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Trying to find old 8k sram chips for HP-75c calculator pod

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Bud:
Not corrosion, that stuff is under the resistors too. Probably glue.

David Hess:

--- Quote from: RichardM on June 07, 2019, 12:48:43 am ---Thanks. Yes the device runs off battery power and hence the contents are retained when powered off. Prob not a good idea mixing low standby versions with other versions ?
--- End quote ---

It just means that you will want one of the low standby power versions which are common but mixing them is not a problem.  Low standby power versions come in several grades so if you replaced them all with the best ones, standby time could be improved.

RichardM:
Google reveals that the HP-75C/D was code named Kangaroo, and the HP-71B was code named Titan, and were developed concurrently by two “competing” teams of HP engineers.  Not sure if there was any Australian input to the code name back then ? Kangaroo was based on the HP-85 desktop computer and its development was suggested and promoted by HP Labs (corporate) and not the calculator division.  Titan was inspired by the calculator division as the next generation.

Richard

RichardM:

--- Quote from: wraper on June 06, 2019, 03:19:26 pm ---https://www.ebay.com/itm/1pcs-HM6264FP-15-64kBit-Static-RAM-Memory-HM6264-SO28L-HITACHI/263389473756?hash=item3d533c6bdc:g:q0wAAOSwi5RaNWtU
EDIT. this likely will have higher power consumption in standby.

https://www.aliexpress.com/item/Free-shipping-10PCS-LOT-HM6264ALFP-12T-HM6264LFP-10-HM6264ALFP-10-HM6264BLFP-10LT-HM6264ALFP-SOP-28-IC/32873394779.html?spm=2114.search0104.3.2.ede13981tbMYNp&ws_ab_test=searchweb0_0,searchweb201602_8_10065_10068_319_10059_10884_317_10887_10696_321_322_10084_453_10083_454_10103_10618_10307_10820_10821_10303_537_10302_536,searchweb201603_52,ppcSwitch_0&algo_expid=f18d8506-affa-4ca3-b79e-98f6a26c6969-0&algo_pvid=f18d8506-affa-4ca3-b79e-98f6a26c6969

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=HM6264ALFP&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=HM6264lFP

--- End quote ---

Not sure how to navigate this minefield :) Wary about incorrectly ordering 64k replacements instead of 8k.

What is the difference between ALFP and LFP, also between LFP-15 and LFP-12T etc ? The AliExpress ones are HM6264ALFP-12T and not HM6264LFP-15 as are in the device now. Are they suitable ?

Also what type of capacitors are they ?

Thanks again.

oPossum:
There aren't 64k SRAM in that package. The next common step up is the 62256. That is 32k and 32 pins.

The general format of part numbers for 8k SRAM is M6264PK-S

Where...
M designates the manufacturer
6264 designates 8k byte (64 k bit)
P is power (nothing for standard, L for low power, LL for ultra low power)
K is package (mfg specific, DIP, SMD, etc)
S is speed in 10s of nanoseconds (12 == 120ns, etc)

Based on the original part number you want something that is low or ultra low power, 150ns or faster, and SOIC package.

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