开云体育

475 Triggering Issue -- Expanded to trigger ckt.s in general.

Rob #86611 开云体育 Sorry to jump in with questions on another person’s original…I did change the subject line so to not dilute the original thread… ? I have not seen anyone suggest putting together a trigger system/ckt that doesn’t rely on tunneling diodes and wiring something in to bypass the triggering in the 475 altogether with something else.. ? Not that I would know if this is even possible. However, given the plethora of USB Oscilloscopes, the years that have passed and the overall issues with tunneling diodes…. I can but assume that there is an IC or other buildable ckt./kit out there that would be plug and play at some level. ? Conversely this whole line of thought may be naive? Admittedly I have not researched tunneling diodes to even know what makes them special and/or why there were used in triggering ckts, etc. If someone could pass links on resources for learning or give a concise working man’s explanation of all that; I would be appreciative. ? Thanks as always for the band width Rob toggle quoted message Show quoted text From: TekScopes@... [mailto:TekScopes@...] On Behalf Of Max Mazza Sent: Saturday, January 26, 2013 8:14 PM To: TekScopes@... Subject: [TekScopes] Re: 475 Triggering Issue -- Will recent 468 Triggering Issue Thread Help Me? ? ? --- In TekScopes@..., "stan_katz" wrote: > > I have an ancient 475 scope which works fine with an external trigger, but will not trigger on any of the internal sources. Should I start by reviewing the recent 468 triggering issue thread to get me going? If not, can anyone recommend a thread I should start with? Of course, I'd be delighted to receive help on this thread. > > Stan > I think the TD is the problem. I got a similar problem in my 3B4 plugin. Try to detach one terminal of the TD CR566 (using adequate protection against heating, like a pliers) and check if the behavior is the same. If the TD is defective (i.e. open), the trigger still works, but only in presence of sufficiently steep and large signals, like square waves and/or external trigger pulses (which are generally square waves or pulses). With sinewaves it's likely that trigger doesn't work, but with squares do. The same test may apply to CR556 (the arming TD). You can also check for the presence of a pulse signal on either bases of Q556 and Q566. If they're present, all the circuitry preceding Q556/566 are well-working. Max
David Hess Member Profile All Messages By This Member #86615 There is no two terminal replacement circuit for a tunnel diode which could come even close to their switching speed. As far as I know, all later Tektronix trigger circuits used integrated circuits. What I would try is replacing the tunnel diode section of the trigger circuit with a fast differential Schmitt comparator but I imagine there is some tricky reason it would not perform as well. Take a look at the 7D15 trigger circuit for an example. On Sat, 26 Jan 2013 20:38:54 -0600, "Rob" <rgwood@...> wrote: Sorry to jump in with questions on another person's original.I did change the subject line so to not dilute the original thread. I have not seen anyone suggest putting together a trigger system/ckt that doesn't rely on tunneling diodes and wiring something in to bypass the triggering in the 475 altogether with something else.. Not that I would know if this is even possible. However, given the plethora of USB Oscilloscopes, the years that have passed and the overall issues with tunneling diodes.. I can but assume that there is an IC or other buildable ckt./kit out there that would be plug and play at some level. Conversely this whole line of thought may be naive? Admittedly I have not researched tunneling diodes to even know what makes them special and/or why there were used in triggering ckts, etc. If someone could pass links on resources for learning or give a concise working man's explanation of all that; I would be appreciative.

Previous Topic Next Topic