Help me get started on a middle-aged HP 'scope power supply?

[ben7]

Re: Help me get started on a middle-aged HP 'scope power supply?

If it false triggering, that can be due to poor filtering of noise or spike in the sensing circuits.

Thats what I am thinking too

[willray]

Re: Help me get started on a middle-aged HP 'scope power supply?

Thats what I am thinking too

That's definitely on my list of things to check, but I while I can see it trigger in free-running mode on another scope, I haven't managed to catch it in one-shot memory yet.

The weird thing is that when I see it trigger, the startup "current" (really voltage on U4), looks completely differ than what I see when it starts cleanly. This might just be because the spike is so brief and what catches the eye when it starts is the post-spike running characteristic signal, while the clamped shutdown lets the spike be more visually obvious, but it's also possible I've got some bimodal behavior going on here.