Re: My 2465B has arrived + A5 Board leaky caps cleanup
Hi Alex,toggle quoted messageShow quoted text
The design of the front panel is such that all of
the displays states are in registers that get strobed
whenever anything is changed on the front panel. That
shows up as a brief flash of all lights.
The 2465B uses 74F logic for those registers, the older
2465 used 74LS logic, and fairly dim LED's. The blink
is scarcely noticeable with the older 2465. The 2465B
uses much brighter LED's, and the blink is quite apparent.
With 350MHz bandwidth comes a lot of ambient noise. Cut
the bandwidth, and you will cut the noise. That is why
the scope has the 20MHz bandwidth limit switch on the
Working amounts of power supply ripple are not generally
noticeable. Large amounts, usually cause erratic operation.
An example of erratic operation would be trigger jitter.
The 2465B is not a frequency counter, and the A5 board's
10MHz reference has nothing to do with sweep or frequency
The way the 2465 family creates its sweep is by using a
miller integrator, and precision integration capacitors.
The way it measures frequency is rather convoluted, but
depends entirely on the sweep accuracy.
Think of it this way, the sweep is generated by charging
a capacitor with a constant current. It is correlated
to both the graticules, and the cursors during calibration.
The frequency measuring method uses the trigger hybrid
and a DAC to measure the zero crossing points of the
waveform, and uses the delay sweep to measure the time
between the zero crossing points. The CPU then performs
the inversion, and the display shows that number as the
frequency. It is not a frequency counter!
It is standard practice of most sellers to remove all
calibration stickers, and stickers showing previous
ownership before the sale. Although I don't sell a lot
of scopes, when I do, I blow out the dust from the inside,
clean the outside, and the CRT, make any repairs, and
calibrate the scope, complete with zeroing the counters.
It would look as you are describing your scope, regardless
of how old it really is. If I cannot repair it, and clean
it up to that degree, it becomes a parts source.
According to Manuel Maseda, Option 46 is the military
version of the scope (OS-288/G) that includes option 10
(IEEE-488), and 2 probes.
On Tue, Oct 30, 2018 at 01:11 PM, Chuck Harris wrote:Hi Chuck, this certainly makes a lot of sense. Thanks for clarifying it, never heard this simple and logical explanation from anyone else, other that people being very happy when they see low numbers on those counters on a newly acquired scope. This one does not have any past cal stickers at all, so wonder if it ever was calibrated after being purchased.