Date   
Re: TDS3000B calibration

 

Bump?

David

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David C.
Partridge
Sent: 16 March 2020 11:28
To: TekScopes
Subject: [TekScopes] TDS3000B calibration

Why am I thinking of running a calibration? The trigger point is not
indicated correctly for faster signals - if I feed it a "fast rise" pulse
from the CG551AP, the trigger point is shown at about the 2% point of the
step signal even though the trigger is set to 50%. There a few other
things that weren't quite "on the mark" that I noticed as I ran through the
Training Manual. I'm hoping a calibration will sort all this out.

Timebase though appears "spot on" which is good. Is it possible to skip
steps in the calibration - no point re-doing the timebase calibration if it
is right ...

Before I attempt to run the full calibration procedure on my TDS3000B, I
want to be sure that I can generate all the necessary signals, and that the
nature of the signals is clearly called out in the calibration process once
it starts running.

I have SG503, SG504, CG551AP, and a CG5001 (with pulse heads for the last
two).

Cheers
David

Re: Type 184 Power Indicator Light

david
 

Dialight makes a led bulb 507-4859-3332-500, Vf=20V , mA=20, that fits that holder on the 184

Re: 184 Time mark Gen. Needs filter caps

david
 

I have been hesitant to touch the adjustments , but wondering if the pot on 50mS circuit is making intermittent contact. The capacitor must be discharging at random levels to cause the instability that I see in time mark display. How is it possible for that cap to discharge at a different voltage each time? It's not just the interval that is wrong, there are random short interval's in the pulse train. Also there is overshoot in the negative direction on pulses. Diode D312 should clamp output pulse at ground, is this diode is bad and allowing negative overshoot? I will post picture of bad pulse train in folder "184 Time mark Gen. Needs filter caps"
David

Re: Beware of cheap "crock-a-gator" clips

Brian Symons
 

Does anyone know of a reasonably priced source of the double insulated silicon wire that has a different colour inner core so that you can see if the wire is worn or damaged?

I saw that silicon wire was fairly reasonably priced but haven't seen this type of wire.

I just thought if I was going to the effort of making up test leads then I might as well make them as good as possible.

Regards
Brian.

Re: 184 Time mark Gen. Needs filter caps

Tom Gardner
 

I presume you have tried tweaking all the trimmers, as per the manual.

These are analogue dividers. Their operation is that the input pulse deposits a glug of charge onto a capacitor, thus raising the voltage across the capacitor. When sufficient pulses have deposited sufficient glugs and the voltage has risen above a threshold, the output transistor conducts providing a pulse for the next stage, and the capacitor is discharges. Rinse and repeat.

The amount the voltage rises with a pulse depends on an RC time constant. Hence for reliable operation you need a good input pulse and the right RC value.

So, apart from the capacitor you mention, you might need to consider that trimmers contact can vary, and that (carbon) composition resistors value can rise(?) over time.

On 20/03/20 00:59, david via Groups.Io wrote:
Checked ripple carefully with 1x probe and short ground spring. Ripple is 24mV on -30V , 30mV on +12V , and is 62mV on 125V. worst one is -30V. The other two not that far from specs. Don't think that power supply is the problem now. The new filter cap's fixed it. Markers are good through 10mS, but the 50mS divide by 5 circuit is not working correctly. Has a good 10mS signal at diode D300 input to 50mS to 5S section. Output from first divider is no good, not stable interval, it varies, this is why all the 50ms to 5S steps are bad. I'm trying to understand how this circuit functions, I suspect its probably a bad capacitor. Maybe C303
David

Re: Tek scopes on the job at NASA

tgerbic
 

Albert,
I bought two 60s era 561RAs a few decades ago used at NASA Ames Research Center in Mountain View California. Some like them appear in the video as they were common at NASA.

It would be cool to find one of mine in an old NASA/Ames photo or video.

Regards

Tek scopes on the job at NASA

Albert LaFrance
 

And there are a lot of them in this wonderful 1960s film about NASA's
communications hub, the Goddard Space Flight Center in Greenbelt, MD:

< <https://www.youtube.com/watch?v=FasWGbEGx2w>
https://www.youtube.com/watch?v=FasWGbEGx2w>



Albert

Re: Beware of cheap "crock-a-gator" clips

Michael A. Terrell
 

You can buy 100 red or black for under &10.00 on eBay







On Wed, Mar 18, 2020, 10:42 PM Richard Knoppow <dickburk@...>
wrote:

I've also had problems with ready made clip leads. The
cheaper ones have crimped leads which will pull out easily. The
clips are cheap enough to buy in quantity. You can get flexible
meter lead wire for the bodies of the leads. I don't know where
you get the insulating boots but probably you can buy clips with
them.

On 3/18/2020 6:55 PM, n4buq wrote:
Thank you for posting this. I decided to test my set and the very first
one was very intermittent. I removed the plastic boots and, sure enough,
one end was not soldered to the clip. I plan to check all of them.

Fortunatly, the wire in mine appear to be a bit better than you describe
- maybe 22-ga stranded so resoldering is all I plan to do.

I wonder how many times things didn't work right and I never thought to
check for that as being the problem.

Thanks,
Barry - N4BUQ
--
Richard Knoppow
dickburk@...
WB6KBL




Re: 184 Time mark Gen. Needs filter caps

david
 

Checked ripple carefully with 1x probe and short ground spring. Ripple is 24mV on -30V , 30mV on +12V , and is 62mV on 125V. worst one is -30V. The other two not that far from specs. Don't think that power supply is the problem now. The new filter cap's fixed it. Markers are good through 10mS, but the 50mS divide by 5 circuit is not working correctly. Has a good 10mS signal at diode D300 input to 50mS to 5S section. Output from first divider is no good, not stable interval, it varies, this is why all the 50ms to 5S steps are bad. I'm trying to understand how this circuit functions, I suspect its probably a bad capacitor. Maybe C303
David

Re: Grey, blue or clear? filter colors

Harvey White
 

Just as a further bit of trivia.

Kodak used to (and perhaps still does) sell films in large rolls.

If you had a film loader (and I did), you could load your own 35mm cassettes with bulk film.

Very much cheaper.

Fine grain positive release film had an ASA (ISO now) that I estimated at about 6.

The grain, which you may not know, is the size of the particles, think size of pixel on LCD display, not resolution, which is related to (film) screen size, is larger for the higher sensitivity films.  It worked out to higher the sensitivity, the more grain (and you could change that with development, too), and lower sensitivity = less grain = more resolution.

If you're making contact prints, sandwitching negative film to the fine grain (etc) film, you don't care how long the exposure takes.  This was made as a way to make black and white slides from a black and white negative.

Naturally, I tried to take pictures with it.

ASA (ISO) of 6.

If this were an IQ, a house plant would be smarter.

VERY insensitive, but under sunlight conditions, capable of taking a VERY detailed 35 mm picture as long as it wasn't moving... too fast... maybe at all.....

Develop it in Dektol (a Kodak product) or maybe Microdol (don't remember) and you get B&W slides rather easily .

Been playing with photography (certainly the old stuff, and the newer stuff) for a long while.

Ya gotta learn somethin' I guess.....

Harvey

On 3/19/2020 10:07 AM, Tony Fleming wrote:
Harvey you are the best! I'm amazed the amount of knowledge you have in so
many fields!
I would love you as my neighbor!!!
Thanks again for helping us Harvey!

On Wed, Mar 18, 2020 at 8:45 PM Harvey White <madyn@...> wrote:

IIRC, the blue (P11, I think) was rich in blue and ultraviolet.
Orthochromatic films, at that time (and still) are blue sensitive and
not red sensitive. Panchromatic films were sensitive to blue, green,
yellow, and red. A portrait taken with orthochromatic film would not
look normal because the red component would not be picked up. For
accurate gray scales you needed Panchromatic film.

Kodak fine grain positive release film was an ortho, blue sensitive film
that was used for making B&W transparencies of negatives. Kodalith was
an orthochromatic film that could be developed to an intense black and
was used for PCB master negatives.

Blue phosphors were used because the film they recorded on was very
sensitive, (high ASA rating, and it was ASA then, not ISO) and could be
developed under red light (which the film couldn't see). Panchromatic
film had to be developed in total darkness, or at the best, under a very
faint green light. The film was still sensitive to green light, but the
human eye is most sensitive to that, so that's the right color for the
dimmest possible light.

Most black and white films were panchromatic, except for some special
purpose films mentioned above.

The P1 phosphor was green, but not necessarily efficient and could burn
in. Once developed, the P31 phosphor was highly efficient and had good
resistance to burnin. Hence, lots of scope tubes. P12 was orange,
there was an odd (P10?) phosphor that darkened with an electron beam and
had to be erased with heat, it was somewhat of a one shot.) P4 was the
standard white phosphor, and P22 was the tricolor dot phosphor. P7 was
an odd one, a two layer phosphor with a long persistence phosphor
closest to the screen (yellow), and a blue/UV phosphor that excited the
yellow phosphor. It gave a blue trace with a yellow fadeaway, and was
used for radar.

Harvey


On 3/18/2020 3:36 PM, Clark Foley wrote:
As I recall after some 40 years or so, the 7603 shipped with the grey
filter/implosion shield 337-1700-00 installed and the other two filters
came along for the ride as standard accessories. As these served as
implosion shields, one of them should always be installed. The was another
shield as part of the EMI gasket option that had a conductive surface. I
don't recall if that one had a metal mesh or not. We referred to the grey
as neutral density and it gave the best overall viewing contrast. We
recommended the clear for maximum writing rate. I don't remember if there
was any technical advantage for the blue. Check the 7603 manual and you
will find standard accessories, the blue and clear filters along with the
calibrator adapter cable, listed near the end of the book.



Re: help tek 475 power supply

Roberto
 

hi Roger thanks, info I have resumed the repair in these days after a pause, however measuring the transistor outside the pcb would seem good at least that it is not defective and an attempt to replace it
Roberto

Re: Grey, blue or clear? filter colors

Tony Fleming
 

Harvey you are the best! I'm amazed the amount of knowledge you have in so
many fields!
I would love you as my neighbor!!!
Thanks again for helping us Harvey!

On Wed, Mar 18, 2020 at 8:45 PM Harvey White <madyn@...> wrote:

IIRC, the blue (P11, I think) was rich in blue and ultraviolet.
Orthochromatic films, at that time (and still) are blue sensitive and
not red sensitive. Panchromatic films were sensitive to blue, green,
yellow, and red. A portrait taken with orthochromatic film would not
look normal because the red component would not be picked up. For
accurate gray scales you needed Panchromatic film.

Kodak fine grain positive release film was an ortho, blue sensitive film
that was used for making B&W transparencies of negatives. Kodalith was
an orthochromatic film that could be developed to an intense black and
was used for PCB master negatives.

Blue phosphors were used because the film they recorded on was very
sensitive, (high ASA rating, and it was ASA then, not ISO) and could be
developed under red light (which the film couldn't see). Panchromatic
film had to be developed in total darkness, or at the best, under a very
faint green light. The film was still sensitive to green light, but the
human eye is most sensitive to that, so that's the right color for the
dimmest possible light.

Most black and white films were panchromatic, except for some special
purpose films mentioned above.

The P1 phosphor was green, but not necessarily efficient and could burn
in. Once developed, the P31 phosphor was highly efficient and had good
resistance to burnin. Hence, lots of scope tubes. P12 was orange,
there was an odd (P10?) phosphor that darkened with an electron beam and
had to be erased with heat, it was somewhat of a one shot.) P4 was the
standard white phosphor, and P22 was the tricolor dot phosphor. P7 was
an odd one, a two layer phosphor with a long persistence phosphor
closest to the screen (yellow), and a blue/UV phosphor that excited the
yellow phosphor. It gave a blue trace with a yellow fadeaway, and was
used for radar.

Harvey


On 3/18/2020 3:36 PM, Clark Foley wrote:
As I recall after some 40 years or so, the 7603 shipped with the grey
filter/implosion shield 337-1700-00 installed and the other two filters
came along for the ride as standard accessories. As these served as
implosion shields, one of them should always be installed. The was another
shield as part of the EMI gasket option that had a conductive surface. I
don't recall if that one had a metal mesh or not. We referred to the grey
as neutral density and it gave the best overall viewing contrast. We
recommended the clear for maximum writing rate. I don't remember if there
was any technical advantage for the blue. Check the 7603 manual and you
will find standard accessories, the blue and clear filters along with the
calibrator adapter cable, listed near the end of the book.





Re: Beware of cheap "crock-a-gator" clips

Harold Foster
 

All:

These are the ones I use and I am very happy with them:

https://www.mouser.com/Mueller-Electric/Test-Measurement/Test-Equipment-Accessories/Test-Clips/_/N-7uqds?P=1z0zl4dZ1yyx2rqZ1z0yxl5
https://www.mouser.com/Mueller-Electric/Test-Measurement/Test-Equipment-Accessories/Test-Clips/_/N-7uqds?P=1z0zl4dZ1yyx2rqZ1z0z0lw

Those links should work, but if not:

Mouser, Test Equipment Accessories, Mueller Electric, Test Clips, Alligator Clips (Miniteur & Insulators)

Hal

Re: help tek 475 power supply

Roger Evans
 

If you look at this thread;

https://groups.io/g/TekScopes/topic/7642352

you will find possible replacements but the ordering of the pins is different so you will need a little ingenuity in fitting it. Basically you cut some of the pins short so they don't connect to the existing PCB pads and then solder wire with a sufficient current capability between the short pins and the PCB pads.

Regards,

Roger

Wanted: Two probe power sockets from 475/485/Various 7000 series

 

Hi folks

I'm making a probe power supply for the P6201/P6202A probes. I've got the
PSU and case part sorted out. All I need now is a couple of the probe
power sockets

Before I dash out and purchase new Lemo ones, does anyone have a spares mule
'scope they could spare a couple of these from?

Thanks
David

Re: help tek 475 power supply

Roberto
 

Hi all SJE924 NPN transistors with which I can replace it?
Thank
Roberto

Re: 492AP Memory Battery

Doug Wilson <calmissile@...>
 

Thanks, I put two on order tonight.

Re: Tek 5441 Scope

rbassham@...
 

lists...Thanks for that explanation, I'd stared at that circuit for some time. I've always been a user of test equipment in two way radio and broadcast mainly, since retired. About a year ago I fell heir to about 6 pickup truck loads of Tek equipment from a friend that passed and this is a whole new experience.

Re: 492AP Memory Battery

Sergey Kubushyn
 

On Wed, 18 Mar 2020, Doug Wilson wrote:

Has someone investigated the replacement of the memory backup battery
located on the memory board? Mine measures 2.8V and the schematic lists it
as a 3V battery. What are the consequences to the operation of the
analyzer when the battery drops too low?

The battery has a sticker on it that identifies it as Catalyst Research
Corp 2736. An internet search does not list any for sale. Is there a
direct replacement someone has found or is it necessary to make a kludge
from some other replacement?
Panasonic CR-2450/G1AN (DigiKey P661-ND) works fine. You'll have to bend the
pins a bit but no biggie. There are 5,324 in stock as of right now.

It is what I use for 494AP instruments.

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Re: Grey, blue or clear? filter colors

Chuck Harris
 

Graticule lights are purely for photography.
The black graticule lines against an unlit screen
is higher contrast, and what I use most of the time.

Tek should have used a green filter, but they chose
market branding over function.

-Chuck Harris

Edward Prest wrote:

I took some pictures of the filters in front of the 466 scope and posted them here (Tek 466 P2 phosphor ...). This is kitchen table stuff but in daylight and fairly bright. The tube phosphor itself is a very light cream color so it does not help the contrast. If chemists could have made a black phosphor that glowed...

The images are all shot at the same exposure but the truth is they are a little less contrast-y that the naked eye. Here they are detailed from a to j...
Image a is bare CRT
b is the Tektronix clear plastic - does nothing optically
c is the neutral grey. Contrast is a better than shown here. Reflections don't help.
d is the Tek blue filter.

Of these 4 its a close toss up - neutral grey slightly edging out blue. Note the plastic has a lot of reflection. A dulling coat should be helpful.

I tried green theatrical gels...
e is one layer green gel.
f is two layers, two is better than one as the contrast is good and grid is still visible.
g is two green gels topped by the Tek neutral grey-makes a very contrast-y image but grid is mostly gone.

I have Tek metal CRT filters from another smaller scope I just put in front of this CRT.
h is metal on left and bare CRT on right.
j is metal on left and Tek neutral grey on right.

My conclusions are that because the metal screen type is non reflective - effectively a dark hole - it easily beats the neutral grey but grid is not usable.

The double green is quite good. Why didn't Tek make a green filter? Marketing?

The graticule lights can't do much against the sun - they are for lab work only.