Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!


 

Jim Ford wrote:

I'd be wary of problems that go away by themselves.
Well, if the problem had simply stopped without my touching anything, I would agree with you (and then some: a problem that goes away by itself is likely to return with friends). In my case I suspect that one lead of the cap had been bent down and was making contact with a neighboring signal trace, shorting out the cap. I straightened the leads after desoldering it while measuring it on my multimeter, so when I reinstalled the cap I did so with straightened leads that couldn't touch the circuit board in the wrong places. I still find it amusing that I didn't replace any parts and still managed to fix the problem, but some problems on the 475 are like that: cleaning drum switch contacts, and cleaning and reseating socketed components are the two examples that leap to mind. Removing heavy dust build-up could also improve the performance of a really dirty scope, but you might expect that if the dust were causing significant overheating then some components might also be permanently damaged.

-- Jeff Dutky

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