From: cd@notformail.com   
      
   On Mon, 24 Oct 2022 20:38:01 -0400, Phil Hobbs   
    wrote:   
      
   >Cursitor Doom wrote:   
   >> Hi all,   
   >>   
   >> So my main analogue scope, a Tek 2465A, has gone faulty. Keeps blowing   
   >> main fuses (the 2A one on the rear panel). I opened the case and found   
   >> two RIFA caps that had obviously blown, so replaced them, but it's   
   >> still blowing fuses. I can't be 100% certain, but I'm pretty sure   
   >> there's a fault with the PSU board as I get the briefest whiff of   
   >> burning from that area each time I put a new fuse in and power up. The   
   >> new fuse blows again before I get to see any smoke coming from   
   >> anywhere at all. I'm linking to a diagram of the PSU as I'm not   
   >> familiar with this circuit topology. If anyone can spot a component   
   >> here that could have gone low-resistance and might be a good candidate   
   >> for out-of-circuit testing, by all means let me know.   
   >> Thanks,   
   >>   
   >> CD.   
   >>   
   >>   
   >> https://disk.yandex.com/i/UhxATIy-6Y0LIA   
   >>   
   >   
   >Yikes.  When a fuse blows, you replace it *once*.  If it blows again, it   
   >ain't the fuse or a line transient.   
      
   Yeah, well twice in this case. Replacing the RIFAs *usually* does the   
   trick (I have to say, in a half-arsed defence of my appalling   
   conduct).   
      
   >   
   >Start with a DMM and check for shorted diodes in the input bridge and   
   >then for a shorted filter cap at its output.  (The schematic is more or   
   >less completely illegible, or I'd give the ref des.)   
      
   Not sure what you're viewing it with, Phil. Others don't seem to have   
   that problem and have been able to see the part numbers okay.   
      
   >   
   >Next most likely is a switch FET.   
      
   Yes, the chopper is always a prime suspect with SMPSs   
      
   >   
   >Cheers   
   >   
   >Phil Hobbs   
   >(proud owner of a 2467 that he almost never uses)   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)