Author Topic: Repair of Tek TDS3014B - need a source for a DS1742W NVRAM  (Read 6001 times)

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Offline MarkL

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Re: Repair of Tek TDS3014B - need a source for a DS1742W NVRAM
« Reply #25 on: August 26, 2019, 04:19:55 pm »
Well, it finally happened.  The DS1742W battery died in my TDS3054.  The scope was purchased in 1999, so that's 20 years.  Not too bad.  The symptoms were that the settings and SPC constants were retained, but the clock stopped when the scope was powered off.  The time when the scope was powered off was retained.

As mentioned in the above posts from two years ago, I purchased a backup DS1742W from an HK seller knowing this would eventually happen.

After removing the dead DS1742W, placing it next to the replacement made it quite obvious it was a fake.  See photos below.  I hadn't noticed the size difference before and it's significantly larger than stated in the Maxim datasheet.  I also noticed that there was no battery bump visiable on the bottom of the original.

820323-0

820329-1

For the record, the ebay seller was "crystal830303".

I soldered in a 24-pin socket and plugged in the fake.  To no surprise, the battery was dead in the fake.  It behaved in the same way; settings were retained, but the clock wouldn't run when the scope was powered off.

Since I had nothing to lose, I proceeded to cut into the old DS1742W.  Placing a strong, small magnet against the case allowed me to locate the battery near the top on the right hand side.  I sliced the top off with a razor saw, dug out the old battery, and replaced it with an external one.  Photos below.

It took a couple of hours and works great now.  Maybe that will hold for the next 20 years, at which point I probably won't care anymore.
820335-2

820359-3

820341-4

820347-5

820353-6
« Last Edit: August 26, 2019, 04:23:46 pm by MarkL »
 
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Offline Jwalling

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Re: Repair of Tek TDS3014B - need a source for a DS1742W NVRAM
« Reply #26 on: August 26, 2019, 05:30:41 pm »
Nice work!

That seller is still selling them. Looks identical to the one you bought.
https://www.ebay.com/itm/282116689792?

87 sold!
6 positive feedbacks on it. WTF?

    by 9***s
    During past 6 months
    Beijing to SanFran: 25days slow! Bag: anti-static. Foam, Bubble: not. Items OK.
    by e***o
    During past 6 months
    Fast shipping, excellent packaging, items as described, highly recommended!
    by z***2
    During past 6 months
    Good communication, Fast shipping, Great eBayer, Thanks!
    by z***2
    During past year
    Good communication, Fast shipping, Great eBayer, Thanks!
    by i***o
    During past year
    Ok
    by l***y
    During past year
    Got the order ontime and in good condition



Jay

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Offline MarkL

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Re: Repair of Tek TDS3014B - need a source for a DS1742W NVRAM
« Reply #27 on: August 27, 2019, 12:22:16 am »
Nice work!
Thanks!

Quote
That seller is still selling them. Looks identical to the one you bought.
https://www.ebay.com/itm/282116689792?

87 sold!
6 positive feedbacks on it. WTF?
Fake reviews?  Or maybe they work long enough for people to give it a good review?  Mine sat around in the packing tube for 2 years.  With a real DS1742 with that date code, 2 years wouldn't have mattered.

Since I wasn't ever going to use it, I broke my fake one open with a sharp chisel.  Somewhat less finesse than my work in the previous post, but definitely satisfying.

The main chip was an unmarked 24-pin DIP with two extra connections on either end (never saw that before!).  One pair was connected to the crystal and the other pair to the battery (or was at least involved somehow with the battery).

It sat on a PCB with some resistors and one 6-pin chip (U1).  U1 was marked with "10A45".  I didn't bother trying to track down the code to find out what it was.  The main chip's 24 legs were extended through the PCB to the external pins.

There was nothing that identified who really made it.  Even the battery had no manufacturer name on it (except a small "SC" under the yellow wrap).  The voltage on the battery was 0.87V.

High-res photo below of the extracted pieces, if it's of any interest/help.
 
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Offline f14

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Re: Repair of Tek TDS3014B - need a source for a DS1742W NVRAM
« Reply #28 on: August 27, 2019, 12:52:21 am »
seem in my case  I think I will mod external battery in old chip and don't need wait the new chip arrived . when new chip arrived I will test this  working or not  :palm:
btw I think a fake chip use too much current make internal battery runs out of power sooner . it is very usual in cheap chinese caliber the battery dead after some months even turn off
« Last Edit: August 27, 2019, 12:57:21 am by f14 »
 

Offline Jwalling

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Re: Repair of Tek TDS3014B - need a source for a DS1742W NVRAM
« Reply #29 on: August 27, 2019, 09:42:42 am »
They spend quite a bit of effort to do this. I just don't understand why they don't make a product that friggin' works! |O
All those TDS3K scopes are reaching the age where they are going to need those chips replaced. Tek sold a ton of them, there's real money to be made -  you could easily get $30 each for a working unit...
Jay

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Offline MarkL

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Re: Repair of Tek TDS3014B - need a source for a DS1742W NVRAM
« Reply #30 on: August 27, 2019, 03:55:29 pm »
I can think of a few other possibilities for DS1742W replacements.

The first is to use the DS1744W.  The DS1744W has more SRAM than is needed and is in a 28-pin DIP package.  An adapter board could be designed which grounds pulls high the unused address pins and, in the case of the TDS3000 series, moves the package out of the way of the chassis.

The DS1746W and DS1747W are also possible, but are even bigger with 32 pins.  But it looks like they would still fit in the space available with an adapter board.

The DS1744WP could also be used similarly.  The package is a module which is meant to to be surface mounted, and then the battery and crystal are snapped on top after reflow.  It's more expensive than the DIP version, but maybe the battery cap could be removed and replaced after it was depleted.  I don't know for sure since I've never actually seen one in person.

Alternatively, the chips are exposed on the DS1744WP module and they could be removed and remounted onto a smaller board that would have the same dimensions as the original DS1742W, with of course a crystal and battery.

Unfortunately, I wasn't able to find any matches for the RTC chip just by itself that has the same register layout as the DS174x series.  That would be nice.  I'm guessing the RTC chip has an SRAM controller on it which handles the power down and addressing, so probably any SRAM would do.  Maybe ordering and examining a DS1744WP would reveal which RTC chip was being used.

Lastly, the access is slow enough for the -150 and -120 parts that maybe some really fast microcontroller could emulate the RTC and SRAM.  But that would take a lot more work, and probably get ripped off instantly by the counterfeiters.


The DS1744W and later parts are currently available, at least for the time being, according to the EOL/NRND spreadsheet at Maxim:

  https://www.maximintegrated.com/en/products/nla/index.mvp

Any of these solutions would probably end up being in the $40-$50 range (at least).

EDIT: Fixed unused pins description.
« Last Edit: September 08, 2019, 04:32:22 pm by MarkL »
 

Offline MarkL

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Re: Repair of Tek TDS3014B - need a source for a DS1742W NVRAM
« Reply #31 on: September 08, 2019, 04:30:44 pm »
I said:
...
The first is to use the DS1744W.  The DS1744W has more SRAM than is needed and is in a 28-pin DIP package.  An adapter board could be designed which grounds the unused address pins and, in the case of the TDS3000 series, moves the package out of the way of the chassis.
...
No one caught this, but since the clock registers are at the high addresses in memory, the unused (highest order) address pins need to be pulled high, not grounded.  Otherwise the clock registers would not be accessible.

Not sure anyone is interested in this option, but I didn't want to leave bad information out there.
 

Offline steve_01

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Re: Repair of Tek TDS3014B - need a source for a DS1742W NVRAM
« Reply #32 on: May 31, 2020, 01:47:23 pm »
Hi,

Annoying as it IS but quite expected. I did order and recieved a blacktopped DS1742W-120!
It was a really bad blacktopped device, seems to be original part - but grinded away original marking!

Tryed to choose someone serious with low neg. feedback, but there is none I guess.

I have grinded off the CR1225 as MarkL did show on the original part. Thanks, havnt finalized it yet - but there is + and - solderable bits!

As suggested, there must be tons of TDS3xxx - out there with bad lithium batterys ; witch is a pretty good scope even today. I have the 3032-300MHz one!

Really isnt there a working replacement part yet!? Like MarkL is suggest - it should not be difficult to make a emulator using a fast microprocessor with DMA
and low RTC current. its very possible to make, but more difficult to get it *CE/FCC* aproved. Well, I guess Dallas got some big $ for disable all replacement
parts from Techtronics and many other manufactories. The registers are not the same on any other DS-xxxx device i have looked on, how annoying - and expected!

/Steve
« Last Edit: May 31, 2020, 01:50:32 pm by steve_01 »
 

Offline MarkL

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Re: Repair of Tek TDS3014B - need a source for a DS1742W NVRAM
« Reply #33 on: May 31, 2020, 05:57:02 pm »
You might be interested in this series of posts:

  https://www.eevblog.com/forum/repair/tds3014-adventures-(seeking-75-75mhz-oscillator)/msg2733286/#msg2733286

Instead of just musing on what could be done, user james_s went to the trouble of actually making an adapter board for a DS1744WP module to replace the DS1742W.  The board files are up on github.  The adapter board is a much more eloquent route if you don't mind spending a little extra.
 

Offline steve_01

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Re: Repair of Tek TDS3014B - need a source for a DS1742W NVRAM
« Reply #34 on: June 01, 2020, 11:51:54 am »
Hi Mark!

Thanks for the heads up. Actually I did finallize the DS1742W-150 modified original with a CR2032. Should last for the rest of my life!
And you should have the credit for that rev-eng. digging. The dude on the other thread has access to a X-Ray .. that would be a nice tool!
Having astma - and many times did use nitric acid fumes to hack into such things..  ^-^

And for the other thread and using a overprices Black Box Time Keeper, is not anything I would ever do. Dallas/Maxims weird prices on those is outrages!  :'(

Looked on a suitable microcontroller with DMA and sleep-mode for RTC and 8K SRAM - with 10 microamps current in sleep mode, and a 110 mA lithium
should last more that 20 years. This processor is priced 1.5 USD (BGA) and I could do this very good on a simple board - and be even smaller than the black boxes for USD 25!?

I spend a lot of time doing stuff just like that above, just for fun and liking rev-eng. stuff. Done my whole life! Stupd - but fun! :-DD

We will se if I finalize such a board, i put the project in a pile of other to-do-maybe projects .. 8)
 

Online james_s

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Re: Repair of Tek TDS3014B - need a source for a DS1742W NVRAM
« Reply #35 on: June 01, 2020, 06:37:14 pm »
I'm certainly not opposed to having alternatives to the Dallas parts, although the PowerCap versions of their products are not potted, they're exposed PCBs with a replaceable battery. It's true that they're not cheap as ICs go, but with these scopes regularly selling for ~$1k+ spending <$100 on a long term repair seems cheap to me. I see it as a permanent fix, buy it once and it should last the life of the scope, 10 years from now you can pop the cap off and solder in a new coin cell. I only have one TDS3000 scope so the adapter was by far the cheapest solution even if I only value my time at minimum wage.
 

Offline steve_01

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Re: Repair of Tek TDS3014B - need a source for a DS1742W NVRAM
« Reply #36 on: June 02, 2020, 04:25:14 pm »
I'm certainly not opposed for you making those adapter boards. But like you said, its not sure they fit in any other devices using the DS1742.

For the supply of those expensive Time Keepers, Maxim have maybe desided to keep this device active or not!?

A bit confusing, stating the DS1744 is NLA - No longer active on this link (searching for DS1744) :

https://www.maximintegrated.com/en/products/nla/index.mvp

But active in this link:

https://www.maximintegrated.com/en/products/analog/real-time-clocks/DS1744.html
 
However, I did some quick timing test (on CE/OE) - just to see how fast my Techtronics TDS3032 was accessing the NVRAM.
And its about 250 nanoseconds, some strange timing makes it harder to emulate the DS174X - so I most certainly dont proceed with this project.

And when i bouht my TDS in the 90's it was prices around 5K USD , so its like you say $100 is not much money.

« Last Edit: June 02, 2020, 04:32:43 pm by steve_01 »
 


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