Battery problem w/ Dallas DS1287

[glitch]

That looks nice. When are you planning on selling the completed GW-1225-1? I would be interested in getting one for sure.

No definite timeline, I PMed you about getting a prototype version though.

Coincidentally I have done a lot of work on the DS1225. This is because they are used to hold the calibration constants in the TEk 2465B scope.

Heh, I laid out the GW-1225-1 due to having a piece of test equipment in the shop with a dying DS1225Y Same with the GW-1220-1 too, as mentioned it now lives in a Prema DMM.

After a lot of research on the topic, I moved away from the DS1225 to Ramtron FRAM

Yeah, FeRAM is *great* when it'll work in an application! I'm thinking about doing a module that qualifies the chip select for situations in which it's grounded. I've found quite a few things that either ground *CS or assert it before the address lines are fully settled. Some things hammer it too hard for me to feel like it's a good replacement, too -- things where the NVRAM isn't just storing configuration or calibration values, but is also being used as part of main memory.

I was the first person to install these in Tek 2465B's

First to write it up, anyway

Here is the original article I wrote back in 2013, and I have been running FRAM in my scopes since that time. There are some interesting remarks in the article about Autostore - Shadow Ram STK12C68 option I tried and a MRAM (Magnetoresistive Ram, that never came into being, even though its data sheet circulated the net) I use this type number (CY9C6264) as a "probe" if some supplier claims to have it in stock, you can then know they are not a genuine stocking supplier.

http://worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf

Great writeup! Thanks for sharing it!

 

[Hugo Holden]

Since I published the article about FRAM in Tek 2465B's I started to get emails for all over the world thanking me for the work and the paper. I still get 2 or three emails a year about it. If somebody else did also find the FRAM worked in this particular application before me, its a shame they didn't publish that. At the time when I researched it, there were posts on some scope forums explaining why it was not an option and wouldn't work, so that would have put most people off the notion of trying it for themselves. Also one interesting thing about the auto-store shadow (quantum trap) types, is I found they could be confused and corrupted by rapid power cycling, at least in the 2465B application.

If the 2465B loses its calibration, it requires the correct Tek generators to re-calibrate (not generic generators) and it is a slow process, takes at least 1.5 to 2 hours. So those Dallas battery RAMS are a real PITA in this case.

Ramtron were an interesting company, they started off in Australia and moved to Colorado Springs, Nikola Tesla's old stomping ground.

 

[glitch]

At the time when I researched it, there were posts on some scope forums explaining why it was not an option and wouldn't work, so that would have put most people off the notion of trying it for themselves.

Funny how often Internet experts are *certain* something won't work without having tried it for themselves, eh? "But it simulates that way!"

If the 2465B loses its calibration, it requires the correct Tek generators to re-calibrate (not generic generators) and it is a slow process, takes at least 1.5 to 2 hours. So those Dallas battery RAMS are a real PITA in this case.

For sure, first thing is always to back up the NVRAMs! Even if you're out of calibration, at least you have a starting point. A lot of the older stuff isn't worth having to send into a calibration lab if you're stuck in a situation like the 2465B, where you must have specialized equipment. Shame to see it scrapped or otherwise not used over the contents of a NVRAM.

 

[Hugo Holden]

A lot of the older stuff isn't worth having to send into a calibration lab if you're stuck in a situation like the 2465B, where you must have specialized equipment. Shame to see it scrapped or otherwise not used over the contents of a NVRAM.

It seemed a real shame to me that a lot of good Tek scopes got trashed because of those darstardly NVrams. Also, to re-cal the scopes, they often had to be shipped across country to "calibration houses" (don't get me started, already too late). This risked damage to the instrument, because every stage in the shipping is equivalent to throwing the item down one flight of stairs.

Some of the work I have seen done by "certified calibration houses" includes scraping old cal stickers off with screwdrivers, over-tightening screws, wrong sized screwdrivers, brutal force applied to delicate adjustments in attenuators , mutilation of pcb tracks & components, soldering skills of a 7 year old, a total lack of respect for the instrument and "Hopeless" calibration errors, but sporting a fresh calibration sticker over the damaged paint where the other sticker was scratched off.

So I bought all the Tek generator equipment required to calibrate the 2465B myself (and refurbished that too) and I do the job myself, not having to ship the scope anywhere and have it damaged by the carelessness of a third party, saves a small fortune too.

 

[glitch]

(don't get me started, already too late)

You're not kidding! We adjust most of our older equipment in-house, just because it's so difficult to find a calibration shop that does good work *and* will handle older equipment. We've got a few items that get outside calibration, but basically it's just high precision stuff that we use to set up non-traceable transfer standards for doing our own stuff. It's cheaper and easier to acquire older metrology-grade standards than to deal with super long turnaround times and wrecked equipment. I guess that's why a lot of shops just junk the older test equipment as soon as it has any issues.

I sometimes think about getting set up to offer actual traceable calibrations and repairs on older/vintage test equipment, I just don't know if anyone would actually pay for it or want the service.

 

[Shadow Lord]

Well I got the prototype DS1225Y from GW yesterday and installed it in my motherboard. It looks great (love the LED). I still need to read/write the EISA cfgs to it but so far so good:

 

[wrljet]

Yeah, if it doesn't work with a 12885, a 12887 definitely won't do it -- there's a 12885 inside every 12887.

<snip>

 

[alank2]

I loved the idea of FRAM, but one issue I did not like was that if you try to read or write in a low voltage situation (<5V if it is 5V FRAM), even a read will destroy data and it will be lost because it can't be rewritten because of the low voltage. This probably isn't too much of a risk if using a battery though as long as that battery has enough voltage.

 

[wrljet]

This one still works, amazingly enough. 1995 date code.