Re: Strange Tek2440 issue


Vince Vielhaber
 

Szabolcs, from here (TekScopes) posted a method of accessing the internal battery of the Dallas NVRAM modules using a heat gun and a scraper. The difference in these modules was that there were two batteries that were visible. Anyway I scraped down to pin 7 of the DS1210 and soldered a wire to it on each module. I ran those to a small circuit board where I had a battery holder and two diodes on it. The diodes fed the voltage to each of the modules.

When I put it back together it didn't work. Then I noticed I forgot to plug in one of the ribbon cables!

Anyway, the subject for the post I mentioned above is:

Easy method for NVRAM battery replacement

Vince.

On 08/30/2020 05:53 PM, Bob Albert via groups.io wrote:
Not your current problem but I replaced the NVRAM chips in my 2440 and the scope doesn't work. I switched one of them back and still no joy. I will try the other one.
I probably got some counterfeit modules from China. I am hoping it will be fixed when I put the old one back. How did you fix yours?
Bob
On Sunday, August 30, 2020, 02:37:52 PM PDT, Vince Vielhaber <vev@...> wrote:


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:

---------------------------------------------------------------------
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.
----------------------------------------------------------------------

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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