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Performance Check on a 2215A


 

Among my menagerie is a recently acquired 2215A which I had to perform minor repair work on, but otherwise seems to be in fine condition. I would like to do some adjustment on channel 1, whose trace jumps up two divisions when switching from 5 mV/div to 2 mV/div, but the service manual seems to indicate that I should first do the performance check before doing the adjustments. The problem, of course, is that I don't have most of the equipment specified for the performance check. Specifically I don't have a calibration generator, leveled sine wave generator, or a time mark generator. Looking online it appears that acquiring any of those items will set me back hundreds, if not thousands, of dollars.

I have a cheap 3 MHz function generator (analog, uncalibrated), a Leo Bodnar fast pulse generator, a DM501, a DC503, a couple of fairly nice handheld multi-meters (an Extech 22-816 and a Tek DMM916), a nice bench power supply with current and voltage limits, and a passel of assorted components, including crystal oscillators of various frequencies up to at least 50 MHz. Is there some way that I can rig up something that would get me through the performance test with some reasonable level of confidence?

I'm willing to splash out for one of the relatively inexpensive Chinese digital signal gens (e.g. the KKmoon/Koolertron/whatever FY6900), but that's about the limit of my budget. I've also seen shockingly cheap RF signal generators that go way higher than anything I would need, and wondered if that might be useful for testing my oscilloscopes (if not for actual calibration).

So far I have been relying on comparative measurements between all my instruments of unknown accuracy. My feeling is that they all seem to be in good shape, since their readings all agree to within a few percent. My feeling is that I should be able to use a combination of multi-meters, counter timers, and known voltage sources (e.g. the bench power supply/voltage regulators, fresh batteries, etc.) to establish the accuracy of one or more instruments, and then work outward from that stable spot, but I'm not entirely confident in my own reasoning.

-- Jeff Dutky


John Gord
 

Jeff,
While you are waiting to accumulate enough equipment for the performance check, you could just do the "attenuator step balance" adjustment to minimize the trace shift at 2mV/div. It shouldn't have much impact on gain or transient response. (You should let the scope warm up for 20 minutes or so before the adjustment.)
Older scopes had a front panel trimpot for this, so it was essentially a user adjustment.

--John Gord

On Sun, Nov 29, 2020 at 10:42 PM, Jeff Dutky wrote:


Among my menagerie is a recently acquired 2215A which I had to perform minor
repair work on, but otherwise seems to be in fine condition. I would like to
do some adjustment on channel 1, whose trace jumps up two divisions when
switching from 5 mV/div to 2 mV/div, but the service manual seems to indicate
that I should first do the performance check before doing the adjustments. The
problem, of course, is that I don't have most of the equipment specified for
the performance check. Specifically I don't have a calibration generator,
leveled sine wave generator, or a time mark generator. Looking online it
appears that acquiring any of those items will set me back hundreds, if not
thousands, of dollars.

I have a cheap 3 MHz function generator (analog, uncalibrated), a Leo Bodnar
fast pulse generator, a DM501, a DC503, a couple of fairly nice handheld
multi-meters (an Extech 22-816 and a Tek DMM916), a nice bench power supply
with current and voltage limits, and a passel of assorted components,
including crystal oscillators of various frequencies up to at least 50 MHz. Is
there some way that I can rig up something that would get me through the
performance test with some reasonable level of confidence?

I'm willing to splash out for one of the relatively inexpensive Chinese
digital signal gens (e.g. the KKmoon/Koolertron/whatever FY6900), but that's
about the limit of my budget. I've also seen shockingly cheap RF signal
generators that go way higher than anything I would need, and wondered if that
might be useful for testing my oscilloscopes (if not for actual calibration).

So far I have been relying on comparative measurements between all my
instruments of unknown accuracy. My feeling is that they all seem to be in
good shape, since their readings all agree to within a few percent. My feeling
is that I should be able to use a combination of multi-meters, counter timers,
and known voltage sources (e.g. the bench power supply/voltage regulators,
fresh batteries, etc.) to establish the accuracy of one or more instruments,
and then work outward from that stable spot, but I'm not entirely confident in
my own reasoning.

-- Jeff Dutky


 

John,

That was exactly the adjustment I was planning to do, but the admonition in the introduction to the adjustment procedure cowed me. I had first just read through the vertical adjustment procedure, and it did not appear to require special equipment, and sounded like it could be done on its own.

Thank you for justifying my desire for slack.

-- Jeff Dutky