Emax

electrolitics dont leak any more that was the old types from the 60,70,s the new types dont use oil 

the caps fail due to heat which causes oxidiation build up inside the cap which makes it harder to hold charge when it can no longer hold charge 

they dont fail if not used or over time in storage it the over use and the leaving the psu on constanly not powering down the instruments which is what happens in expensive studio,s where they are left on 24/7

and the cap does not get chance to cool down 

its hard to tell by looking at a cap if its heat damaged the best way is an oscilliscope which can show you the charge and discharge sequence which will show you if the cap is damaged or not

80 oc cap is only good for 3-4000 hours at 80 oc if you replace for 105 oc grade thay will work for 10-20000 at max 105oc temp 

so you can see that if an instrument is kept on all the time and reaches a max temp of 80 oc then 4000 hours at this max temp wont last for very long 

so switch of when not in use they last longer 

i have an mirage from new and a emax from new that still work from there original psu these machines are over 20+ years old and still going strong but i only switch them on when needed so the caps never get hot enough to oxidise
  ----- Original Message ----- 
  From: rpcfender 
  To: emax@yahoogroups.com 
  Sent: Sunday, November 29, 2009 1:14 PM
  Subject: [emax] Re: Emax II RIP? (not!)


    
  Electrolytic caps have a number of failure modes.
  They can leak the dielectric and that either appears on the PCB or the top of the cap (which is what yours look like).
  The cap can swell and distort the case, easy to spot on the top. Even the rubber bung at the bottom can pop out.

  They can dry out as well which usually you can't spot.

  They can sometimes develop a short although you would know from the smell and sometimes the bang.

  And some other not so obvious failure modes as well.

  Sometimes they exhibit these signs but still work, but it is better to replace them.

  Electros can fail even if the unit is unplugged in the cupboard unused for a few years.

  Don't know anything about electronics, can get help? Start by replacing the caps , electrolytic ones first.

  Word of warning............
  capacitors store charge.
  Electrolytic ones (as the are usually a high value) can store a lethal charge.
  The electro caps in a some types of power supplies are across mains voltage. Here in Australia this is 240v and can kill you even after the power is turned off. You need to wait for it to discharge and check it with a volt meter.

  Sounds like replacing the whole PS was the right thing to do.

  Royce

  --- In emax@yahoogroups.com, "Daniel Baum" <daniel@...> wrote:
  >
  > 
  > 
  > 
  > >The electro caps looked stuffed, which is typical for the age and they are 
  > >the first port of call in a rebuild.
  > 
  > Excellent. That means that the original diagnosis from chevytravelleruk was 
  > correct and that changing the power supply was justifed.
  > 
  > If I could have rebuilt it myself, then it would have been better to have 
  > done so. However, since I would have had to pay someone else to do it, it 
  > was about the same price to get a brand new one.
  > 
  > How can you tell that they're stuffed, BTW? It would be useful to know.
  > 
  > Thanks,
  > 
  > Daniel
  >



  


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