Tektronix Technical Forums are maintained by community involvement. Feel free to post questions or respond to questions by other members. Should you require a time-sensitive answer, please contact your local Tektronix support center here.

TDS644A NVram / Serial Parallel

Questions in this forum area are community supported. Tektronix does not regularly monitor posts in this area.
Post Reply
Gorgon
Posts: 20
Joined: March 31st, 2011, 5:54 am

TDS644A NVram / Serial Parallel

Post by Gorgon » November 14th, 2011, 8:34 am

Sad news - my lovely TDS644A has lost it's memory :-(.

It appears as though the Serial / Parallel board has gone faulty and somehow caused corruption of the NVRAM.

The scope will not boot at all with the Serial/Parallel card installed , and although without it - it does boot , but the NVRAM is obviously corrupt.
( Cal initialisation error ).

So - I'm pleading - does anyone have the calibration software - or even a dump of a TDS644A nvram , or the TDS640A nvram.

( For those who followed my scope in the past - it has already been 'capped' :-) )

As an added bonus if I do get the TDS600 series adjustment software - I plan to find a way to get it to run with other gpib options - via DosBox under linux.
( It will require me to write some extra code for DosBox ).

Gorgon
Posts: 20
Joined: March 31st, 2011, 5:54 am

Re: TDS644A NVram / Serial Parallel

Post by Gorgon » November 15th, 2011, 10:45 am

Many thanks to a kind forum member - I have restored my nvram - although the calibration will be out - i can perform SPC and get useful waveforms :-) again.

I'm still looking for the TDS600 field adjustment tool if possible.

Alternatively if someone knows the memory locations where the calibration data is stored ;-) I could possibly start work on creating my own adjustment software.

Gorgon
Posts: 20
Joined: March 31st, 2011, 5:54 am

Re: TDS644A NVram / Serial Parallel

Post by Gorgon » December 6th, 2011, 2:02 am

The serial / parallel board is now also fixed.

For those interested it appears as though capacitor leakage had caused eventual failure of U8 - a dual 2 to 4 line decoder (74F139)

The IC was replaced - the board thoroughly cleaned - and functionality restored.

For those of interest I started to draw the schematic ( the parallel side mostly - and the address decoding ).

rochoz
Posts: 90
Joined: October 8th, 2011, 9:55 pm

Re: TDS644A NVram / Serial Parallel

Post by rochoz » December 6th, 2011, 11:32 am

Hi Gorgon,

I'm curious, what kind of error was your serial/parallel option giving? Or was it just not working? What I've found in the 500A/600A series of scopes is that if you have a serial/parallel option present it automatically finds it and activates it, but if it doesn't find the option it automatically takes it off the option list. Of course, this is with a working serial/parallel option. So perhaps an option board that has a problem actually acts different.

Another question. Did the electrolyte cause the U8 part itself to become defective? Or did it damage a trace to the IC? I've never seen the electrolyte cause any damage to ICs, but I suppose it is certainly possible.

Gorgon
Posts: 20
Joined: March 31st, 2011, 5:54 am

Re: TDS644A NVram / Serial Parallel

Post by Gorgon » December 7th, 2011, 6:16 am

The first I knew of a problem was the scope not booting. No display and all leds on the front panel illuminated.

The 7 seg display would flicker between a couple of numbers ( I think 8+9 , but could be something else ).

After lot's of trial and error I eventual found that the scope would boot correctly without the ser/par board.

Unfortunately the scope had then hosed the nvram :-(

I had previously replaced all the electrolytics - but I guess I hadn't cleaned thoroughly the serial/parallel board.

To track down the fault I worked out most of the schematic and decided to eliminate possible options - first I removed the 74F240 ( buffer ) - and the scope would now boot - but the board was not detected.
The errorlog showed an error something like "ERROR: diagnostic test failure optRS232DuartIO, ** addr = 0xe000038 exp data = 0x7f actual ... "

I cleaned around the 74F240 , replaced it - but again the scope wouldn't boot.

Looking at the schematic - the only possibility would be the 74F139 as it was used to directly enable the F240.

Removed / cleaned replaced - still the same fault ( and I noticed the characteristic "whiff" when desoldering the F139 ).

So - replaced the F139 ( actually with an ACT139 ) - and all was well again.

I can only guess that a low resistance path was created by the electrolyte leakage - leading to the death of the F139 - otherwise it was co-incidence.

With the faulty F139 - the F240 buffer was driving the bus all of the time - thus stopping the scope from booting.

Regards.

ebukey
Posts: 48
Joined: May 10th, 2010, 3:44 am

Re: TDS644A NVram / Serial Parallel

Post by ebukey » December 8th, 2011, 3:34 am

rochoz wrote:Hi Gorgon,
What I've found in the 500A/600A series of scopes is that if you have a serial/parallel option present it automatically finds it and activates it, but if it doesn't find the option it automatically takes it off the option list.
Hello,
I don´t confirm that.
After power on I get an error with the installed serial/parallel option: Wrong HW configuration error..... with my TDS5** scopes.


Regards,
Markus

cap
Posts: 397
Joined: May 1st, 2009, 8:16 pm

Re: TDS644A NVram / Serial Parallel

Post by cap » December 8th, 2011, 10:07 am

This seems like a pretty harmless question for one of the tek guys...

It seems to me that the TDS500/600's would kind of choke on the printer option, but if you cleared the error log, maybe tried to power it on with the memory switch in the unprotected mode, then fully power it up, that it would get past this. But maybe I always calibrated them and that cleared this up. I can recal this being an issue but not a problem that would not go away.

On TDS500A/600A I don't recall this being a problem at all. The scope performs a presence test at power on and the hardware is either their or not.

cap

rochoz
Posts: 90
Joined: October 8th, 2011, 9:55 pm

Re: TDS644A NVram / Serial Parallel

Post by rochoz » December 8th, 2011, 1:06 pm

I have tried several times on my 644A with and without the ser/parallel option. If it's there, it recognizes and uses it. If not, it doesn't use it. No errors at startup either way.

However, if there was a problem where the ser/parallel board was loading the bus (as Gorgon mentions), than that is a completely different problem. I can see where that would cause the scope to not boot up because the NVRAM is on the same bus as the boot code. And although it seems unlikely, I suppose it could corrupt the NVRAM because the CPU would not be allowed to write ANYTHING to the NVRAM other than all 0s for Fs depending on how the 240 was driving the bus. If the CPU was attempting to write a different value to the NVRAM in a checksumed area, it would get corrupted. I don't know how/why the scope would do this, but if the data bus is getting clobbered I supposed it's plausible.

Nice piece of debug work, Gorgon. This is the first I've heard of the electrolyte eating a part, but its good to know.

ebukey
Posts: 48
Joined: May 10th, 2010, 3:44 am

Re: TDS644A NVram / Serial Parallel

Post by ebukey » December 9th, 2011, 7:17 am

The serial/parallel option is functioning very well,
but the errorlog gets longer and longer ....


Markus

rochoz
Posts: 90
Joined: October 8th, 2011, 9:55 pm

Re: TDS644A NVram / Serial Parallel

Post by rochoz » December 9th, 2011, 5:46 pm

Ebukey,

What model of scope do you have? I assumed you had a 644A, but your most recent post indicates that it might be a TDS5XX scope. In that case, this would make sense.

The TDS640A, TDS644A, and TDS544A will all auto-detect the serial parallel option and will not present an error at boot time when it is installed or missing.

The TDS540 (non-A suffix), on the other hand, acts much different. The TDS540 will give you an error if the serial/parallel option is missing or installed when it's not expecting it. If you have a TDS500 series scope without the A suffix, I would expect the behavior you mention. I would expect the TDS520 or the TDS640 to be similar, but I have never played with one of those scopes in person to know for sure.

I only know this from experience, there is no documentation anywhere that I have ever seen that describes any of this behaviour, its just from my own experience with the different models of this scope.

ebukey
Posts: 48
Joined: May 10th, 2010, 3:44 am

Re: TDS644A NVram / Serial Parallel

Post by ebukey » December 12th, 2011, 3:19 am

Yes,
I use TDS540 scopes without suffix.



Markus

rochoz
Posts: 90
Joined: October 8th, 2011, 9:55 pm

Re: TDS644A NVram / Serial Parallel

Post by rochoz » December 13th, 2011, 12:12 pm

In that case it makes perfect sense, that is the same behavior I've seen on the TDS540 scopes...that is, the config specified in the NVRAM needs to match what it finds attached to the scope.

Post Reply

Return to “Other or Discontinued Oscilloscopes”

Who is online

Users browsing this forum: No registered users and 5 guests