Date   

Re: 7904 - Very Dim Trace

Jim McIntyre
 

...Which is what I just did. No joy.

The replacement Z-axis board didn't change the symptoms.


Looks like I have a spare now. Grr...


Re: CRT colored display filters

 

Hi David,
I have wondered about this as well.
But I would like to add one more personal observation to the question of
phosphor color. On some occasions it has been my impression that the color
of a phosphor has changed somewhat while I have been using a scope. This has
only happened on a few occasions - just often enough that I wondered about
it but not often enough that I could say what may have caused it or to have
attempted to account, in scientific terms, for what environmental factors
(if any) made me notice this.
My limited knowledge of phosphors tells me that the phosphor can't possibly
be changing over time periods of minutes or a few hours, but my eyes tell me
there was a significant color shift from more green to more blue, or
vice-versa. This has happened so infrequently that I can't even be sure the
color change was always the same.
On the other hand, the human eye / brain combination is capable of
discerning several million colors so it is possible that I really did see a
color change.
Maybe the explanation was as simple as changing the brightness of the CRT
which caused a different element in the phosphor to come alive, or maybe it
was because I turned off the incandescent lights and turned on the
florescent lights (or vice-versa) in the room.
Has anyone else noticed the color change?
Dennis Tillman W7PF

-----Original Message-----
Sent: Tuesday, February 16, 2016 4:17 PM
To: TekScopes@yahoogroups.com
<snip>
One thing I have wondered about however is why older Tektronix P31 phosphors
look green and newer ones look turquoise. I do not think that is related to
CRT acceleration voltage because I have seen the same model of oscilloscope
with the older one looking green and the newer one, but still old, looking
turquoise.
------------------------------------
Posted by: David <davidwhess@gmail.com>
------------------------------------


Re: CRT colored display filters

 

I have a couple things to add to this.

High brightness environments can result in sharper images as seen by
the eye because the pupil contracts increasing the depth of field.

Some colors are better than others for sharpness because achromatic
correction is done in the brain and a certain color balance is
assumed. The Exploratorium in San Francisco had an amazing display
where you could literally see this in action.

The eye has poor resolution (and sensitivity) in blue and violet. Take
a look at blue and violet business signs at night.

One thing I have wondered about however is why older Tektronix P31
phosphors look green and newer ones look turquoise. I do not think
that is related to CRT acceleration voltage because I have seen the
same model of oscilloscope with the older one looking green and the
newer one, but still old, looking turquoise.


Re: Introduction of myself!

 

I was referring to the "Firmware upgrade and ROM reliability improvement" part of the
"Tek mod kits and parts replacement" page you sent me
The critical parts here are the Mostek ROMs. Four are used. It's quite possible to get pin-compatible EPROMs to use as replacements and the binary contents for all EPROMs are easily found. So, even if you decide you'll wait for ROM breakdown, you will be able to repair your 7854. I'm not sure if the new FPLA's internal code is different across -xx versions. If it isn't, you could even use the later s/w with the original FPLA.
One of my 7854's still has Mostek ROMs. Few modern EPROM programmers seem to support devices like the Mostek pin-compatible MCM68766, of which I have a complete set, so I haven't yet made a new ROM copy set.

Raymond


Re: Introduction of myself!

 

That is new since I last visited Hakanh's site. He has been busy.

That modification is not the same as the later combined RAM and ROM
card which was used in the late 7854s.

Since it uses the original ROM board, you would still need to find
2763 pinout EPROMs, the FLPA, and whatever part would be needed for
the 2k x 8 memories.

As a practical matter the easiest way to update it is burn a ROM image
which combines the original ROMs and the patch data from the FLPA and
EPROMs into 4 x 2763 pinout EPROMs which are still available; I think
this combined image is available online. 2764s can be used instead if
the board is modified or maybe if an interposed is used; interposers
to convert the 2763 pinout to the 2764 pinout are common for video
game retrofits.

It was a while ago now but I searched for this information before
considering the 7854 and then when I got one, it was a late model that
used the alternative combined RAM and ROM board which I had no idea
even existed.

On 16 Feb 2016 15:12:53 -0800, you wrote:

Raymond,

I was referring to the "Firmware upgrade and ROM reliability improvement" part of the "Tek mod kits and parts replacement" page you sent me the link to for the 7T11/A mod parts list. I surfed thru it for a few minutes and looked at the parts that pertain to equipment I have - so I know what should have been done if they were properly updated before I obtained them.

That specific update for the 7854 sounds to me to be a fairly important, and possibly critical one after all the time that has passed since the year it should have been updated in.

This is the link to the specific Mod page I was speaking of:

http://www.hakanh.com/dl/docs/kitinstructions/045-0056-00.pdf http://www.hakanh.com/dl/docs/kitinstructions/045-0056-00.pdf

Also, this is the specific unit I purchased. B030771 S/N - My guess is that this is of the early version production.
http://www.ebay.com/itm/Tektronix-7854-Oscilloscope-Mainframe-with-Waveform-Calculator-for-Repair-/291679909626?_trksid=p2047675.l2557&ssPageName=STRK%3AMEBIDX%3AIT&nma=true&si=cZheso%252BTqMILxftiQZIuAGiBXu4%253D&orig_cvip=true&rt=nc http://www.ebay.com/itm/Tektronix-7854-Oscilloscope-Mainframe-with-Waveform-Calculator-for-Repair-/291679909626?_trksid=p2047675.l2557&ssPageName=STRK%3AMEBIDX%3AIT&nma=true&si=cZheso%252BTqMILxftiQZIuAGiBXu4%253D&orig_cvip=true&rt=nc


Re: Tek 465 intensity problem

Brian Bloom
 

I sent you a link to a 0777 CRT brand new for uber cheap over on EEV. I don't know how to PM anyone on here. I hope you scoop it up in time!!! I'm quite tempted to snatch it up myself, but I know that you actually need it.


CRT colored display filters

 

This is a very interesting topic to me, as I worked for years to improve cockpit displays, and came across a lot of relevant info over the years. some kind of barrier was required to protect the operator from CRT implosion, and resulting eye damage, so you will often see both a clear and colored filter in place, one is for minimal safety (clear) and one for display enhancement (colored).
with some phosphors, like P7, the color of the filter also selects for the fast or slow phosphor characteristic. You have probably seen the odd orange CRT filter on slow displays (medical, SA, etc.), that transmits the slow component of P7.

The human eye sees mainly by CONTRAST, not intensity, which is a bit counter-intuitive. we always think BRIGHTER is better, but in fact the Mk. 1 Human Eyeball prefers more contrast to improve readability. this is why there are so many MIL-STD specs for minimum contrast on knobs, indicators, displays, text, etc. 10:1 is the minimum standard.


So, to improve the contrast between the surrounding phosphor (which looks white, and offers terrible contrast) and the lit trace, Tek first used green contrast filters (to match the P1/P31 phosphor), and most early scopes came that way, with "neutral gray" as an option. the more the filter makes the BACKGROUND look black, and makes the trace stand out, the better your eye resolves it. Unfortunately, Tek also used the lit or unlit graticule at the CRT face to provide calibration, the darker the filter, the less visible it was when unlit, so many guys pulled the filter out to see the graticule. Turning on the graticule lighting would have actually worked better in most cases. Often the graticule lamps or overlay on 500 series copes were tinted red to give a really nice display/cal contrast. The optical trick with any display filter is to provide minimal trace loss, and maximum background darkening.



Tek migrated to the blue filter by the time the 400 series appeared, and it provided a good compromise between background contrast and graticule readability at all times. Plus, it looked a bit more modern and set them apart from other vendors (and, the Tek company color was blue). I found that color worked pretty well in most cases, but for real performance, especially at high sweep rates, a neutral gray or gray polarizing filter, and slightly lighting the graticule is great. That gives the best possible display when there's not a lot of energy in the trace or the room light is very bright. It is actually lossier than the green, however.



I keep green and gray polarizing filter sheets from Polaroid in stock for tuning up displays when the original filters have disappeared, but it did not ever exist in blue, so I never got any.


all the best,
walter

sphere research


Re: Bringing up to snuff a Tek 465M

 

Right, David very informative, thanks.

Raymond


Re: Bringing up to snuff a Tek 465M

 

On 16 Feb 2016 14:58:34 -0800, you wrote:

The reason I think it is secondary emission and not an optical effect
I see both the outer, constant and abruptly delimited shape, which speaks for the secondary emission, *and* intensity-dependent amplitude and spread of bleeding around the trace, which I see as the scattering/dispersion in the phosphor and aluminium coating. Interesting to discuss this, David! Unfortunately, I think I'll have to stop soon since my observations aren't very sharp at this late hour...

Raymond
I suspect almost all of the intensity dependent spreading around the
spot is caused by an increase in emission area from the cathode which
prevents proper focus. This is also why aged CRTs with low cathode
emission have a thick trace even at normal intensities where it should
still be sharp.

If it was an optical effect, then removing the PDA to produce a dimmer
spot would also decrease the spreading but that is not the case where
I have tested it. Under that condition, the spot spreads
significantly even though the brightness is low from a lack of PDA. Of
course this also increases the spot size simply because the electrons
have more time to spread out.


Re: Introduction of myself!

Brian Bloom
 

Raymond,

I was referring to the "Firmware upgrade and ROM reliability improvement" part of the "Tek mod kits and parts replacement" page you sent me the link to for the 7T11/A mod parts list. I surfed thru it for a few minutes and looked at the parts that pertain to equipment I have - so I know what should have been done if they were properly updated before I obtained them.

That specific update for the 7854 sounds to me to be a fairly important, and possibly critical one after all the time that has passed since the year it should have been updated in.

This is the link to the specific Mod page I was speaking of:

http://www.hakanh.com/dl/docs/kitinstructions/045-0056-00.pdf http://www.hakanh.com/dl/docs/kitinstructions/045-0056-00.pdf

Also, this is the specific unit I purchased. B030771 S/N - My guess is that this is of the early version production.
http://www.ebay.com/itm/Tektronix-7854-Oscilloscope-Mainframe-with-Waveform-Calculator-for-Repair-/291679909626?_trksid=p2047675.l2557&ssPageName=STRK%3AMEBIDX%3AIT&nma=true&si=cZheso%252BTqMILxftiQZIuAGiBXu4%253D&orig_cvip=true&rt=nc http://www.ebay.com/itm/Tektronix-7854-Oscilloscope-Mainframe-with-Waveform-Calculator-for-Repair-/291679909626?_trksid=p2047675.l2557&ssPageName=STRK%3AMEBIDX%3AIT&nma=true&si=cZheso%252BTqMILxftiQZIuAGiBXu4%253D&orig_cvip=true&rt=nc




---In TekScopes@yahoogroups.com, <hewpatek@...> wrote :

> Were the memory boards changed as part of an upgrade to older models?
>
I don't know the answer to your question, i.e. I don't know if an upgrade was available from Tek.

For a full upgrade the rear panel (with the fan opening and keyboard socket) would have to be replaced as well, since the two backup power banana sockets would go and a switch installed to allow selecting either running on backup power (Li battery) or restarting with system test after power up. The difference is obvious between the original version and the new version rear panel.

I do know that it's quite easy to modify the computer main board to accomodate the new integrated ROM/RAM board: Only one power supply wire need be connected to an unused connector main board pin. The old boards will work in the new model but not vice versa without installing the (power) wire.

One of my 7854's is a late version separate ROM/RAM version with new GPIB software ("1.03") in non-Mostek ROMs. Apart from the apparently improved GPIB handling, replacing the deteriorating Mostek ROMs could be an advantage. So, the OP could be lucky on two levels: Old Mostek separate ROM/RAM, old non-Mostek separate ROM/RAM, new integrated Li-backup ROM/RAM board.

Raymond


Re: Bringing up to snuff a Tek 465M

 

The reason I think it is secondary emission and not an optical effect
I see both the outer, constant and abruptly delimited shape, which speaks for the secondary emission, *and* intensity-dependent amplitude and spread of bleeding around the trace, which I see as the scattering/dispersion in the phosphor and aluminium coating. Interesting to discuss this, David! Unfortunately, I think I'll have to stop soon since my observations aren't very sharp at this late hour...

Raymond


Re: Probes for 2445A

Malcolm Hunter
 

I did reply directly to you, but your replies came back to the list. Not
sure why that happened.

Malcolm


On 16 February 2016 10:51:27 p.m. "hewpatek@gmail.com [TekScopes]"
<TekScopes@yahoogroups.com> wrote:

One has a small broken spot on the housing on one side and a sticker on the
other.
The other one has neither. Unless they removed the sticker (the side that's
broken would be
face down in the other picture so that's hard to tell), I think they're
different.
Sorry to have caused the noise. Doing too many things at the same time
(freq. compens. aof a 7A26 as well) and it's almost midnight here. I guess
I should stop...

Raymond



Re: CRT article

ae5i@...
 

You are certainly right about the Micro Channel Plate CRT! That's a true wonder to behold....

I'd lot rather use one of them than anything with an LCD display. One of the great things about the 7104 is that it just displays what comes in the inputs. The operator interprets what's there. With any digital scope, the scope is showing you what IT thinks is coming in the inputs. I'd rather do the interpreting myself.... :-)


Tom AE5I


Re: Probes for 2445A

Malcolm Hunter
 

However the second one has damage to the plastic of the connector as well
as a crack in the casing.

I'd opt for the Texas probes if the Tek ones were over $50 each, but I do
prefer the Tek. It also appeals to my slightly OCD nature.

Malcolm


On 16 February 2016 10:45:16 p.m. Malcolm Hunter
<malcolm.r.hunter@gmail.com> wrote:

Yes, I'm pretty sure they are different.

Malcolm


On 16 February 2016 10:29:04 p.m. "Barry n4buq@knology.net [TekScopes]"
<TekScopes@yahoogroups.com> wrote:

One has a small broken spot on the housing on one side and a sticker on the
other. The other one has neither. Unless they removed the sticker (the
side that's broken would be face down in the other picture so that's hard
to tell), I think they're different.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "hewpatek@gmail.com [TekScopes]" <TekScopes@yahoogroups.com>
To: TekScopes@yahoogroups.com
Sent: Tuesday, February 16, 2016 4:15:16 PM
Subject: [TekScopes] Re: Probes for 2445A

I found these two P6131s in the States: #361487515390 and #121890749622
AFAI can see, this is the same item twice. Same photograph even or am I
wrong? I share your views on the way the cable is tied. One of the worst
things one can do to probe cables is cause damage by torsion.

David H is right where he states that all the accessories would be there with
the (new) Texas probes.
Disadvantages of these Texas probes: More expensive than our most recently
addressed items, less flexible cable, slightly bigger probe body.
The P6131 (and other probes in this family) allows HF adjustment as well,
after removing the plastic cover of the attenuator block. This is how you
"modify"the probes for better behaviour with non-24XX 'scopes.

Raymond




Re: Probes for 2445A

 

One has a small broken spot on the housing on one side and a sticker on the other.
The other one has neither. Unless they removed the sticker (the side that's broken would be
face down in the other picture so that's hard to tell), I think they're different.
Sorry to have caused the noise. Doing too many things at the same time (freq. compens. aof a 7A26 as well) and it's almost midnight here. I guess I should stop...

Raymond


Re: Probes for 2445A

Malcolm Hunter
 

Yes, I'm pretty sure they are different.

Malcolm


On 16 February 2016 10:29:04 p.m. "Barry n4buq@knology.net [TekScopes]"
<TekScopes@yahoogroups.com> wrote:

One has a small broken spot on the housing on one side and a sticker on the
other. The other one has neither. Unless they removed the sticker (the
side that's broken would be face down in the other picture so that's hard
to tell), I think they're different.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "hewpatek@gmail.com [TekScopes]" <TekScopes@yahoogroups.com>
To: TekScopes@yahoogroups.com
Sent: Tuesday, February 16, 2016 4:15:16 PM
Subject: [TekScopes] Re: Probes for 2445A

I found these two P6131s in the States: #361487515390 and #121890749622
AFAI can see, this is the same item twice. Same photograph even or am I
wrong? I share your views on the way the cable is tied. One of the worst
things one can do to probe cables is cause damage by torsion.

David H is right where he states that all the accessories would be there with
the (new) Texas probes.
Disadvantages of these Texas probes: More expensive than our most recently
addressed items, less flexible cable, slightly bigger probe body.
The P6131 (and other probes in this family) allows HF adjustment as well,
after removing the plastic cover of the attenuator block. This is how you
"modify"the probes for better behaviour with non-24XX 'scopes.

Raymond




Re: CRT article

 

Hi Dwayne,
The "ideal" filter in high ambient light conditions is a circularly
polarized filter. The ambient light passing through it is circularly
polarized in one direction (CW or CCW, I don't remember which), but when it
reflects (off the glass CRT in this case) the direction of circular
polarization is reversed. So none of it is able to get back through the
filter. The light from the phosphor goes through the filter (and is also
polarized) but since it doesn't reflect before getting to the viewers eye it
is not blocked.
The filter improves the CONTRAST, but any filter (including this one)
reduces the BRIGHTNESS. There are situations where this is an acceptable
compromise. The viewing hood is another good compromise. For analog scopes
the best solution by far was the Micro Channel Plate. But then with the
advent of digital scopes CRTs were quickly replaced with LCDs which had the
additional advantage of color.
Dennis Tillman W7PF

-----Original Message-----
Sent: Tuesday, February 16, 2016 7:13 AM
Subject: [TekScopes] CRT article
<snip>
I was also intrigued by the notation that most scopes came with a grey
filter. In my very limited experience, I have not seen one remain with the
scope over the years, or tried one. How effective are they? I found some
used ones (incorporated into a light hood) for my 475 on eBay.
------------------------------------
Posted by: Dwayne Verhey <tekscopes@verhey.org>
------------------------------------


Re: Bringing up to snuff a Tek 465M

 

The reason I think it is secondary emission and not an optical effect
is that it cuts off abruptly at the edge of the halo and the diameter
of the halo does not change with intensity. The elections always hit
the phosphor with the same energy from the total acceleration creating
the same secondary emission; intensity just varies how many of them
there are.

On 16 Feb 2016 14:26:45 -0800, you wrote:

I totally agree with you, David re. the bleed not being caused by the mesh. I totally missed the dot-concentric nature of the "halo". and the brightness tapering off nicely instead of the interference-like rings that accompany the mesh' effect. Secondary (electron) emission is a possibility but photon scattering/dispersion and bleed within the phosphor could be part of it. The video was made in relatively low light as well.

Raymond


Date set for next Sphere Stuff Day/Ham Swap Meet

 

After lots of data collection, historical weather checking, and polling, Saturday, APRIL 9th
is the date for the next Sphere Stuff Day and Okanagan Valley-wide Radio Amateur swap meet. This gives those in Washington & Oregon time to recover from Puyallup, and should be good weather for both travel and display for everybody. This will be at Sphere Research, in West Kelowna, BC, about 4 hours from Vancouver. See our website for all the contact details and exact address. Starts 9am, but set up for those to display starts at 7am, and we can accommodate 2 Rvs and some limited overnight guests.

We will have tons of test equipment, (Tek, HP, Boonton, Fluke, PMI/Wavetek and much more) spare parts, plug-in modules, manuals and salvage units. Also tons of free electronic goodies of all kinds, as well as dirt cheap items, PLUS a wide range of ham gear and related items from ICOM to Collins for selling, swapping and testing. There is a lot of very cool stuff we are clearing out to make space, so whether you want RF parts, transmitting tubes, test gear, CRTs, nicads, scopes, meters, parts or what-have-you, you WILL find it here. There will also be solar panels, tons of high quality panel meters, Tek 11K items, time code systems (for that home launch pad you've been working on), and a huge assortment of crystals, filters and precision oscillator modules. Susan will also provide Visa/MC and Paypal services for payments if needed.



Want space to show and sell your gear, just CONTACT WALTER to reserve a spot, strictly first come, first served. Trunk/truck sales are fine, or you can set up a table, as you wish. We can provide power for some locations, and we will have some interesting test gear to allow you to demo and verify your stuff. YES, we take requests for specific items you may be interested in, and YES we will post a list in advance of some key items and prices for those that just can't get up here, but shipping costs can be annoying for big items, which is exactly why we suggest showing up in person. Those that have been here in the past have had a great time, so we invite you to drop by and snorkel through the goodies to your heart's content. Plus, who knows what fabulous treasures others will bring to trade?



We may also be able to set up a BBQ spot for snacks, and we will have off-air frequency checks, RF power testing, and a master frequency reference to let you check your counters and other gear. Plus, lots of help and advice from a great cross-section of people you don't get to see so often.


All in all, it should be a great time. RSVP if you need exhibit space, or just to say hi, and remember that we do take requests to set out just the items you need (we have 4 storage buildings, we can't set it ALL out). If you have been missing a good surplus store experience for a while, come by and get that taken care of here!


Remember, Saturday, April 9th. I will post again as we get closer to remind you of the date.



all the best,
walter & susan (walter2 -at- sphere.bc.ca)
sphere research corp.
http://www.sphere.bc.ca/test


Re: Probes for 2445A

n4buq
 

One has a small broken spot on the housing on one side and a sticker on the other. The other one has neither. Unless they removed the sticker (the side that's broken would be face down in the other picture so that's hard to tell), I think they're different.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "hewpatek@gmail.com [TekScopes]" <TekScopes@yahoogroups.com>
To: TekScopes@yahoogroups.com
Sent: Tuesday, February 16, 2016 4:15:16 PM
Subject: [TekScopes] Re: Probes for 2445A

I found these two P6131s in the States: #361487515390 and #121890749622
AFAI can see, this is the same item twice. Same photograph even or am I
wrong? I share your views on the way the cable is tied. One of the worst
things one can do to probe cables is cause damage by torsion.

David H is right where he states that all the accessories would be there with
the (new) Texas probes.
Disadvantages of these Texas probes: More expensive than our most recently
addressed items, less flexible cable, slightly bigger probe body.
The P6131 (and other probes in this family) allows HF adjustment as well,
after removing the plastic cover of the attenuator block. This is how you
"modify"the probes for better behaviour with non-24XX 'scopes.

Raymond



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