Re: E4402B SA power problem - need DC socket connections
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The other area of the PSU to look at is standby power and startup circuit. In the older 859x series there is a Schottky diode HSMS-2800 that goes leaky. It's function is to rectify the output from a low current oscillator to generate a pull up voltage for the turn on signal. If it drops too low, the PSU shuts down. Higher temperatures increase leakage, which could cause these symptoms.
I don't know how relevant they are, but I posted traced schematics of the 8591E PSU to the files section a few weeks ago.
Chris G4MWQ
Well, well, well!? I put 12V on the DC connector and removed the mains and the SA fired up.? about 12V at the plug at 7A when running, from a commercial switchmode 13.8V psu.
And it stayed fired up for 3 hours until I got bored and turned it off.? The display was perfect, no error messages, doing exactly what I expected, which was nice.
This means that the fault must lie in the very first stage of the PSU, where the ac is rectified and down-converted to 15V or so.
Maybe dried-out main reservoir caps giving excessive ripple. or rectifier(s).
I've got other things to attend to now but will get back to this in a week and get the PSU out and some caps changed.
I also used the EEVBlog mechanism to install a narrow bandwidth option "upgrade" and it works beautifully!
Good result all round for now.?
Thanks for the help.
-Jeremy
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