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Old 25th Sep 2023, 3:51 pm   #1
Smithdoor
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Default Dual Trace /Electronic Switch build

Look at building a Electronic Switch for my oscilloscope.
Please comment on the schematic

Dave
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Old 25th Sep 2023, 5:40 pm   #2
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Default Re: Dual Trace /Electronic Switch build

I wonder if it might be easier to use more modern components, maybe 74lvc1g3157 for the switching. Input/output voltage range would be limited to 0-5v, so would need to have some kind of input attenuator and protection circuit. These are in surface mount package, but sot-23-6 are not too difficult to hand solder.
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Old 25th Sep 2023, 11:36 pm   #3
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Default Re: Dual Trace /Electronic Switch build

Quote:
Originally Posted by Mark1960 View Post
I wonder if it might be easier to use more modern components, maybe 74lvc1g3157 for the switching. Input/output voltage range would be limited to 0-5v, so would need to have some kind of input attenuator and protection circuit. These are in surface mount package, but sot-23-6 are not too difficult to hand solder.
It is interesting.
Look at specific sheet.
Protection could be a Zenor diode and fuse.
I would like find it in DIP if goes up in smoke it easy to replace.

Thank you
Dave
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Old 26th Sep 2023, 1:02 am   #4
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Default Re: Dual Trace /Electronic Switch build

Zener diodes aren't much use for protectinf fast signals. They have a surprising amount of junction capacitance, also they conduct like normal diodes in the other direction.

So any protective shunt needs low capacitance fast diodes to do the clamping, with zeners and a bias supply making the voltage level the fast diodes clamp to.

David
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Old 26th Sep 2023, 8:42 pm   #5
Ed_Dinning
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Default Re: Dual Trace /Electronic Switch build

Hi Folks, back in the late 60's early 70's Peter Cairns designed several scope circuits that were published in RC, WW, PW and PTV.
These all used common discreet components.
It might be worth a look to see if you can find them, if no luck mail me and I'll see what can be found when I get a minute

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Old 27th Sep 2023, 3:30 am   #6
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Default Re: Dual Trace /Electronic Switch build

Here one that looks good
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Old 27th Sep 2023, 4:48 pm   #7
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Default Re: Dual Trace /Electronic Switch build

Here is my drawing on electronic switch.

Dave
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Old 27th Sep 2023, 11:30 pm   #8
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Default Re: Dual Trace /Electronic Switch build

This how to use a Electronic Switch by Heathkit.

Dave
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Old 29th Sep 2023, 3:12 am   #9
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Default Re: Dual Trace /Electronic Switch build

Here is a better information on using a Electronic Switch

FYI I used my Eico 488 on my 435 without using SYNC.
If looking for the SYNC it can located on front panel, on back of Oscilloscope or on Horz input and switch to SYNC and may not be labeled but on Switch.
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Old 29th Sep 2023, 5:26 pm   #10
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Default Re: Dual Trace /Electronic Switch build

Here a different schematic I am looking at.
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Old 4th Oct 2023, 1:55 pm   #11
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Default Re: Dual Trace /Electronic Switch build

Here latest schematic on a simple electronic switch.
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Old 6th Oct 2023, 8:44 pm   #12
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Default Re: Dual Trace /Electronic Switch build

Latest update
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Old 7th Oct 2023, 4:16 pm   #13
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Default Re: Dual Trace /Electronic Switch build

This is all transistor electronic switch.
Please comments

Dave
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Old 10th Oct 2023, 12:33 am   #14
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Default Re: Dual Trace /Electronic Switch build

Update getting closer to finishing.
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Old 10th Oct 2023, 7:33 am   #15
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Default Re: Dual Trace /Electronic Switch build

I'd copy a circuit from eg the Tektronix 453. All discrete, with ch1/ch2/chop/alt/add switching too. 50MHz bandwidth.

But your options are going to be of very limited bandwidth with simple potentiometers as input attenuators. Switched attenuators with careful compensation are essential if you want a bandwidth more that a few hundred kHz.

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Old 10th Oct 2023, 2:10 pm   #16
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Default Re: Dual Trace /Electronic Switch build

Thank you for your input.

I would worry about 50 MHz but most oscilloscopes that need a Electronic Switch is only rated for 5 MHZ.
The cellphones using the mic plug is only rated for 40KHZ.

The components are rate for 250Mhz

Dave


Quote:
Originally Posted by Craig Sawyers View Post
I'd copy a circuit from eg the Tektronix 453. All discrete, with ch1/ch2/chop/alt/add switching too. 50MHz bandwidth.

But your options are going to be of very limited bandwidth with simple potentiometers as input attenuators. Switched attenuators with careful compensation are essential if you want a bandwidth more that a few hundred kHz.

Craig
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Old 10th Oct 2023, 2:27 pm   #17
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Default Re: Dual Trace /Electronic Switch build

Here spec I am looking.
Trying to do better that the 1960's.

Dave


Quote:
Originally Posted by Craig Sawyers View Post
I'd copy a circuit from eg the Tektronix 453. All discrete, with ch1/ch2/chop/alt/add switching too. 50MHz bandwidth.

But your options are going to be of very limited bandwidth with simple potentiometers as input attenuators. Switched attenuators with careful compensation are essential if you want a bandwidth more that a few hundred kHz.

Craig
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Old 10th Oct 2023, 6:42 pm   #18
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Default Re: Dual Trace /Electronic Switch build

Here is a updated schematic.


Quote:
Originally Posted by Craig Sawyers View Post
I'd copy a circuit from eg the Tektronix 453. All discrete, with ch1/ch2/chop/alt/add switching too. 50MHz bandwidth.

But your options are going to be of very limited bandwidth with simple potentiometers as input attenuators. Switched attenuators with careful compensation are essential if you want a bandwidth more that a few hundred kHz.

Craig
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Old 12th Oct 2023, 6:54 pm   #19
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Default Re: Dual Trace /Electronic Switch build

Here update close to end.
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Old 13th Oct 2023, 4:28 pm   #20
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Default Re: Dual Trace /Electronic Switch build

This includes parts ID and protection resistors
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