Strange Tek2440 issue


Vince Vielhaber
 

I picked up a 2440 on ebay that had the dead nvram battery problem. Got that fixed up with an external battery. Ran thru the self cal and ext cal and all seems fine, except when the sweep rate is turned above 100 or 200 ns.

In trying to research this a bit, the only thing I could find was on one of the Tek forums back in 2017 but there were zero responses. Here is how the other person described the problem:

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The 5 volt regulated rail is getting crowbared when the scope Sec/Div is set to 100ns or faster. If save is pressed at a slower setting the Sec/Div can then be set to any value without the 5 Volt rail getting pulled down. It appears the issue only occurs during an active acquisition cycle at 100ns Sec/Div or faster.
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While I didn't measure the 5v rail, the screen shrinks a couple of times as the waveform changes, the inputs get switched to GND and the display goes blank. Sometimes, if I'm quick enough, I can turn the sweep back down (1us or slower) and it'll recover, but I still have to go to the input coupling and switch the inputs off of GND.

Anyone seen this or have any ideas what's going on?

Thanks!
Vince.
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K8ZW http://www.metalworkingfun.com http://www.hamradio.fun

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