Dual Trace /Electronic Switch build - UK Vintage Radio Repair and Restoration Discussion Forum

Smithdoor · 25th Sep 2023, 3:51 pm

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

Dave

Mark1960 · 25th Sep 2023, 5:40 pm

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.

Smithdoor · 25th Sep 2023, 11:36 pm

Quote:

Originally Posted by Mark1960

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

Radio Wrangler · 26th Sep 2023, 1:02 am

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

Ed_Dinning · 26th Sep 2023, 8:42 pm

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

Ed

Smithdoor · 27th Sep 2023, 3:30 am

Here one that looks good

Smithdoor · 27th Sep 2023, 4:48 pm

Here is my drawing on electronic switch.

Dave

Smithdoor · 27th Sep 2023, 11:30 pm

This how to use a Electronic Switch by Heathkit.

Dave

Smithdoor · 29th Sep 2023, 3:12 am

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.

Smithdoor · 29th Sep 2023, 5:26 pm

Here a different schematic I am looking at.

Smithdoor · 4th Oct 2023, 1:55 pm

Here latest schematic on a simple electronic switch.

Smithdoor · 6th Oct 2023, 8:44 pm

Latest update

Smithdoor · 7th Oct 2023, 4:16 pm

This is all transistor electronic switch.
Please comments

Dave

Smithdoor · 10th Oct 2023, 12:33 am

Update getting closer to finishing.

Craig Sawyers · 10th Oct 2023, 7:33 am

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

Smithdoor · 10th Oct 2023, 2:10 pm

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

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

Smithdoor · 10th Oct 2023, 2:27 pm

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

Dave

Quote:

Originally Posted by Craig Sawyers

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

Smithdoor · 10th Oct 2023, 6:42 pm

Here is a updated schematic.

Quote:

Originally Posted by Craig Sawyers

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

Smithdoor · 12th Oct 2023, 6:54 pm

Here update close to end.

Smithdoor · 13th Oct 2023, 4:28 pm

This includes parts ID and protection resistors

25th Sep 2023, 3:51 pm	#1
Smithdoor Pentode Join Date: May 2023 Location: Clovis, California, USA. Posts: 191	Dual Trace /Electronic Switch build Look at building a Electronic Switch for my oscilloscope. Please comment on the schematic Dave Attached Thumbnails

25th Sep 2023, 5:40 pm	#2
Mark1960 Octode Join Date: Mar 2020 Location: Kitchener, Ontario, Canada Posts: 1,195	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.

26th Sep 2023, 1:02 am	#4
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,234	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 __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

26th Sep 2023, 8:42 pm	#5
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,015	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 Ed

27th Sep 2023, 11:30 pm	#8
Smithdoor Pentode Join Date: May 2023 Location: Clovis, California, USA. Posts: 191	Re: Dual Trace /Electronic Switch build This how to use a Electronic Switch by Heathkit. Dave Attached Thumbnails

29th Sep 2023, 3:12 am	#9
Smithdoor Pentode Join Date: May 2023 Location: Clovis, California, USA. Posts: 191	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. Attached Thumbnails

10th Oct 2023, 7:33 am	#15
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,864	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. Craig __________________ Doomed for a certain term to walk the night