TDS 300 Series NVRAM (DS1644) Backup Options? - Page 1
Forum section: electronics / repair

author: reject902
author_rank: Newbie
timestamp: September 12, 2021, 04:49:17 pm
content: Hello!I had posted a somewhat similar topic on this a few years back, but never got any feedback--figured I'd try my luck again.Back in 2018, I acquired a TDS380 in pretty good condition (lightly used, Option 14 installed, ~160 power ups) and with a working DS1644 NVARM which was happily keeping it's calibration constants while at the same time taunting me with the unknown as to when it was going to give up the ghost on me. This was a scope I picked up basically to poke around with as a beginner scope. It was pretty cheap at the time and it appealed to my vintage tech lover side. I really wanted to dump the NVRAM contents and write it out to a new chip, but I wasn't finding a good method to go about doing that reliably. That said, I never really bothered with using it (projects really didn't need scope work at that time) and it sat stored away in a closet for the past 3 years.Fast forward to today--I powered it up and surprisingly, it's still keeping time (was actually only just over 2hrs off from the actual time--even the date was right) and still hasn't lost its calibration constants.I'd really like to back up the NVRAM contents before this chip decides it's time to give up. I've read thru quite a few posts about backing up the NVRAM on certain Tek scopes, but I'm not sure if I actually have options or just a single option with TDS 300 series.From what I've found:Desolder the DS1644 and read it in with a programmer. This method doesn't seem to be overwhelmingly successful though, either due to the aging battery voltage or heat applied when desoldering, where in the end the data is ultimately lost. This is the only method I've seen referenced as being used for the TDS 300 series.Dump the NVRAM contents via GPIB, maybe? Not sure if this is possible, as I can only find references on doing this with later series (TDS 5xx/6xx/7xx/8xx) scopes. Is such a method possible with the TDS 300 series?Dump the NVRAM contents to a Floppy, maybe? Again, this seems to be something where I find references on doing this with later series scopes. Is this possible with the TDS 300 series?Is option #1 the only real way to go about this on the TDS 300 series scopes? Is there a way to do this like option #2 or #3?Any advice is greatly appreciated.Thanks!

author: reject902
author_rank: Newbie
timestamp: September 15, 2021, 08:25:47 am
content: I ended up going with option 1 and was successful.It was a little tricky, so hopefully other methods can be discovered to pull the contents.

author: Teichhermelin
author_rank: Regular Contributor
timestamp: September 15, 2021, 08:43:00 am
content: I always do it this way ... so far without any problems. Then install a base afterwards ... saves work in 10 years ... ;-)

author: Анатолий
author_rank: Newbie
timestamp: April 21, 2025, 11:00:40 am
content: Добрый день! Не могли бы вы поделиться содержимым nvram ds1644-120 , и методикой перепрошивки этой микросхемы? У меня такой же осциллограф (tds340a) , при включении и при диагностике выдавал две ошибки - калибровки и сбора данных. Одну из них удалось устранить (ошибка сбора данных) путём замены микросхемы AS7C164 , а вот с ошибкой калибровки ничего не получается. Пытался сделать внешнюю калибровку , но не удаётся : по напряжению сбивается сразу же на первом шаге ( - 1,5вольт) , а при попытке калибровать по частоте , при переходе на шаг калибровки 10 наносекунд выдаёт ошибку (у меня генератор 60 МГц). Буду благодарен за любой ответ и любую помощь.

author: Анатолий
author_rank: Newbie
timestamp: April 23, 2025, 08:45:06 am
content: Всем добрый день! Удалось мне прошить ds1644-120 и теперь у меня полностью исправный осциллограф tds340a. )