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Kirk Fraser
09-18-2011, 04:52 PM
I unfortunately have a Tek TDS 220 which claims 100 MHz but fails to deliver it effectively. Apparently one needs a multiple of that rating to show Propeller signals. Phil-Pi's waveform display posts are excellent but his scope is no longer manufactured.

What is your recommendation for a good cheap scope suitable for 100 MHz Props or more? I'm open to any manufacturer, even a PC add-on.

Leon
09-18-2011, 05:07 PM
I use an old Tek 2235 100 MHz scope which works very well. A weak point is the timebase selector switch, which can be intermittent and sometimes needs a bit of fiddling. A 100 MHz scope is only suitable for 100 MHz sine wave signals, of course.

kwinn
09-18-2011, 05:18 PM
I tried to download the TDS 220 manual but got a DNS error so could not determine the analog bandwidth or sampling rate. If the scope sampling rate is 100MHz you will get poor results with 80MHz signals. I did however find there is a safety recall on this scope concerning the ground connection. It is possible this may have some effect on your measurements. Take a look at http://www.tek.com/service/safety/tds200/faq.html to see if it applies to your scope.

Phil Pilgrim (PhiPi)
09-18-2011, 06:34 PM
I use an old Tek 2235 100 MHz scope which works very well. A weak point is the timebase selector switch, ...
I finally had to mothball my 2235 for just that reason. That "switch" is actually a camshaft with cams that press tactile switches in the PCB. Unfortunately, the camshaft can acquire a bow after awhile, and some of the cams will no longer reach their assigned switches. Years ago, I was able to get a new camshaft assembly from Tek, to replace the bent one, and it worked great again until the replacement shaft bent with age. I don't know if parts are still available for it, though.

BTW, if you can get a new shaft and disassemble the scope to replace it, there's a chassis ground wire that has to be unsoldered just to get the case apart.

-Phil

Leon
09-18-2011, 06:56 PM
Thanks, Phil. I'd assumed it was a problem with the PCB rather than the camshaft, in which case I might have tried designing one and getting it made. Replacement parts are no longer available.

Kirk Fraser
09-18-2011, 07:01 PM
I tried to download the TDS 220 manual but got a DNS error so could not determine the analog bandwidth or sampling rate. If the scope sampling rate is 100MHz you will get poor results with 80MHz signals. I did however find there is a safety recall on this scope concerning the ground connection. It is possible this may have some effect on your measurements. Take a look at http://www.tek.com/service/safety/tds200/faq.html to see if it applies to your scope.

I looked up the serial numbers but mine is outside the recall range. Thanks.