I noticed nvram replacements for the TDS784D on ebay

[radioguy123]

Just wondering if anyone has bought the nvram replacements for TDS series scopes from this ebay seller.
It would be great if these were the real deal. If so I wonder how he does it.
Here is the ebay link.

https://www.ebay.com/itm/Tektronix-TDS784D-700x-600x-exact-functional-replacement-for-DS1486-and-DS1250Y/302913384290?hash=item46870b6f62:g:uuwAAOSw9V5bFXZt

[james_s]

There's nothing particularly challenging about building a NVRAM. The RTC parts are considerably trickier but some can be replaced by newer Dallas parts as I did for the DS1742W.

$100 though?? Maybe a $30 kit would pique my interest, otherwise I'll just hack new battery into mine when I reach that point.

[radioguy123]

Yeah that's what I thought. $100 does seem a bit steep.
But since their not making these parts anymore what are we going to do ?
I haven't seen anyone hacking into a DS1486. I have heard they have 2 batteries.

[james_s]

Looking again I see it says you get a set of two chips for that price so I suppose that's not too bad considering what new Dallas parts cost. Looks like it's the same PCB for both only one has what I suspect is a 8 pin RTC chip on it. The NVRAM is trivial, the RTC less so. I wonder if he's using an ARM microcontroller to go between the parallel bus and serial RTC. The pictures look like they are deliberately concealing the bottom with whatever ICs are used.

[snoopy]

Is there anything important stored in these RAM's that would create issues swapping out the originals ?

[james_s]

No, just the settings, stored waveforms, error log, stuff like that. The cal constants are all in EEPROM on the acquisition board.

[Jwalling]

No, just the settings, stored waveforms, error log, stuff like that. The cal constants are all in EEPROM on the acquisition board.

Options and SPC constants are stored in the DS1486, but options are easily recovered.

[snoopy]

No, just the settings, stored waveforms, error log, stuff like that. The cal constants are all in EEPROM on the acquisition board.

Options and SPC constants are stored in the DS1486, but options are easily recovered.

Then if it only costs 100 bucks it's still a great deal considering the capability of these scopes

[radioguy123]

Yes I noticed that both of the boards in his picture are labeled 1486. Just the populated parts are different, at least on top.
He does look like he is concealing what ever is on the bottom of the board.
That's why I was wondering if anyone had taken him up on the deal.
So we could reverse engineer. 

[james_s]

On one hand it's clear he's just a hobbyist trying to make a few bucks on his project and he's not gonna get rich selling these things so I don't really want to screw him. On the other hand I'd really like to know how they work because I've dealt with these Dallas parts before and am always curious about this sort of thing and given a choice I'd rather roll my own than buy something anyway.

[radioguy123]

You can tell there is a chip on the bottom. But you can't see what it is. Probably the ram.
Then there is probably something else under the battery.
It would be nice to be able to roll our own.

[james_s]

Assuming that 8 pin IC is a RTC, it's gonna need a microcontroller to talk to that and talk to the parallel bus. Actually this might not be all that hard to sort out just knowing what we know. Microcontroller to connect to the 8 data lines and chip select, enough of the address lines to decode when the RTC registers are being read. Some of the modern microcontrollers should be fast enough to directly talk to the parallel bus. Then you need a SRAM and power control IC.

[snoopy]

You can tell there is a chip on the bottom. But you can't see what it is. Probably the ram.
Then there is probably something else under the battery.
It would be nice to be able to roll our own.

Is it really worth the time when you can buy it ready to go for 100 bucks ?

[radioguy123]

Yeah you're probably right snoopy. He will even load them with the software of your choice.
Just handing over the money won't help you learn anything though. 

[james_s]

It's not really worth the time, but I'd still prefer to roll my own, I just like doing things that way. Also I'm curious how it's done.

[oPossum]

Probably similar to this... http://www.glitchwrks.com/2018/03/17/gw-1244-1

[snoopy]

Yeah you're probably right snoopy. He will even load them with the software of your choice.
Just handing over the money won't help you learn anything though. 

But you have probably got better things to do with the scope than trying to fix it. Don't get me wrong I have had to fix some of mine but if there is an easier path to go down it's probably worth the time you save

[Black Phoenix]

The only thing I would change on his design was to instead of soldering the batteries directly to the PCB and using the batteries with spot-welded legs were to change to CR2032 holders and batteries.

Probably similar to this... http://www.glitchwrks.com/2018/03/17/gw-1244-1

Exactly like that.

[ArcticGeek]

I actually purchase one of these just because I was very curious how he designed this.  I only purchased the DS1486 replacement, and he was willing to sell that to me for $70.   This is still very expensive, but I had to know what he did.

The central part of the design consists of a DS1384 RTC controller; this part is identical to the DS1486 without an SRAM.  The DS1384 sits underneath the battery, and an SRAM is on the bottom side of the board.  Once you add the SRAM to the DS1384, you have something that is identical to a DS1486.  I suspect this is exactly what is inside the encapsulated DS1486 - a DS1384, an SRAM, and a couple of coincell batteries.  The DS1384 actually has inputs for TWO backup batteries if desired. 

I must admit it's a fairly clever design, although the layout seems less than optimal.  The bad part of the design is that the DS1384 is obsolete just like the DS1486, so if you buy any of those parts you will have to buy off of Alibaba, Ebay, or a broker somewhere so the quality is questionable.  However, the DS1384 does not have an internal battery like a DS1486 does so it is arguably less risky to buy these parts.  But I worry that the mileage on these parts may vary wildly.

After paying $70 for one of these from Ebay I have been busy trying to design my own DS1486 replacement.  I actually have a design complete, both the schematic and PCB layout are done.  What I did was use an available DS1746 as a sub for the DS1486, but I re-map the regs from lower memory to upper memory that the DS1486 requires.  I do this by inverting address bits A4-A16 and then using a GAL16V8 to remap A0-A3. 

I think this will work, but there are some differences between the 2 register banks if you look at the datasheets.  For example, the enable oscillator (EOSC) bit is in a different spot...but I doubt if the TDS sets/clears it.   I won't know if it works until I actually get my boards back and test it.

[radioguy123]

So articgeek this guy is actually not telling the truth about his part not being obsolete ? Or has he actually found another part that he is using now.
How long ago did you buy this part from him ?

[ArcticGeek]

I purchased this part from the seller on Ebay in the middle of September this year.   The DS1384 is definitely obsolete,  but the datasheet is still available on the Maxim website.  I don't know when the DS1384 became obsolete, but the DS1486 went obsolete somewhere around 2009, so I'm guessing it was around that time.

Even though the DS1384 is obsolete, the part does not have an internal battery so there isn't a shelf life associated with it like the DS1486.

[radioguy123]

Yeah I see a seller on ebay with some of those ds1384's. He's wanting like $17 for those.
Something tells me there is not a very large supply of those.
Still he's being a little bit disingenuous telling us that their not obsolete.

[james_s]

I don't understand what you mean, his devices that he's selling are not obsolete, i.e. they're still available newly built from him. He's not selling the bare Dallas RTC chips and claiming those are still manufactured and he's not selling obsolete devices with built in non-replaceable batteries. His product looks 100% legit to me. True he won't be able to build them forever but that's the case for anything.

[Alfons]

I do not understand what's going on here. If the things he sells work, where is the problem?

[radioguy123]

Well I was told above by articgeek that the DS1384 that he uses to make these knockoff's are obsolete. So he will run out and not be able to make more.
Also he says that the devices that he uses to make these from are not obsolete in his ebay ad. Unless he has found another chip other than the DS1384. that is a lie.

[james_s]

You're either being extremely pedantic or you are confused. Explain to me what difference it makes if one of the parts he's using to make these is still manufactured or not because I don't grasp it? I also don't see where he says the parts he makes them with are currently available, obviously the potted blocks from Dallas are obsolete because they are no longer made and they have non-replaceable internal batteries so they will all become stale and die. His parts are obviously not obsolete because he's still manufacturing them. One of the ICs he uses to make them is no longer made but so what? He still has them and is still manufacturing his part, his devices that he is selling have no internal battery and are still being produced by him, so they are not obsolete. It is irrelevant whether the components they use are still produced or not provided he has sufficient stock to supply the demand.

Calling it a lie is frankly absurd. The issue here is your reading comprehension. I just went and looked and it says "This part is not obsolete with no replacement like the original." That means the part (this assembly he is selling) is currently manufactured and available, you can buy one right now and you will get a brand new assembly. This is in contrast to the DS1486 which is no longer produced and no longer sold, you cannot go and buy a brand new one anywhere, they are obsolete. None of this means that he has to use all currently produced parts to build it or that he must be able to supply these in infinite numbers for an infinite period of time, that would be ridiculous. No product can be delivered indefinitely, even if I design something now with all cutting edge parts, eventually some of those parts will go out of production. As long as I have sufficient stock I can continue to sell newly built products and supported, my products would not be obsolete.

[ArcticGeek]

The other thing I would add is the seller's design is sound and works well, and his claim that is a 100% compatible replacement is true.  Although he may charge $70 for it, it's a decent design none the less.  I have no idea where he got his stock of DS1384 parts.  For all I know he worked for a company that bought a bunch of them and had some left over, but who knows.  My concern would be that if he bought these parts from Ebay or Alibaba the parts might be fake/faulty and fail over time.  Since these parts don't have an internal battery the shelf life concern is removed though so maybe that isn't a huge concern.

I have a number of the TDS6XX/7XX scopes, and the DS1486 that is inside them is a concern of mine.  I must confess I've purchased several (maybe 10?) of the DS1486 parts on Ebay from various vendors on Ebay.  Some work, most don't.  Most are probably either rejects or fake parts that are relabeled.  Even those that work are very questionable in my view.  I probably could have requested a refund from Ebay for these parts, but for a few dollars it's hardly worth my time and hassle. 

The DS1486 is fairly important in the TDS6xx/7xx scopes because it holds not only the time but also the SPC constants.  When the battery dies in the part you'll likely have to rerun SPC every time you power on the scope.  You will also likely get an error on startup.  That's a pain in the you-know-what.  A worse scenario is if the part fails such that the SRAM can't be read/written at all the scope will not boot.   A quick solution would be to simply replace the DS1486 with a DS1245 128K SRAM in the same package; that will keep the SPC constants alive but the date/time will still be set the same as the last time you set it on the scope.  That might be okay but I really kind of like have the date/time stamp on any waveforms I save or plot.  But that's just me, and others might find that okay.  So that's why I've started this project to design my own to replace the part - now all I need is the time to do it!

[radioguy123]

Keep us informed on your progress Articgeek. Do you plan on using the DS1384 ? I hope you share your ideas.

[Labrat101]

the batteries are quite easy to replace . They can be rimaled out the battery can normally felt by a slight bulge in the top surface of the chip. or a small magnet will locate it as it is 3.3 lithium battery . with a little care, i takes about half an hour
the battery top lead cut and then pried  up to get the bottom lead . solder 2 wires to a new battery .
I have replaced 2 of these batteries on my 20 year old scope .

[Labrat101]

You can tell there is a chip on the bottom. But you can't see what it is. Probably the ram.
Then there is probably something else under the battery.
It would be nice to be able to roll our own.

The whole top half of the chip only contains the battery and the Xtal which sits the opposite  side to the battery.
The ram is about 1mm under the bottom of the battery . about center chip . on some models the top is clipped and
can be removed removed  basically the top 1/4 inch approx is just plastic shell holder.

[james_s]

I think he's talking about the replacement parts being sold, not the originals.

I too have replaced the battery in a number of different Dallas bricks, although the result is not particularly pretty. I do wish they had just molded a coin cell holder into the top of the package right from the factory, potting a battery is stupid, soldering a module with a potted battery to the board in an expensive instrument is asinine.

[Rollin Hand]

Can you keep me inform about your results.I like to make one of the modules.Thanks

[cuebus]

Hi all,

For a few days now I've been researching and developing a board for making a functional replacement for the DS1486 and DS1250.
I've had the ebay woes like many of us here and just can't seem to find a source for any NOS 2008 or 2009 date coded modules (which is when they stopped production?), and the nearly $100 cost for a genuine new DS1250 is just ridiculous.

First, about the DS1486:
I tore apart one of my DS1486s that is genuine, and as many of you guessed it is simply a low power SRAM chip with a DS1384FP acting as the controller, a 32khz crystal, and two tabbed BR1632 lithium cells sitting on top of the two chips. The DS1384FP (44pin 10x10mm QFP) is unobtainium as well, but I was curious about a number of sellers selling something labeled DS1384G which is a 48pin 7x7mm QFP. I was sort of expecting this to be a sanded and relabeled DS1558 or something else entirely, but after looking at several pictures of the DS1386P and DS1486P Powercap modules you can actually see a 48pin QFP on them labeled DS1384G. I'm inclined to think this may have been an internal production part that Dallas made to get the smaller, thinner footprint of the 7x7 QFP, which also seems about a millimeter shorter in height. I'm consulting Maxim right now to see if I can get a pinout of this chip but so far they don't even seem to know what I'm talking about 
Nevertheless, by tracing back pins on those powercap modules and with some help and educated guesswork from the DS1558 datasheet which shares the 48 pin QFP footprint, I think I've figured out the pinout of the DS1384G.
I've made a layout on KiCad that I currently have in production at OshPark and I plan to use the Batten Allen leadframes to create a DIP package out of this and test it out.

I would love to get some feedback on board layout, since this is actually my first ever layout of this type of circuitry (usually doing audio). The layout was pretty difficult with such little board space and so many traces to run.
Also if anyone else has any thoughts on the DS1384G chip and my conclusions, perhaps I can gain some more insight.

About the DS1250:
Once again, this is fairly straightforward in using a run of the mill low power SRAM chip with a DS1312 controller. Actually, the part is labeled DS13C12, which once again, I cannot find any information about so I'm once again guessing it was an internal Dallas production part made for some specific reason. However, the ordinary DS1312 should be a perfectly suitable replacement. I'm using the 8 pin SOIC DS1312-2+. The DS1312 only has inputs for 1 battery which also matches up with the DS1250 only having 1 battery.

I would love to be able to make DS1650 exact replacements too using the (speculated) DS1610 controller, but I've not found any source for that part, and coupled with the fact that Tek scopes don't use the extra functionality it's not really necessary anyway.

[YetAnotherTechie]

I would love to get some feedback on board layout, since this is actually my first ever layout of this type of circuitry (usually doing audio). The layout was pretty difficult with such little board space and so many traces to run.

At first glance, increase the annular ring of the battery holder pins, they take a lot of heat to solder and being larger would make them more forgiving. In fact, it looks to me that most of the annular rings are very thin, especially the vias. You have enough space to make them larger and easier/cheaper to manufacture.

[cuebus]

Success! I have built both boards and programmed both and they are both fully functional in my TDS540C. My guesses about the pinout for the DS1384G seem to be correct. My only wonder is if it actually uses the 2nd battery pin as this part seemed designed exclusively for powercap modules which only had one battery. Luckily, battery voltage can be monitored easily by measuring directly on the replacements.

I plan to tidy up the design on the DS1486 replacement board a bit. Once I've done that, I'll upload the gerbers here if anyone's interested in getting them made. Oshpark will make 3 boards for $6 shipped.

[Tantratron]

Success! I have built both boards and programmed both and they are both fully functional in my TDS540C. My guesses about the pinout for the DS1384G seem to be correct. My only wonder is if it actually uses the 2nd battery pin as this part seemed designed exclusively for powercap modules which only had one battery. Luckily, battery voltage can be monitored easily by measuring directly on the replacements.

I plan to tidy up the design on the DS1486 replacement board a bit. Once I've done that, I'll upload the gerbers here if anyone's interested in getting them made. Oshpark will make 3 boards for $6 shipped.

I own one TDS540C so if you're OK to build extra set with both chips, i'll pay you to save me time.
I live in France, what country do you live ?
Thank you, Albert

[cuebus]

Happy to start making these to order for anyone interested - there's at least a relatively ample supply of DS1384Gs out there and the DS1312 is still in production.
Incidentally Maxim just got back to me and confirmed the DS1384G was an internal part and will not give any information about it.

Total cost to make these in small quantities breaks down like this:
DS1250:
PCB: $2.13
DS1312 controller: $8.89
SRAM: $7.23
CR1632 Battery: $1.32
Pin Headers: $1
Total: $20.57

DS1486:
PCB: $2.13
DS1384G controller: $12.95
SRAM: $2.63
Crystal: $0.51
CR1632 Batteries: $2.64
Pin Headers: $1
Total: $21.86

Once labor, solder, flux, flux cleaner and shipping charges for materials are factored in, $50 per chip is actually not a totally unreasonable ask   
I'm in the US. DM me if you're interested. I'm in the middle of preparing a move so lead time might be a week or two at the moment.

[james_s]

Nice job, I'd be interested in the gerbers, this is the sort of thing I'd prefer to build myself for fun. I had started laying out a board but if you have a working layout there's not much point in me reinventing the wheel.

IIRC there's a TI battery controller in a SO-8 package which is quite a bit cheaper than the Dallas part that does the same thing.

[cuebus]

TI's part is the BQ2201 which shares more characteristics to the DS1210 than the DS1312. Around year 1998 Dallas switched to using DS1312 inside their DS1250 modules, having previously used the DS1210. I believe the switch was due to the DS1312 having even lower battery drain.
From Dallas itself in an old change notice:
"All devices with date code 9826 or earlier will be built using the DS1210. All devices with date code 9827 or later will be built using the DS13d12.
...the  DS13d12  will  give  these  modules  50  microamp  standby  currents  (versus  5mA  for DS1210-based devices ) and will provide enhanced immunity to data loss caused by out-of-spec voltage transient."

Using the DS1312 seems like the right part here. My goal has also always been to not only build functional replacements, but as-near replicas as possible including battery count and size (DS1250 always had 1 1632 battery and DS1486 always had 2 1632 batteries).
Dallas used a variety of SRAM manufacturers for their parts, but my DS1486 had a Sony low power SRAM drawing 1 microamp during data retention in it. There are a few readily available chips on Mouser from Cypress and Alliance that meet the same data retention current draw.

Only long term tests will show whether my design will actually run these for 10 years on battery as the original guaranteed. Luckily, measuring the battery voltage is possible at all times, even when the scope is running (though I'd advise against this!)

[james_s]

Well I'll certainly make a pair of these once the gerbers are available. My scope is still working fine on the original chips but I know they're on borrowed time. I could hack in new batteries but I like the bare un-potted pcbs better.

[cuebus]

I started a new thread for this:
https://www.eevblog.com/forum/repair/dallas-ds1486-and-ds1250-replacement-designs/

All gerbers and BOM can be found there 

[CaptDon]

I bought the full set for a TDS644B and a single part for the TDS644A.
Both of my scopes are now 100% like factory new!! I downloaded and
sent him my files which he pre-loaded for me so it was plug and play!!
I would only say he should have used coin cell holders instead of the
solder-in style batteries. I am super pleased that both scopes are working
and will be for many years to come. The seller also responds quickly to
emails even prior to buying the product!!

[james_s]

I bought the full set for a TDS644B and a single part for the TDS644A.
Both of my scopes are now 100% like factory new!! I downloaded and
sent him my files which he pre-loaded for me so it was plug and play!!
I would only say he should have used coin cell holders instead of the
solder-in style batteries. I am super pleased that both scopes are working
and will be for many years to come. The seller also responds quickly to
emails even prior to buying the product!!

If you have the video trigger board installed then coin cell holders would make the chips too tall. Even without them it was a tight fit in mine using low profile IC sockets. If I'd had even lower profile pins to put on the modules that would provide a bit more clearance though.

[Tantratron]

If you have the video trigger board installed then coin cell holders would make the chips too tall. Even without them it was a tight fit in mine using low profile IC sockets. If I'd had even lower profile pins to put on the modules that would provide a bit more clearance though.

Not sure if this is a safe test to do but was wondering two questions.

Say you remove both NVRAMs from their socket then restart the TDS oscilloscope, will this brick for ever the TDS ?

Later if you re-plug in the sockets each NVRAM, does the TDS will work again ?

Additionally, what are the symptoms of an actual DS1486 and DS1650 going progressively with low voltage potted battery ?

[james_s]

My recollection is that one of the two is necessary for the scope to boot, the other can be removed and it will still boot up. In both cases if you replace the missing part normal operation will be restored.

Symptoms I've seen when similar Dallas parts get low batteries are the RTC stops advancing while the power is off and in the ones that are just NVRAM they will start randomly getting corrupted. I was surprised when I cut into a DS1742W that was getting flaky and found the battery was only at 0.8V, it would still hold the memory, it just wasn't advancing the clock when the scope was shut off.

[Tantratron]

My recollection is that one of the two is necessary for the scope to boot, the other can be removed and it will still boot up. In both cases if you replace the missing part normal operation will be restored.

Symptoms I've seen when similar Dallas parts get low batteries are the RTC stops advancing while the power is off and in the ones that are just NVRAM they will start randomly getting corrupted.

Since I have now a few TDSxxx/C/D where I did install 32 pins sockets for ease to install/remove the DS1486, the DS1250Y and replica, indeed the TDS can correctly boot and run with only DS1486. So wether there is a DS1250Y present or removed, the boot will only check presence of DS1486 to complete the initialization.

I did try to actually install one DS1250Y inside the DS1486 socket then program via GPIB-USB a copy of the DS1486, we loose the RTC (clock feature) but the TDS boots then runs very OK with all its other functions.

So unless someone needs to save waveforms, otherwise the DS1250Y is not really useful for the oscilloscope to function good. It all comes down then to find a replacement kit for the DS1486 to offer the time/day/year or just put instead a DS1245Y as it was suggested by @ArticGeek which can be purchased.

[ArcticGeek]

I have been lurking and reading this forum but haven't been posting - mostly due to the fact that I don't spend that much time with my hobby in the summer - too busy with yard work and barbecue!

I have built the DS1486 boards that cuebus designed and have had decent luck with them.  You can find that post here
https://www.eevblog.com/forum/repair/dallas-ds1486-and-ds1250-replacement-designs/msg2954864/#msg2954864

I have built a few failing Cuebus units due to my lack of soldering skills with a TSSOP package and fine pitch parts.

I have also designed a small board that adapted a DS1486P part to a 32-pin DIP package.  The DS1486P is the same part that is in the 34 pin PCM package.  The DS1486P is still somewhat available, I've found some in China and I also found some in Canada. 

There are a few pros/cons of that approach:

1.  The 34pin PCM package is a lot easier to solder than TSSOP packages.  If you're skilled at soldering this isn't a big deal, but for me it's much easier.

2.  The SRAM parts used inside the DS1486P are typically much lower power than anything you can buy.  I've measured the power of both the Cuebus design and the purchased DS1486P power.  The Cuebus design can vary wildly depending on which SRAM you buy even though specs are identical.  For example, using an ISSI low power SRAM I measured the battery current to be 2.71uA on 1 unit and 2.47uA on another unit.  This equates to a battery life of somewhere around 11 years if using qty 2 of the 120ma-hr lithium battery.  Replacing that SRAM with a Renesas RL1P part reduced the battery current to 784nA and 735nA respectively - improving the battery life 3x to 35 years plus.  Typical battery current of several DS1486P parts was 297nA, 382na, and 378nA.  All of these measurements with taken with register 0x09=0x03 which means the oscillator is ON.  (Running with oscillator off is MUCH lower, around 20nA).  This works out to be about the same battery life, but you need to be careful which part you buy, and be VERY careful with cleanliness after you solder.

3.  The DS1486P battery can be replaced easily without soldering.

4.  The Cuebus build-your-own approach is a bit cheaper, depending on how much you pay for the DS1486P part.

I can also confirm that the TDS series of scopes boot fine without the DS1250, its the DS1486 timekeeper that is critical for boot operation.

If I can find the time I might post my design for the DS1486P adapter, but right now I've been busy at work and summer activities seem to consume a lot of my time.

[Tantratron]

I actually purchase one of these just because I was very curious how he designed this.  I only purchased the DS1486 replacement, and he was willing to sell that to me for $70.   This is still very expensive, but I had to know what he did.

The central part of the design consists of a DS1384 RTC controller; this part is identical to the DS1486 without an SRAM.  The DS1384 sits underneath the battery, and an SRAM is on the bottom side of the board.  Once you add the SRAM to the DS1384, you have something that is identical to a DS1486.  I suspect this is exactly what is inside the encapsulated DS1486 - a DS1384, an SRAM, and a couple of coincell batteries.  The DS1384 actually has inputs for TWO backup batteries if desired. 

I must admit it's a fairly clever design, although the layout seems less than optimal.  The bad part of the design is that the DS1384 is obsolete just like the DS1486, so if you buy any of those parts you will have to buy off of Alibaba, Ebay, or a broker somewhere so the quality is questionable.  However, the DS1384 does not have an internal battery like a DS1486 does so it is arguably less risky to buy these parts.  But I worry that the mileage on these parts may vary wildly.

Regarding the eBay sold design of the DS1250Y, does anybody knows what Nonvolatile Controller with Lithium Battery Monitor chip is used ?

When you look on some of his add on eBay with remote batteries, we see it is 8 pins chip (DS1250Y) and confirm 44 pins (DS1384) instead of DS1384G (48 pins) for the DS1486 board (see attached pictures).

On a side note, does anybody knows if the DS1384G has two separate inputs (two batteries) or only one battery since it is used on DS1486P PowerCap hence one battery ?

[cuebus]

A lot of good info here ArcticGeek. I looked at the DS1486P as well but I think at the time I designed this I couldn't actually find vendors selling them. I'm sure supply comes and goes for these kinds of surplus/obsolete parts.

As you say, the SRAM selected by Dallas/Maxim is very low current draw. I imagine they had the resources to either purchase ultra-low current devices or select them from a standard batch. I tested the ISSI part you mention and also got 2.5-3uA draw. This part is labeled low power however it is anything but.
If you use cypress, alliance, or the renesas memory you mentioned, you will get .7-1uA current draw with RTC on. With 2 batteries that equates to a lifetime of about 19.5 years worst case.

There's been both successes and failures of people building these and I must admit that the reason for these failures seems to be complex and varied in nature- including whether a device is programmed on an external programmer or within the scope itself after initialization. I'm no longer pursuing any troubleshooting on this project so I haven't been able to figure out any exact causes but Tantratron has 3 of these (that I programmed externally and then tested in my own TDS540C) and has had trouble programming them in circuit in his scope via tekfwtool. He's been doing some low level debugging so I suggest anyone who is having issues reach out to him for more information.

FWIW- my own replica I built last february is still going strong.

[Tantratron]

There's been both successes and failures of people building these and I must admit that the reason for these failures seems to be complex and varied in nature- including whether a device is programmed on an external programmer or within the scope itself after initialization. I'm no longer pursuing any troubleshooting on this project so I haven't been able to figure out any exact causes but Tantratron has 3 of these (that I programmed externally and then tested in my own TDS540C) and has had trouble programming them in circuit in his scope via tekfwtool. He's been doing some low level debugging so I suggest anyone who is having issues reach out to him for more information.

FWIW- my own replica I built last february is still going strong.

First I really want to thank @cuebus (Robin) for his research, reverse engineering and design of his kit which really contributes to maintain these legendaries TDSxxx/C/D oscilloscopes.

If there is enough interest, we (I) could create a synthesis new thread to cover both this thread and this other one https://www.eevblog.com/forum/repair/dallas-ds1486-and-ds1250-replacement-designs/ for deeper investigation.

It seems clear that cuebus design works so it is just a topic to secure its use, its programmation because clearly we have reports of some replicas which just work fine and other ones which failed. Why no idea for the moment except I do confirm that one replica still works fine in my lab since june 24th in my TDS794D. However the other replicas are partially failed, one did work fine during 10 days in my TDS784D then started to brick my oscilloscope. The other one never worked including my TDS540C and each symptoms are different.

I did connect one Console Port and might purchase a SALEAE logic 16 Ch analyzer which I need to repair another TDS784D major boot failure, see this thread https://www.eevblog.com/forum/repair/major-boot-failure-tds784d/

What I can tell you for the moment, during the boot there will be only test check on DS1486. For example, the boot firmware will try writing a sequence of 12345678 in the DS1486 then read. With one replica, I do get a read of 56785678 so it declares a failure but this very same DS1486 replica does generate some RTC including the clock.

The other failed replica will pass the 12345678 test but will fail writing the RTC registers, no clock test output as a result as well as every 1Kb page full of FFs.

Again the 3rd replica has been running strong since last june 24th...

[Tantratron]

Hello and Happy New Year2023 to everybody,

Here is an update since last july 2021 where for a few months, I operate now a 16 channels logic analyzer to repair my TDS784D. In the last weeks, I've decided to probe or check the Kernel Data bus (KD), lower 5 bits address of KA along with the control signals of both DS1486 and DS1250Y in order to understand why two replicas of DS1486 failed.

As a reminder, I have 3 replicas set (set #1, set#2 and set #3) where first the good news, the set #2 still work perfect and strong on my TDS794D since june 2021. I do not use too much my TDS794D (less contract on 2 GHz) so I've installed replica #2 inside my TDS754D, still works fine after some tekfwtool and/or tektool work => this proves cuebus design to work.

So I have stored #1 which failed working after 2 weeks back in 2021 and the #3 which never worked (boot failure).

Regarding the #3 replica and thanks to my 16 channels logic analyzer, probing the J40 edge connector and control pins (CE, OE and WE) then I was able to isolate the Kernel test then other sequence.

The protocol decoding shows that during the boot, the Kernel system will first try to write 0x12 0x34 0x56 and 0x78 from address 0x10 then read back them from the DS1486. This address zoning belongs to the 50 bytes internal DS1384G, remember the DS1384G has 64 bytes protected by battery, the first 14 bytes being the RTC and controls. So the Kernel first check writing 4 bytes into that space to see if DS1486 is OK. I could compare with good TDS working and good DS1486 spares to clearly see that replica #3 failed that test.

So I knew where to look first and using my DMM, I've discovered that DS1486-A1 was not soldered or good joint. I did reflow with flux 1/4 of the DS1486 chip. Launch again the boot, same failure so I've decided to patiently DMM check more then I've discovered a short between two pins, namely DS1486-A10 and DS1486-CE. So using again my flux and soldering reflow on the other 1/4 part of the chip, finally got it right then I was happy, the kernel boot test finally pass but later during system boot, again failure.

Since it was Christmas time, some holiday and free time, I have continue to DMM check and found out 2 more SMD soldering issues even though visually all seemed OK. There was first a short between DS1486-A5 and DS1486-A6 then the SRAM pin, namely the AS6C1008-A5 was not soldered. So I end using lot of flux, redo all the reflow, re-solder and finally it worked 

The repaired replica #3 has been now installed permanent into my TDS794D since january 4th, 2023 so we shall see its endurance through time. In the immediate conclusion, the design of cuebus works again so the topic is really the method of soldering, the PCB etching and manufacturing.

As for the replica #1 which worked 15 days back in 2021 then permanently failed, I'll try to see later this year why it does not work with this methodology.

Albert

[Tantratron]

A quick update where both DS1486 replicas #2 and #3 work fine respectively on my TDS784D and my TDS794D.
So the design of cuebus works fine, just requires special care on the soldering.