Dallas DS1486 and DS1250 Replacement designs - Page 1
Forum section: electronics / repair

author: cuebus
author_rank: Unknown
timestamp: March 08, 2020, 08:44:52 pm
content: Hi all,I've made successful replacements of the Dallas DS1486 and 1250 chips that so many of us have been trying to find replacements for.Based on extensive research on parts and understanding how these chips work, I've come up with the attached board designs.My DS1486 uses the DS1384G controller chip, which is an internal engineering part Dallas made for their PowerCap modules when they were still in production. It is identical to the DS1384FP as far as I can tell, with the exception of being in a 48 pin LQFP rather than 44 pin MQFP. I determined the pinout through trial and error and help from the DS1558 datasheet, which is a similar controller in the same package.I'm not sure where suppliers are getting their DS1384G parts, but the parts I've purchased from this supplier are working correctly:https://specialtypartsinc.com/products/1-pc-ds1384g-dallas-ic-rtc-clk-calendar-par-48-mqfp-1There is also a chinese supplier on ebay. I have not tested that part.My DS1250 uses the DS1312S-2 controller chip which is still in production, and the same part Maxim uses in current production DS1250 modules.These are not only functional replacements but as close to replicas of the originals that I've been able to make using currently available parts. Battery size, count, and components are, aside from footprints and PCB layout, the same as original.BOM is attached. The SRAM you use is not critical, as long as it is 5V, low standby power (1uA at ambient temps), and the same pinout.OshPark will make 3 boards for around $6 shipped.Some tips:Measure the battery voltage before you mount them. I've had issues with mouser delivering batteries that are DOA and measure less than a volt.Solder all surface mount devices first. On the fine pitch devices on the 1486, BE SURE THERE IS NO SOLDER SHORT. My first attempt fried both chips on the board because I actually had a solder bridge BEHIND the leads that I didn't easily see. Use plenty of flux.Next solder the batteries. Be sure there's clearance enough so that the pcb header pins won't be touching the battery tabs.Do the pin headers last.On all devices, make sure not to have too much dwell time with your iron. If you have enough flux, the SMD pins will take solder fully in less than a second. I also recommend using the lowest possible temp on the SMD devices.After you've constructed the board and washed away flux, be sure to let it rest for quite a while before programming to it. You need the SRAM to come back to ambient temperature internally before programming it.I would love to hear anyone report back how it's working for them after building them.There are already many other threads on programming them so I won't include anything about that here.Good luck!

author: cuebus
author_rank: Unknown
timestamp: March 08, 2020, 08:45:52 pm
content: Pics

author: james_s
author_rank: Super Contributor
timestamp: March 08, 2020, 09:37:26 pm
content: Excellent, thanks! The NVRAMs in my TDS784 are still working just fine however they're around 20 years old now so they're on borrowed time. This is a much cleaner solution than hacking in external batteries as I've been doing with Dallas chips and will be easily maintainable in the future. The key of course being the RTC chips themselves which are not going to be available forever.

author: Cubdriver
author_rank: Unknown
timestamp: March 09, 2020, 01:12:54 am
content: Thanks for posting. While I don't need themright now, I'm tagging this for future reference. Nice work.-Pat

author: bitseeker
author_rank: Super Contributor
timestamp: March 09, 2020, 04:21:39 am
content: Likewise. Good stuff, cuebus!

author: Rollin Hand
author_rank: Regular Contributor
timestamp: March 10, 2020, 03:56:37 pm
content: Can someone sell me 4 pc boards?Thank you.

author: james_s
author_rank: Super Contributor
timestamp: March 10, 2020, 04:00:33 pm
content: JLC PCB will sell you 5 boards for $2.

author: Rollin Hand
author_rank: Regular Contributor
timestamp: March 10, 2020, 04:09:57 pm
content: I need them already build ,I am a retired person from the electronic field and my vision dont respond to me,with batteries.Thanks

author: james_s
author_rank: Super Contributor
timestamp: March 10, 2020, 04:14:37 pm
content: There is a seller of similar boards on ebay, I think he charges $100 for a pair which is not unreasonable. This design here was created for those who like to DIY, I doubt anyone is going to be able to build them for you cheaper than those others are.

author: cuebus
author_rank: Unknown
timestamp: March 10, 2020, 10:27:25 pm
content: I'm willing to build boards for $50 for each one myself. I did a breakdown of the cost on another thread and it costs about $21 in materials for each chip in small quantity amounts. Add solder, flux, and cleaning materials, and the total cost is probably around $25. It takes about an hour to make both boards.Only issue is that I am in the middle of a move, so I won't be able to start making these for about another month to month-and-a-half.I recommend OSHPark for making the PCBs. They use US fabs so lead times are quicker and US environmental regs are in effect.I have a single DS1486 prototype that I can sell immediately if anyone wants it. It's an older board design, and I had a slight pin misalignment issue with the design so had to bend the pins slightly inward, but it works fine. It's actually the one in the photo. I'll sell it at cost, $25+shipping. I can leave the TDS540C programming or erase the chip before sending. Either way, even if you do have a TDS540C, I believe you will need to redo the SPC constants if you use someone else's data.

author: Rollin Hand
author_rank: Regular Contributor
timestamp: March 11, 2020, 02:25:53 pm
content: can you send me an invoice to paypal.ToRubyg6178Thanks

author: CaptDon
author_rank: Super Contributor
timestamp: April 15, 2020, 01:46:37 pm
content: I have spent a large amount of time examining my TDS644A memory map to understand the NVRAMaddressing. There are a large number of variants of the 'A' model and the schematics through TekWikihave been an incredible help!! My TDS644A has only the DS1286 and the 512K DS1650Y. There are manyzero ohm jumpers on the CPU board for memory configuration. The 'A' model is very different than the'B' model. The 'A' unit is directly related to the TDS544 series and shares much with that line. The floppydump tool from FLYTE on this forum is incredible!! The minimalfloppydumper works best on the 644A andyou can use the .bin file with any sensible programmer to program an aftermarket DS1250 replacementpart. DON'T BUY THE FAKE CHINESE CRAP!!!! I have two .bin dumps of my TDS644A if someone mayneed a copy. Mine has the GPIB/FLOPPY/MATH options from the factory. There is hardware steering logic74F27/74F30/74F32 to allow the first 16 bytes of the DS1286 timer to override the first 16 bytes of theDS1650Y. These are called out as 'bar NVRAM1' and 'bar NVRAM2'. Note that the U1106 and U1107 isthe same socket, the timer fills only the first 28 pins OR the second NVRAM uses all 32 pins.

author: CaptDon
author_rank: Super Contributor
timestamp: April 22, 2020, 01:16:17 pm
content: I bought the newly designed DS1650Y replacement part from the Ebay seller. He normallysells the DS1250Y/DS1486 set as a kit but allowed me to buy only the DS1250Y to replacemy DS1650Y. I used the minimalfloppydumper from FLYTE to save my TDS644A data (only512K needed in this scope) and with some indulgence did get the scope working 100%perfect with no boot errors!!! A word of CAUTION!! As has been noted by others, unsolderingthe old chip will almost certainly destroy any data in it!!! Create your backup bin FIRST!!!I used the most care possible when unsoldering and removing the old chip. I placed itcarefully into a programmer/reader and read the old data.....TOTALLY SCRAMBLED!!!I did retrieve a workable TDS644A .bin file and not sure if it may help any of you folkswith the older related 5XX series or not. Cheers!!! Now, on the fix my TDS644B!!

author: james_s
author_rank: Super Contributor
timestamp: April 23, 2020, 07:08:55 am
content: I built a pair using the PCBs posted here, I had a brain fart and installed a chip backwards on both of them but noticed the error and flipped it around before I tried applying power. In the end both worked perfectly, along with the backup and restore scripts and my scope is working perfectly with the replacements. I got the RTC chip from a China seller, I was concerned it might be a fake but it works fine so I think it's the real deal.

author: cuebus
author_rank: Unknown
timestamp: April 29, 2020, 01:24:38 am
content: James, great job on assembly, those look more pro than mine!Glad it's working for you.I think it's pretty unlikely to find fakes of the LQFP RTC chip unless they are just remarked junk parts of some other chip... The chip is so specific and it's not like it's an op amp where you can take a handful of various low performance op amps and remark them as higher performance chips and the circuit will probably work, especially in audio applications,...and a number of people will probably never know the difference.I'd still be curious to know though where suppliers even got this chip. It was an internal Dallas engineering part, as confirmed by Maxim, and never sold to the public. I'm guessing at some point there was a surplus auction somewhere and these found their way into various suppliers' hands.

author: james_s
author_rank: Super Contributor
timestamp: April 30, 2020, 04:57:30 am
content: I think if it was going to be a fake, it would be some random useless part that doesn't even attempt to mimic the correct IC. I remember a few years ago one of the "maker" focused companies got burned on a batch of AVR microcontrollers that turned out to be obsolete voltage regulators for PC motherboards or something like that, re-marked as atmega chips.My guess would be those Dallas ICs are surplus parts from a company that was building modules for Dallas. Wouldn't surprise me if they farmed out the production at some point.

author: KG7AMV
author_rank: Frequent Contributor
timestamp: May 15, 2020, 08:00:27 pm
content: 100 Thumbs Up..Thanks

author: Johnny10
author_rank: Frequent Contributor
timestamp: May 15, 2020, 08:10:19 pm
content: Great Thread!

author: Tantratron
author_rank: Frequent Contributor
timestamp: July 04, 2020, 05:24:34 am
content: Has anyone in Europe reproduced or build the NVRAM's kit ?

author: radioguy123
author_rank: Regular Contributor
timestamp: October 26, 2020, 07:16:54 pm
content: CUEBUS are you going to sell kits ? How difficult are these boards to build ?

author: Rasz
author_rank: Super Contributor
timestamp: October 27, 2020, 05:24:37 am
content: Quote from: james_s on March 08, 2020, 09:37:26 pmBut there is nothing wrong with RTC chips to begin with. I find it a little crazy spending $50 on something fixable by replacing $1 battery (with a dremel or disposable soldering iron tip)

author: james_s
author_rank: Super Contributor
timestamp: October 27, 2020, 06:47:11 am
content: Quote from: Rasz on October 27, 2020, 05:24:37 amExcept when there is, I did have one that failed.I have bodged on replacement batteries lots of times but I liked the idea of having clean, bare, un-potted and easily serviced modules in my scope that don't require any surgery, and $50 is peanuts in the grand scheme of things. I've spent far more building far less useful hobby projects.

author: whatboy
author_rank: Regular Contributor
timestamp: January 04, 2021, 04:17:31 pm
content: Thank you very much Mr. cuebus, for your valuable time and by sharing this info!!!but what chip is the U1 in the DS1250Y board???

author: whatboy
author_rank: Regular Contributor
timestamp: January 04, 2021, 05:29:49 pm
content: Just order 5 and 5 boards online, for 20 bucks with shipping!

author: whatboy
author_rank: Regular Contributor
timestamp: January 13, 2021, 01:26:10 pm
content: Got the boards from JLCPCB but the holes are too small for the pin headers...

author: picburner
author_rank: Frequent Contributor
timestamp: January 13, 2021, 02:48:44 pm
content: Thisis the correct header for those holes.

author: whatboy
author_rank: Regular Contributor
timestamp: January 13, 2021, 07:32:00 pm
content: Thank you very much!!!

author: VE2JFQ
author_rank: Contributor
timestamp: January 25, 2021, 12:23:50 am
content: hello, i have a problem with a ds1286 real time clock. i am a telecom technician, i have 3 ifr com-120b. all three the ds1286 battery has died! i managed to find three ds1286 in montreal, my problem is that i want to read and program them. i'm not a programmer, but i have a tl866 2 plus, but it doesn't take ds1286 or ds1284 (which contains 50bits of data. like time clock, serial number and options. i'm thinking of taking a pic programmer or arduino. I don't know these are two programs! what do you suggest to me? thank you and good day jacques

author: Rasz
author_rank: Super Contributor
timestamp: January 25, 2021, 01:09:32 am
content: battery died - nv ram is empty ram

author: Tantratron
author_rank: Frequent Contributor
timestamp: January 25, 2021, 04:47:39 am
content: Quote from: VE2JFQ on January 25, 2021, 12:23:50 amWhat test equipment are coming your DS1486 ?

author: VE2JFQ
author_rank: Contributor
timestamp: January 25, 2021, 12:40:18 pm
content: it's not a ds1486 it's a ds1286. this is a telecom test set. com-120b manufactured by ifr. ifr no longer supports com-120b

author: Ian.M
author_rank: Super Contributor
timestamp: January 25, 2021, 01:00:26 pm
content: VE2JFQ multiposted the above (#27) query.The original thread is here:https://www.eevblog.com/forum/programming/watchdog-programming-ds1286-and-others-need-help/

author: Insatman
author_rank: Frequent Contributor
timestamp: February 09, 2021, 04:04:18 am
content: I have built both boards using recommended components. The DS1250 programmed and works just fine using my GQ-4x4 programmer. I built two and tested them in my TDS784D. The problem is trying to program the DS1486 replacement boards. Again I built two and both refuse to program. I also bought two of the Chinese copies from UT-Source and these program and work just fine in the 784D. Since the GQ-4x4 does not support the DS1486, I have been using the DS1245 setting. This seemed to work ok on the Chinese chips with the exception of verification errors. I had assumed these were from the RTC bytes having changed. Again both Chinese chips work just fine in the 784 with no test errors and all original scope options preserved. My question is how to program the DS1486 replacement chips? Can it be done with a GQ-4x4? If so with what settings?Some details. The Dallas 1384G ICs were purchased from the recommended source in TX. All other parts were ordered from Digikey with the exceptions of the batteries as DigiKey will not ship them internationally. Instead I used coin battery holders and purchased batteries locally. The coin holders require a bit of pin bending as the spacing is slightly different from the PCB layout, but only 50 mills, so easy to bent to fit.The Chinese chips are marked with 2015 and 2016 date codes. Since Dallas stopped making these chips in 2009 they must be clones or refurbished.In first photo top row are Chinese chips, next are original from 784D, bottom row are replacement designs.2nd photo shows Working Chinese DS1486 and replacement DS1250 in 784D.The Chinese chips were sold as used, but appear new. The lead spacing is a bit off on the 1486 parts, but I was able to push them into a mill-max machined socket with a little persuasion.

author: Tantratron
author_rank: Frequent Contributor
timestamp: February 09, 2021, 04:29:02 am
content: Quote from: Insatman on February 09, 2021, 04:04:18 amIt is straightforward if installing both new DS replicas on the logic A11 board of your TDS784D (your TDS oscilloscope becomes the programmer). I recommend you first solder two 32 pins sockets on the PCB, after you plug your DS1486 and DS1250Y replica into the sockets. Then dumping (old NVRAMs) and writing the NVRAM's (replicas), the firmware thanks to a Github repo compilationhttps://github.com/ragges/tektoolswhere in my case, I've used my MacBook Air and a GPIB-USB from National Instruments. For instance, I've used and found very practical thetekfwtooltool, again with MacOS where it was seamless and easy which should run easy with Windows, Linux...

author: Insatman
author_rank: Frequent Contributor
timestamp: February 09, 2021, 05:32:15 am
content: Quote from: Tantratron on February 09, 2021, 04:29:02 amUnfortuately I do not own an NI GPIB-USB unit. I have an HP unit which I have been unable to get to work with the tektool software.

author: Tantratron
author_rank: Frequent Contributor
timestamp: February 09, 2021, 07:00:26 am
content: Well from what I've read here or in tektronix forum, it will tricky or catch 22 or chicken and egg situation to properly write the DS1486 via an external programmer. The first 20 bytes or more seems to have a specific protection or whatever affecting some external writing devices which is why I did prefer to invest into GPIB-US from NI then tektools which are open sourced.By the way, did you dump (read) the content of both DS1486 and DS1250Y prior desoldering them from the A11 board ?

author: Insatman
author_rank: Frequent Contributor
timestamp: February 09, 2021, 08:50:39 am
content: Quote from: Tantratron on February 09, 2021, 07:00:26 amIt's interesting to note that I was able to write to the Chinese clone DS1486 just fine using the external programmer but that the replacement version gives an immediate error message.I tried using the floppy dump utility prior to desoldering the original chips. I got a file but have never used it. Once the chips were desoldered, I was able to read them on the GQ-4x4 easily. I used the DS1245 profile for the DS1486. My 784D had DS1250 rather than the DS1650 some others have. I had purchased DS1650 ICs. So I read the original DS1250 with that profile and wrote the data to the DS1650 profile to the Chinese close chips. I've tested all four of the Chinese chips and they work just fine in the scope (2x DS1486 and 2x DS1250). Also the DS1250 replacement chips work as well.

author: Tantratron
author_rank: Frequent Contributor
timestamp: February 09, 2021, 08:56:57 am
content: Oups... you're very right where the other method I've totally forgot to suggest was the floppy disk (member @FLYTE utilities). I tend to not use it because I prefer the GPIB-USB with tekfwtool (member @SVEN utilities) but have you then tried writing the DS1486 and DS1250 replicas of @Cuebus member via the Floppy method ?

author: Insatman
author_rank: Frequent Contributor
timestamp: February 10, 2021, 02:13:03 am
content: Quote from: Tantratron on February 09, 2021, 08:56:57 amWell, I have a problem that prevents both methods (GPIB and floppy). Turns out the 784D refuses to boot with the replica DS1486 installed. The sequence gets stuck with the numeric display displaying two digits alternately forever. Once I replace the replica DS1486 with either the original or clone DS1486, the scope boots normally.

author: Tantratron
author_rank: Frequent Contributor
timestamp: February 10, 2021, 06:22:17 am
content: If you're certain that your PCB etching, your soldering and your chipset are correct then maybe the reason or a clue could be related to the fact your TDS784D runs with firmware 7.X version. I say this because most replication so far were done by C serie TDSxxx model (version 5.x) plus D series TDS do have two type of A11 and A10 boards non compatible where either you use 6.x firmwares or 7.x firmwares.

author: madao
author_rank: Frequent Contributor
timestamp: February 10, 2021, 06:47:37 am
content: DS1486 with wrong image shouldn't stopped booting . Firmware status doesn't matter. Unit refuse to starting, if NVSRAM is dead or away.possible: dead IC or bad solder joint or contact issuses of DS1486 replica is causes of failure.I own modded TDS784D (FW7.3) with DS1486 replica. No issuses. But i have one DS1384 with DOA. Unit starting with him, but extremely high battery consumption and Clock doesn't run... gnarf!

author: Ian.M
author_rank: Super Contributor
timestamp: February 10, 2021, 09:46:34 am
content: If you don't find any obvious dry joints or bridges on the DS1486 module with good lighting and decent magnification, IMHO you've reached the point where you need to be able to functionally test it.e.g. Use an Anduino Mega (or other 5V Arduino with enough I/O pins) and the DS1486 module in a breadboard, with the Vcc supply to it fed via two diodes + a pulldown resistor, with a shorting link across the diodes for normal operation, removed to test its write-protect mode. Write a sketch to repeatedly dump the RTC + let you change any RTC register, and write another one that tests the RAM, looking for stuck data and address lines and stuck bits. Hint: 1K series resistors in each data line make bus contention non-hazardous if you make a mistake coding the sketches transitions between reading and writing the data bus.

author: Insatman
author_rank: Frequent Contributor
timestamp: February 11, 2021, 04:15:32 am
content: Quote from: madao on February 10, 2021, 06:47:37 amYes I had heard that the 784D should have booted even without the DS1486 replica being programmed. So something must be wrong. I built two examples and both exhibit the same behavior, both in the programmer and the 784D. Note when I attempt to boot the 784 the numeric display oscillates between 6 and 8, if that means anything.so...I could have two bad DS1384 (bought from Specialty Electronics in TX, USA)...not likely. Both boards could have an identical or similar construction fault...most likely.I will de-solder the battery holders on both PCBs and give them a through inspection.In the meantime, the 784D is working fine and passed SPC today. I plan on replacing the hard-drive with a compact-flash drive as soon as I can obtain parts and transfer the disc image. The present hard drive was made in 1998 and I'm nervous about how long it will last. The CRT was replaced with a color LCD kit a couple of years back and the floppy drive was replaced with a USB floppy emulator at that time.

author: james_s
author_rank: Super Contributor
timestamp: February 11, 2021, 08:21:43 am
content: Quote from: Insatman on February 11, 2021, 04:15:32 amThat sounds like the DS1486 is in test mode. This causes one of the pins to oscillate at a frequency, 512hz IIRC to allow you to measure the frequency of the internal crystal. This will of course result in unpredictable behavior of whatever device it is installed in. I ran into this some time back when I was trying to program a similar Dallas RTC in a regular EPROM/flash programmer. Read the datasheet and it explains how to enable and disable test mode, I ended up using an arduino mega and wrote a little program to do it.

author: Insatman
author_rank: Frequent Contributor
timestamp: February 13, 2021, 06:04:03 am
content: Quote from: james_s on February 11, 2021, 08:21:43 amThe replica DS1486 is based on the DS1384G. Looking at the datasheet of the DS1384G, I cannot find any mention of a test mode.

author: Insatman
author_rank: Frequent Contributor
timestamp: February 13, 2021, 06:25:02 am
content: I desoldered on of the battery holders on each of the two DS1486 replica units. This was done to be able to uncover and inspect the DS1384G IC solder joints. I did find one definite solder bridge on one unit. I found a few other possible shorts on both units and cleaned up everything I saw. Since the datasheet for the DS1384G says to ground the unused battery input if only one was used, I did that.Behavior in the Eprom programmer was unchanged. The IC can be read or verified as blank as a DS1245. The IC cannot be written however and immediately generates an error code. Both units behave the same.Behavior in the 784D is also unchanged. The 784D does not boot and the numeric display oscillates between "6" and "8". The scope behaves the same way if the DS1486 socket is empty. Upon installation of the original or Chinese copy DS1486, the 784D works normally.Maybe I just have two bad DS1384G? Either originally or I killed them during soldering.

author: james_s
author_rank: Super Contributor
timestamp: February 13, 2021, 07:34:48 am
content: Quote from: Insatman on February 13, 2021, 06:04:03 amFrom the DS1384 datasheet: "SQW - Square Wave (output): This pin can be programmed to output a 1024 Hz square wave signal.When the signal is turned off, the pin is high Z."On the DS1486 this is shared with the /INTA pin. Have you tried scoping the pins to see if one has a square wave on it?

author: Insatman
author_rank: Frequent Contributor
timestamp: February 13, 2021, 09:50:22 am
content: Quote from: james_s on February 13, 2021, 07:34:48 amI have checked pin 30 on the DS1486 replica and got nothing but a little noise. I do see 32kHz on the crystal, so at least that is working.

author: cuebus
author_rank: Unknown
timestamp: February 22, 2021, 12:24:36 am
content: Hi Insatman,I'm the designer of this replacement. I figured I would give some insight of things I've run across having built a number of these now.a) you did mention that you had solder bridges that you fixed after already testing them. You likely already fried the chips at this point. I can't say for sure which pins would or wouldn't cause the chip to die but my first build I also had a solder bridge and the chip was dead.I also had an issue earlier this year with some flux that was highly conductive without me realizing it, and fried a number of chips during testing because I've usually tested before washing to avoid having to wash twice if I have to do any rework.b)Ever since I switched to a solder paste workflow I've had none of the aformentioned issues and I highly suggest if people have the tools to use solder paste with standard QFP and TSSOP stencils. If you're using external flux, you have to make sure that the board is absolutely spotless. This is hard to do with flux that gets under the chips unless you have an ultrasonic cleaner.c)Lastly I'm not sure how you're programming these, but I've found the TL866 (which is most people's go-to cheap programmer) extremely unreliable with the DS1486 in DS1245 mode. I really don't know what the cause is of the issue but I find often that data at the beginning of the chip is unable to be read correctly meaning if you try to make a binary dump of the data, you better be sure you don't have a bunch of FF in the first 0-100 rows. Each read tends to give me a different amount of data, yet the chips work fine in my scope, including the clock which is the first row of data. I have a theory that the TL866 might be trying to read the data too quickly after applying power. It looks like the DS1245 has a startup time of 125ms while the DS1486 is 200ms. I need to see if I can apply 5V externally without damaging the programmer to test this theory. I suppose I could lift the power pin to try that.I recommend using the tektool or tekfwtool process that has been documented on this forum reasonably well.Hope this helps you and anyone else working on this.Quote from: Insatman on February 13, 2021, 09:50:22 am

author: Tantratron
author_rank: Frequent Contributor
timestamp: July 12, 2021, 05:21:18 am
content: Quote from: james_s on April 23, 2020, 07:08:55 amHi James, what method to program both replicas have you used ?

author: Tantratron
author_rank: Frequent Contributor
timestamp: July 16, 2021, 06:42:19 am
content: Quote from: Insatman on February 13, 2021, 06:25:02 amWether on C serie or D serie, during the boot sequence check (15 steps from 1 to E), there is specific step number 11 (B) which makes a local verification of DS1486 (will write sequence of 1 2 3 4 5 6 7 8 then read if same values). If there is no DS1486 installed or the DS1486 has an internal failure, it will generate .B error by choosing DIP switch check mode value 11 (decimal). Otherwise it will go alternate 6 and 8 as you seem to report but I recommend that you specifically DIP switch choose step number 11 (decimal) or B (hexa) which would raise the failure .B where DOT means failure. If the test pass then you will have only B flashing.On a side note, if there is no DS1250Y installed then no problem because these TDSxxx-C/D can actually run only with DS1486.

author: Tantratron
author_rank: Frequent Contributor
timestamp: July 16, 2021, 12:02:33 pm
content: Quote from: james_s on February 13, 2021, 07:34:48 amWith my own replica, I do have 1KHz square wave on pin-32 but do you confirm if this is the case the device cannot work ?Albert

author: Chalcogenide
author_rank: Regular Contributor
timestamp: September 20, 2021, 10:16:03 am
content: If anyone is interested, I came up with a design that replaces a DS1245 or DS1250 with a non volatile MRAM. It's more expensive than an SRAM + battery backup solution, but it should be the ultimate "set and forget" replacement since no battery for backup is needed. I only tested it with a TL866 and on a Keithley 2001, but if anyone is interested let me know and I will share the BOM and gerbers. I also have a couple of partially populated boards if someone wants to give a try.

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 20, 2021, 12:43:59 pm
content: Quote from: Chalcogenide on September 20, 2021, 10:16:03 amHello,A few questions as an owner and repairing few TDSxxx/C/D oscilloscope.What are the memory speed access of your prototypes -70 -100 or -120 (ns)Any hope to have a design based on MRAM technology with internal RTC to replace the DS1486What pins form factor does you prototype uses, flat like legacy DALLAS or roundedTechnically it weems we can replace a failed DS1486 by either a DS1245Y or DS1250Y where of course we loose the RTC feature. I have tried using one legacy DS1250Y-100 and it worked.Note that the DS1250Y in the TDSxxx/C/D main board does not need to be installed, the oscilloscope only needs the DS1486-120 installed to properly boot and run (check this other post and informationhttps://www.eevblog.com/forum/testgear/i-noticed-nvram-replacements-for-the-tds784d-on-ebay/msg3610951/#msg3610951). Of course you'd loose the save memory option but we can live without it or download waveforms via GPIB-USB.Since you're based in Italy, I'm based in France then I could try on TDSxxx/C/D if you do not have one.Grazie, Albert

author: Chalcogenide
author_rank: Regular Contributor
timestamp: September 20, 2021, 03:39:11 pm
content: The MRAM I chose is the Everspin MR0A08BYS35 (DS1245) or MR2A08AYS35 (DS1250) which are 35 ns parts, plus a voltage translator TI TXS0108E which I guess shouldn't add more than 20 ns at the most. The spare boards I have were assembled at JLCPCB and the only things missing are the MRAM (which I only bought one to fit on the Keithley 2001) and the pin headers (I have used round pins on mine but I guess you could solder in whatever kind).I have no plan on tackling the DS1486 because at that point using a battery is unavoidable so more conventional SRAM based approaches are probably the way to go.PM me for more info.

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 21, 2021, 07:38:37 am
content: Quote from: Chalcogenide on September 20, 2021, 03:39:11 pmSo I guess you generate via another chip the 3.3V from the 5V required to properly voltage match interface ?The real problem with these legacy DALLAS then Maxim DSxxxx NVRAMs and RTC's, they were all designed for 5V bus and power supplies. Now to make a replication is complex because most components are 3.3V only so you need to add other chips.The memory access time could be an issue as well where the legacy DSxxxx has battery controller with Vdd controler voting who supplies energy to the memory. The power up of old main boards and PSUs (i.e. TDSxxx oscilloscope) can be tricky and not meet the transients of new replicas then boot fail.

author: Chalcogenide
author_rank: Regular Contributor
timestamp: September 21, 2021, 09:16:59 am
content: Yes, there's an LDO to supply the 3.3V to the various ICs on the board. I am hesitant to provide the design files before verifying that it works in at least some other instrument... in the 2001 the Dallas chip is only used as a buffer to store measurements and it's neither accessed particularly fast nor strictly required for boot, so I can only attest that my design behaves like a normal Dallas chip when used in these conditions. The MRAM has an internal "UVLO" of sorts to deal with power-up and power-down, but I have no idea whether it's enough; the MRAM has a startup time of 2 ms after VDD reaches 3.0 V (so given the dropout of the LDO, when the 5V rail reaches something in the order of 3.5 V). It is probably fast enough but I am not sure.

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 21, 2021, 09:55:13 am
content: Hello Chalcogenide,Well technically and as mentioned before, if we focus on TDSxxx/C/D oscilloscope and decide to drop the RTC feature, it works to install inside the DS1286 slot either DS1250Y or DS1650Y. The way the DS1486 is wired does not actually use the 512K, only the 128K. So it seems replacing a DS1486-120 by either a DS1250Y DS1650Y DS1245Y or DS1250Y works.Note that i've only tried DS1250Y and DS1650Y so cannot confirm about the 2 others but some members seem to have confirmed DS1245 or DS1250 do work as a replacement for DS1486.However there is a strange thing which I still do not fully understand hence my caution. Installing the DS1250Y clone designed by cuebus inside the DS1486 does not work. It should since after all this a memory with battery backup but maybe the SRAM used is too fast, too slow or too whatever.With the TDSxxx/C/D the processor board is 68040, the data and address bus is clocked at 2.5MHzAlbert

author: madao
author_rank: Frequent Contributor
timestamp: September 21, 2021, 02:39:39 pm
content: I confirm: DS1245 works in my TDS784D and TDS754CClock doesn't running.. It is in most case not important.regardsmattt

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 22, 2021, 02:23:58 pm
content: Quote from: madao on September 21, 2021, 02:39:39 pmHello Matt, what specific DS1245 model did you try (DS1245Y or DS1245AB voltage rating.... -70 -85 -100 or -120 memory speed) ?Thanks, Albert

author: whatboy
author_rank: Regular Contributor
timestamp: December 17, 2021, 03:29:56 pm
content: At last I manage to make 3 sets for my 3 oscilloscopes TDS 684 A, B and C, but only could program one set, already installed and working, the other two sets gives me errors with the DS1250, when programming in my LAB TOOL-48UXP programmer, at first I didn't knew why, but after testing the chip CUEBUS made and kindly shared, I noticed that the DS1312 is not switching the voltaje from the battery, the chip is dead, if you put iton the programmer it will supply 5V to the memory, but once the 5V are gone, no BAT voltaje is switched to the memory, so all info written is gone. And yes, if you read it after, it will give you all 0's, I do not know if I kill the DS1312 or if it came that way, did not put it wrong, not the battery, have to buy more and see. I still am happy to manage to set up at least one osci!

author: Teichhermelin
author_rank: Regular Contributor
timestamp: December 17, 2021, 04:36:03 pm
content: Could the board be used for other DS types?

author: whatboy
author_rank: Regular Contributor
timestamp: December 17, 2021, 05:11:33 pm
content: You can check it out with the datasheet of each chip!

author: cuebus
author_rank: Unknown
timestamp: December 18, 2021, 04:24:15 am
content: Check the orientation of the DS1312S-2. Note that it faces pointing down with pin 1 facing the middle of the pcb. The SRAM and controller should be facing each other. In hindsight this might have been bad design but it's been about 2 years since I designed this...Did you get your DS1312S-2 from a reputable supplier? It's still a current part, so there should be no problems getting genuine working parts from Mouser, digikey, etc.

author: whatboy
author_rank: Regular Contributor
timestamp: December 20, 2021, 02:47:40 am
content: There is a line on pin one, so I did put it right!, and no, I bought them from ebay, the seller was from USA thought, next time I will buy from mouser!

author: Tantratron
author_rank: Frequent Contributor
timestamp: December 20, 2021, 05:54:06 am
content: Quote from: whatboy on December 17, 2021, 03:29:56 pmThank you where it is interesting that you bring the issue on DS1250 replica or emulation.On my side as reported in this other threadhttps://www.eevblog.com/forum/testgear/i-noticed-nvram-replacements-for-the-tds784d-on-ebay/msg3613318/#msg3613318among 3 complete kits (DS1486 and DS1250), only one set is still working now since last june.I really have no idea on what root cause or multiple root causes but wether DS1486 or DS1250 now we have enough members which has good soldering skills to not confirm 100% replica effect. In my case, all the programming was done using the tekfwtool application through the GPIB-USB interface from National Instruments. Others have used an external programmer, I do not have one so far but unless I'm wrong, many times I've repaired different TDSxxx/C/D the reprogrammed their orginal Dallas DS1486 and DS1250Y, it worked always via GPIB.Albert

author: m3vuv
author_rank: Super Contributor
timestamp: December 20, 2021, 11:17:13 am
content: has anyone tried doing this for a DS1230Y-100 ?

author: whatboy
author_rank: Regular Contributor
timestamp: September 20, 2022, 07:40:54 pm
content: UPDATE!!!Hello, I have 3 1GHz oscilloscopes, TDS684 A/B/C the A has a broke screen (the flyback is bad) and 2 hybrid modules bad, use'em to rapair the other two ones, I got the gerbers from CUEBUS and got the parts, although I didn't thought it would work, made 3 sets, but 1 I fsk it up and burn the RTC chip, but managed to make 2 working sets and put it on the 2 working oscis... even thought I bought the wrong parts, wrong size of memory bad quality crystal and batteries!!! I was about to quit, and they work, all 3 of them, but like I say burnt one set, but since I do not have the money to fix the A one which is the one with the screen and bad modules, I only use one (C) and wanted to sell the B one but can find a buyer, it was sitting all alone and just test it today and it is working, was concern a little because it gave me NULL readings on all 4 channels, but deleted the memory and it work! boots up and everything!So, I guess mine are working 100%

author: whatboy
author_rank: Regular Contributor
timestamp: September 20, 2022, 07:42:43 pm
content: you can see I had to bend the pins inwards to fit on the board!!! I really suck!!!

author: max-bit
author_rank: Frequent Contributor
timestamp: January 10, 2023, 04:58:37 pm
content: Does anyone have a diagram of this DS1486 adapter?Including edit files (not gerber) and/or schematicI would like to correct it to the DS1384 version in a 44 pin housing and use even better SRAM memories (newer and other types)The undoubted problem here is the DS1384 chip, which is difficult to access (price!)Couldn't some other IC DS be used?

author: max-bit
author_rank: Frequent Contributor
timestamp: January 10, 2023, 05:12:51 pm
content: DS1558 ?https://datasheets.stg-maximintegrated.com/en/ds/DS1558-DS1558Y.pdf

author: Tantratron
author_rank: Frequent Contributor
timestamp: January 12, 2023, 05:10:03 am
content: Quote from: max-bit on January 10, 2023, 05:12:51 pmThis chip will not work as many others, check the first posthttps://www.eevblog.com/forum/repair/dallas-ds1486-and-ds1250-replacement-designs/msg2954864/#msg2954864mentioning DS1558. One reason being the address space of registers (i.e. data, time...), the other is that DS1384 has 64 bytes protected which are used during the boot.Albert

author: TERRA Operative
author_rank: Super Contributor
timestamp: January 16, 2023, 01:08:12 am
content: My turn to be on the hunt for a number of replacement DS1486 chips....I have successfully made a drop-in replacement for the DS1225Y using FM16W08 FRAM chips on a 1-to-1 pinout SOIC28 to DIP28 adapter PCB, and my next trick will be trying out something to replace DS1250Y chips, maybe flash RAM. Gotta look into is a bit deeper.The tricky bit with the DS1486 is of course that DS1384 chip. Has anyone found a suitable substitution?

author: james_s
author_rank: Super Contributor
timestamp: January 16, 2023, 04:00:15 am
content: I made an adapter to use a FRAM, I forget which one yet but it may be the same part you used. Unfortunately it hasn't quite worked in anything I've tried it in yet due to the way those parts require CE (I think?) to go high between writes or something like that. They are hardware compatible with NVRAM but not always a drop in replacement for existing equipment unless you can modify the firmware.

author: max-bit
author_rank: Frequent Contributor
timestamp: January 16, 2023, 03:59:02 pm
content: DS1384G such as from the adapter are still available on ebay.I just ordered 5 pieces so I will make 5 adapters3-4 pieces will be for sale.Probably in about a month.The price will be "at cost"I still have a question if anyone has a schematic for the DS1486 replacement.Yes I can redraw from PCB but...

author: Tantratron
author_rank: Frequent Contributor
timestamp: January 16, 2023, 04:14:27 pm
content: Quote from: max-bit on January 16, 2023, 03:59:02 pmNote some recent progress herehttps://www.eevblog.com/forum/testgear/i-noticed-nvram-replacements-for-the-tds784d-on-ebay/msg4632898/#msg4632898Let's see how it goes through time.

author: max-bit
author_rank: Frequent Contributor
timestamp: January 17, 2023, 09:47:00 pm
content: There may be some incompatibilities.But in general it should work.

author: Tantratron
author_rank: Frequent Contributor
timestamp: January 18, 2023, 08:01:26 am
content: Quote from: max-bit on January 17, 2023, 09:47:00 pmUpon your analysis, what would be the incompatibilities of cuebus design ?

author: ltarjanyi75
author_rank: Contributor
timestamp: June 15, 2023, 08:55:00 pm
content: +1 successful build of cuebus design (for the first try). I have just put them into my 744A.Ordered the DS1384G (3 pcs) from China and it works perfectly, PCB from jlcpcb.I have tested the board outside of the scope first with an Atmega4809 on a breakout board (didn't had an Arduino Mega or similar with lots of GPIO. It was quite a mess with all the jumper wires but worked) and with some arduino sketch. I could read/write the NVRAMs and could get out the squarewave from the assembled 1486 board.I also copied the NVRAM backups made from the scope to the boards before putting them into the scope. It booted up and worked with it, but had some problems (e.g. it froze when I went to the error log menu). Probably I made some mistake during the write, which I did not compare byte by byte with the backup, just did a quick eye check...So I restored the backups with tektool to the NVRAMs and it works! Big thanks to cuebus!(Check the soldering carefully pin by pin as others suggested before! It is easy to make shorts...)