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Old 26th Jun 2013, 4:43 pm   #15
maninashed
Rest in Peace
 
Join Date: May 2011
Location: Preston, Lancashire UK
Posts: 955
Default Re: Tektronix 465B Scope - Some problems.

Dave, main smoothing cap failure is becoming very common on these scopes now, and the interference can be coming from a number of sources. You need to measure the psu rail outputs with another scope. Check each rail for ripple and take it from there using the data indicated in the manual. If the ripple is 50hz its the caps, if its 100hz, its a partial failure in one of the bridge rectifiers, these are common failures. I doubt that 3 caps in parallel will have a sufficiently low esr for the demands of your scope, use the best quality you can obtain, the originals were Sprague, and they are very good, rated for 25000hrs use at 85deg.
Caps of this quality are not cheap. These scopes were very expensive when new, and this is just one reason why.
Bill
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