Yes, another 3458A repair and NVRAM replacement to RAMTRON FRAM

[james_s]

Make pins? You can buy breakaway strips of machined pin male-male header strips.

[rastro]

I'm not familar with these.  Do you have part number/vendor or pictures?
Thanks

[james_s]

http://www.ebay.com/itm/10-PCS-40-Pin-2-54mm-Gold-machine-Single-Row-Straight-Male-Pin-Header-/281699010399?hash=item419691c75f:g:WNcAAOxyjNlRyqBg

[rastro]

Got them thanks.

[Greybeard]

What FRAM can be used for replacement of CAL-RAM?

FM1608, FM16W08 or FM16L08?
FM1808, FM18W08 or FM18L08?

RAMTRON or Cypress?

DIL28 or
SOP28 + SOP-to-DIL-Adapter PCB?

What do you think?

[Tektron]

I can only state what I have checked with my own hands.
I used CYPRESS FM16W08 with SOP28 + SOP-to-DIL-Adapter PCB for CALRAM. The use of an adapter in this location is mandatory; this allows you to match the pinout of the footprint on the board with the microcircuit pinout by cutting and closing the conductors on the ADAPTER, but not on the board.

For general purpose RAM, I used the CYPRESS FM18W08-SG with SOP28 + SOP-to-DIL-Adapter PCB. However, in this location, the use of an adapter is not required, so most likely a DIL28 housing can be installed.

[TheSteve]

I have used DIP FM1808's in my 3458A's. I use an adapter PCB for the cal ram. In the hi/low ram locations the FM1808 can be plugged right in, no adapter needed. For programming/reading the cal ram it is super easy, just unplug the FM1808 from the adapter and read/write directly in your programmer.

Myself and volvo_nut_v70 had adapter PCB's made for the 3458A and the Datron/Wavetek line of meters and calibrators(pic attached).

[Greybeard]

Thanks for your replies.

I understand now:
An adapter is needed for DIL28 FRAM at CAL-RAM position, because pinout is different to original DALLAS DS1220 NVRAM.

On the other side:
I could program SOP28 FRAM directly on the programmer, then solder it to the modified adapter PCBs.
If reprogramming is needed I could build one adapter DIL28 to DIL28 that unmake the modifications of the SOP28 to DIL28 adapter.

Does FM1x_08, FM1xW08 or FM1xL08 matter? Wide supply voltage - low power (?)

Does producer (RAMTRON / Cypress) matter?

What cheap programmer can be recommended?

BTW: Steve, what is the jumper on your second pic used for?

[TheSteve]

Thanks for your replies.

What is the jumper on your second pic used for?

That is the Wavetek/Datron version of the FRAM adapter. The config with the jumper is specifically for the 4920/4920M and 4950. These models have real time clocks that share the battery power with the original nvram. When a FRAM is installed we don't want it draining the battery so we use the jumper to connect to an existing header on the PCB to give us normal ground instead of the original isolated battery connected ground. The Wavetek/Datron devices use a dedicated static ram and a separate backup battery. All Wavetek/Datron adapters also require some logic gates to adapt to the FRAM.

Here is a picture of the other side of the assembled modules. You can see we also have jumpers to set the unused address lines high/low.
I have the adapters installed in 3458A's, a Datron 1281, 4920M and a 4708 calibrator.

[Greybeard]

I don't know, if the DALLAS RAMs sit in sockets in my '58A, but if i have to unsolder them, will data remain safe in the chips, or is there a risk to corrupt data by shorting pins?

[Dr. Frank]

1. As you did not assemble a socket by yourself, it's s probably still soldered in.
2. Desoldering is very easy, but first make sure, that you really have the old version, i. e. really the Dallas ones. A desoldering station is recommended. Pins are smaller than the holes, so no problem.
3. It's really necessary to read out the CalRam content via GPIB before desoldering.
4. Shorting is not the problem, because w/o operating voltage, the chip should be inoperative and immune, but obviously the heat is a problem. There are examples, where the Ram was OK, but failed directly after desoldering.
5. Read the Ram after desoldering and compare

[TheSteve]

As Dr Frank has said a vacuum desoldering tool generally makes it quite easy to remove the original nvram's. I had no problem with any data loss when removing mine but do your best to backup the data via gpib before hand. They are all soldered from the factory - so if there are sockets someone else has been in there previously.

[Greybeard]

They are all soldered from the factory - so if there are sockets someone else has been in there previously.
Thanks for clarifying.

1. As you did not put a socket in by yourself, its probably still soldered in.
No I have not opened this device yet, but I'm pretty sure it's the old version.

2. Desoldering is very easy, but make sure first, that you really have the old version. A desoldering station is recommended. Pins are smaller than the holes, so no problem.
Often desoldering iron tips has same outer diameter of the lands ("Lötaugen") on the PCB, and when you move the tip a bit, it can contact/short the neighbour land.

3. It's really necessary to read out the CalRam content via GPIB first.
This was my plan.

4. Shorting is not the problem, because w/o operating voltage, the chip should be inoperative and immune, but obviously the heat is a problem. There are examples, where the Ram was OK, but failed directly after Desoldering.
Interesting, because the tracks of the leadframe are not very short for DIL24/28 packages.

5. Read the Ram after desoldering and compare.
That's a good idea, I will do so.

Can I stock the unsoldered NVRAMs sitting in conductible ESD foam without discharging the internal battery?

[Dr. Frank]

Can I stock the unsoldered NVRAMs sitting in conductible ESD foam without discharging the internal battery?

Probably yes, because the RAM does not lose its content, when soldered inside the conducting circuit. Also all pins are on same potential, and no supply voltage is present, so an activation is impossible.
The internal battery has no discharging connection to the pins, so no problem either.
Frank