From: trevor@home.net   
      
   On 18/03/2018 11:08 AM, ~misfit~ wrote:   
   > 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? :-)   
   >>   
   >   
   > 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...   
      
   True, might help someone else, and I wouldn't want to discourage that.   
   I'm just amazed at how many people answer 20 year old posts because they   
     don't even realise it. :-)   
      
   Trevor.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)