H744 regulator whistle - test-drb@ccmp.vtda.org

13 Jan 2002

On Jan 13, 20:28, Tony Duell wrote:
...
  > On Jan 12, 20:14, jpero(a)sympatico.ca wrote:
 >
 > > Sounds like PSU is reacting to overloading or medium shorts
 > > downstream of that PSU outputs.  Also can happen with dried
 > > up capacitors (too high ESR).
 >
 > I don't think it's any of those.  The regulators all make a similar
noise
...
   when I put
them on a dummy load drawing 5A, on the bench.  And I'm sure 
 Have you tried a lighter _or heavier_ load? It can make quite a
 difference. 
Yes, it changes the pitch somewhat (as I would expect) and it gets slightly
louder with a heavier load.

...
   it's not
bad caps, as two of them are ones I repaired recently. 
 Which, if any, capacitors did you replace? 
In one H744, all the electrolytics (the output one had gone, so I figured I
might as well do the lot).

-- 
Pete						Peter Turnbull
						Network Manager
						University of York