I'm amazed at the life of these Dallas parts (16 years or more?). I designed in a number of Dallas parts in the 1990 timeframe. They started to lose data retention about 7 to 8 years later.
The difference has to be in the environment. We were building telecom test equipment, used indoors and out, and frequently left to die for long periods of time.
The Tek scopes on the other hand, may have frequently been left on in an indoor environment. I'm convinced that internal leakage in the switch / logic probably keeps the batteries "topped off" (I know, they are lithium). Others have voiced this theory in the past.
So, if you want good batteries, buy a scope with a dim CRT ;)
Den
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--- In TekScopes@..., "nukescope" <vtp@...> wrote:
Interesting, it certainly is possible if the newer scopes have a sectored 5V flash. These scopes are old enough not to have a read-while-write type of flash so there is either another flash for the cal data or during calibration the code runs on SRAM. My old TDS544A definitely had a 12V erase/pgm bulk block flashes and stores calibration information in NVRAM. IIRC, the NVRAM was DS1650 for which TI BQ4015 should work also but be a lot cheaper than the Dallas part.
Regarding the NVRAM, I had trouble reading it in a programmer so that was my primary reason for digging up the GPIB memory read commands and protocol. Make good use of the code, I spent a lot of time decompiling the kernel ROM in order to find out everything necessary.
The flashes in my TDS544A were AM28F010 which tend to keep their contents very well, actually so well that they are difficult to erase after 20 years of use (in another application).
But still, backing all the stuff up would be good. Maybe sometime someone (or me) even writes a secondary bootloader so we can rewrite the flashes.
-NS
PS. I like the sellers associated risk list, particularly item #3.
--- In TekScopes@..., "denyhstk" <denyhstk@> wrote:
You all may be interested to know that an Ebay seller of "Tektronix battery modules" has a list of models which (according to Tek, he says) do not store cal constants in either the NVRAM or the RTC/NVRAM, hence no danger of losing cal with chip replacements. Interesting stuff I have not had time to verify.
Den
