Re: 2445A calibration

Max Vlasov
 

On Wed, Oct 17, 2018 at 02:08 PM, Siggi wrote:


Did you measure the +1.36/-1.24V references after your repair (and DAC
re-calibration)? I'd be most interested to know what the final values of
those reference voltages were against the centered +1.25/-1.24 DLY REF
output.
Apparently 0.5% from the calculated value is too far out, but the -1.25V
value on the schematics is still 0.25% out - the truth is out there!
I've measured the +1.36/-1.25V test points today with two Agilent 34401A. So, the results are the following:

On the working o-scope the points are stable with a time (4 digits after the decimal point stay where they are, both meters agree).
TP-1.25 = -1.2498V (3mV off the simulation here: https://groups.io/g/TekScopes/photo/74577/0?p=Name,,,20,1,0,0 simulated 1.2468V, calculated -1.2469V, 0.24% off the target)
TP+1.36 = 1.3680V (6mV off the simulation. simulated 1.3619V. calculated 1.3620V, 0.44% off the target)

As highlighted before, the pin 13 of J119 is perfectly centered CCW=-1.250V, CW=1.250V

However, I haven't measured 14.2K and 13.0K resistors. They have bent legs, didn't want to damage or compromise them.

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