Jonathan wrote:
Perhaps that's why people aren't interested in 20 MHz "student" or "TV" 'scopes but will spend money on USB connected device that claim 100+ MHz bandwidth...
Jonathan knows about, what I'm about to post.... Note that I cast those 20-40Mhz scopes as alternatives to logic probes; a low bar. It defies my old-person 20th century mind, that someone would try to debug TTL logic and 4MHz processors with a logic probe and interpret a blinking LED. When most any 'scope with triggered sweep will provide means to check timing and logic states at 8-bit processor speeds. Not to mention, funny logic levels that will confuse gates, and indicate fried TTL drivers or possibly shorted lines and connections. I'd say most 1970's microcomputer failures could be "caught" with this class of oscilloscopes, used with some knowledge and experience and a TTL data book. What such scopes won't do, is catch "glitches", odd logic events due to faulty timing or noise artifacts treated as logic signals. That's when a 100Mhz true analog bandwidth starts to become useful. And at that, you may need a storage 'scope to catch one-off events. While I've bought and used simple "TV repairperson scopes" - I actually see better 'scopes than that, go begging. One I picked up Sunday, has some kind of digital storage, but otherwise analog. The other is a lower-end Tek scope with some digital controls. One acquired late last year, was 40Mhz and had some digital display features. As for USB-based "oscilloscopes", those are analog-digitizing devices which use a PC for display and operation. Sample rate does not equal bandwidth, an LCD does not equal a CRT. (hooking thumbs in suspenders) While I don't know much about 'dem fancy, hew-hess-bee, citi-fied ways of readin' logic levels; it seems to me that an honest, middlin' bandwidth, analog 'scope, with a bright green CRT, can do the job, 'jest *fine*. I'll take a bank of ten-turn potentiometers and toggles, over a click-and-pray virtual test panel, any day. Uncle Herb -- Herbert R. Johnson, New Jersey USA http://www.retrotechnology.com OR .net preservation of 1970's computing email: hjohnson AAT retrotechnology DOTT com alternate: herbjohnson ATT retrotechnology DOTT info