Trigger generator for recurrent sweep scope.

Back in the day when all the cheap scopes (Eico, Heathkit, etc) were recurrent sweep, simple trigger sweep circuits were published in the hobby magazines.

My wife's school has an Eico 460, which they love, that could use a simple trigger circuit. They don't want my dusty Tek T922. (too complicated).

Does anyone have a link to one of those articles. I have been searching and haven't found any. The next step is to go to the library and thumb through the archive of Radio-Electronics and Popular Electronics. Or design one-- I rather just cobble up an old design.

Thanks,

Steve.

Many of the old scopes had AC coupled horizontal paths. Not conducive to stopping the sweep. mike

Is that actual triggered sweep, or just syncing?

Thirty years ago, the wave of articles on adding triggered sweep used a 555 as a ramp generator. The incoming signal would be fed through a bit of circuitry to get a pulse, and that would trigger the 555. That would be fed in somewhere into the scope to replace the existing ramp generator.

I'm pretty sure the basic 555 circuit, as a triggered ramp generator for a scope, was in "Electronics", in "Designer's Casebook" or "Engineer's Notebook" which were full of circuits sent in by readers, because all of the articles were basically the same.

Checking Howard Berlin's 555 book 1976, the thing I am thinking of was in "Electronics" for October 11, 1973. I see no mention of the author.

There was quite the wave of articles about this sort of adaptor, and they all used the same basic scheme. There were even a few build your own oscilliscope articles, which hadn't been seen in some years at the time, because semiconductors made it a new project.

Michael

Hello Win,

They usually didn't have any triggering. My old Hameg 207 will only 'synchronize'. There you have that extra knob for 'coupling'. Too loose and it won't catch, too tight and it'll distort the waveform. But I am still using that 30 year old thang for mundane stuff. It is small and has the rigidity of a tank.

Some people tried to build real trigger circuits for these. Quite a few of such projects in magazines were baloney, they suggested a unijunction transistor. That would probably have worked nicely except that you could never really get any. Also, these old scope needed a lot of dead time between sweeps. The BW of the driver for the horizontal plates was maybe a MHz, if that.

Regards, Joerg

Did they do that on newer revs? The one we have access to can "sync" but not trigger. The sweep is always recurrent.

I think it is DC-coupled however.

Thanks, I'll see if I can find that one.

ftp://bama.sbc.edu/downloads/eico/460/ has the manual for the scope for a free download.

Insist that they learn to operate the Tek. The only difference, other than the bells and whistles, is the triggered sweep. Everything else on the panel of the scope is gingerbread.

It's hard to express the feeling of triggering your first scope trace. ;-)

(and it'll be a HEXX of a lot easier than trying to trigger a scope that's not designed for it.)

Cheers! Rich