Date   
Re: Tek 485 short sweep

Bruce Atwood
 

If low deflection (short sweep) was caused by a HV problem it would mean
that the HV was too high, not too low. Could be a problem in the HV
feedback loop but to get only a 1/2 scale trace you would need twice the
HV, seems hard to do.

On 12/24/2019 3:07 PM, stephen white wrote:
On Tue, Dec 24, 2019 at 12:31 AM, Reed Dickinson wrote:

VM176
You would think that the multiplier either works or it doesn't.. Since I have a trace but it is not wide enough to cover the entire screen that the multiplier is working not well enough I guess, must be some big loss in there.
steve



.
--
Bruce Atwood PhD
Department of Astronomy
The Ohio State University
100 West 18th Ave., Room 4055
Columbus, OH 43210

Phone 614.314.0189
FAX 614.292.2928

Re: 1502 TDR project - using bench supply

Harvey White
 

Be very careful with the amp hour ratings on the C size cells. Some manufacturers put an AA sized cell in a big wrapper for the C form factor.  You might be just as happy with AA, depending.  You may find that *real* C sized batteries have a significantly larger rating then the fakes.  We're talking name brands here.

Harvey

On 12/24/2019 1:17 PM, Mark Pilant wrote:
Just to wrap this up....

Since I have been only having marginal success with the cap/resistor
NiCd substitute, I have decided on my alternative.

My plan is to cut some aluminum blanks the same size as the finned
end plate of the original battery pack.  From there, I'll drill the
necessary holes to allow the new plate to be screwed to the TDR (with
the original thumb screws) as well as the original plastic battery
frame.

I'll then drill a hole in the new plate for a standard coaxial power
connector to allow an external wall supply to be connected to the
banana plugs of the original.  The original end plate will just be
kept in the cover; so it doesn't get separated from the unit.

I was thinking of making up one battery pack, but so far, all the
"C" side NiCd flat top batteries are too long by about 0.1".  In
looking around, the "shorter" ones appear to have all been flat top
batteries, while the "longer" ones were the button top batteries.
However, now even the flat top batteries seem to have the same length
at the button top batteries.  Sigh.

- Mark  N1VQW



Re: tektronix 7S14 batteries and time base question

Miguel Work
 

Thanks, I know, but the question was If ired is more efficient than visible light diodes. This is my configuration with ir, 6 digits stable


https://groups.io/g/TekScopes/photo/131745/9?p=Created,,,20,2,0,0

Thank you

12ax7
 

Just a quick thank you to Menahem from Condor Audio. I bought Menahem’s 2465 capacitor replacement kit about 7 months ago and finally got time to do the replacement.
Even though it had been quite a while, Menahem was extremely helpful, courteous and responsive, especially with my nuisance “newbie” Tektronix repair questions.

Thank you Menahem.

And, a shout out to John C for his recommendation to join this group and for his sage TekScope advice.

Now on to a 2465 fan replacement, calibration and some unusual screen behavior that I'll post in a separate topic.

Happy holidays to all,
Jeff

Re: Tek 485 short sweep

Mlynch001
 

Siggi,

That is an excellent book. One of the most useful for the older analog scopes. I have read through this in the past, but am reviewing this yet again. I just found a nice (and very cheap) 485 and a 465 that have nice bright traces, but need some TLC in other areas. I always get something from this book. Should be required reading for any novice scope tech or hobbyist. You old pros in the group probably have this memorized. Superb information.

Thanks for reminding us about this..

--
Michael Lynch
Dardanelle, AR

Re: Tek 485 short sweep

stephen white
 

On Tue, Dec 24, 2019 at 12:31 AM, Reed Dickinson wrote:


VM176
You would think that the multiplier either works or it doesn't.. Since I have a trace but it is not wide enough to cover the entire screen that the multiplier is working not well enough I guess, must be some big loss in there.
steve

Re: tektronix 7S14 batteries and time base question

Bruce Griffiths
 

That's not efficiency, as its not the ratio of power out to power in.
The efficiency is actually significantly less than your calculation indicates.
Your "efficiency" is irrelevant if you are attempting to replace a 1.35V Mercury cell with a LED operating in the photovoltaic mode. Output noise, impedance and tempco etc are more important in such an application.

Bruce

On 25 December 2019 at 05:48 Miguel Work <harrimansat@...> wrote:


IR wins! :)

Efficiency
IR 1,16 0,85 73,28%

RED 1,9 1,3 68,42%

YELLOW 2 1,2 60,00%

BLUE 3,2 2,3 71,88%



-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de Carl Hallberg via Groups.Io
Enviado el: martes, 24 de diciembre de 2019 3:39
Para: TekScopes@groups.io
Asunto: Re: [TekScopes] tektronix 7S14 batteries and time base question

Hi Dennis,
I don't have a problem gluing ground down LEDs together.  Don't know if the glue will turn translucent with age.  As far as what color to use, I'll give some examples:
Input voltage across LED at 20mA       to        Output voltage using 10Megohm input voltmeter

INFRARED   1.16V                                                 INFRARED  0.85V

RED   1.9V                                                            RED   1.3V

YELLOW  2.0V                                                      YELLOW  1.2V

BLUE    3.2V                                                          BLUE    2.3V

When I used wide angle LEDs, (manufactured with flat tops) the close proximity provides enough coupling to give good results.

Changing the drive current on the input side doesn't change the output side very much.  Voltages given are not exact.  Do we care about efficiency?  When I use to design digital circuit using transistors, Beta was selected for worse case of 10.  Very inefficient, but wouldn't fail over Military temperature range.  I don't know where we can get die upon die selected color LEDs.

Carl Hallberg
  






On Monday, December 23, 2019, 5:34:55 PM CST, Dennis Tillman W7PF <@Dennis_Tillman_W7pF> wrote:





Hi Chuck and John
I was surprised that several people ground the LED ends flat and glued them together. This seems counter intuitive to me for several reasons.

These are the reasons I think that grinding down the LED ends is not a good idea. I would appreciate it if you could explain the flaws in my thinking.
1) The polished surface of the LED lets the most light out. Wouldn’t a ground down (rough) surface scatter and block a portion of the emitted light.
2) The LED's dome shape focuses the light into a fairly narrow angle which increases the likelihood that the majority of the emitted light can be aimed right at the die of the LED that will convert the light to electricity.
3) Crazy Glue may appear clear to humans but what are its optical absorption characteristics? Does it absorb any of the wavelengths generated by the LED emitter?

On the other hand I think there are advantages to grinding the ends flat:
1) The ground end combination takes up a fraction of the volume of two unground LEDs.
2) Mating the two LEDs flat against each makes it easier to align them to each other.

It seems to me that the greatest conversion efficiency will come when you can place a bare emitting LED die on top of the die of the receiving LED. At that point every emitted photon can kick out an electron in the receiving PN junction.

IR light is another issue I'm confused about. I think I must have misunderstood but it sounded like some people think IR LEDs would make a good choice for emitters. Wouldn't just the opposite be true since a photon's energy, E, is proportional to its frequency, v, as in E = hv.  Do IR LEDs emit more photons (greater brightness) and that is why they are a good choice? If so does the same thing apply for the receiving LED - which would have a high conversion efficiency resulting in the largest number of electrons being produced?

Dennis Tillman W7PF

-----Original Message-----
From: Chuck Harris
Sent: Monday, December 23, 2019 7:15 AM
Subject: Re: [TekScopes] tektronix 7S14 batteries and time base question

Hi John,
That has been my experience as well.  I did a long stint in a lab where we were doing IR spectroscopy, using lasers.
When I tried to make such a bias device, I ground both LED's ends flat, and welded them together with crazy glue.  I figured that it would reduce reflections at the red I was using.
I couldn't get spit out of them... measured with a 200M input impedance meter...  I guessed the older LED's just weren't bright enough.
Or, maybe the mechanism is not reciprocal?
-Chuck

John Griessen wrote:
On 12/22/19 11:30 PM, Chuck Harris wrote:
If I have been following correctly (always suspect), aren't we using
an LED illuminated by another LED to behave as a photo diode, and
produce the bias voltage for the switch?
One thing for sure from back when I worked with near IR LEDs and laser
diodes in a narrow beam system is that what absorbs IR or reflects or
not is not obvious from our visible light experience...  So, the
efficiency could be because the incoming IR light "gets in" instead of
reflecting.  They are both designed only to output, yet one is being used to receive...

Longer IR tends to go through more things that look black to us, and
probably go right through the plastic of LED lamps without much
refraction so angle and placement can be whatever.



--
Dennis Tillman W7PF
TekScopes Moderator







Re: tektronix 7S14 batteries and time base question

Bob Headrick
 

Efficiency as measured by voltage transfer, it would be interesting to compare power transfer efficiency. With 20mA on the driven LED is it possible to get even a few microamps of output current?

- Bob W7OV

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Miguel Work
Sent: Tuesday, December 24, 2019 8:49 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] tektronix 7S14 batteries and time base question

IR wins! :)

Efficiency
IR 1,16 0,85 73,28%

RED 1,9 1,3 68,42%

YELLOW 2 1,2 60,00%

BLUE 3,2 2,3 71,88%

Re: Tek 485 short sweep

Siggi
 

On Tue, Dec 24, 2019 at 12:16 AM Harvey White <madyn@...>
wrote:

The horizontal input has a calibrated deflection factor. Adjust the
vertical to the same factor, put a sinewave into both, and you should
get a 45 degree line.

If the amplifier is ok, and the problem is in the sweep, then you should
be able to center the horizontal dot (no sweep, x only). It should have
about the same travel (L and R) with the positioning control.
I like this method - put the scope in X/Y mode and input a sine or triangle
wave. Also, if you haven't seen this document before, give it a read:
https://www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf.
Because oscilloscopes are a measurement instrument with calibrated sweeps
and triggers and stuff, they can often be coaxed to diagnose their own
faults by milking the front panel.

Re: 1502 TDR project - using bench supply

Tom Gardner
 

Sounds like a good plan; nothing original is destroyed.

I think I would use a standard IEC C14 "kettle lead" panel mounted male plug, simply so I can reuse the many kettle leads I already have.

Happy holidays.

On 24/12/19 18:17, Mark Pilant wrote:
Just to wrap this up....

Since I have been only having marginal success with the cap/resistor
NiCd substitute, I have decided on my alternative.

My plan is to cut some aluminum blanks the same size as the finned
end plate of the original battery pack.  From there, I'll drill the
necessary holes to allow the new plate to be screwed to the TDR (with
the original thumb screws) as well as the original plastic battery
frame.

I'll then drill a hole in the new plate for a standard coaxial power
connector to allow an external wall supply to be connected to the
banana plugs of the original.  The original end plate will just be
kept in the cover; so it doesn't get separated from the unit.

I was thinking of making up one battery pack, but so far, all the
"C" side NiCd flat top batteries are too long by about 0.1".  In
looking around, the "shorter" ones appear to have all been flat top
batteries, while the "longer" ones were the button top batteries.
However, now even the flat top batteries seem to have the same length
at the button top batteries.  Sigh.

- Mark  N1VQW

Re: 1502 TDR project - using bench supply

Mark Pilant
 

Just to wrap this up....

Since I have been only having marginal success with the cap/resistor
NiCd substitute, I have decided on my alternative.

My plan is to cut some aluminum blanks the same size as the finned
end plate of the original battery pack. From there, I'll drill the
necessary holes to allow the new plate to be screwed to the TDR (with
the original thumb screws) as well as the original plastic battery
frame.

I'll then drill a hole in the new plate for a standard coaxial power
connector to allow an external wall supply to be connected to the
banana plugs of the original. The original end plate will just be
kept in the cover; so it doesn't get separated from the unit.

I was thinking of making up one battery pack, but so far, all the
"C" side NiCd flat top batteries are too long by about 0.1". In
looking around, the "shorter" ones appear to have all been flat top
batteries, while the "longer" ones were the button top batteries.
However, now even the flat top batteries seem to have the same length
at the button top batteries. Sigh.

- Mark N1VQW

Re: Tek 485 short sweep

DaveH52
 

My mistake it was the 95V supply,
C582 and C584 on the motherboard.

Re: tektronix 7S14 batteries and time base question

Chuck Harris
 

I guess it depends on what race you are running.

If the race is to get to 1.3V with the fewest parts, not
so much of a win for IR...

IR LED's, in general were more efficient than the others...
or at least originally, I think blue may have that win
for power today.

I haven't paid much attention to the Frankenstonian mixes
that are the LED's of today. Today, if it is really bright,
it is probably a blue LED pumping a fluorescent bit to
generate the desired color.

Note that he is using like to like combinations. I would
be most interested in mixing things up a bit.

Perhaps IR driving, or a blue driving one of the others?

-Chuck Harris

Miguel Work wrote:

IR wins! :)

Efficiency
IR 1,16 0,85 73,28%

RED 1,9 1,3 68,42%

YELLOW 2 1,2 60,00%

BLUE 3,2 2,3 71,88%


Re: tektronix 7S14 batteries and time base question

Miguel Work
 

IR wins! :)

Efficiency
IR 1,16 0,85 73,28%

RED 1,9 1,3 68,42%

YELLOW 2 1,2 60,00%

BLUE 3,2 2,3 71,88%



-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de Carl Hallberg via Groups.Io
Enviado el: martes, 24 de diciembre de 2019 3:39
Para: TekScopes@groups.io
Asunto: Re: [TekScopes] tektronix 7S14 batteries and time base question

Hi Dennis,
I don't have a problem gluing ground down LEDs together.  Don't know if the glue will turn translucent with age.  As far as what color to use, I'll give some examples:
Input voltage across LED at 20mA       to        Output voltage using 10Megohm input voltmeter

INFRARED   1.16V                                                 INFRARED  0.85V

RED   1.9V                                                            RED   1.3V

YELLOW  2.0V                                                      YELLOW  1.2V

BLUE    3.2V                                                          BLUE    2.3V

When I used wide angle LEDs, (manufactured with flat tops) the close proximity provides enough coupling to give good results.

Changing the drive current on the input side doesn't change the output side very much.  Voltages given are not exact.  Do we care about efficiency?  When I use to design digital circuit using transistors, Beta was selected for worse case of 10.  Very inefficient, but wouldn't fail over Military temperature range.  I don't know where we can get die upon die selected color LEDs.

Carl Hallberg

On Monday, December 23, 2019, 5:34:55 PM CST, Dennis Tillman W7PF <@Dennis_Tillman_W7pF> wrote:





Hi Chuck and John
I was surprised that several people ground the LED ends flat and glued them together. This seems counter intuitive to me for several reasons.

These are the reasons I think that grinding down the LED ends is not a good idea. I would appreciate it if you could explain the flaws in my thinking.
1) The polished surface of the LED lets the most light out. Wouldn’t a ground down (rough) surface scatter and block a portion of the emitted light.
2) The LED's dome shape focuses the light into a fairly narrow angle which increases the likelihood that the majority of the emitted light can be aimed right at the die of the LED that will convert the light to electricity.
3) Crazy Glue may appear clear to humans but what are its optical absorption characteristics? Does it absorb any of the wavelengths generated by the LED emitter?

On the other hand I think there are advantages to grinding the ends flat:
1) The ground end combination takes up a fraction of the volume of two unground LEDs.
2) Mating the two LEDs flat against each makes it easier to align them to each other.

It seems to me that the greatest conversion efficiency will come when you can place a bare emitting LED die on top of the die of the receiving LED. At that point every emitted photon can kick out an electron in the receiving PN junction.

IR light is another issue I'm confused about. I think I must have misunderstood but it sounded like some people think IR LEDs would make a good choice for emitters. Wouldn't just the opposite be true since a photon's energy, E, is proportional to its frequency, v, as in E = hv.  Do IR LEDs emit more photons (greater brightness) and that is why they are a good choice? If so does the same thing apply for the receiving LED - which would have a high conversion efficiency resulting in the largest number of electrons being produced?

Dennis Tillman W7PF

-----Original Message-----
From: Chuck Harris
Sent: Monday, December 23, 2019 7:15 AM
Subject: Re: [TekScopes] tektronix 7S14 batteries and time base question

Hi John,
That has been my experience as well.  I did a long stint in a lab where we were doing IR spectroscopy, using lasers.
When I tried to make such a bias device, I ground both LED's ends flat, and welded them together with crazy glue.  I figured that it would reduce reflections at the red I was using.
I couldn't get spit out of them... measured with a 200M input impedance meter...  I guessed the older LED's just weren't bright enough.
Or, maybe the mechanism is not reciprocal?
-Chuck

John Griessen wrote:
On 12/22/19 11:30 PM, Chuck Harris wrote:
If I have been following correctly (always suspect), aren't we using
an LED illuminated by another LED to behave as a photo diode, and
produce the bias voltage for the switch?
One thing for sure from back when I worked with near IR LEDs and laser
diodes in a narrow beam system is that what absorbs IR or reflects or
not is not obvious from our visible light experience...  So, the
efficiency could be because the incoming IR light "gets in" instead of
reflecting.  They are both designed only to output, yet one is being used to receive...

Longer IR tends to go through more things that look black to us, and
probably go right through the plastic of LED lamps without much
refraction so angle and placement can be whatever.



--
Dennis Tillman W7PF
TekScopes Moderator

Re: OT: measuring tiny distances

Chuck Harris
 

The easiest way is to make the core in halves, and to
create the gap with a known thickness spacer where the
gap should be.

Another way is to make the core "V" shaped where the gap
should be, and carefully grind/lap away the core material
until the gap presents itself.

These were methods used in the early tape recorders... I
would imagine that similar methods were used in the disk
heads.

-Chuck Harris

snapdiode via Groups.Io wrote:

Ahhh, the units in my reference are microINCHES. I see. 80 microninches is two microns. And they are talking about "future" media from the perspective of 1980.
OK, so 10 microns gives .39 mils.
This makes sense!
Thanks!
You wouldn't happen to know how these things were built, do you? :)
Happy Holidays everyone!



Re: OT: measuring tiny distances

snapdiode
 

Ahhh, the units in my reference are microINCHES. I see. 80 microninches is two microns. And they are talking about "future" media from the perspective of 1980.
OK, so 10 microns gives .39 mils.
This makes sense!
Thanks!
You wouldn't happen to know how these things were built, do you? :)
Happy Holidays everyone!

Re: OT: measuring tiny distances

Albert Otten
 

On Tue, Dec 24, 2019 at 04:50 AM, snapdiode wrote:


Dear massed wisdom of this group, how would you measure the head gap of a floppy disk r/w head?
By counting pixels on a microscope pic I've arrived at the more or less believable 0.35 mils, or 0.009mm . One thing's for sure, it's tiny.
But that number is ten times smaller than the one reference I found that says it is 80 microns, or 0.08mm.
As a very crude guide the gap width is something like the bit length in the tracks. Now (total track length)/(total bit capacity) is in the order of 10 um for an 8 inch floppy. I wouldn't thrust that 80 um.

Re: Tektronix ORS2488/ORS622 SDH/SONET Reference Receiver

Melvin Gleep
 

Great! Many Thanks!

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of zenith5106
Sent: Dienstag, 24. Dezember 2019 12:04
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tektronix ORS2488/ORS622 SDH/SONET Reference Receiver

On Mon, Dec 23, 2019 at 05:18 PM, Melvin Gleep wrote:

so I am hoping someone can provide me with access to a user guide, service manual, or anything related.
https://www.ebay.com/itm/TEKTRONIX-ORS-2488-USER-MANUAL-MANUAL-ORIGINAL-BOOK/362272483855?hash=item54591f6a0f:g:VB0AAOSwcj5ZWzFT

/Håkan

Re: Tektronix ORS2488/ORS622 SDH/SONET Reference Receiver

 

On Mon, Dec 23, 2019 at 05:18 PM, Melvin Gleep wrote:

so I am hoping someone can provide me with access to a user guide, service manual, or anything related.
https://www.ebay.com/itm/TEKTRONIX-ORS-2488-USER-MANUAL-MANUAL-ORIGINAL-BOOK/362272483855?hash=item54591f6a0f:g:VB0AAOSwcj5ZWzFT

/Håkan

Re: Tektronix ORS2488/ORS622 SDH/SONET Reference Receiver

Melvin Gleep
 

Hi Roy,

Thanks for the links. The first link was already available in my referenced link. Regarding the second link, I have registered myself there and will place a request as soon as my registration has been approved.

I hope that will turn up something useful.

I plan to play around with building a fiber optics digital network at home, just for fun.

Best regards.
Melvin

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Roy Thistle
Sent: Montag, 23. Dezember 2019 21:42
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tektronix ORS2488/ORS622 SDH/SONET Reference Receiver

Hi Melvin:
There is,
https://www.artisantg.com/info/ATG0yxxv.pdf
and
https://groups.io/g/ManualExchange/topics
You have an optical fiber based digital network to test/quantify?
Best wishes and regards.
Roy