Tweaking Old Analog Oscilloscope

Ultima Thule · 2nd November 2005, 09:24 AM

Hi,

I have had an idea for some time that I would like to change some components and upgrade the powersupply inside my scope to gain better performance of it, it's today 40 MHz and I would like to double the speed of the scope and get sharper and stronger wave trace ray on the CRT.

Have anyone done something similar and have anything to share, it would be fun to hear your story!

I have thought about to change especially esential transistors to faster ones with perhaps a bit lower noise too, changing vital capacitors and old dry el-lytes.
The CRT would need a better PSU as the mains frequency can be seen on the screen and have a bit too thick trace on the CRT, and changing the horisontal deflection transistor to faster ones with low Cob and so on.
I believe it to be posible to get better performance on a bit over 15 years old scope as component technology have also developed.

Comments?

Cheers Michael

Ultima Thule · 12th November 2005, 03:16 PM

I guess this is not a hot topic but bump this post up after zero replies over a week...

I_Forgot · 12th November 2005, 04:11 PM

Designing amplifiers/sweep circuits for oscopes is not a trivial task. This is one instance where the commercial product is almost always better than what you could do yourself.

It sounds like what you are talking about is completely rebuilding your scope. While it is possible, it is not practical. By the time you're done, it will have been cheaper to get another scope that has the specs you want. I suggest selling the old scope and applying the money plus a little more to get one that meets your requirements.

Surplus scopes can be pretty cheap if you know where to look. Go to ham radio swap-meets. You'll find what you want pretty quickly. I have a military surplus 100 MHz HP scope that I picked up for $75 a few years ago. That is not atypical.

TD

ctviggen · 16th November 2005, 03:04 PM

Wow, $75 is good. I was thinking more like several hundred. Is yours analog or digital?

I_Forgot · 16th November 2005, 10:22 PM

Analog.

I think I spent another $150 for a set of new probes for it. Scope probes are interesting devices, and selecting them is not nearly as simple as you might think. Tektronix's web site has at least one app note about how to properly match probes to a scope. You might check it out. Maybe the performance limitation you are experiencing is due to mismatch between your probes and scope.

Improving scope performance is unfortunately not as simple as putting in "faster" transistors.

I_F

anatech · 16th November 2005, 10:44 PM

That's true. The standing current in the deflection drivers will have to go up for one. The rest of the problems I don't want to think about.

Fix up the older 'scope. There is a lot you can do with it. Buy a better one if you need it.

-Chris

dnsey · 17th November 2005, 07:23 AM

I've been thinking about almost the opposite idea!
A scope has low noise, low distortion, sensitive amlifiers. How well would they work as audio pre-amps? One of these days, I'll tap into my old scope, and try it.

anatech · 17th November 2005, 12:10 PM

Hi dnsey,

Quote:

A scope has low noise, low distortion, sensitive amlifiers. How well would they work as audio pre-amps? One of these days, I'll tap into my old scope, and try it.

Some of the new preamp designs are based on osilloscope circuitry, probably some older ones too. Let us know when you try this.

-Chris

2nd November 2005, 09:24 AM	#1
Ultima Thule diyAudio Member Join Date: Jan 2004 Location: Koskenkorva Land	Tweaking Old Analog Oscilloscope Hi, I have had an idea for some time that I would like to change some components and upgrade the powersupply inside my scope to gain better performance of it, it's today 40 MHz and I would like to double the speed of the scope and get sharper and stronger wave trace ray on the CRT. Have anyone done something similar and have anything to share, it would be fun to hear your story! I have thought about to change especially esential transistors to faster ones with perhaps a bit lower noise too, changing vital capacitors and old dry el-lytes. The CRT would need a better PSU as the mains frequency can be seen on the screen and have a bit too thick trace on the CRT, and changing the horisontal deflection transistor to faster ones with low Cob and so on. I believe it to be posible to get better performance on a bit over 15 years old scope as component technology have also developed. Comments? Cheers Michael __________________ "If transistors are blueberries and FETs are strawberries, then tubes must be.. pears" Michael 29th January 2010

12th November 2005, 03:16 PM	#2
Ultima Thule diyAudio Member Join Date: Jan 2004 Location: Koskenkorva Land	I guess this is not a hot topic but bump this post up after zero replies over a week... __________________ "If transistors are blueberries and FETs are strawberries, then tubes must be.. pears" Michael 29th January 2010

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12th November 2005, 04:11 PM	#3
I_Forgot diyAudio Member Join Date: Jan 2005 Location: Phoenix, Az.	Designing amplifiers/sweep circuits for oscopes is not a trivial task. This is one instance where the commercial product is almost always better than what you could do yourself. It sounds like what you are talking about is completely rebuilding your scope. While it is possible, it is not practical. By the time you're done, it will have been cheaper to get another scope that has the specs you want. I suggest selling the old scope and applying the money plus a little more to get one that meets your requirements. Surplus scopes can be pretty cheap if you know where to look. Go to ham radio swap-meets. You'll find what you want pretty quickly. I have a military surplus 100 MHz HP scope that I picked up for $75 a few years ago. That is not atypical. TD

16th November 2005, 03:04 PM	#4
ctviggen diyAudio Member Join Date: Oct 2005	Wow, $75 is good. I was thinking more like several hundred. Is yours analog or digital?

16th November 2005, 10:22 PM	#5
I_Forgot diyAudio Member Join Date: Jan 2005 Location: Phoenix, Az.	Analog. I think I spent another $150 for a set of new probes for it. Scope probes are interesting devices, and selecting them is not nearly as simple as you might think. Tektronix's web site has at least one app note about how to properly match probes to a scope. You might check it out. Maybe the performance limitation you are experiencing is due to mismatch between your probes and scope. Improving scope performance is unfortunately not as simple as putting in "faster" transistors. I_F

16th November 2005, 10:44 PM	#6
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	That's true. The standing current in the deflection drivers will have to go up for one. The rest of the problems I don't want to think about. Fix up the older 'scope. There is a lot you can do with it. Buy a better one if you need it. -Chris

17th November 2005, 07:23 AM	#7
dnsey diyAudio Member Join Date: Mar 2004 Location: Shropshire, England	I've been thinking about almost the opposite idea! A scope has low noise, low distortion, sensitive amlifiers. How well would they work as audio pre-amps? One of these days, I'll tap into my old scope, and try it.

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