidlines show a 4700uf 25V has to be less than 0.099
ohm ESR, and a 4700uf 50V has to be less than 0.071 ohm ESR.]

So, which is it:

A 2800uf capacitor marked as 4700uf?
A less than 0.1 ohm ESR cap with 1 ohm ESR?
A fib about the capacitance value?

You state that any of us can do the same test at anytime...
How is that so? You didn't tell us anything about the
brand X capacitor we are testing against... So, I guess
absent any information we have to take your word.

Absent more information, I probably won't.

-Chuck Harris

M Yachad wrote:

MachineGuy
(I’d really like to address you by your real name!)

Thanks for that info from the tin-man.
I can certainly relate to the manufacturer’s published data.
I will take this into consideration the next time I have to select caps.

To address certain points:
1. I am not at all biased against Panasonic caps. They are superb, and I use the EB in Linear audio applications all the time. They are my go-to for that specific application.
2. I also use the Panasonic TSHA and ED/EE Snap-ins as my go-to PSU filter capacitors, with Nichicon GU as my second choice.
3. So, the question arises, WHY do I NOT recommend the EB in THIS Tek PSU application?
4. It is important to understand the function of a cap in each particular place in the circuit. In any PSU application, the AC ripple BETWEEN the Bridge rectifier and the Regulators is enormous. AFTER the regulators, the AC ripple is negligible.
5. A few years ago, to quieten my curiosity, I did a test on an older amplifier using 4 new apparently identical 4700uF 25V and 50V capacitors mounted BETWEEN the Bridge and the bank of Regulators (some 78xx, 79xx, 317, 319). The Nichicon HE caps reduced the residual AC ripple to approx 1V p-p (with no discernible difference between the 25V and 50V cap). The other caps reduced the residual ripple to 2V p-p. See attached pictures. This is a test which any of you can easily do, any time.

https://groups.io/g/TekScopes/album?id=59343


6. That proved to me that the HE has a significant advantage in reducing AC ripple, over another respected brand-name cap. On the datasheets, all the numbers pretty much matched up, but in the real world of flowing voltage and current, my scope waveform showed a substantially significant advantage to the HE.
7. However, AFTER the regulators, where ripple is negligible, an EB is an excellent choice. The superior capability of the HE regarding ripple damping is of no advantage here.

On this Tek PSU, has anyone actually done any research to specify each cap’s function? From the postings here, I don’t think so. I haven’t. So, unless someone is willing to go and locate each cap on the circuit, and determine whether it is in a low-ripple part of the circuit (where an EB would be acceptable), or it is in a high-ripple part, I think that we need to globally specify HE or PW (functionally equivalent), in order to be on the safe side for ALL applications. That’s what I did, with full confidence that my choice would give me the lowest ACTUAL ripple on all circuits.

If a user installs EB in a high-ripple area BEFORE the regulators, will the machine work? Of course it will.
But will it work as well, if an HE or PW is installed? My test states not.
After all, a SMPS with loads of AC ripple in all parts of the circuit, is NOT like a linear PSU, at all.

It’s the difference in being able to tune a high-performance engine, to get the last ounce of available HP out of it.

The posters who are asking these questions are people who do NOT have any substantial electronics background, theory or practice. I think it is incumbent on us (the techs with long experience) to point them in a direction which will give them an optimal and safe solution, so that they don’t have to tear their hair out, buying parts which don’t fit, or worrying whether what they choose will last or not.

Regarding the Lifetime numbers of the data provided by MachineGuy:

A 5000Hr lifetime is provided for a (boiling) CONSTANT temperature of 105°C. If the caps in my Tek scope are reaching that temperature, then my scope is on the way to the garbage dump, very quickly, and the 5000hr lifetime is functionally irrelevant.

I have measured the temperature of my HE caps in my A2A1/A3 PSU block, and the hottest individual cap temperature which I measured was 38°C. The average temp of the caps was room temperature.
And it IS hot here in Israel – I’m not just talking about the fires from the Gazan terrorists.

https://www.eetimes.com/author.asp?section_id=183&doc_id=1279791

“For every 10 degree Centigrade decrease in operating temperature, the capacitor life is extended by a factor of two.”

So, if my HE caps are running at a constant 40°C, then their expected lifetime is 5000 x 2 to the power of 6 (=64, check my math) = 320,000 hrs = more than 36 years; scope on all the time, never being switched off.

Given that the data supplied above stated that cap’s casing would breakdown after about 15 years, then there is no apparent benefit HERE of choosing a 10000 hr cap over a 5000 hr, except for the status.

So, IMO what we should be concerned about, is WHAT does the waveform look like at all the HIGH-RIPPLE positions in this Tek SMPS PSU circuit, and then select the cap which dampens that ripple most effectively. To my experience, the Nichicon HE fits the bill most effectively.

Menahem





Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)

 

Typo - that 319 regulator should be a 337!


Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)

 

MachineGuy
(I’d really like to address you by your real name!)

Thanks for that info from the tin-man.
I can certainly relate to the manufacturer’s published data.
I will take this into consideration the next time I have to select caps.

To address certain points:
1. I am not at all biased against Panasonic caps. They are superb, and I use the EB in Linear audio applications all the time. They are my go-to for that specific application.
2. I also use the Panasonic TSHA and ED/EE Snap-ins as my go-to PSU filter capacitors, with Nichicon GU as my second choice.
3. So, the question arises, WHY do I NOT recommend the EB in THIS Tek PSU application?
4. It is important to understand the function of a cap in each particular place in the circuit. In any PSU application, the AC ripple BETWEEN the Bridge rectifier and the Regulators is enormous. AFTER the regulators, the AC ripple is negligible.
5. A few years ago, to quieten my curiosity, I did a test on an older amplifier using 4 new apparently identical 4700uF 25V and 50V capacitors mounted BETWEEN the Bridge and the bank of Regulators (some 78xx, 79xx, 317, 319). The Nichicon HE caps reduced the residual AC ripple to approx 1V p-p (with no discernible difference between the 25V and 50V cap). The other caps reduced the residual ripple to 2V p-p. See attached pictures. This is a test which any of you can easily do, any time.

https://groups.io/g/TekScopes/album?id=59343


6. That proved to me that the HE has a significant advantage in reducing AC ripple, over another respected brand-name cap. On the datasheets, all the numbers pretty much matched up, but in the real world of flowing voltage and current, my scope waveform showed a substantially significant advantage to the HE.
7. However, AFTER the regulators, where ripple is negligible, an EB is an excellent choice. The superior capability of the HE regarding ripple damping is of no advantage here.

On this Tek PSU, has anyone actually done any research to specify each cap’s function? From the postings here, I don’t think so. I haven’t. So, unless someone is willing to go and locate each cap on the circuit, and determine whether it is in a low-ripple part of the circuit (where an EB would be acceptable), or it is in a high-ripple part, I think that we need to globally specify HE or PW (functionally equivalent), in order to be on the safe side for ALL applications. That’s what I did, with full confidence that my choice would give me the lowest ACTUAL ripple on all circuits.

If a user installs EB in a high-ripple area BEFORE the regulators, will the machine work? Of course it will.
But will it work as well, if an HE or PW is installed? My test states not.
After all, a SMPS with loads of AC ripple in all parts of the circuit, is NOT like a linear PSU, at all.

It’s the difference in being able to tune a high-performance engine, to get the last ounce of available HP out of it.

The posters who are asking these questions are people who do NOT have any substantial electronics background, theory or practice. I think it is incumbent on us (the techs with long experience) to point them in a direction which will give them an optimal and safe solution, so that they don’t have to tear their hair out, buying parts which don’t fit, or worrying whether what they choose will last or not.

Regarding the Lifetime numbers of the data provided by MachineGuy:

A 5000Hr lifetime is provided for a (boiling) CONSTANT temperature of 105°C. If the caps in my Tek scope are reaching that temperature, then my scope is on the way to the garbage dump, very quickly, and the 5000hr lifetime is functionally irrelevant.

I have measured the temperature of my HE caps in my A2A1/A3 PSU block, and the hottest individual cap temperature which I measured was 38°C. The average temp of the caps was room temperature.
And it IS hot here in Israel – I’m not just talking about the fires from the Gazan terrorists.

https://www.eetimes.com/author.asp?section_id=183&doc_id=1279791

“For every 10 degree Centigrade decrease in operating temperature, the capacitor life is extended by a factor of two.”

So, if my HE caps are running at a constant 40°C, then their expected lifetime is 5000 x 2 to the power of 6 (=64, check my math) = 320,000 hrs = more than 36 years; scope on all the time, never being switched off.

Given that the data supplied above stated that cap’s casing would breakdown after about 15 years, then there is no apparent benefit HERE of choosing a 10000 hr cap over a 5000 hr, except for the status.

So, IMO what we should be concerned about, is WHAT does the waveform look like at all the HIGH-RIPPLE positions in this Tek SMPS PSU circuit, and then select the cap which dampens that ripple most effectively. To my experience, the Nichicon HE fits the bill most effectively.

Menahem


Re: Tek 2337 (looks mint) on Goodwill.

Dave Casey
 

Same form factor as the 2335 and 2336; each one has a different feature in
integrated lid. The 2336 has an LCD readout of the intensified sweep time.
My first scope was a 2336; still have it as my go-to portable.

Dave Casey

On Sat, Jun 16, 2018, 11:10 AM Artekmedia <manuals@...> wrote:

Looks like it is very clean, If I still lived in Ft worth I'd run over
and turn it on to check it out. has probes and all.

100MHz Analog Scope ( later 150MHz version I think) plus a built in DMM
More info over on Tekwiki

Godwill in the auction business ..who knew

-DC
manuals@...

On 6/16/2018 11:47 AM, David Berlind wrote:
I'm sure everyone here has seen one of these. But I haven't. Is it some
sort of hack of a digital scope? It looks mint (and cool).

https://www.shopgoodwill.com/Item/53877130

I have no affiliation with the seller.



--
Dave
Manuals@...
www.ArtekManuals.com