Rohde & Schwarz HMO1212 clock battery poblem SOLVED!

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This tip is specific to the HMO1202 series, but ya never know . . .

I bought a R&S HMO1212 oscilloscope after watching Dave's teardown video back in early 2016 and it has worked without a problem until early November 2017. Then it greeted me with a message that the "clock battery" was depleted or missing. I put that off until I had some free time as the battery replacement needed the case to be opened. So yesterday I set about making the repair. What could be easier? I had followed Dave's Prime Directive: "take it apart!" when the 'scope first arrived, so there was no drama getting the case open and putting in a new battery.

The plot thickens . . . The new battery failed after a few minutes. Same thing for another one--this time I checked the voltage first, duh. 3V+ OK
Clue 1: the 'failed' battery showed less than 2V on removal
Clue 2: the voltage on the 'failed' battery was increasing while being measured
Clue 3: there did not appear to be a drain on the battery when measured with the case open; power on or power off
Clue 4: ditto using a bench PS as a surrogate for the battery

At this point I surmised that the problem was not the fault of the oscilloscope and since I had 'load-tested' the batteries, not their fault either. So I cleaned the battery and the contacts with IPA and consigned myself to setting the date and time each time I used the 'scope.

Then, as I was putting the case back on the 'scope, I noticed through one of the vent-slots a piece of fabric brush against the visible side of the battery. The fabric had been glued inside the case, but a section near the vents had pulled loose.

What's that 'fabric' stuff and why is it in there?
What do you think I measured with my ohm-meter with probes on the 'fabric'?

I'll leave the solution on this thread later today . . .

[ealex]

was it a part of a RF gasket (conductive) ?

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Close, so close . . .
Conductive it was, yes. Looked like cloth; measured less than one ohm.
Not an RF gasket--it covers all the inside back of the case--I'm thinking a Faraday cage.

I glued it back in place, so no more drain on the coin-cell battery. When it was loose, it shorted the + side of the coin cell to ground, etc. Why did it come loose? The only thing I can think of was the 'scope was on for an extended time during the Summer and then off for nearly two months.

Hello, Rohde & Schwarz: you might want to look into this . . ..