Date   

Re: tektronix 7S14 batteries and time base question

Dave Wise
 

How about a power MOSFET gate driver IC? There are lots of those around.

Dave Wise

On Dec 26, 2019, at 9:30 AM, Tom Bowers via Groups.Io <pvhengineering=gmail.com@groups.io> wrote:

I haven't been following too closely, but just remembered some old Western Electric parts that Vishay still makes. These may be of value to consider for this mercury battery replacement. Take a look at the Vishay LC1262, an LED coupled to a diode stack, dual. I see Mouser has stock.

Tom Bowers



Re: tektronix 7S14 batteries and time base question

Tom Bowers
 

I haven't been following too closely, but just remembered some old Western Electric parts that Vishay still makes. These may be of value to consider for this mercury battery replacement. Take a look at the Vishay LC1262, an LED coupled to a diode stack, dual. I see Mouser has stock.

Tom Bowers


Re: tektronix 7S14 batteries and time base question

 

On Thu, Dec 26, 2019 at 04:39 AM, Gary Robert Bosworth wrote:


It is a shame that the original spacing for the batteries was so tight. I
realize the need to keep the leads short, but it makes it difficult to
replace the Mercury cells in such a tight spot. It would be nice if
someone could come up with a tiny hybrid fix that could be dropped into the
small footprint.
Bruce Griffiths wrote:
Just use SMT LEDs.
However the photocurrent will need to at least 50 uA to ensure that output impedance is low enough.
A shunt capacitor across the output LED may also be required.
Leon Robertson wrote:
Would a led to photodiode optocoupler work?
A lot has been written about this subject over the years and several people showed their (photovoltaic) suggestions.
Examples:
- A few years ago, Ed Breya made a nice write up about this subject on Tekwiki under "7S14/Repairs":
http://w140.com/tekwiki/wiki/7S14/Repairs

- My LED-LED album "7S14 sampler mod using LED Photovoltaics" in the photos section of this Group and on TekWiki ("7S14").

Raymond


Type 576 HV transfomer replacement part. UPDATE

Mlynch001
 

Good Morning!

Here is an update on my Type 576 Curve Tracer HV Transformer replacement project.

I have completed the testing phase without a problem. The transformer and unit ran for a total of 135 hours including approximately 60 on-off-on power cycles. Performance of the rest of the unit was perfect throughout the test. Output voltages were stable and remained within nominal ranges (as noted previously) throughout the test. The transformer (and unit) ran at ambient temperatures of between 50 - 85 deg Fahrenheit, exhibiting no signs of heating, when checked with a non-contact thermometer. This was a non-destructive test, I was not willing to expose my Type 576 to abnormal conditions or excess stress. Therefore, I do not know which (if any) abnormal condition would cause this transformer to fail. All in all, this transformer has proven reliable and I am ready to place my initial order with the factory. Please let me know before Friday, January 5th, 2020 as to your desire to purchase one or more of these as previously discussed. I am offering this pricing to Members in order to say "thank you" for all the patience, kindness, assistance and advice that many on this forum have freely provided to me over the past couple of years.

Here are some more details:

1. Cost to members of this group on this initial order: $107.50 each, including USPS Priority Mail Shipping to the USA only.
2. International shipping is in addition and based on cost to your address by USPS. International Buyers are responsible for any and all local taxes, tariffs or duty assessed on their shipment.
3. Limited Warranty is provided: Warranty term is 6 months from Date of Original Purchase and to the original buyer only. This is a NON-COMMERCIAL Warranty. Other terms and conditions may apply
4: Any units not spoken for by members of the group will be sold on E-Bay at a substantial premium over "member" price above (Plus shipping).
5. Payments for units purchased must be completed by Pay Pal on a Pre-Paid basis. Anyone else wanting one (or more), may contact me off list at mlynch002@gmail.com and I will send payment instructions to you privately.
6. Members who previously reached out to me for this product are encouraged to contact me to confirm your needs and to make payment arrangements before Jan 5, 2020.
7. Any Members having additional questions or comments may also contact me off list at mlynch002@gmail.com

Finally, I want to give a heartfelt "THANK YOU" to Chuck Harris, who graciously provided critical guidance and essential advice for me during this project. As always, Chuck was unselfish and very detailed as to what I had to do to be successful. Without his advice and encouragement, my confidence in proceeding with this project would not be nearly as high. Chuck is a seemingly bottomless well of knowledge and never holds back in sharing that knowledge and experience with others on this forum. To all the others of the group who offered advice, encouragement and interest in this project, I thank you as well.

Looking forward to a few long dead Type 576 Curve Tracers rising from the ashes.

Sincerely,

--
Michael Lynch
Dardanelle, AR


Re: tektronix 7S14 batteries and time base question

Bruce Griffiths
 

That's 2 series connected silicon photodiodes with a shunt capacitor per battery.

Bruce

On 26 December 2019 at 17:03 Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote:


You'll need to series stack a couple of silicon photodiodes for that to work.
The photocurrent will need to be around 50 microamps or so to keep the output resistance low enough.
A shunt capacitor may also be required.

Bruce
On 26 December 2019 at 16:51 Leon Robinson <leon-robinson@sbcglobal.net> wrote:


Would a led to photodiode optocoupler work?

Leon Robinson    K5JLR

Political Correctness is a Political Disease.

Politicians and Diapers should be changed
often and for the same reasons.

On Wednesday, December 25, 2019, 9:39:19 PM CST, Gary Robert Bosworth <grbosworth@gmail.com> wrote:

It is a shame that the original spacing for the batteries was so tight.  I
realize the need to keep the leads short, but it makes it difficult to
replace the Mercury cells in such a tight spot.  It would be nice if
someone could come up with a tiny hybrid fix that could be dropped into the
small footprint.

Gary

On Tue, Dec 24, 2019 at 11:21 AM Bob Headrick <bobh@proaxis.com> wrote:

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%





--
Gary Robert Bosworth
grbosworth@gmail.com
Tel: 310-317-2247







Re: tektronix 7S14 batteries and time base question

Bruce Griffiths
 

You'll need to series stack a couple of silicon photodiodes for that to work.
The photocurrent will need to be around 50 microamps or so to keep the output resistance low enough.
A shunt capacitor may also be required.

Bruce

On 26 December 2019 at 16:51 Leon Robinson <leon-robinson@sbcglobal.net> wrote:


Would a led to photodiode optocoupler work?

Leon Robinson    K5JLR

Political Correctness is a Political Disease.

Politicians and Diapers should be changed
often and for the same reasons.

On Wednesday, December 25, 2019, 9:39:19 PM CST, Gary Robert Bosworth <grbosworth@gmail.com> wrote:

It is a shame that the original spacing for the batteries was so tight.  I
realize the need to keep the leads short, but it makes it difficult to
replace the Mercury cells in such a tight spot.  It would be nice if
someone could come up with a tiny hybrid fix that could be dropped into the
small footprint.

Gary

On Tue, Dec 24, 2019 at 11:21 AM Bob Headrick <bobh@proaxis.com> wrote:

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%





--
Gary Robert Bosworth
grbosworth@gmail.com
Tel: 310-317-2247






Re: tektronix 7S14 batteries and time base question

Leon Robinson
 

Would a led to photodiode optocoupler work?

Leon Robinson    K5JLR

Political Correctness is a Political Disease.

Politicians and Diapers should be changed
often and for the same reasons.

On Wednesday, December 25, 2019, 9:39:19 PM CST, Gary Robert Bosworth <grbosworth@gmail.com> wrote:

It is a shame that the original spacing for the batteries was so tight.  I
realize the need to keep the leads short, but it makes it difficult to
replace the Mercury cells in such a tight spot.  It would be nice if
someone could come up with a tiny hybrid fix that could be dropped into the
small footprint.

Gary

On Tue, Dec 24, 2019 at 11:21 AM Bob Headrick <bobh@proaxis.com> wrote:

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%





--
Gary Robert Bosworth
grbosworth@gmail.com
Tel: 310-317-2247


Re: tektronix 7S14 batteries and time base question

Bruce Griffiths
 

Just use SMT LEDs.
However the photocurrent will need to at least 50 uA to ensure that output impedance is low enough.
A shunt capacitor across the output LED may also be required.
Bruce

On 26 December 2019 at 16:38 Gary Robert Bosworth <grbosworth@gmail.com> wrote:


It is a shame that the original spacing for the batteries was so tight. I
realize the need to keep the leads short, but it makes it difficult to
replace the Mercury cells in such a tight spot. It would be nice if
someone could come up with a tiny hybrid fix that could be dropped into the
small footprint.

Gary

On Tue, Dec 24, 2019 at 11:21 AM Bob Headrick <bobh@proaxis.com> wrote:

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%





--
Gary Robert Bosworth
grbosworth@gmail.com
Tel: 310-317-2247



Re: tektronix 7S14 batteries and time base question

Gary Robert Bosworth
 

It is a shame that the original spacing for the batteries was so tight. I
realize the need to keep the leads short, but it makes it difficult to
replace the Mercury cells in such a tight spot. It would be nice if
someone could come up with a tiny hybrid fix that could be dropped into the
small footprint.

Gary

On Tue, Dec 24, 2019 at 11:21 AM Bob Headrick <bobh@proaxis.com> wrote:

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%





--
Gary Robert Bosworth
grbosworth@gmail.com
Tel: 310-317-2247


Tek 475 with no +15v Supply, help needed

Py1dkw@...
 

First if all, woukd like to wish all a Merry Christmas and a Happy New Year
I recently bought a 475 scope,  which is not cosmetically beautiful, but all components are original not a sign of previous maintenance. 
I am trying to fix the power supply. This time I do have the 2450 V, so I was glad because of the hard to obtain high tension multiplier.
I've tested the power supply :
110V = OK
50V = OK
5V = OK
+15V = 0 V
-15V = 0 V
-8V = 0 V

Are the regulation comparators of both -8 and -15v powered by the +15V. ? So, my problem comes from this line.
I measured the resistance between +15V and GND and I got 0.2 OHMS.
There is a short-cut between the +15 and GND. I had disconnected the vertical board terminals, and opened the white jump in the main board.
I had checked all tantalum capacitors in the main board that goes from +15V line, disconnected one leg and diodes to ground too.
Many thanks to all !
Sam Rocha 
Py1dkw


Re: Tek 2235 Repair

chipbee40
 

From your photo on eevblog it looks like your trigger is set to VERT MODE and LINE. Set it to CH1 and INT and AC. Cant see your other settings but P-P Auto would be best.


Re: Thank you

Lawrance A. Schneider
 

Congratulations for your thank you.

larry


Re: tektronix 7S14 batteries and time base question

Bruce Griffiths
 

If its intended as a Mercury battery replacement in the 7S14 the output impedance is important, if its more than a few hundred ohms it will have a significant effect on the preamp dynamics.
The output voltage is also important.

Bruce

On 25 December 2019 at 10:19 Miguel Work <harrimansat@hotmail.com> wrote:


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



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@hotmail.com> 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@ridesoft.com> 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







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