From: legg@nospam.magma.ca   
      
   On Mon, 11 Sep 2023 11:27:28 -0000 (UTC), Andrew Smallshaw   
    wrote:   
      
   >Hi all   
   >   
   >I've recently picked up an old Weir bench PSU and recalibrated it   
   >to within quite sharp tolerances.  However, the front panel meter   
   >(switchable between voltage and current, although the schematic   
   >shows it is working as voltmeter in both modes) reads accurately,   
   >but the settling time must be a good 10-15 seconds before it stops   
   >oscillating back and forth.   
   >   
   >I haven't got as far as pulling the meter out yet but I expect   
   >obtaining a compatible replacement will be difficult.  Looking at   
   >online it seems most practical sources sources address electrical   
   >damping for brief transients in the signal, this is rather the   
   >mechanical side of things.  Basic research suggests pneumatic   
   >damping is the usual order of the day but I haven't found anything   
   >relating to actual maintenance and adjustment.   
   >   
   >Does anyone have practical experience or is a replacement meter   
   >the usual approach?   
      
   . . . . unless the meter is reading a real disturbance . . .   
      
   There's probably a failed capacitor inside that needs replacing.   
   Could even be an electrolytic across the meter terminals.   
   Most sensitive moving coil meters (<1mA) are pretty much self-   
   damping and won't require much filtering to average a measurement.   
      
   RL   
      
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