Re: Tek 2467B Erratic Intensity controls
Chuck Harris <cfharris@...>
The processor has no knowledge of how fast the DAC is working.toggle quoted messageShow quoted text
It simply sends the DAC a value, and assumes it does its job.
I can think of a scenario that could be in play. All of the
controls are digitized, processed, made analog, and have their
analog value stored in a sample-and-hold gate.
Because the sample-and-hold gate is a capacitor that is holding
a charge, the CPU has to refresh that charge at regular intervals,
or it will leak down.
Suppose the MUX that charges the sample-and-hold capacitor is
broken so that it is high resistance, instead of its usual very
The CPU will set the DAC to the appropriate voltage, and the
broken MUX will charge it a little, then at each refresh interval,
the CPU will set the DAC to the same value, and the broken MUX
will charge it a little more... each refresh putting a little
more charge into the cap until it eventually reaches full charge.
You will see this as the control moving very slowly.
peter bunge wrote:
Yes they are 'sticky' especially if I move ch2 then ch1. Also the digital