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Another A5 board repair attempt - work in progress


Rogerio O
 

Thank you all for the continued support, specially Siggi and Leo.
Since it seems that I will need to calibrate the scope anyway, I need to replace the dead NVRAM.
There is a very good article suggesting the use of the Ramtron FM16W08-CS as a suitable replacement that I have uploaded to the files section.
The next problem is how to program the Ramtron Chip using a cheap programmer.
Fortunately I have found this information and built the adapter for the T866A that I have (see photos uploaded to this project album).
Using this adapter I could try some NVRAM images I have found in the files section
Unfortunately none of them got the scope rid of the TEST4 FAIL4 error and caused other error to appear.
So I decided to load a copy of the scope's DS1225 to the FRAM and move on.
The error and the dotted lines came back so I will try to do a CAL08 as suggested above.
I will post the results as soon as I have them.
Roger


Siggi
 

On Mon, Nov 9, 2020 at 1:50 PM Rogerio O <rodd414@gmail.com> wrote:

Thank you all for the continued support, specially Siggi and Leo.
Since it seems that I will need to calibrate the scope anyway, I need to
replace the dead NVRAM.
There is a very good article suggesting the use of the Ramtron FM16W08-CS
as a suitable replacement that I have uploaded to the files section.

The same article discusses adding a heatsink to U800. Personally I think
this is unnecessary and unadvisable. It's been discussed here at nauseum
that messing with the screws on the package tab can kill the chip by
pulling on the leadframe. Not to derail your thread, but I just thought I'd
mention this in case you're unaware of previous discussions about U800
heatsinking.


The next problem is how to program the Ramtron Chip using a cheap
programmer.
Fortunately I have found this information and built the adapter for the
T866A that I have (see photos uploaded to this project album).
Using this adapter I could try some NVRAM images I have found in the files
section
Unfortunately none of them got the scope rid of the TEST4 FAIL4 error and
caused other error to appear.
So I decided to load a copy of the scope's DS1225 to the FRAM and move on.
The error and the dotted lines came back so I will try to do a CAL08 as
suggested above.
I will post the results as soon as I have them.
Good luck.


Chuck Harris
 

To simplify your work, I will tell you several things:

1) the RAMTRON FRAM programs like a plain old RAM, or NVRAM
chip, for the most part.

2) there is one unique feature, that involves internal muxing
of the data and address lines, which will cause some programmers
to get the first and last byte of the FRAM wrong. Fortunately,
it doesn't matter because the first byte is recreated by the scope's
program every time the scope is turned on, and the last byte is
not used.

3) the 2465B likes the FRAMS very much. I expect the FRAMS will
still be running strong in 100 years.

4) Test 04, Fail 4 is *not* a valid error code.

The only valid codes are (0-F)1, (0-F)2, (0-F)3, or 1(0-F)

The only valid time you can have a "4" as the second digit
of Fail is if there is a "1" in the first digit.

From time to time, my customers pull out the NVRAM chips and
replace them so as to avoid my repair fee. I have found cut
traces right along side of the NVRAM pads where they accidentally
cut the trace by being too aggressive with the desoldering.

Cut traces on the NVRAM make for unpredictable behavior from
the CPU.

Check every NVRAM pad for continuity with any trace that connects
to the pad on the underside of the A5 board. Use your DVM.

-Chuck Harris

Rogerio O wrote:

Thank you all for the continued support, specially Siggi and Leo.
Since it seems that I will need to calibrate the scope anyway, I need to replace the dead NVRAM.
There is a very good article suggesting the use of the Ramtron FM16W08-CS as a suitable replacement that I have uploaded to the files section.
The next problem is how to program the Ramtron Chip using a cheap programmer.
Fortunately I have found this information and built the adapter for the T866A that I have (see photos uploaded to this project album).
Using this adapter I could try some NVRAM images I have found in the files section
Unfortunately none of them got the scope rid of the TEST4 FAIL4 error and caused other error to appear.
So I decided to load a copy of the scope's DS1225 to the FRAM and move on.
The error and the dotted lines came back so I will try to do a CAL08 as suggested above.
I will post the results as soon as I have them.
Roger






tekscopegroup@...
 

On Mon, Nov 9, 2020 at 10:50 AM, Rogerio O wrote:
There is a very good article suggesting the use of the Ramtron FM16W08-CS as a
suitable replacement that I have uploaded to the files section.
The next problem is how to program the Ramtron Chip using a cheap programmer.
Fortunately I have found this information and built the adapter for the T866A
that I have (see photos uploaded to this project album).
On my 2465B (above B050K) I have been using a FM16W08 FRAM chip in place of the original 1225 NVRAM for about 2 years now. Some people at EEVBlog have reported sporadic scope startup or shutdown problems while using a FRAM and experiencing some data corruption issues, as I recall something to do with the WE line needing to be pulled (can't remember if to hi or lo) through a resistor and that seemed to have solve those issues. In my case no need for that and so far so good, it was just plug n play. Be sure to get a good quality low profile socket and a SOIC to DIP converter for the FRAM chip. Got mine at Mouser, I can post PNs if of any help. I used a GQ-4X4 programmer for both the 1225 and 16F08.