RAM calibration data backup with Lithium Battery Question - Page 1
Forum section: electronics / testgear

author: wolfalex
author_rank: Regular Contributor
timestamp: February 20, 2014, 01:30:57 am
content: Hello,This is my first post here on this Forum, and therefore I want to say Hello to everybody, and thank you in advance for all your Help in FutureThe reason for my first post is the following:I got some old used Test-Equipment on Ebay: a 3478a HP multimeter, a HP 5316a counter and a Tektronix 2221A 100 MHz Analog/Digital Scope, and because I have foundalready a lot of information about the 3478 multimeter + empty lithium battery -> problem topic I know what I have to do first to rescue the cal dataBut now I'm wondering If maybe also the 5316 counter or the Tektronix 2221A scope could also have a lithium battery inside it, and the same issue as the 3478a is waiting for me?I think I found a video or website regarding a 2440 or 2430 tektronix scope where you can see that the used some sort of strange RAM chip with internal battery which also seemsto backup some RAM data, and therefore I'm really afraid I could miss something.Unfortunately also after a hour long search for the 2221A service manual I was not able to find it. So maybe one of you has more information about the 5316a or the tek 2221Aand if there is a Lithium battery inside which should be changed soon, or other issues which are waiting to be found.Thank you very much in advance,Alex

author: wolfalex
author_rank: Regular Contributor
timestamp: February 20, 2014, 10:03:41 pm
content: It seems the Tektronix 2221 scope wasn't really that widely used as I hoped forI found also the links again for the Tektronix 2440 or 24XX scopes regarding the battery if somebody is interested in it:http://www2.informatik.hu-berlin.de/~dschneid/elektronik/geraete/tek2440/index.en.htmlhttp://www.pmelforum.com/index.php?topic=1162.0http://www1.tek.com/forum/viewtopic.php?f=5&t=5350http://ko4bb.com/dokuwiki/doku.php?id=test_equipment:replacing_backup_battery_on_tek_2246_scopehttps://www.eevblog.com/forum/chat/tektronix-2445a-backup-battery/But it's sad that this doesn't tell me if I have the same problem with the 2221 scope, which is also half digital.Or did I miss something?Thank you very much, Alex

author: wolfalex
author_rank: Regular Contributor
timestamp: February 21, 2014, 11:28:11 pm
content: I did more research, and I'm now very sure that the 2221A has also an internal lithium battery. If somebody is interested why I believe that, here the summaryIt seems the Tek 2230 is out of the same family, or at least is somehow comparable in design. This is also backed up somehow in the following discussion:https://www.eevblog.com/forum/projects/insides-of-tektronix-2230-dso/I was able to find the service manual for the Tek 2230 in the internet, and the electrical parts list shows an item A21B1"Battery, DRY: 3.0V, 1200 MAH, LITHIUM". I found also the schematic on page 448 showing the battery.It seems to power 4 RAM devices, which I find remarkable. I thought there would be maybe one device only.So maybe I'm going to change this battery too, only to be sure I do not lose any data. And Sorry for my boring monologue , but I thought maybe someone is interested in the outcome

author: David Hess
author_rank: Super Contributor
timestamp: February 25, 2014, 01:45:43 pm
content: The lithium battery if used in the Tektronix 2221, 2221A, 2230, and 2232 series was only used to backup the waveform and/or configuration memory. Unlike the 2440 series, these oscilloscopes do not store calibration constants in memory so there is no need to worry about losing them.The 2221 and 2221A are single timebase versions of the 2230 and 2232 and were not as common. The even rarer 2224 is a 60 MHz version of the 2232. The 2230 only included the lithium backup battery with the waveform memory that came with the optional GPIB or serial interfaces.

author: wolfalex
author_rank: Regular Contributor
timestamp: February 25, 2014, 03:22:07 pm
content: Hello David,thank you so much for your answer and this information. I have the 2221A with the additional GPIB option. Do you know what happens when the battery is dying? Are there a lotof error messages to quit, or startup time does increase dramatically? I guess if you say configuration is saved in there too, that i have to do configuration again after each start.But if the scope otherwise works normally I think I will not change the battery anyway. I was already afraid I have to open the complex thing

author: David Hess
author_rank: Super Contributor
timestamp: February 25, 2014, 04:08:48 pm
content: As far as I know the 2221A will operate in exactly the same way as a 2232 when the battery goes dead. The stored waveforms and configuration will be lost and during POST (power on self test), a low battery warning will be displayed.The earlier 2230 does not even save the configuration when the lithium backup battery is installed (as far as I know. Neither of my 2230s has the battery option and my research shows that the configuration is never saved so I have not bothered to add it.) and it is completely useable. The 2232 has a better user interface so I would not consider the lack of restoring the previous configuration a problem. Often though I use my 2232 instead of my 2230 because I do want to keep waveforms stored from earlier sessions.

author: wolfalex
author_rank: Regular Contributor
timestamp: February 25, 2014, 05:00:48 pm
content: Thanks again for your detailed information. It really helped me a lot, especially because I was not able to find much information about the 2221A. And thanks to you I alsonow know the differences between the different devices from this group. It is somehow overwhelmingI can't wait to unpack my new scope from the package today and see how everythink looks like. I know that before the shipment it did not show any errors or warnings and therefore thebattery should be ok now. But thanks to you I also know now that I'm not going to change it.. I can live with a warning message at the startup. And waveform storage is not soimportant for me. And maybe you have seen my other topic regarding the 3478A battery swap... I'm not sure if I want to do something like that in the near futureSo I think today I will hopefully enjoy my first CRT scope with character display. I can't wait to power it up.

author: David Hess
author_rank: Super Contributor
timestamp: February 25, 2014, 06:31:02 pm
content: My 2230 and 2232 are pretty much my go-to oscilloscopes for general use and the 2221 and 2221A are pretty much identical except for lacking the delayed timebase. The ability to switch between analog and digital storage display modes works out very well and all of them support peak detection which I consider mandatory in a DSO.]I have an HP3478A that I need to think about changing the battery in but have not gotten around to it yet. That is a case where extreme caution must be observed to prevent losing the calibration data.

author: wolfalex
author_rank: Regular Contributor
timestamp: February 25, 2014, 10:35:54 pm
content: I have just taken my "new" scope out of the box, and immediately tested it. Everything seems to work fine, and I'm really happy and impressed. I really like the character display onthe CRT, and especially the cursor function. But I think I got a little headache from the CRT because I'm not used to look at something like that anymoreNow I only have to learn more about how to use the thing, the menu possibilities and so on. In Austria I have a new Hameg HMO1024 DSO too which I'm used now, and sowith this scope everything is kind of different again for me.For example before I tried to do a "single shoot trigger" to save a startup process, but I was not able to do it somehow.

author: David Hess
author_rank: Super Contributor
timestamp: February 26, 2014, 04:31:15 pm
content: Quote from: wolfalex on February 25, 2014, 10:35:54 pmSingle shot acquisitions (SGL SWP) use the normal (NORM) trigger setting because in P-P AUTO mode, the sweep timeout will trigger a sweep if there is no trigger. The 2221A and relatives enforce this by making them exclusive of each (When you select SGL SWP the P-P AUTO and NORM buttons are released.) but that means you also lose the peak to peak trigger feature which makes sense since there is no peak to peak trigger information available. Most or all of my older oscilloscopes work the same way.That means you have to have the normal mode trigger level set correctly for single shot acquisitions to work. I usually adjust it by operating the oscilloscope in normal mode to adjust the trigger and then switching to single shot mode.

author: wolfalex
author_rank: Regular Contributor
timestamp: February 27, 2014, 05:15:06 pm
content: Thank you very much for the nice description of the trigger possibilities and the SGL button. Yesterday I tried it again, and I succeeded. Now I can fully utilize the digitalpossibilities of this nice scopeI also tried the diagnostics functions for the first time. All Tests did pass. But interesting is: when I run the NV RAM check the scope tells me that this function is not installed.So if the NV RAM is the lithium battery option you have talked about before, then it seems there is no battery in my unit at all anyway. So believe you were true with yourinital answer, and that it is a special function anyway.

author: David Hess
author_rank: Super Contributor
timestamp: February 28, 2014, 05:32:52 am
content: I am fuzzy on some aspects of the of the 2221 and 2221A and do not have much documentation on them. On the 2230, the NVRAM was part of the optional RS-232 and GPIB communication boards and as far as I know, is only used to save waveform records and not configuration setups. On the 2232 it is standard with the battery being mounted on the reverse side of the processor board and it saves both waveform records and configuration setups. Going by the datasheets, the 2221 which is similar to the 2230 had no NVRAM option and the 2221A which is similar to the 2232 has battery backed up memory but only for saved setups and 3 x 1k records or 1 x 4k record.On the 2221A user manual that I have, it mentions that the memory is backed up by a lithium battery but maybe this only applies to the setup memory? I do not know.

author: wolfalex
author_rank: Regular Contributor
timestamp: February 28, 2014, 05:19:54 pm
content: Yes, it is somehow complicated to understand the differences between the different family members and options. For example I have the GPIB interface on the scope, and thereforeI should have the battery in it. And it seems there was also a prestored waveform in the scope. But then the NVRAM test tells me no NVRAM is installed. But maybe thats another optionBut I do not have to know everything, as long as the scope will run also with a empty battery. And thanks to you I know that already. I spend over 1 hour cleaning every single knob andbutton of the unit, and now everything looks so much betterI was also able to find the hidden menue and the famous Wizard and Tek Logo. It is a great pleasure to see easter eggs like that.I thought It would be fun to add two pictures of my scope here. I have to learn adding a picture to a post anyway

author: David Hess
author_rank: Super Contributor
timestamp: February 28, 2014, 06:20:56 pm
content: Here are a couple of photos from my 2232 and 2440 making the same measurement. The 2232 has a tricky noise reduction algorithm which makes the second trace look better than it really is compared to the 2440. The 2232 (and 2221A) record length is halved in dual channel mode which explains the odd look of the filled in area.

author: wolfalex
author_rank: Regular Contributor
timestamp: March 01, 2014, 03:14:30 pm
content: Thank you very much for posting the pictures of your scopes. Does the peakdet mode mean, that the scope makes multiple sweeps over the periodic waveform, and finds out for each point in time the minimum and maximum voltage reading, and then plots both points for each point in time on the scope screen? Because this would explain the center part of the waveform as a big variation over timeIf it is like that, then this is for sure a very useful mode.What kind of signal is this? I'm sure it is not the probe cal signal output which I didOne thing which is very interesting in your pictures is the graticule illumination. Either the 2221A doesn't have it, or I know now that it is broken at my unit. I have the knob for it, and the manual states something about it...but I can turn the knob as much as I like... I never get the red glow. It is always darkDo you know how the graticule illumination works?

author: David Hess
author_rank: Super Contributor
timestamp: March 01, 2014, 04:33:02 pm
content: Quote from: wolfalex on March 01, 2014, 03:14:30 pmNo. Peak detection means that the digitizer runs at the full rate and for each waveform record point, the highest and lowest values are stored. What you are describing would be an envelope detect mode which these oscilloscopes also support where the highest and lowest values are stored over multiple waveform acquisitions.Peak detection is a good way to avoid aliasing but as used here, the 2232 captures any glitches down to 10 nanoseconds and the 2440 captures any glitches down to 2 nanoseconds at any sweep speed. Glitches that would normally occur between sample points are captured and displayed.The 2221A like the 2232 supports both modes and labels them PEAKDET (Peak Detect) and ACCPEAK (Accumulate Peak).One of the reasons I did not buy a Rigol DSO a couple years ago was because it lacked peak detection mode.QuoteThe photos show a couple of signals from the switching power supply of a 7000 series oscilloscope mainframe at startup. They are examples of what *should* occur during proper operation.QuoteThe graticule illumination is generated by a set (2?) of small incandescent bulbs located at the bottom edge of the CRT. Since they are wired in series, if only one burns out all illumination is lost. They are easy to replace after removing the CRT front cover but be careful not to damage the flexible circuit which goes to the buttons on the bezel.I know the 2230 lacks graticule illumination so I suspect the 2221 lacks it as well but the 2221A should have it since it is based on the 2232.The 2232 uses a pair of #2182 grain of wheat lamps which are T-1 3/4 size, 14 volts, and 80 milliamps:http://www.mouser.com/Optoelectronics/Lamps-Holders/Lamps/_/N-5g6r?P=1z0ys5r&Keyword=2182&FS=TrueThe #2162 could also be used. It would be brighter but will not last as long.

author: wolfalex
author_rank: Regular Contributor
timestamp: March 01, 2014, 06:13:20 pm
content: Quote from: David Hess on March 01, 2014, 04:33:02 pm

author: David Hess
author_rank: Super Contributor
timestamp: March 01, 2014, 08:13:43 pm
content: Quote from: wolfalex on March 01, 2014, 06:13:20 pmPeak detection is done digitally after the analog to digital conversion in a 2221A, 2232, or any DSO you are likely to come across. Successive samples are compared on the digital side to the current high and low values in the acquisition record and only the highest and lowest are saved.The 2440 series however does operate in the way you describe where peak detection occurs before sampling. That is tricky to do at variable sample rates and as far as I know, it is the only DSO series to work that way. The reason for this is that the 2440 series uses CCDs for sampling and the waveform record instead of a fast analog to digital converter, logic, and RAM. Some of the early TDS series oscilloscopes use the same basic design as the 2440 series but they did away with peak detection. Through the 1990s, this was faster than using the fastest analog to digital converters, logic, and RAM by 2 to 4 times.In both cases, peak detection works on single sweeps. Envelope detection uses multiple sweeps and usually uses peak detection if available as well on each sweep.QuoteIn both pictures, it shows a filled in area where the maximum and minimum values of the input may have fallen between points in the waveform record. If peak detection had not been used, there would have been the risk of aliasing. On a more modern DSO with a short record length, the display would have been the same. On a modern DSO with a long record length, a variable persistence display should display something similar to what an analog oscilloscope would show but the low end DSOs I have used so this poorly.

author: Alectronic
author_rank: Newbie
timestamp: October 10, 2021, 04:22:38 pm
content: I today replaced both 32K SRAMs U664 and U350 by FRAM FM1808 24 pin RAMs.I hoped that I still could self diag and externally calibrate my oscilloscope but sadly now my scope is useless! Although they tell calibration is easy and only about 2 pages in the service manual.Sadly after replacing the troubled old 32K SRAMs by 24 pin FRAMs FM1808 my scope no longer reacts on any of the buttons and no longer gives any display text messages anymore.And copying both SRAMs failed so not what I hoped or expected. Is there any way to restore and calibrate my 2440 scope without using the external Gpib bus? Or does anyone made a copy of a working SRAM chip that I can use to at least use my scope again? I already removed jumper J156 but it made no useful difference.It was no battery issue but just a replacing the old RAMs issue. So whatever you do be warned that there is no easy calibration possible anymore after this!!