My 6632A s/n 3145A-06821
Symptoms:
- power on is ok; no self test errors on the display;
- VSETing from the front panel to values greater then 5/6 Volts triggers OVP.
Checks:
- with these symptoms always double check the sensing terminals (S+ and S-): they must not be left floating. Be sure they are directly connected to output terminals on the rear terminal strip or to a remote load. For testing purposes mine were connected to the terminal terminals on the rear output strip;
- checked OVP circuit as per SM: voltages at U110 are ok; both R158 and R155 checked ok.
Further investigation:
• 0.1 Volts < VSETs < 4/5 Volts work but the readback (front panel) is out of, say, 15% and slightly unstable; the actual output is about 4x VSET and highly unstable: it jumps randomly up and down few volts.
NOTE: from now on I connected my Arduino GPIB controller to the unit so that I can quickly issue commands to it without pushing the control panel buttons.
This is the result of “VSET 2” GPIB command:
The first spike is the direct consequence of VSET 2; the second is just pure random noise. Please note the rms voltage is more then 4 Volts instead of 2. The peak reached by the first spike was 20.4V, barely not enough to trigger OVP.
