Re: Hi,I'm new to the group.
Best guess is one of the glass support rods in the crt fractured and
dropped a few tiny shards of glass inside the tube. These would
damage the expansion mesh creating the "confetti". It's a guess,
but one I've seen more than once. 465 tubes are not hard to come by.
-ls-
"emilypetersen1991" <s-petersen@...> wrote:
toggle quoted message
Show quoted text
I have been searching posts,and with google and I can't seem tofind
the answer,My 465 scope seems to be working properly except for some
sparkles,artifactsn,and reflections on the screen,intensity and focus
seem to work at it should.It appears to throw confetti on the screen.
I was wondering where would be a good place to look?is it an amplifier
problem,or a crt voltage problem?
Thanks,
Scott
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Yahoo! Groups Links
|
Re: Hi,I'm new to the group.
Hi Scott,
I have never seen that one but ripple on the power supply can do weird things. Check for ripple.
Jerry Massengale
toggle quoted message
Show quoted text
-----Original Message-----
From: emilypetersen1991
To: TekScopes
Sent: Wed, Oct 10, 2012 8:54 pm
Subject: [TekScopes] Hi,I'm new to the group.
?
I have been searching posts,and with google and I can't seem tofind the answer,My 465 scope seems to be working properly except for some sparkles,artifactsn,and reflections on the screen,intensity and focus seem to work at it should.It appears to throw confetti on the screen.
I was wondering where would be a good place to look?is it an amplifier problem,or a crt voltage problem?
Thanks,
Scott
|
Re: Jumpy trigger control on Tektronics 475
You mentioned you had it open and looked at the power supplies. What did
you see? It looks like something has about a one Hz period. Probe through the
trigger board, the vertical amp board, etc. looking for that 1 Hz signal. I
still think it is a power supply issue as my first guess. Do you have another
scope that you can use to look around with? Take a look on one or both vertical
deflection plates and work back towards the vertical channel switch.
?
?
Tom
toggle quoted message
Show quoted text
----- Original Message -----
Sent: Wednesday, October 10, 2012 9:06
PM
Subject: [TekScopes] Re: Jumpy trigger
control on Tektronics 475
?
Here's a new video that could help.
or
---
In TekScopes@...,
"Max Mazza" wrote:
>
>
> Do the
following:
> use the 1KHz square wave signal from the calibrator in
either channels. If the trigger starts decently but with the sinusoidal wave
at the same frequency not, one of tunnel diodes in the trigger circuit is
gone.
> Check with the same signal first in channel A, then in channel
B. There are separate trigger generators for chan A and B.
> It's
difficult that both channel have tunnel diodes burned.
> Don't try to
check TDs with a standard VOM. A curve tracer is required.
> Check for
presence of very abrupt change of about 400 mV across the tunnel diode (CR786)
when trigger starts.
>
> Max
>
|
I have been searching posts,and with google and I can't seem tofind the answer,My 465 scope seems to be working properly except for some sparkles,artifactsn,and reflections on the screen,intensity and focus seem to work at it should.It appears to throw confetti on the screen.
I was wondering where would be a good place to look?is it an amplifier problem,or a crt voltage problem?
Thanks,
Scott
|
Re: Jumpy trigger control on Tektronics 475
Came through 4 times Sent on the TELUS Mobility network with BlackBerry
From: "dawtesla2" <dawtesla2@...>
Sender: TekScopes@...
Date: Thu, 11 Oct 2012 01:07:46 -0000 To: <TekScopes@...> ReplyTo: TekScopes@...
Subject: [TekScopes] Re: Jumpy trigger control on Tektronics 475
?
Here's a new video that could help.
or
--- In TekScopes@..., David <davidwhess@...> wrote:
>
> I noticed that and wonder if the relatively low video camera frame
> rate is disguising what is really going on.
>
> On Mon, 08 Oct 2012 22:08:41 -0400, "Tom Miller"
> <tmiller11147@...> wrote:
>
> >I would open it up and check the power supplies for voltage and ripple per the manual. It seems to be jumping sync at a periodic rate.
>
|
Re: Jumpy trigger control on Tektronics 475
Here's a new video that could help.
or
toggle quoted message
Show quoted text
--- In TekScopes@..., David <davidwhess@...> wrote:
I noticed that and wonder if the relatively low video camera frame
rate is disguising what is really going on.
On Mon, 08 Oct 2012 22:08:41 -0400, "Tom Miller"
<tmiller11147@...> wrote:
I would open it up and check the power supplies for voltage and ripple per the manual. It seems to be jumping sync at a periodic rate.
|
Re: Jumpy trigger control on Tektronics 475
Here's a new video that could help.
or
toggle quoted message
Show quoted text
--- In TekScopes@..., "jtjewell83" <jtjewell83@...> wrote:
And we need to see the beginning of the sweep (i.e., the trigger point). Right now, I'm thinking it's off screen. Move the trace horizontally to the right so the sweeps starts about a half a division in from the left side, and post another video if you can.
Regards,
Jimmy
--- In TekScopes@..., "jtjewell83" <jtjewell83@> wrote:
Is the scope's 10X Magnifier on? I cannot tell from the video. That would make the gitter of the sound card look 10 times worse than it really is.
On Tue, 09 Oct 2012 01:43:05 -0000, "dawtesla2" <dawtesla2@>
wrote:
I got this oscilloscope a few days ago. I put up a 1 Khz sine wave (from PC sign wave gen.) to test it. But my sine wave won't stabilize. When stopped, it dances around a bit with a slight pulse. All this makes it difficult to make a proper frequency reading. It's a great scope except for that. Does anyone have any idea what the problem is?
Here's a video link
Thanks, Derek
dawtesla2@
|
Re: Jumpy trigger control on Tektronics 475
Here's a new video that could help.
or
toggle quoted message
Show quoted text
--- In TekScopes@..., "Tom Jobe" <tomjobe@...> wrote:
I may have missed it... but did you check all of the low voltages, and the ripple on each of them?
tom jobe...
----- Original Message -----
From: jtjewell83
To: TekScopes@...
Sent: Tuesday, October 09, 2012 6:11 PM
Subject: [TekScopes] Re: Jumpy trigger control on Tektronics 475
And we need to see the beginning of the sweep (i.e., the trigger point). Right now, I'm thinking it's off screen. Move the trace horizontally to the right so the sweeps starts about a half a division in from the left side, and post another video if you can.
Regards,
Jimmy
--- In TekScopes@..., "jtjewell83" <jtjewell83@> wrote:
>
> Is the scope's 10X Magnifier on? I cannot tell from the video. That would make the gitter of the sound card look 10 times worse than it really is.
> >
> > On Tue, 09 Oct 2012 01:43:05 -0000, "dawtesla2" <dawtesla2@>
> > wrote:
> >
> > >I got this oscilloscope a few days ago. I put up a 1 Khz sine wave (from PC sign wave gen.) to test it. But my sine wave won't stabilize. When stopped, it dances around a bit with a slight pulse. All this makes it difficult to make a proper frequency reading. It's a great scope except for that. Does anyone have any idea what the problem is?
> > >
> > >Here's a video link
> > >
> > >
> > >
> > >
> > >Thanks, Derek
> > >
> > >dawtesla2@
> >
>
|
Re: Jumpy trigger control on Tektronics 475
Here's a new video that could help.
or
toggle quoted message
Show quoted text
--- In TekScopes@..., "Max Mazza" <mmazza@...> wrote:
Do the following:
use the 1KHz square wave signal from the calibrator in either channels. If the trigger starts decently but with the sinusoidal wave at the same frequency not, one of tunnel diodes in the trigger circuit is gone.
Check with the same signal first in channel A, then in channel B. There are separate trigger generators for chan A and B.
It's difficult that both channel have tunnel diodes burned.
Don't try to check TDs with a standard VOM. A curve tracer is required.
Check for presence of very abrupt change of about 400 mV across the tunnel diode (CR786) when trigger starts.
Max
|
Re: Problem with a Tek SC-504 Scope (part of Tm 500 series)
On 10/10/2012 07:10 PM, Ray wrote: Don't know if I should also pose
the question on TekScopes2@... <mailto:TekScopes2%40yahoogroups.com>. I don't yet know the
distinctives of the two lists. 2 allows more OT. Go ahead and post there also since the two are relatively separate. Don't have a SC504. Is your manual same as this one? Else ask Dave, (artekmedia) for a pdf manual for sale. Check PS volts and suspect bad caps is the starting point. Then tell details and get regaled with decisive tests to perform, cutting opinions, and know how.
|
Re: Bright dots at start of the trace on a 547
Sorry, David, I was looking at the A Sweep Generator when I wrote that.
I was referring to R371 and D372, collectively across the C-B junction of Q373.
Dave Wise
toggle quoted message
Show quoted text
-----Original Message-----
From: TekScopes@...
[mailto:TekScopes@...] On Behalf Of David
Sent: Wednesday, October 10, 2012 5:09 PM
To: TekScopes@...
Subject: Re: [TekScopes] Re: Bright dots at start of the trace on a 547
I thought that resistor was for snubbing any oscillation when a low
impedance is present at both the base and emitter since the 2N2207 is
not slow. 47 ohms in series with a base is not usually significant in
other respects for a signal transistor.
I do not have either of the high voltage transistors I suggested
immediately handy but if Ren¨¦ has problems, I can pick some up and
break out my 547 to run some tests and make some measurements. I
gather from his posts that the unblanking is happening quickly enough.
In his place with a 2N2207 that died of old age, I would probably go
through and change all of them while checking for proper operation.
|
Re: Make a backup of your TDS5xx/6xx/7xx memories
I'm amazed at the life of these Dallas parts (16 years or more?). I designed in a number of Dallas parts in the 1990 timeframe. They started to lose data retention about 7 to 8 years later.
The difference has to be in the environment. We were building telecom test equipment, used indoors and out, and frequently left to die for long periods of time.
The Tek scopes on the other hand, may have frequently been left on in an indoor environment. I'm convinced that internal leakage in the switch / logic probably keeps the batteries "topped off" (I know, they are lithium). Others have voiced this theory in the past.
So, if you want good batteries, buy a scope with a dim CRT ;)
Den
toggle quoted message
Show quoted text
--- In TekScopes@..., "nukescope" <vtp@...> wrote:
Interesting, it certainly is possible if the newer scopes have a sectored 5V flash. These scopes are old enough not to have a read-while-write type of flash so there is either another flash for the cal data or during calibration the code runs on SRAM. My old TDS544A definitely had a 12V erase/pgm bulk block flashes and stores calibration information in NVRAM. IIRC, the NVRAM was DS1650 for which TI BQ4015 should work also but be a lot cheaper than the Dallas part.
Regarding the NVRAM, I had trouble reading it in a programmer so that was my primary reason for digging up the GPIB memory read commands and protocol. Make good use of the code, I spent a lot of time decompiling the kernel ROM in order to find out everything necessary.
The flashes in my TDS544A were AM28F010 which tend to keep their contents very well, actually so well that they are difficult to erase after 20 years of use (in another application).
But still, backing all the stuff up would be good. Maybe sometime someone (or me) even writes a secondary bootloader so we can rewrite the flashes.
-NS
PS. I like the sellers associated risk list, particularly item #3.
--- In TekScopes@..., "denyhstk" <denyhstk@> wrote:
You all may be interested to know that an Ebay seller of "Tektronix battery modules" has a list of models which (according to Tek, he says) do not store cal constants in either the NVRAM or the RTC/NVRAM, hence no danger of losing cal with chip replacements. Interesting stuff I have not had time to verify.
Den
|
Re: Tantalums cant take surges. (Subject was Aluminium versus Tantalum Electrolytics)
Not in a real company, Craig.That is why there are company part
numbers. When a new number is established, approved vendors are listed
and if that list needs to be updated, that is done through Engineering
Change Order. I used to work for a memory company and there was always
pressure to put Winnbond (a Taiwanese packaging house) on approved
list. Purchasing would bring salesman to throw a pitch for Winbond and
usual argument was that memory for Siemens was made on the same
production line; somehow those salesman could never answer question
what happens to the lot which Siemens refuses. Even in a rinky dink
memory company that was end of argument for bringing in cheap memory.
Miroslav Pokorni
On 10/10/2012 2:24 AM, Craig Sawyers wrote:
toggle quoted message
Show quoted text
?
> I don't know about Tek. products, but my experience in a
similar position
is
> that the engineering staff specify suitable capacitors, but
purchasing
seek the
> cheapest available, which may have an inferior service life, or are
"Chinese"
> copies.
>
> Geoff
The Tek tant short-circuit death syndrome is usually for gear built in
the
70's and early 80's, so long before China became an economic superpower
and
started spitting out electronic components.
Craig
|
Problem with a Tek SC-504 Scope (part of Tm 500 series)
I have a very nice SC-504 80 MHz scope mounted in the right hand 2 slots of a TM-504 . It has worked well for me for years.
However, I recently turned it on and the scope trace will not resolve to a fine line vertically as it should. It seems to be internally modulated by about 3/4 of a division of vertical noise across the horizontal trace.
The focus or astig controls have no effect on the noise. It does not appear to be any sort of an external RFI, etc., as inserting the internal filters or grounding the input, doesn't change the displayed noise.
The noisy trace problem persists on both channels even if connected to the cal test point. In the cal mode, the changes in vertical sensitivity is working correctly, but the top horizontal portion of the square wave has the same erroneous noise at any vertical sensitivity. The noise stays the same displayed amount in all input settings.
The horizontal triggers OK. Rotating the seconds/div knob works as it should, but does not give any clue as to any time interval or frequency, of the source of the noise. It appears to be random noise.
Before I dig into it, does anyone have any experienced suggestions as to how to track the problem down and repair it? As a guess, I would think it's a capacitor break down somewhere in the vertical output amplifier circuit, because it's in both vertical channels.
I have the large extender for TM-500 modules and a photocopy of the manual (the drawing is pretty small and a bit hard to read). I do not have a small extender board to match the small (other) connector on the back of the scope. It may or may not be needed for troubleshooting this. I have a 465 to troubleshoot with.
This is my first posting to this list. Don't know if I should also pose the question on TekScopes2@.... I don't yet know the distinctives of the two lists.
Your attention is appreciated.
Ray, W4BYG
|
Re: Bright dots at start of the trace on a 547
I thought that resistor was for snubbing any oscillation when a low impedance is present at both the base and emitter since the 2N2207 is not slow. 47 ohms in series with a base is not usually significant in other respects for a signal transistor. I do not have either of the high voltage transistors I suggested immediately handy but if Ren¨¦ has problems, I can pick some up and break out my 547 to run some tests and make some measurements. I gather from his posts that the unblanking is happening quickly enough. In his place with a 2N2207 that died of old age, I would probably go through and change all of them while checking for proper operation. I do like sockets for transistors. My favorite trick has been to use flush mounted collet socket pins although mounting them flush takes more time. They work great for TO-92 as well as signal diode, resistor, and capacitor leads: I did not have to flush mount those but did just for the heck of it. The 723 regulators ran hot enough to cause the original plastic sockets to become loose. On Wed, 10 Oct 2012 13:57:38 -0700, David Wise <david_wise@...> wrote: You have more data than I. But consider the application. It has to
generate a 70V step, as fast as possible, but the most important part
is the last little bit, otherwise the trace will be dim at the start of
the fastest sweeps. Note that they put in a resistor that isolates the
anti-saturation clamp diode from the base - that could only be to
minimize C-B capacitance outside the transistor. The transistor is
driving a high-impedance load; I don't see current-handling ability
figuring very large. But the ultimate test is to pop in a candidate
and give it a spin. Yay sockets!
Dave Wise
-----Original Message-----
From: TekScopes@...
[mailto:TekScopes@...] On Behalf Of David
Sent: Wednesday, October 10, 2012 1:13 PM
To: TekScopes@...
Subject: Re: [TekScopes] Re: Bright dots at start of the trace on a 547
I found a bunch of different Cob values (up to 12pF!?) for the 2N2207
with unclear test conditions so I am not convinced 2.5pF Cob is a
magic value. Low Ic small junction transistors are not as common as
they used to be and I suspect the better gain characteristics of an Ic
200mA transistor might make up for the higher output capacitance of
the larger junction in this case.
The 547 I recently acquired works fine as far as I can tell except for
dirty switches and potentiometers but I have started taking notes on
it.
On Wed, 10 Oct 2012 09:39:47 -0700, David Wise
<david_wise@...> wrote:
Good catch, George. I only searched for "-300V" to "-70V", forgetting that the staff is sloppy about voltage polarities.
Searching for positive breakdown voltages yields many many hits.
And good point, David Hess, but the 2N2207's 2.5pF Cob is specified at 6V.
Dave Wise
|
Re: Bright dots at start of the trace on a 547
I agree. Looks like the 2SA1145 is the best fit so far. Good find! - George
From: David Wise To: "TekScopes@..." <TekScopes@...> Sent: Wednesday, October 10, 2012 10:15 AM Subject: RE: [TekScopes] Re: Bright dots at start of the trace on a 547
?
In my opinion, the 2SA1145 is your best bet from Mouser.?
It?specifically lists low Cob as a feature, and it's 2.5pF typical?at
10V, and fT=200MHz.? KSA992 is runner-up with 2pF typical?at 30V and
fT=100MHz.? Both are cheap and plentiful.? Get them while they still
are.
?
Dave Wise
Here is another choice, ?
Vcbo =-120V, Ccbo ~ 2-3 pF, Ft ~ 100MHz. (Mouser 7 cents each!)
-?George
From: David
To: TekScopes@...
Sent: Tuesday, October 9,
2012 7:23 PM
Subject: Re:
[TekScopes] Re: Bright dots at start of the trace on a
547
?
Both of the ones I listed are available from Mouser. The 2N5401
and
2N6520 both have a Cob of 6.0pF maximum at 10 and 20
volts
respectively but Cobo falls with Vcb so at 60 volts it will be
significantly lower. From the graph of Cob versus
voltage, it looks
like they both could easily be 2.5pF at 60
volts.
|
Re: Jumpy trigger control on Tektronics 475
Do the following:
use the 1KHz square wave signal from the calibrator in either channels. If the trigger starts decently but with the sinusoidal wave at the same frequency not, one of tunnel diodes in the trigger circuit is gone.
Check with the same signal first in channel A, then in channel B. There are separate trigger generators for chan A and B.
It's difficult that both channel have tunnel diodes burned.
Don't try to check TDs with a standard VOM. A curve tracer is required.
Check for presence of very abrupt change of about 400 mV across the tunnel diode (CR786) when trigger starts.
Max
|
Tek 2465/7904/7904A/7104 lot in Livermore, CA
Looks like it could be a great deal if you can comply with the amazingly
strict pickup rules...
|
Re: Tantalums cant take surges. (Subject was Aluminiumversus Tantalum Electrolytics)
On Wed, 10 Oct 2012, Stefan Trethan wrote: That explains that then, they measure a few percent lower at 1kHz.
It's unfair to accuse a manufacturer of penny pinching if you don't
meet their specified testing conditions (usually 120Hz). It gives same readings at 120Hz for capacitance if it can measure it (>100uF). For 10-100uF range the most accurate results are at 400 Hz. 1KHz is a convenient test frequency giving wide range with relatively good accuracy. It might give up to 3% error at the boundary F/C ranges where it barely measures capacitance (too high F for big C or too low F for small C) but it is never 20%. If you want to get most of it, sure you have to choose a proper frequency. But for 3 digits 1KHz is good for measuring almost anything. Also capacitance itself does not vary that much with frequency. ESR varies orders of magnitude more. Saving a few percent of foil is probably not worth the hassle of
having to meet tighter tolerances caused by leaning towards the lower
end. More likely they used to go above nominal with the old caps It does. And almost all big manufacturers has shown tendency towards saving a penny risking a buck. It doesn't make sense in a long run but who thinks farther than a quarter? Does it make sense to lay off the best (those with highest salaries) to make a nice profit figure? Can you name a company that did not fell to a temptation of using cheaper chinese capacitors in high frequency high ripple applications and thus avoided massive failures because of blown capacitors? Remember, profit of saving a penny is now and this is when the higher management gets their bonuses for making profit. Failures are later and they are not punished for those. And no one of them is going to work for a particular company forever -- they will go to a different one for making that one more profitable too once they are done with their current one (i.e. once it is destroyed by making it more profitable.) because tolerances were asymmetrical back then. Nope. Old ones usually fall in the middle of their tolerance range. If it was +80/-20% the majority of 1,000uF capacitors had 1,300uF capacitance. And even +/-20% ones rarely went under 100%. It was also understood that it is better to overshoot than undershoot as far as capacitance goes. I'll check out the test data to see if the distribution is offset when
I get the chance.
ST
On Wed, Oct 10, 2012 at 10:23 PM, Sergey Kubushyn <ksi@...> wrote:
On Wed, 10 Oct 2012, Stefan Trethan wrote:
At 1kHz that's just about spot on specification for the taiyo yuden part.
The impedance at this frequency will be what, 15, 16 Ohms? Not sure
why you'd worry.... I do not worry. It is not about using it at a particular frequency.
At what frequency did you measure capacitance? Just so that we don't
waste both our time again. 1KHz. And I don't have time to waste too.
ST
On Wed, Oct 10, 2012 at 9:22 PM, Sergey Kubushyn <ksi@...> wrote:
On Wed, 10 Oct 2012, Stefan Trethan wrote:
On Wed, Oct 10, 2012 at 6:59 PM, Sergey Kubushyn <ksi@...> wrote:
There were bunch of 10uF 25V ones
that I was going to replace with 1206 SMD X5R ceramics but to my surprise
those dipped tantalums had something like 300mOhm ESR that is actually
BETTER than ceramics (Taiyo Yuden 10uF 25V 1206 X5R ceramics of recent
manufacturing that I had several reels in my parts bins have something like
350mOhms ESR.) At what frequency? The ceramic should have well below 10mR at 100kHz
according to specification, and I just don't see how it could be
otherwise considering the construction. 1KHz. This is actual measured values. As for the specifications majority of
manufacturers don't give any values on ESR in their datasheets. It is
"common knowledge" they are "very low ESR" but reality check shows totally
different picture. If you look at e.g. NIC NMC High CV Series datasheet (one
of the few who give data on ESR) you'll see a ESR vs Frequency chart. It
clearly shows that MLCCs are better when going into MHz range but they are
nothing to write home about at lower frequencies.
Regarding the generally low capacitance value on electrolytics, I have
extensive test data for Rubycon and Nippon Chemicon at work and will
check if they are consistently at the lower capacitance tolerance. Once again, I do NOT have very extensive data, just several hundred
capacitors. It might be not a representative sample but I could not find a
SINGLE one of recent manufacturing that was 100% of stated capacity or
higher. On the old ones I could not find more than couple of pieces that
were under 100%.
ST
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* Las Vegas NV, USA < > Miracles require 24-hour notice. *
*
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*
* KSI@home KOI8 Net < > The impossible we do immediately. *
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
*
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|
I have no affiliation with the seller.
-Kurt
|
David Hess
Sergey Kubushyn