Data Precision 2020 Function Generator repair

[srb1954]

Another question (maybe a noob’s one): My other unit has the MAX354-9920 PSU installed in it. In terms of voltage, current and ripple measurements it works fine though every time it is turned off I can hear a clicking noise for like 20 secs from it; it kind of reminds me the noise old CRTs were making.

Any idea what could be the source or the noise? Is yours making the same noise when power is cut?

No obvious noise from my unit although I didn't take the lid off to get a closer listen and my 70-year old ears aren't so great these days.

I would take a look at the capacitors in the PSU as, with the age of the unit, some of these have probably dried out. In my unit a 100uF capacitor on the supply to the SMPS controller chip had dried out and caused all sort of strange start-up symptoms.