Date   

Re: tektronix 7S14 batteries and time base question

Bruce Griffiths
 

Hi Dennis

Some issues with the 7S14 sampler circuit schematic (1988 version)

1) The avalanche bias adjust circuitry shown in the schematic doesnt work. The 470 ohm resistor should be connected between the collector of the npn (Q20) transistor and HV.

2) The sampling pulse generator circuitry shown produces zero output.
The tapped shorted microstrip delay lines that shape the output from the avalanche transistor have been omitted from the schematic. These are obvious in the actual physical layout.

Any mismatch between the 2 series resistors will result in sampling pulse residue at the preamp input.

The sampling pulse width will be around 350ps or thereabouts (effective sampler risetime specified as 350ps).

Have started playing with an LTspice simulation (omitting blowby compensation for now).

Bruce

On 27 December 2019 at 16:42 Dennis Tillman W7PF <dennis@ridesoft.com> wrote:


Hi Bruce,
Thank you for your post on using clear epoxy to bond LEDs to each other. I chopped off the ends of a white source LED and a red receiving LED with a sharp razor and I glued them together with clear epoxy as he said to do. Preliminary results show an insignificant difference in the output voltage this pair generates. I will be doing more testing to determine this and other things I experiment with in the next few days. I will report my results to the group.

In the original 070-1410-00 7S14 manual I have (Dec, 1973) the resistors in series with the mercury cells (R1 and R2) are 200 ohms each. In the 1985 revision (Apr, 1985) they are 2,000 ohms. The change took place at serial number B030000 and above.

The mercury cells reverse bias the sampling diodes until a strobe pulse forward biases them. Strobe pulses are extremely short. So even under heavy usage the current drain from the cells will have a very small duty cycle. It would be helpful to know how long a strobe pulse lasts and what voltage they go to. Has anyone done this?

The low duty cycle means a very low overall current drain on the cell. But during each strobe the diodes are forward biased and it is important that they get all the forward current they need to conduct. The very low internal resistance of the mercury cell means it can provide any forward biased current the diode draws. The 2K series resistance of R1 (and R2) will limit the current surge to ~500uA which is fine for the cell but that is much more than the output LED of the mercury cell replacement can provide.

A small value low voltage capacitor could store the charge coming from the output LED and provide all the forward bias current needed by the sampling diodes when they are strobed. The voltage it stores is less than 2V. I would suggest it be a low leakage capacitor because of the minute current coming from the LED. Glass capacitors are a good choice since they are cheap and have virtually no leakage. As an example, a 0.033uF glass capacitor (like the ones shown in this link are no bigger than a 1/4W resistor. Unfortunately I could not find surface mount glass capacitors for some reason.
https://www.goldmine-elec-products.com/prodinfo.asp?number=G23938

Has anyone mentioned what the sampling diode technology is? If so I missed it. Also, someone mentioned a few months ago the temperature coefficient of the sampling gates. I went looking for where it was mentioned but I couldn't find it. I would think it would depend on the sampling diode technology. If anyone can remind me what the Tc was and what technology the sampling diodes are (I would guess they are silicon Schottky diodes) I would appreciate it. It affect many things we should consider when designing our substitute mercury cell such as turn-on voltage, current drain, strobe pulse duration, temperature coefficient, etc.

At this point in time I am the beneficiary of many experiments and suggestions on replacements for the 7S14 mercury cells. Previous informal random experimentation seems to have recently shifted to detailed discussions of important design considerations. What would help me make a contribution of my own is 1) knowing the technology of the sampling diodes, and 2) documenting the strobe pulse's voltage, duration, and current drain on the battery. I'm hoping someone can help me with #1. I can do #2 myself.

I welcome comments since, as far as I know, some of my thinking hasn't been discussed yet.

Dennis Tillman W7PF

-----Original Message-----
From Bruce Griffiths
Sent: Monday, December 23, 2019 4:17 PM

LED encapsulation is clear epoxy. Clear epoxy is best suited to bonding LEDs end to end. Either mechanical preparation of the mating surfaces or priming is required. Done properly the roughened ends are thoroughly wet by the bonding epoxy and the joint is invisible.
The refractive index of cyanoacrylate adhesives is somewhat lower than that of epoxies.
For a Lambertian source like a LED, butt coupling is effective. Intervening optics doesn't improve the coupling. The dome lens on the LED doesn't collimate the light so that an intermediate lens is required to maximise coupling if this method is chosen.

For maximum coupling when butt coupling the separation of the 2 LED die should be comparable with the source diameter, However reflected light from the cupped lead frame of the LED may relax this requirement a little.
Optocouplers use butt coupling with a thin transparent insulating film between the emitter and the detector.
The peak response of a LED used as a photodetector occurs at a wavelength that differs slightly from its emission peak when used as an LED.
Most of this was covered in the HP optoelectronics Handbook around 1970-80.

Bruce

On 24 December 2019 at 12:34 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



--
Dennis Tillman W7PF
TekScopes Moderator



Re: 465M Junker

KB6NAX
 

Wrong number, Brian. The vertical input dual FET in the 465M is 151-1090-00 thru -04. TO-78 or TO-99 package with same pinouts as 2N5911. Be careful with cross references. There's often large divergences in specs but sometimes that doesn't matter, sometimes it's critical. I try to get the right parts the first time. Thanks and Happy New Year to you.

Arden

-----Original Message-----
From: Brian Bloom via Groups.Io
Sent: Thursday, December 26, 2019 3:31 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 465M Junker

If memory serves me correctly, the package for a 2N5911 has a different lead configuration from the 151-1032-00 Tek part. I'm also going to note that all my references for this part are labeled "2N5911A".

If you want to do some cross referencing of the datasheets, there's a 2N5911 datasheet available on TekWiki and the 151-1032-00 data is on page 205 of the Tek cross-reference guide that's available from Sphere's website.

Sphere seems to have stock of used 151-1032-00's for $10 USD each, where it's also listed as "2N5911A".

Happy New Year!
-Brian


Re: tektronix 7S14 batteries and time base question

 

Hi Bruce,
Thank you for your post on using clear epoxy to bond LEDs to each other. I chopped off the ends of a white source LED and a red receiving LED with a sharp razor and I glued them together with clear epoxy as he said to do. Preliminary results show an insignificant difference in the output voltage this pair generates. I will be doing more testing to determine this and other things I experiment with in the next few days. I will report my results to the group.

In the original 070-1410-00 7S14 manual I have (Dec, 1973) the resistors in series with the mercury cells (R1 and R2) are 200 ohms each. In the 1985 revision (Apr, 1985) they are 2,000 ohms. The change took place at serial number B030000 and above.

The mercury cells reverse bias the sampling diodes until a strobe pulse forward biases them. Strobe pulses are extremely short. So even under heavy usage the current drain from the cells will have a very small duty cycle. It would be helpful to know how long a strobe pulse lasts and what voltage they go to. Has anyone done this?

The low duty cycle means a very low overall current drain on the cell. But during each strobe the diodes are forward biased and it is important that they get all the forward current they need to conduct. The very low internal resistance of the mercury cell means it can provide any forward biased current the diode draws. The 2K series resistance of R1 (and R2) will limit the current surge to ~500uA which is fine for the cell but that is much more than the output LED of the mercury cell replacement can provide.

A small value low voltage capacitor could store the charge coming from the output LED and provide all the forward bias current needed by the sampling diodes when they are strobed. The voltage it stores is less than 2V. I would suggest it be a low leakage capacitor because of the minute current coming from the LED. Glass capacitors are a good choice since they are cheap and have virtually no leakage. As an example, a 0.033uF glass capacitor (like the ones shown in this link are no bigger than a 1/4W resistor. Unfortunately I could not find surface mount glass capacitors for some reason.
https://www.goldmine-elec-products.com/prodinfo.asp?number=G23938

Has anyone mentioned what the sampling diode technology is? If so I missed it. Also, someone mentioned a few months ago the temperature coefficient of the sampling gates. I went looking for where it was mentioned but I couldn't find it. I would think it would depend on the sampling diode technology. If anyone can remind me what the Tc was and what technology the sampling diodes are (I would guess they are silicon Schottky diodes) I would appreciate it. It affect many things we should consider when designing our substitute mercury cell such as turn-on voltage, current drain, strobe pulse duration, temperature coefficient, etc.

At this point in time I am the beneficiary of many experiments and suggestions on replacements for the 7S14 mercury cells. Previous informal random experimentation seems to have recently shifted to detailed discussions of important design considerations. What would help me make a contribution of my own is 1) knowing the technology of the sampling diodes, and 2) documenting the strobe pulse's voltage, duration, and current drain on the battery. I'm hoping someone can help me with #1. I can do #2 myself.

I welcome comments since, as far as I know, some of my thinking hasn't been discussed yet.

Dennis Tillman W7PF

-----Original Message-----
From Bruce Griffiths
Sent: Monday, December 23, 2019 4:17 PM

LED encapsulation is clear epoxy. Clear epoxy is best suited to bonding LEDs end to end. Either mechanical preparation of the mating surfaces or priming is required. Done properly the roughened ends are thoroughly wet by the bonding epoxy and the joint is invisible.
The refractive index of cyanoacrylate adhesives is somewhat lower than that of epoxies.
For a Lambertian source like a LED, butt coupling is effective. Intervening optics doesn't improve the coupling. The dome lens on the LED doesn't collimate the light so that an intermediate lens is required to maximise coupling if this method is chosen.

For maximum coupling when butt coupling the separation of the 2 LED die should be comparable with the source diameter, However reflected light from the cupped lead frame of the LED may relax this requirement a little.
Optocouplers use butt coupling with a thin transparent insulating film between the emitter and the detector.
The peak response of a LED used as a photodetector occurs at a wavelength that differs slightly from its emission peak when used as an LED.
Most of this was covered in the HP optoelectronics Handbook around 1970-80.

Bruce

On 24 December 2019 at 12:34 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



--
Dennis Tillman W7PF
TekScopes Moderator


Trying to bring back a AA501

Eric
 

So I am finally working up the nerve to put an AA501 on the bench and run it through its checks. From a preliminary check in It looks like the voltage section is working well and tracking with my meter that is freshly in cal. However, it seems the distortion side needs some help. I have not tried to do a calibration on it yet as I have been a little nervous to open it up. With a shorting bar on the inputs it says 0.0079% distortion. With the outputs floating it is about 0.0303% with a signal applied from a wein bridge at about 1Khz 6.5V Pk I get a distortion figure of 100.3% distortion. On a scope that oscillator is a clean sign wave. On volts a 6.5V Pk voltage reads 4.65 VRMS. Math says it should be 4.63 so that could be with in the margin of error. A fluke 8840A reads 6.54~ off the peak detector of the oscillator. Any gotcha’s I should know about a AA501 before I start running through the service manual. I have had to repair the front connector it was very loose to the case. But that has been repaired.


Re: Tektronix 2465

Jose Alfredo
 

Tks for the feedback Panos, I'm afraid I'll have to go through the calibration process.

Em 26/12/2019 19:37, Panos escreveu:

Hi.
From your video I think that your Grid Bias setting is too high or out of range. The sure is that the dots in the bottom of the screen indicate a loss of your calibration settings. :-(

Panos


Re: Tektronix 2465

GerryR <totalautomation1@...>
 

One of the calibration procedures produces those series of dots when setting the vertical limits, if I remember correctly. It would appear that whatever initiates that procedure is somehow "stuck on." I'll try to find which procedure it is and report back.

GerryR
KK4GER

----- Original Message -----
From: "Jose Alfredo" <alfredo@itesh.com.br>
To: <TekScopes@groups.io>
Sent: Thursday, December 26, 2019 3:38 PM
Subject: [TekScopes] Tektronix 2465


Hello everybody,

I just bought this Tektronix 2465 oscilloscope here in Brazil. When turned on, you can see blinking dots on both, upper and down fields, that show the unit status - see my video on https://youtu.be/NDc4gKDbCQI. Have any of you had any similar experience that could help me fixing it?

Thanks

Jose Alfredo C. Santos




Re: 465M Junker

Brian Bloom
 

If memory serves me correctly, the package for a 2N5911 has a different lead configuration from the 151-1032-00 Tek part. I'm also going to note that all my references for this part are labeled "2N5911A".

If you want to do some cross referencing of the datasheets, there's a 2N5911 datasheet available on TekWiki and the 151-1032-00 data is on page 205 of the Tek cross-reference guide that's available from Sphere's website.

Sphere seems to have stock of used 151-1032-00's for $10 USD each, where it's also listed as "2N5911A".

Happy New Year!
-Brian


Re: Tektronix 2465

Panos
 

Hi.
From your video I think that your Grid Bias setting is too high or out of range. The sure is that the dots in the bottom of the screen indicate a loss of your calibration settings. :-(

Panos


Re: tektronix 7S14 batteries and time base question

Bruce Griffiths
 

The 7S14 uses a 2K resistor in series with each battery.
20uA photocurrent implies a slope resistance of around 2.5K for a photodiode with n =2.
This more than doubles the series resistance and adds some nonlinearity as well.
Simulating the sampler and preamp (including blowby compensation) will be helpful in establishing the effects of using photodiodes instead of batteries. Start with batteries to give a baseline for comparison.
Then substitute photodiodes (diode driven by current source should suffice) to see the effect of varying the photodiode current and the effect of shunt capacitors across the diodes.

Bruce

On 27 December 2019 at 08:58 Dave Wise <david_wise@phoenix.com> wrote:


Oh, LH1262, not LC1262. Short-circuit current is a few uA, I wonder what it puts out at a couple volts. There are lots of PV-output SSR's, many of which put out more, but still only 10-20uA max. IIRC, an expert told us we need at least 50uA.

Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Dave Wise via Groups.Io <david_wise=phoenix.com@groups.io>
Sent: Thursday, December 26, 2019 11:54 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] tektronix 7S14 batteries and time base question

Can you confirm that part number, Tom? Mouser returns zero hits on "LC1262".
And what's the output current? This is probably one of those photovoltaic-output SSR's like I mentioned a moment ago.

Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Tom Bowers via Groups.Io <pvhengineering=gmail.com@groups.io>
Sent: Thursday, December 26, 2019 9:30 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] tektronix 7S14 batteries and time base question

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













Tektronix 2465

Jose Alfredo
 

Hello everybody,

I just bought this Tektronix 2465 oscilloscope here in Brazil. When turned on, you can see blinking dots on both, upper and down fields, that show the unit status - see my video on https://youtu.be/NDc4gKDbCQI. Have any of you had any similar experience that could help me fixing it?

Thanks

Jose Alfredo C. Santos


Re: tektronix 7S14 batteries and time base question

Tom Bowers
 

Sorry, LH1262 is correct. LCs were a different family

Tom

On Thu, Dec 26, 2019 at 12:59 PM Dave Wise <david_wise@phoenix.com> wrote:

Oh, LH1262, not LC1262. Short-circuit current is a few uA, I wonder what
it puts out at a couple volts. There are lots of PV-output SSR's, many of
which put out more, but still only 10-20uA max. IIRC, an expert told us we
need at least 50uA.

Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Dave Wise
via Groups.Io <david_wise=phoenix.com@groups.io>
Sent: Thursday, December 26, 2019 11:54 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] tektronix 7S14 batteries and time base question

Can you confirm that part number, Tom? Mouser returns zero hits on
"LC1262".
And what's the output current? This is probably one of those
photovoltaic-output SSR's like I mentioned a moment ago.

Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Tom Bowers
via Groups.Io <pvhengineering=gmail.com@groups.io>
Sent: Thursday, December 26, 2019 9:30 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] tektronix 7S14 batteries and time base question

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














465M Junker

KB6NAX
 

Been a long time since visiting TekScopes. In the mean time I restored over half a dozen 455 scopes, the ignored 50 MHz sibling of the 465M (heh, heh, much easier to work on with plug in transistors). I always pitty the less appreciated, that's why I rescue homeless dogs. Well, I happened on a homeless 465M on the 'Bay and brought it home. Like a homeless dog I got it for free minus the shipping. It arrived shipping damaged so the seller refunded my purchase price of $24.00. Yes, it's a "fix or toss" junker. I'm working on the fix part. Among its myriad of problems It came without it's CH1 input dual FET. So I found a number of 2N5911 offerings and ordered one. But the question on my mind while waiting for the post man is, are there any "gotchas" regarding replacing any make 2N5911's or for success do I really need to find a genuine Tek part? Happy New Year!


Re: tektronix 7S14 batteries and time base question

Dave Wise
 

Oh, LH1262, not LC1262. Short-circuit current is a few uA, I wonder what it puts out at a couple volts. There are lots of PV-output SSR's, many of which put out more, but still only 10-20uA max. IIRC, an expert told us we need at least 50uA.

Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Dave Wise via Groups.Io <david_wise=phoenix.com@groups.io>
Sent: Thursday, December 26, 2019 11:54 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] tektronix 7S14 batteries and time base question

Can you confirm that part number, Tom? Mouser returns zero hits on "LC1262".
And what's the output current? This is probably one of those photovoltaic-output SSR's like I mentioned a moment ago.

Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Tom Bowers via Groups.Io <pvhengineering=gmail.com@groups.io>
Sent: Thursday, December 26, 2019 9:30 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] tektronix 7S14 batteries and time base question

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

Dave Wise
 

Can you confirm that part number, Tom? Mouser returns zero hits on "LC1262".
And what's the output current? This is probably one of those photovoltaic-output SSR's like I mentioned a moment ago.

Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Tom Bowers via Groups.Io <pvhengineering=gmail.com@groups.io>
Sent: Thursday, December 26, 2019 9:30 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] tektronix 7S14 batteries and time base question

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

Dave Wise
 

There are isolated gate drivers, but it turns out that Mouser's parts in this category require a floating power supply.
But there are SSR's with a photodiode array output, also intended for driving MOSFET gates, which supply photovoltaic power.
Unfortunately, most or all put out only a few microamps. Sorry for the false alarm.

Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of John Griessen via Groups.Io <john=ecosensory.com@groups.io>
Sent: Thursday, December 26, 2019 9:43 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] tektronix 7S14 batteries and time base question

On 12/26/19 11:32 AM, Dave Wise wrote:
How about a power MOSFET gate driver IC? There are lots of those around.
Those will have a common ground, so will still contribute to ground loop induced voltages --> noise.
Or are there opto coupled drivers?

The opto solutions float like a battery and only have some capacitive coupling to outside wiring noise sources.


Re: tektronix 7S14 batteries and time base question

John Griessen
 

On 12/26/19 11:32 AM, Dave Wise wrote:
How about a power MOSFET gate driver IC? There are lots of those around.
Those will have a common ground, so will still contribute to ground loop induced voltages --> noise.
Or are there opto coupled drivers?

The opto solutions float like a battery and only have some capacitive coupling to outside wiring noise sources.


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

21081 - 21100 of 183398