Yes, another 3458A repair and NVRAM replacement to RAMTRON FRAM - Page 1
Forum section: electronics / general

author: TiN
author_rank: Super Contributor
timestamp: January 09, 2017, 04:22:10 am
content: The show must go on, right? One of russian-speaking members,TEKTRONdone quite extensive study on 3458A of his friend, which needed little bit of repairs and NVRAM love. But opposite to most of us, mere lurkers, he did alternative way and replaced NVRAMs not with just fresh DALLAS/MAXIM chips but with battery-free ferroelectric memory from RAMTRON. I translated the article to English and publishing his work with his permissionHere's brief worklog. After initial replacement for NVRAMs, and replacement of exploded mains filter, SELF TEST FAILED AC VOS DAC CONVERGENCE:181 emerged.In HP 3458A Multimeter Assembly Level Repair Manual this error, similar to dozen others have number 204 direct us to assembly A2 (AC Converter 03458-66502). Lot of time was spent on troubleshooting for a root cause, until main amplifier check was done, not limited just to dual JFET Q403, but also to U404 opamp, using DC input signal as reference.Inverting input had +6.654 VDC, non-inverting input +6.973 VDC. Got it, here’s the problem. Normally functioning circuit with opamp cannot have such huge offset (319 mV!), so clearly opamp or related parts are faulty. These Elantec EL2039 600MHz op-amps are prone to fail in old units, so after replacement meter offset was gone and meter reported no problems!Easy fix, yea?FRAM in 3458A:Works happy for over a year.TEKTRON also did some tempco testing with his own DIY LTZ1000A reference, and shared his design:Board was made using laser-printer-toner technology and etchingComparison victims:Full article with detailsas usual hosted on my little site. Worthy read. He also have more to come

author: TheSteve
author_rank: Unknown
timestamp: January 09, 2017, 08:27:38 am
content: Seems the Dallas nvram is dead...

author: Pipelie
author_rank: Regular Contributor
timestamp: January 09, 2017, 08:28:23 am
content: I just replaced the NVRAMs in my HP3458A last week, the total cost of the component is $78 .it's necessary to restored original calibration ROM contents before replaced.after soldered, the NVRAM is dead , all data gone, fortunately, I have backup.

author: Pipelie
author_rank: Regular Contributor
timestamp: January 09, 2017, 08:54:43 am
content: DIP28 FW1808 maybe is the better choice, but hard to fine a brand new,a genuine part.I bought five of there used part, just for test.

author: quarks
author_rank: Frequent Contributor
timestamp: January 09, 2017, 02:17:59 pm
content: I also experimented with FRAM, but have not swapped the original Dallas Chips, because they have many years of lifetime left

author: bingo600
author_rank: Super Contributor
timestamp: January 11, 2017, 04:45:19 pm
content: Nice modJust ordered the partsBut i wonder why he says : Do not mod the board before programming the old calram data in the chip ?If i mod the board first , shouldn't i be able to program it as a DS1220 ?Then i can "verify" that my mod is functioning.Or doesn't the programmer "float" the 4 extra pins , he mounted ?Well i wouldn't mount pins on the last 4 anyway , and prob. do all the wiring/mods on the topside of the adapterboard.Thanx/Bingo

author: Tektron
author_rank: Contributor
timestamp: January 11, 2017, 06:12:07 pm
content: Bingo, because FM16W08 NOT fully compatible with DS1220.It has very important difference: all access to Ramtron must be latched by falling edge of CE, not by low level of CE.I don't know, how work strobing of CE in your programmator, then can't say will it work or not.In my programmator I can't write Ramtron as Dallas.It also don't work in HP3457.But in 3458 it work very well.You can see all info at p.5 of pdf:http://www.cypress.com/file/41731Sorry about my broken english.

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: January 11, 2017, 06:27:52 pm
content: I did something similar with FM1808 for my Datron 1281's replacing the dual CE SRAM with the FRAM. I was able to read it in my GQ-4X programmer.Photos are at the bottom of the article herehttps://xdevs.com/fix/d1281/The meters are currently under test/cal ATM.

author: bingo600
author_rank: Super Contributor
timestamp: January 11, 2017, 06:47:29 pm
content: Quote from: Tektron on January 11, 2017, 06:12:07 pm@Tektron (Your english is fine enough)Thank you for the detailed ansverI have a TL866A and a GALEP5.Wonder if the TL866 has a broken programming DS1220 algorithm, afaik writing wasn't even supported a few releases ago.Edit: Re: 3457A see here (Doesn't it have same MCU as the 3478A ?)https://www.eevblog.com/forum/projects/3478a-fram-modification/msg1005546/#msg1005546http://wolfalex.bplaced.net/te/hp3478a/fram/hp3478a_fram.htm/Bingo

author: BravoV
author_rank: Super Contributor
timestamp: January 11, 2017, 06:52:12 pm
content: Quote from: bingo600 on January 11, 2017, 06:47:29 pmNope, TL866 does not support Ramtron parallel FRAM.Most Dallas/Maxim BBSRAM (DSxxxx series) only needs the Chip Enable (CE) pin to be enabled only "once" for multiple read/write operations, while the F-RAM needs the CE to be toggled at every address change and latched at CE 's edge.

author: bingo600
author_rank: Super Contributor
timestamp: January 11, 2017, 07:32:09 pm
content: Quote from: BravoV on January 11, 2017, 06:52:12 pmStrangeTektronsays he used asuggests a TL866 to program/write both FRAM types with.Maybe Tektron can explain what chip he selected on the TL866 when programming, or what programmer he used.Edit:Well my GALEP5 can write FRAM's/Bingo

author: Tektron
author_rank: Contributor
timestamp: January 12, 2017, 03:45:21 am
content: @Bingo600, thank you for kind words and 3478+Fram.I use this programmer:http://www.phyton.ru/programmers/chipprog-plus.I didn't wrote exactly model in original of article and the programmer is not well known for english-speaking people, that is why (I think), Ilya wrote TL... in translated version.I wrote way which tested and WORKS, other ways must be tested

author: TiN
author_rank: Super Contributor
timestamp: January 12, 2017, 04:15:47 am
content: "Lost in translation". Removed confusing partQuoteIt's not much of english problem, it's about getting brave to post.You guys might get me into few FRAMs to test myself

author: ap
author_rank: Frequent Contributor
timestamp: January 13, 2017, 11:58:34 am
content: Well, one thing is that a programmer is able to make a copy of the calram (write it, applying the correct timing for the active edge of CE), but the other is, what does the 3458A do when trying to update the FRAM during an artifact cal adjustment. Has anybody analyzed that?

author: Tektron
author_rank: Contributor
timestamp: January 14, 2017, 06:20:49 am
content: With F-RAM installed in the 3458 I did many times:CAL 0 - no problem.CAL 10.0000000 - no problem.CAL 10.001678E3 - no problem.ACAL DCV - no problem.ACAL ALL - no problem.Change CAL String - no problem.I did it in December 2015 and repeated in January 2017 (both times with F-RAM installed) - no problem.

author: quarks
author_rank: Frequent Contributor
timestamp: January 14, 2017, 03:48:02 pm
content: My test so far worked without any issues for U121 and U122 with DS1230 to FRAM replacement.U132 DS1220 is also working, but as discribed above, it is tricky to get the CAL data on the FRAM.With my Batronix programmer I can write directly to the FRAM, either with SOIC ZIF programming adapter or with the SOIC-to-DIP28 adapterboard (before the DS1220 PIN modifications).After the modifications, I cannot write to the FRAM in my programmer anymore (which I do not like), but in the 3458A it seems to work.Nevertheless I still use the original Dallas Chips, because they will most likely work for at least 10 years. But it is good to know, that it can be replaced any time I like.

author: Tektron
author_rank: Contributor
timestamp: January 14, 2017, 06:34:52 pm
content: Nice job!But why "ERRor"?Added later.It is two ways for using programmer with modified FRAM:1. Reverse modification, i.e. remove four short and pin 23 of chip connect to pin 23 of adapter (cut it from gnd). Before installing in 3458, return all back.2. Interchangeable modification. Idea (see pic below) must be tested. I haven't ability to test with 3458.

author: quarks
author_rank: Frequent Contributor
timestamp: January 14, 2017, 07:05:39 pm
content: ERR was because I also tested with empty FRAMs to see the behavior and even this passed selftest.

author: Tektron
author_rank: Contributor
timestamp: January 14, 2017, 08:19:06 pm
content: Quote from: quarks on January 14, 2017, 07:05:39 pmThank you.If you did not CAL procedure, then you didn't check writing to CalRam, only reading was tested. ACAL writes to CalRam only if enabled, but CAL writes always.

author: quarks
author_rank: Frequent Contributor
timestamp: January 14, 2017, 08:36:26 pm
content: I did CAL 10V to test it with empty FRAM and it workedYour reversable mod idea looks good, but I think I will next test unmodified SOIC-DIP28 and do all modifications on a separate board which I will stack inbetween. This should give me many options for more experiments.

author: TheSteve
author_rank: Unknown
timestamp: January 15, 2017, 08:55:44 pm
content: Your separate board can even have a jumper address selection so you can have multiple or different copies of the CAL data.

author: Tektron
author_rank: Contributor
timestamp: January 16, 2017, 01:51:19 pm
content: Quote from: TheSteve on January 15, 2017, 08:55:44 pmFor 4 different refboards.Or for 4 different calibrations. For watching long time drift of A9 and ref resistors. Nice idea.

author: bingo600
author_rank: Super Contributor
timestamp: January 16, 2017, 03:59:28 pm
content: We have a lot of skilled people here.One could hope a PCB designer would offer to make an adapter with some jumper config's that would enable us to.1: Do & undo the pins for emulating a Dallas , and a normal FRAM.So we can read/program the chip as a FRAM, and then jumper it as a Dallas.2: Maybe do the Chipselects too.I would expect that quite a few of us in both would be joining a "group order" for such a board, maybe do one for both EU 6 US.Unfortunately i have Zero PCB layout experience/Bingo

author: quarks
author_rank: Frequent Contributor
timestamp: January 16, 2017, 04:28:25 pm
content: I have made a little board, it is not nice, but seems to work fine in the 3458A.For test purposes I again used empty FRAM and did several calibrations (CAL 0, CAL 10, CAL 10k) and ran several self tests. CALNUM was counting up and so far it runs without any problems.So when you need to CAL all new, because CAL NVRAM data is lost, this should work.But with original DS1220 data copied to FRAM I found a data difference in address 0 it is 00h instead of 40h as read from DS1220 and this seems to cause ERRSTR 110 "CALIBRATION REQUIRED -- SCAL" in the 3458A.So far I was not able to write 40h to address 0.Did anyone else have the same issue?

author: bingo600
author_rank: Super Contributor
timestamp: January 16, 2017, 05:40:46 pm
content: Quote from: quarks on January 16, 2017, 04:28:25 pmDid the programmer verify it w. 40h , or give a verify err ?I haven't gotten my devices yet (They're "china time" way) , so 4w+ time i guess.When i get them i can try the Galep5 , but i'd expect Batronix to work equally well ..Actually maybe even better, as it seems like the Galep5 doesn't get device updates anymore./Bingo

author: quarks
author_rank: Frequent Contributor
timestamp: January 16, 2017, 06:37:57 pm
content: my programmer shows this directly after programming.Data on every other address is written correctly.

author: bingo600
author_rank: Super Contributor
timestamp: January 16, 2017, 06:54:04 pm
content: A "trick" could be to make the upper half of the FRAM "active" , and program that one w. the Cal data.That would not solve the mystery of location 0 , but might make it usable.Ohh... And i suppose you forgot to attach the pic' of your batronix output/Bingo

author: Tektron
author_rank: Contributor
timestamp: January 17, 2017, 09:51:44 am
content: Maybe programmer does it.Perhaps you insert in programmer fram with modified address bus? Then, possibly, programmer does not know "short" fram chip. And he wrote all + 1byte in address 800h (I don't know why). This additional byte rewrites address 00 with incorrect info because address bus was modified.For solving may be better will programming full size image. It may be 4 times repeated in ONE file image of ds1220, or one image of ds1220 + 3 "virtual" images (00 or FF filled) in one file. Hard to explain in english, sorry.

author: BravoV
author_rank: Super Contributor
timestamp: January 17, 2017, 11:07:16 am
content: Quote from: Tektron on January 17, 2017, 09:51:44 amJust type here in Russian, and we will wait Tin for translation.

author: quarks
author_rank: Frequent Contributor
timestamp: January 17, 2017, 12:17:29 pm
content: I think I found the problem, it must be the slow "Power-Up to First Access (tPU)" of 10ms from the FM1608B/FM16W08.Older FM1608 were much faster (only 1µS).Therefore my programmer BX48 is most likely just to fast, so the data in the very first address 00h is not written.I hope I find a way to solve this without waiting for an update from Batronix.I reported my finding to Batronix and will give you an update as soon as I have a feedback

author: quarks
author_rank: Frequent Contributor
timestamp: January 17, 2017, 03:49:11 pm
content: for the documentation, here is the report from BX48 programmer after writing the DS1220 data to FM16W08

author: TiN
author_rank: Super Contributor
timestamp: January 17, 2017, 05:35:30 pm
content: Hmm, where this come from, I wonder? Time to go deeper into the hole, to get all the rabbits out.

author: quarks
author_rank: Frequent Contributor
timestamp: January 17, 2017, 06:32:18 pm
content: Hello TiN,what a coincidence, I just tested Todds board with 16W08. DS1220 data was written incl. address 0 and it works in the 3458A without ERRSTR.I am sure that the "normal" SOIC-DIP28 board will also work, as soon as data can be written to address 0.

author: bingo600
author_rank: Super Contributor
timestamp: January 22, 2017, 06:25:44 pm
content: @quarksDid you get your programmer fixed ??Quote from: TiN on January 17, 2017, 05:35:30 pm@TiNWhere did you get those boards ?/Bingo

author: TiN
author_rank: Super Contributor
timestamp: January 23, 2017, 04:06:59 am
content: Emm, I got them fromDatron 1281 article

author: quarks
author_rank: Frequent Contributor
timestamp: January 23, 2017, 08:03:33 am
content: Quote from: bingo600 on January 22, 2017, 06:25:44 pmI have no response/fix from Batronix so far

author: bingo600
author_rank: Super Contributor
timestamp: January 23, 2017, 08:00:37 pm
content: Quote from: TiN on January 23, 2017, 04:06:59 amNot very helpfull info , unless one gets sent 2 free boards for reading the articleAny hints , for getting the boards/Bingo

author: mimmus78
author_rank: Unknown
timestamp: January 23, 2017, 08:18:46 pm
content: Read the article ... where I can signup for the boards?

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: January 23, 2017, 10:34:40 pm
content: I had the boards made at ITEAD Studio. Attached are the Gerbers.I think that the FRAM board may go through another rev based on some ideas listed in this thread. But if you must have them now, you can get a batch made.

author: mimmus78
author_rank: Unknown
timestamp: January 23, 2017, 10:38:53 pm
content: My ram chips were just swapped ... I guess I have some time before next pit stop.Inviato dal mio Nexus 6P utilizzando Tapatalk

author: nidlaX
author_rank: Frequent Contributor
timestamp: January 24, 2017, 07:26:26 am
content: Thanks for the article! I'm going to grab some old RAMTRON FM1608 in DIP28 from eBay to replace the SRAM in my Keithley 193.

author: bingo600
author_rank: Super Contributor
timestamp: January 24, 2017, 03:36:53 pm
content: Quote from: ManateeMafia on January 23, 2017, 10:34:40 pm@MMAny hints to the function of new PCB's ?/Bingo

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: January 25, 2017, 01:43:02 am
content: I wanted the board to be used as a replacement for three different types of memory.1. Dual CE Ram JMP1,JMP2-> pos 2. R1,R2 are installed as pullups. R3 not installed. IC2 installed.2. DS1225 JMP1->pos1 JMP2->nc R1,R2 are installed. R3 not installed. IC2 not installed.3. DS1230 JMP1,JMP2->pos 1. R1,R2 are not installed. R3 is installed. IC2 not installed.JMP1 and JMP2 are zero ohm. I used 4.7k on R1,R2. R3 is zero ohm. I should have labeled it a jumper. IC2 is a 74LS00.R1 and R2 tie the unused address lines high. An alternative design could use a two way switch between VCC and gnd for A13 and A14 for multiple backups.JMP3 was originally added for in-circuit reading but I decided to just use a wire. I have the additional board for my EPROM programmer that seems to work fine.The FM1808 can be substituted for cheaper lower capacity FRAM with the additional savings of R1&R2. Any future boards for my Datron products will use the cheaper FRAM.

author: bingo600
author_rank: Super Contributor
timestamp: January 25, 2017, 05:36:41 pm
content: Quote from: ManateeMafia on January 25, 2017, 01:43:02 amYes please .....Can i have 2..3 boards tomorrow ??/Bingo

author: rastro
author_rank: Frequent Contributor
timestamp: January 26, 2017, 12:10:22 am
content: The F-RAM memories are marketed as 3.3VDC devices although the datasheets indicate a max voltage of 5.5VDC. Is there any concerns about running these chips on high side of their voltage range? Also does the logic levels follow the power supply level?I would like to adapt one of these chips for the HP 8753's which have a very poor ram back that typically can't survive more than day or two powered down.-rastro

author: nidlaX
author_rank: Frequent Contributor
timestamp: January 26, 2017, 12:59:22 am
content: Quote from: rastro on January 26, 2017, 12:10:22 amI think the RAMTRON / Cypress design has simply been upgraded over the years from 4.5V - 5.5V to 2.5V - 5.5V with the W model, so there should be no concerns since none are stated in the datasheet.

author: james_s
author_rank: Super Contributor
timestamp: January 26, 2017, 05:50:57 am
content: While you're not supposed to, it's possible to replace the battery in the DS1220 and similar chips. It's a lithium coin cell potted in the block, it's usually up near the top and can be found with a bit of cutting with a dremel. Once you extract it, solder a CR2032 holder to the remains of the pins that went to it.

author: bingo600
author_rank: Super Contributor
timestamp: February 01, 2017, 04:06:12 pm
content: I guess it's my time now, to install FRAM'shttps://www.eevblog.com/forum/repair/3458-ram-test-1-low//Bingo

author: quarks
author_rank: Frequent Contributor
timestamp: February 12, 2017, 03:35:00 pm
content: just a short update.As already stated, I contacted Batronix about my finding and they were very helpful and responsive.After several not working updates they asked for a chip and I send a FM16W08.This weekend I was able to test their solution and it works now.Unfortunately it is not yet public, because it needs a new Firmware which is not yet officially released.I will give an update as soon as the fix is publicly available.PS: I have a few of the ManateeMafia "Dual CE EPROM Programmer Adapter" boards, which I do not need with my programmer. If anyone is looking for these, feel free to send a PM.

author: rastro
author_rank: Frequent Contributor
timestamp: February 22, 2017, 11:23:52 pm
content: What is everyone doing to make pins for the SOIC-DIP adapter board?

author: james_s
author_rank: Super Contributor
timestamp: February 22, 2017, 11:31:31 pm
content: Make pins? You can buy breakaway strips of machined pin male-male header strips.

author: rastro
author_rank: Frequent Contributor
timestamp: February 22, 2017, 11:35:24 pm
content: I'm not familar with these. Do you have part number/vendor or pictures?Thanks

author: james_s
author_rank: Super Contributor
timestamp: February 22, 2017, 11:43:55 pm
content: http://www.ebay.com/itm/10-PCS-40-Pin-2-54mm-Gold-machine-Single-Row-Straight-Male-Pin-Header-/281699010399?hash=item419691c75f:g:WNcAAOxyjNlRyqBg

author: rastro
author_rank: Frequent Contributor
timestamp: February 22, 2017, 11:53:40 pm
content: Got them thanks.

author: Greybeard
author_rank: Frequent Contributor
timestamp: November 03, 2020, 08:48:10 pm
content: What FRAM can be used for replacement of CAL-RAM?FM1608, FM16W08 or FM16L08?FM1808, FM18W08 or FM18L08?RAMTRON or Cypress?DIL28 orSOP28 + SOP-to-DIL-Adapter PCB?What do you think?

author: Tektron
author_rank: Contributor
timestamp: November 04, 2020, 08:28:20 am
content: I can only state what I have checked with my own hands.I used CYPRESSFM16W08with SOP28 + SOP-to-DIL-Adapter PCBfor CALRAM. The use of an adapter in this location is mandatory; this allows you to match the pinout of the footprint on the board with the microcircuit pinout by cutting and closing the conductors on the ADAPTER, but not on the board.For general purpose RAM, I used the CYPRESSFM18W08-SGwith SOP28 + SOP-to-DIL-Adapter PCB. However, in this location, the use of an adapter is not required, so most likely a DIL28 housing can be installed.

author: TheSteve
author_rank: Unknown
timestamp: November 04, 2020, 05:01:37 pm
content: I have used DIP FM1808's in my 3458A's. I use an adapter PCB for the cal ram. In the hi/low ram locations the FM1808 can be plugged right in, no adapter needed. For programming/reading the cal ram it is super easy, just unplug the FM1808 from the adapter and read/write directly in your programmer.Myself and volvo_nut_v70 had adapter PCB's made for the 3458A and the Datron/Wavetek line of meters and calibrators(pic attached).

author: Greybeard
author_rank: Frequent Contributor
timestamp: November 04, 2020, 09:06:28 pm
content: Thanks for your replies.I understand now:An adapter is needed for DIL28 FRAM at CAL-RAM position, because pinout is different to original DALLAS DS1220 NVRAM.On the other side:I could program SOP28 FRAM directly on the programmer, then solder it to the modified adapter PCBs.If reprogramming is needed I could buildoneadapter DIL28 to DIL28 that unmake the modifications of the SOP28 to DIL28 adapter.Does FM1x_08, FM1xW08 or FM1xL08 matter? Wide supply voltage - low power (?)Does producer (RAMTRON / Cypress) matter?What cheap programmer can be recommended?BTW: Steve, what is the jumper on your second pic used for?

author: TheSteve
author_rank: Unknown
timestamp: November 04, 2020, 09:24:24 pm
content: Quote from: Greybeard on November 04, 2020, 09:06:28 pmThat is the Wavetek/Datron version of the FRAM adapter. The config with the jumper is specifically for the 4920/4920M and 4950. These models have real time clocks that share the battery power with the original nvram. When a FRAM is installed we don't want it draining the battery so we use the jumper to connect to an existing header on the PCB to give us normal ground instead of the original isolated battery connected ground. The Wavetek/Datron devices use a dedicated static ram and a separate backup battery. All Wavetek/Datron adapters also require some logic gates to adapt to the FRAM.Here is a picture of the other side of the assembled modules. You can see we also have jumpers to set the unused address lines high/low.I have the adapters installed in 3458A's, a Datron 1281, 4920M and a 4708 calibrator.

author: Greybeard
author_rank: Frequent Contributor
timestamp: November 04, 2020, 09:40:03 pm
content: I don't know, if the DALLAS RAMs sit in sockets in my '58A, but if i have to unsolder them, will data remain safe in the chips, or is there a risk to corrupt data by shorting pins?

author: Dr. Frank
author_rank: Super Contributor
timestamp: November 04, 2020, 09:58:23 pm
content: 1. As you did not assemble a socket by yourself, it's s probably still soldered in.2. Desoldering is very easy, but first make sure, that you really have the old version, i. e. really the Dallas ones. A desoldering station is recommended. Pins are smaller than the holes, so no problem.3. It's really necessary to read out the CalRam content via GPIB before desoldering.4. Shorting is not the problem, because w/o operating voltage, the chip should be inoperative and immune, but obviously the heat is a problem. There are examples, where the Ram was OK, but failed directly after desoldering.5. Read the Ram after desoldering and compare

author: TheSteve
author_rank: Unknown
timestamp: November 04, 2020, 10:12:04 pm
content: As Dr Frank has said a vacuum desoldering tool generally makes it quite easy to remove the original nvram's. I had no problem with any data loss when removing mine but do your best to backup the data via gpib before hand. They are all soldered from the factory - so if there are sockets someone else has been in there previously.

author: Greybeard
author_rank: Frequent Contributor
timestamp: November 04, 2020, 10:13:52 pm
content: They are all soldered from the factory - so if there are sockets someone else has been in there previously.Thanks for clarifying.1. As you did not put a socket in by yourself, its probably still soldered in.No I have not opened this device yet, but I'm pretty sure it's the old version.2. Desoldering is very easy, but make sure first, that you really have the old version. A desoldering station is recommended. Pins are smaller than the holes, so no problem.Often desoldering iron tips has same outer diameter of the lands ("Lötaugen") on the PCB, and when you move the tip a bit, it can contact/short the neighbour land.3. It's really necessary to read out the CalRam content via GPIB first.This was my plan.4. Shorting is not the problem, because w/o operating voltage, the chip should be inoperative and immune, but obviously the heat is a problem. There are examples, where the Ram was OK, but failed directly after Desoldering.Interesting, because the tracks of the leadframe are not very short for DIL24/28 packages.5. Read the Ram after desoldering and compare.That's a good idea, I will do so.Can I stock the unsoldered NVRAMs sitting in conductible ESD foam without discharging the internal battery?

author: Dr. Frank
author_rank: Super Contributor
timestamp: November 04, 2020, 10:53:14 pm
content: Quote from: Greybeard on November 04, 2020, 10:13:52 pmProbably yes, because the RAM does not lose its content, when soldered inside the conducting circuit. Also all pins are on same potential, and no supply voltage is present, so an activation is impossible.The internal battery has no discharging connection to the pins, so no problem either.Frank