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| I noticed nvram replacements for the TDS784D on ebay |
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| Tantratron:
--- Quote from: cuebus on February 26, 2020, 08:51:15 am ---Success! I have built both boards and programmed both and they are both fully functional in my TDS540C. My guesses about the pinout for the DS1384G seem to be correct. My only wonder is if it actually uses the 2nd battery pin as this part seemed designed exclusively for powercap modules which only had one battery. Luckily, battery voltage can be monitored easily by measuring directly on the replacements. I plan to tidy up the design on the DS1486 replacement board a bit. Once I've done that, I'll upload the gerbers here if anyone's interested in getting them made. Oshpark will make 3 boards for $6 shipped. --- End quote --- I own one TDS540C so if you're OK to build extra set with both chips, i'll pay you to save me time. I live in France, what country do you live ? Thank you, Albert |
| cuebus:
Happy to start making these to order for anyone interested - there's at least a relatively ample supply of DS1384Gs out there and the DS1312 is still in production. Incidentally Maxim just got back to me and confirmed the DS1384G was an internal part and will not give any information about it. Total cost to make these in small quantities breaks down like this: DS1250: PCB: $2.13 DS1312 controller: $8.89 SRAM: $7.23 CR1632 Battery: $1.32 Pin Headers: $1 Total: $20.57 DS1486: PCB: $2.13 DS1384G controller: $12.95 SRAM: $2.63 Crystal: $0.51 CR1632 Batteries: $2.64 Pin Headers: $1 Total: $21.86 Once labor, solder, flux, flux cleaner and shipping charges for materials are factored in, $50 per chip is actually not a totally unreasonable ask ::) I'm in the US. DM me if you're interested. I'm in the middle of preparing a move so lead time might be a week or two at the moment. |
| james_s:
Nice job, I'd be interested in the gerbers, this is the sort of thing I'd prefer to build myself for fun. I had started laying out a board but if you have a working layout there's not much point in me reinventing the wheel. IIRC there's a TI battery controller in a SO-8 package which is quite a bit cheaper than the Dallas part that does the same thing. |
| cuebus:
TI's part is the BQ2201 which shares more characteristics to the DS1210 than the DS1312. Around year 1998 Dallas switched to using DS1312 inside their DS1250 modules, having previously used the DS1210. I believe the switch was due to the DS1312 having even lower battery drain. From Dallas itself in an old change notice: "All devices with date code 9826 or earlier will be built using the DS1210. All devices with date code 9827 or later will be built using the DS13d12. ...the DS13d12 will give these modules 50 microamp standby currents (versus 5mA for DS1210-based devices ) and will provide enhanced immunity to data loss caused by out-of-spec voltage transient." Using the DS1312 seems like the right part here. My goal has also always been to not only build functional replacements, but as-near replicas as possible including battery count and size (DS1250 always had 1 1632 battery and DS1486 always had 2 1632 batteries). Dallas used a variety of SRAM manufacturers for their parts, but my DS1486 had a Sony low power SRAM drawing 1 microamp during data retention in it. There are a few readily available chips on Mouser from Cypress and Alliance that meet the same data retention current draw. Only long term tests will show whether my design will actually run these for 10 years on battery as the original guaranteed. Luckily, measuring the battery voltage is possible at all times, even when the scope is running (though I'd advise against this!) |
| james_s:
Well I'll certainly make a pair of these once the gerbers are available. My scope is still working fine on the original chips but I know they're on borrowed time. I could hack in new batteries but I like the bare un-potted pcbs better. |
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