Electronics > Repair

TDS3014 adventures

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tautech:
Nice adventure, result and write up James !  :-+

james_s:
In case anyone cares, I took a look at my notes today and the power-on hours are simply stored as the number of minutes in hex format in locations x7E0 through x7E4 in the DS1742W. I'm not sure why this wasn't immediately obvious to me last night, I guess I was tired.

james_s:
The comm module arrived today and I was able to use the GPIB interface to easily set the model to TDS3054. After that it showed a DC offset so I ran the SPC routine which passed and took care of that, then I connected my pulser to verify the bandwidth and this confirms a substantial improvement relative to the reference waveform I saved prior to the upgrade. With this done I updated the firmware to 3.41 necessitating another SPC and now it's all good to go. I'm a bit surprised there are still so many lesser models that have not been upgraded to 500MHz given it's so trivially easy to do.

I do intend to reverse engineer the serial portion of the comm module, it might be a few weeks before I have time to dig into that though.

james_s:
After working fine for a while my repaired DS1742W crapped out. It would still function fine with the scope on but every time I shut it off the memory and time get randomly corrupted. The battery is fine and still connected, after messing around with it for a while I suspect the power controller IC inside it has failed, perhaps it was damaged accidentally with 5V from the programmer.

After scouring datasheets I found the still current DS1744 which appears to be identical except for being a 32k part vs 2k. It is also available in a PowerCap package instead of the ridiculous potted battery. If I tie the top four address lines high this should get me something equivalent to the DS1742W. I whipped up a quick adapter board this afternoon, once I've built and tested one I'll post the files.

ArcticGeek:
James,

I think your solution sounds pretty good.   There are a couple other options that I considered but haven't been motivated enough to try yet:

1.  A small interposer board that has male pins on one side (24 pins) and a female socket on the other for a 28 pin DS1744W part.  The DS1744W is still available, and tying the upper address pins would work fine.   The only problem with this approach is the DS1744W part is going to be sitting roughly ~3/8" higher above the board due to the height of the sockets/headers.  I don't know if this is a problem or not in a TDS3000 series scope, I haven't checked the Z height constraints.   The other issue is that in another 15 years or so you'll be stuck finding a replacement for DS1744W because its battery will be dead too, and that part might be obsolete by then.

2.  A small interposer board that has male pins on 1 side (24 pins) and a discrete version of a RTC clock/cal and NVRAM.  From what I can tell, a DS1558 would be a compatible RTC and NVRAM controller....and then you would add a 2K SRAM, a 32Khz crystal, and a coincell battery.   This would have the advantage that you could change the battery down the road should it ever expire and you would not have to worry about it becoming obsolete.  It also would not be as tall as #1 above.  The disadvantage is the design is more complex.

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