From: shaun.at.pukekohe@gmail.com   
      
   Once upon a time on usenet Trevor wrote:   
   > On 17/03/2018 1:22 AM, audioguymn@gmail.com wrote:   
   >> On Friday, July 27, 2001 at 2:34:43 PM UTC-5, MitchSF wrote:   
   >>> Hi, I'm almost finished restoring a KLH Model 21.  I replaced three   
   >>> transistors on the RF board and it now works!   
   >>>   
   >>> The only problem left is a hum from the audio board.  I   
   >>> disconnected it from the input to the board so I'm sure it's not   
   >>> coming from anywhere else.  I replaced the filter capacitor and all   
   >>> electrolytics on the audio board and it's a little quieter, but   
   >>> still there.  The level of the hum doesn't change with the volume   
   >>> control.   
   >>>   
   >>> Any hints would be appreciated!   
   >>>   
   >>> Thanks, Mitch   
   >>   
   >> Hi Mitch. The power supply filters, either of the black color   
   >> are/were a common failure item. They should be replaced. However,   
   >> note that the positive terminal was marked with the stripe as we   
   >> would now associate with the negative terminal. It is also important   
   >> that you do not increase the value of these capacitors as the power   
   >> supply can't handle the extra in-rush and operational paramete5rs.   
   >> Mark - Former National Service Manager, KLH Cambridge.   
   >   
   > Wonder whether he even still has it 17 years later? :-)   
   >   
   > Trevor.   
      
   Probably not - at least not with the issue still (however somebody might...)   
      
   It's good to have a knowledgeable person posting here so let's not be too   
   harsh...   
   --   
   Shaun.   
      
   "Humans will have advanced a long, long way when religious belief has a cozy   
   little classification in the DSM*."   
   David Melville (in r.a.s.f1)   
   (*Diagnostic and Statistical Manual of Mental Disorders)   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)