Date   

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


Re: Tek 2465 Problem

Panos
 

Hi,
this is well known to me, and the voltages seen more than good from the first moment.The subject is that I didn't give the proper attention initially in a low ripple at the + 5 volt line.

Now with the new replaced diodes, some things on screen changed for the better.

A small ripple on the beam during the cold start up disappeared. The same the beam from the cold start up appear immediately and not after 20 seconds. Even the thickness of the trace is now thinner after the warm up time of oscilloscope.

I'm just unfortunate who the diodes were failed by such a rare way. :-\


Re: Tek 485 short sweep

Reed Dickinson
 

I have had this problem with a few 485's I have refurbished and every time it was the X6 voltage multiplier U1600 located on the A15 Transformer Board.  It is supplied by Voltage Multiplier Inc., 8711 W. Roosevelt, Visalia CA  93291, their part number VM176 and sells for $175 in small quantities.  
You can test if U1600 is working but you must be very careful or you will burn out U660, the vertical output IC.  To test U1600 proceed as follows:
1)  Unsolder the connections from the A7 vertical board going from U660 to the CRT.  This removes part of the arcing path which might be present in the next few steps.2)  Pull out the connections to the horizontal plates present near the rear of the A11 Horizontal Amp board.3)  Unplug the two wires going from the hybrid board to the forward connections of the distributed vertical plates.
You have now isolated the CRT and eliminated any chance of damage to any semiconductor components due to a large current surge.  Now start your 485 up and run it for about a minute.  Turn the power off and immediately pull out the high voltage connector going from U1600 to the CRT.  If you get a nice fat spark as the connector clears the plastic socket then you know the X6 multiplier is working.  If you get a spark the problem is in the horizontal output circuit.  Replace all the CRT connections removed in the above numbered steps. If you get no spark replace U1600.  I always replace R1602, a 15K, 1/2W resistor but do not use a film resistor, use a carbon composition one.
Reed Dickinsonreed714@...

On Monday, December 23, 2019, 09:16:12 PM PST, 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.

If you have another scope, you can check for linearity by borrowing a
ramp from it and using it for a horizontal sweep. Good function
generator will also work.

Harvey


On 12/23/2019 1:26 AM, stephen white wrote:
How can we narrow this short sweep to the sweep circuit or to the horizantal amp circuit ???  I am back at this problem child of mine again and am trying to figure which board to chase around on...I have a few more things to check per all the good inputs I have had here but seems like it would a good thing to  determine which board the problem is on..
Any thoughts on this??

Steve




Re: OT: measuring tiny distances

 

Hi snapdiode,
You probably know the density of the media that your drive reads and writes already but it is worth noting that the read/write head gap depends on the magnetic coercivity of the coating on the diskette, and that depends on the capacity of the diskette (360KB, 720KB, 1.44MB, 2.88MB, etc.).

The greater the storage capacity of the diskette the narrower the tracks have to be. Narrower tracks require magnetic material with higher coercivity to be coated on the diskette. In order to read and write these narrower tracks the magnetic field in the gap had to be higher which meant a thinner gap and the width of the gap had to be reduced to squeeze more tracks in.

In summary, the gap width depends on the data density of the floppy so your measurement and the reference may be referring to two different density heads.

Dennis Tillman W7PF

-----Original Message-----
From: snapdiode via Groups.Io
Sent: Monday, December 23, 2019 7:51 PM
To: TekScopes@groups.io
Subject: [TekScopes] OT: measuring tiny distances

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.





--
Dennis Tillman W7PF
TekScopes Moderator


Re: Tek 485 short sweep

Harvey White
 

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.

If you have another scope, you can check for linearity by borrowing a ramp from it and using it for a horizontal sweep. Good function generator will also work.

Harvey

On 12/23/2019 1:26 AM, stephen white wrote:
How can we narrow this short sweep to the sweep circuit or to the horizantal amp circuit ??? I am back at this problem child of mine again and am trying to figure which board to chase around on...I have a few more things to check per all the good inputs I have had here but seems like it would a good thing to determine which board the problem is on..
Any thoughts on this??

Steve



Re: OT: measuring tiny distances

Chuck Harris
 

The usual way to measure such small distances is using
an optical microscope that has an eyepiece with micrometer
controlled moving reference lines. Zero the micrometer
with the reference lines at some known distance... usually
overlapping, and then adjust them to match the head gap.
The micrometer reading gets multiplied by the optics to
arrive at the actual gap.

Absent one of those special oculars, you can use a finely
ruled ruler, placed in the same frame as the gap, and
extrapolate the size of one of the lines to the gap.

If you have some fine wire, that you can measure with a
micrometer, you can compare it to the gap...

When the sizes get even smaller, a scanning electron microscope
can easily perform the same duty.

-Chuck Harris

snapdiode via Groups.Io 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.