Re: 475 Triggering Issue -- Will recent 468 Triggering Issue Thread Help Me?


I am not exactly sure when Tektronix started using tunnel diodes but
the 545 lacks them while the 547 has them which explains the later's
outstanding triggering bandwidth. It may be that they had the only
engineers able to understand how to use them for trigger circuits.

You will not need a very fast oscilloscope to see if the tunnel diode
circuit is operating correctly. Yours should work fine.

On Sun, 27 Jan 2013 03:51:35 -0000, "stan_katz" <stan_katz@...>


Tunnel diodes in a 561A!

Tek must have started using tunnel diodes shortly after they came out in 1960. Leave it to Tek to go with bleeding edge esoteric. Since I'm a rather low budget experimenter, the only other scope I have is a Telequiment D51 "student scope" with a 4mhz bandwidth. Is this scope adequate to view the pulses at Q556/Q566?


--- In TekScopes@..., "Max Mazza" wrote:

--- 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.

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.


Join to automatically receive all group messages.