HP 41C Video interface test. Howto?

[tribidouille]

(07-11-2020 01:08 PM)vassilisprevelakis Wrote:  ...
But let's start from the basics. First check that the power supply is giving correct voltages. E.g. the RAM chips have GND on pin 9 (bottom left) and +5V on pin 18 top right. If you have an oscilloscope you may also want to measure the ripple in case the electrolytic capacitors are feeling their age.
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I measured the DC voltage on the RAM chips: 4.75V.
I could try a tast with the oscillator but I don't know where to plug (pin 9 and 18?) it and what I should see (a flat line for DC?)