I am late to this party but I fixed one smilar unit by replacing the power FET in the switching power supply.? Perhaps yours has a similar problem.
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On Tuesday, January 5, 2021, 04:29:44 PM PST, Mark Hatch <mark2382@...> wrote:
I *really* appreciate all the views here. Lots to think about.
I am ok with replacing the LVPS e-caps and those x2's too. And it will be good to look at the infamous SMD's on A5. Haven't done that yet and I *really* should...
In terms of simpler solutions, anybody think that it could be the power switch on the front? When it first started acting up, I thought sticky relay. But threw that idea out the window when I found no relay in power lines.
Having worked on boat anchors (like I suspect most of you), right after e-caps the next set of problems are caused by dirty/corroded switches. And given that the last (and worst) incident was after I had to put the scope in my shed during are most recent set of rain storms here in No Cal it got me wondering. The shed is dry, but I suspect it still would be damp over that 2-3 days. Perhaps that could lead to corrosion on the switch contacts?? Or am I just having wishful thinking....
I did see in the archives that the switches do go bad, but nobody mentioned intermittent powers. Reading between the lines it sounds like the switch failure was something hard.
Currently, the scope is behaving itself and turning on with the button push like it should...? Would be nice if it failed hard instead of playing "hide and seek" with me....
Regards,
Mark
