Lost Calibration data of Tektronix Logic analyzer ( TLA 7L3 ) while desoldering

[rklan]

Hello all,

I have a logic analyzer from tektronix, the TLA 7L3.
I was working great before.... But I decided to replace the NVRAM, which holds some important data, BEFORE it looses it's data..
The Dallas DS1225-85 chip had a datecode of 1997! and worked fine, until yesterday.
I think the desoldering caused the chip to loose it's data. ( the internal battery was affacted perhaps by this action??)
Now, the analyzer will not boot.
Can anyone help me?
Does anybody  have binary data from this NVRAM?
Is it exchangeable?
From the manual I read that it holds serial numbers and calibration...
Who has suggestions?
Regards Remco

[nctnico]

Get a new acquisition module from Ebay. They cost peanuts (probably less than a replacement chip).

[picburner]

I performed the same procedure to backup the DS1225 of my TLA 7P4.
The operation is a bit risky if precautions are not taken, such as making sure that the desoldering iron is grounded as well as the equipment on which you are working.
The use of an antistatic bracelet is also recommended.
I have my 7P4 backup file but I think it's very different from your 7L3.

[rklan]

Thaks for your reply! I think it is different indeed.
My soldering iron was grounded. But I think my eprom reader was perhaps loading the data pins a bit and the weak battery was affected by that?
Maybe someone has a backup file of the 7L3 and maybe it will work.

[rklan]

I have some news.
I read that you can acces the battery by drilling a hole, and that the contents may be OK when the batt. voltage is not too bad, and you can lift the batt voltage.
I drilled the hole and to my surprise the bat voltage was 3.22 volts!
So, after 22 years, the batt is still in great condition.
I am afraid that I accidently destroyed the contents of the chip, by the desoldering...
If anyone has a backupfile I would be pleased.

[Ordinaryman1971]

So... when you plug it in to the frame... what happens? can you see the module, does it pass diagnostic, does it power on.. do you have orange access light on it when plugged in to the frame?
In any case I have one of those plugins and mine is not recognized when plugged into the frame.
Maybe your firmware is corrupted?
Did you try to reprogram it?

[rklan]

No, I can not see the module. The "ready"led is NOT on.
I must have corrupted the contents of the NVRAM . I don't think the contents of the firmware are damaged. I ordered a new unit on ebay.
perhaps I can read the data of this new unit.
Thanks for thinking along  with me.

[nctnico]

I'd recommend not to mess with the new unit and just use it. You might have damaged your current unit by desoldering, ESD, etc.

[rklan]

That sounds very logical, and thanks.
I will use it first.
The thing is that I am afraid of is,  the "new"battery will lose it's charge also, and than I have the same problem..
But, You are right to use it first and don't mess with it..
I wish I could read it without desoldering....
And only replace it when it has died. not before..
Thanks for your reply


Regards Remco

[nctnico]

Maybe you can read it through the VXI interface. Someone made tools for the TDS500/600/700 oscilloscopes and I don't think the base OS and so on differ that much.

[rklan]

I have an update.
After working with the new unit for a time, I decided to check the NVRAM of this module also.
The chip's datacode was 9705, so very old.
I decided to desolder this chip and read it carefully, paying extra attention to ESD.
It worked!
I could read the contents succesfully.
But the strangest thing is that the new chip, with a fresh datecode of 2017, doesn't do the job.
The analyzer fails @ the NVRAM check....
So, I thought I had ruined the thing for a 2nd time.... But when Installed back the original chip, it worked again!
I repeated this 3 times and it is consistent.
So, the module works OK with the original chip, but fails with the new copy.
And the contents are the same! I checked this with my eprom programmer. They are identical.
The original chip is the DS1225AD-85 and the new replacement is the DS1225AD-85+.
The '+' means only RoHs compatible...So, it should be OK.
What the heck!
Now I am thinking: Did Tektronix use special "best parts"from their suppliers? And that the access time is faster than the spec (85 ns) and that it operated close to/beyond the speed spec??
Should I buy a faster ( 70ns) chip to test?
 

[nctnico]

Did you put an unsoldered device in an IC socket? If yes, then that is likely your problem. I you do these kind of 'upgrades' then solder the original chip into a socket with turned pins and solder a socket with turned pins into the board. This will also help making good contact in your programmer. Unsoldered pins are likely to be dirty and bend enough to make a poor contact. You think you have read the contents correctly but you didn't. If you read the original chip multiple times you'll likely see a different checksum every time.

I assume you verified the new device after loading the data? And there may be a chance the new device is a fake.

[stj]

probably fake, or atleast a re-printed old one.
i dont think they still made them in 2017

what make/brand is it?

[rklan]

Did you put an unsoldered device in an IC socket? If yes, then that is likely your problem. I you do these kind of 'upgrades' then solder the original chip into a socket with turned pins and solder a socket with turned pins into the board. This will also help making good contact in your programmer. Unsoldered pins are likely to be dirty and bend enough to make a poor contact. You think you have read the contents correctly but you didn't. If you read the original chip multiple times you'll likely see a different checksum every time.

I assume you verified the new device after loading the data? And there may be a chance the new device is a fake.

Yes! That is what i did, I used the new, unsoldered device in an IC socket. And the old IC had solder on it.
I used a socket with turned pins, indeed, on the board.
I'll solder the pins of the new IC and try it again. Thanks!

[rklan]

The solder trick didn't help...
I put a little solder on every pin of the new IC, and removed the solder with braid, so that the pins are clean and covered with a very small amount of tin.
Behaviour is the same.
Old IC works new IC fails NVRAM check.
The contents of boths seems very stable and the same..
Strange this.
A what speed does the TLA 7L3 reed the contents? My programmer is probably slow, compared to that.
I think I try a 70 ns version next week.
I find this a very strange phenomenom.

[nctnico]

I think you have a fake chip (as stj already mentioned). It may be slower than specified or a completely different device. I'd leave it as it is. If you really want to upgrade then make a board with an FRAM which replaces the Dallas chip.

[rklan]

Finally, it is working!
I ordered a new device, but now I ordere a faster one than the original one. ( original has 85 ns and new one 70 ns)
I worked right away.
So, now I have a good working logic analyzer with a fresh battery backed NVRAM 
I think the previous one was OK, and original, but that tektronix purchased very good IC's, that were better than spec. And that they used it beyond/at the edge of the spec.
Anyway. All is working fine now.
I am amazed that the battery of the old IC was working OK after 20 years!

Thanks all for helpng me!

[flyte]

FYI:

A bit late as a reply, but AFAIK, all TLA logic modules do not need a valid NVRAM to boot properly. The boot pointers and serial numbers are stored in flash. I have swapped several TLA7P4 w/o backup. They self-calibrate and that's it. It might be there are some factory adjustments lost, but I was not able to observe anything wrong with it after swapping the NVRAM and doing the self cal.

[gslick]

FYI:

A bit late as a reply, but AFAIK, all TLA logic modules do not need a valid NVRAM to boot properly. The boot pointers and serial numbers are stored in flash. I have swapped several TLA7P4 w/o backup. They self-calibrate and that's it. It might be there are some factory adjustments lost, but I was not able to observe anything wrong with it after swapping the NVRAM and doing the self cal.

Aren't the upgraded memory depth and state speed options also stored in the NVRAM? I seem to remember using the hack to upgrade the memory depth and state speed options on one TLA7 module with a dead NVRAM, where the options would remain enabled as long as the system was powered up, but after a power cycle they would revert to the lowest base options. The upgraded options remain enabled across power cycles on other TLA7 modules with good NVRAM.

[flyte]

FYI:

A bit late as a reply, but AFAIK, all TLA logic modules do not need a valid NVRAM to boot properly. The boot pointers and serial numbers are stored in flash. I have swapped several TLA7P4 w/o backup. They self-calibrate and that's it. It might be there are some factory adjustments lost, but I was not able to observe anything wrong with it after swapping the NVRAM and doing the self cal.

Aren't the upgraded memory depth and state speed options also stored in the NVRAM? I seem to remember using the hack to upgrade the memory depth and state speed options on one TLA7 module with a dead NVRAM, where the options would remain enabled as long as the system was powered up, but after a power cycle they would revert to the lowest base options. The upgraded options remain enabled across power cycles on other TLA7 modules with good NVRAM.

Correct, but how to configure these has been public knowledge for quite a while.