Trigger generator for recurrent sweep scope.

[Steven Swift]

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.

 

[Winfield Hill]

Steven Swift wrote...

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.

My memory of the triggering capability of those old 'scopes is
not as sanguine as yours. Ditto for the old counters.

 

[mike]

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

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[John Fields]

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

 

[Michael Black]

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

 

[Joerg]

Hello Win,

My memory of the triggering capability of those old 'scopes is
not as sanguine as yours. Ditto for the old counters.

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

 

[John Fields]

Is that actual triggered sweep, or just syncing?

 

[Steven Swift]

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.

 

[Steven Swift]

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

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

 

[Michael A. Terrell]

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.

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

 

[Rich Grise]

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).

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