In early May the BS250's have finally arrived from China, and the calculator became completely autonomous.
In sleep mode, it consumes less than 2uA (micro-Amps). The natural NiMH battery discharge is probably more than that. The booting is by 0.5-sec press on Cx button; to put back to sleep - A-Cx.
I have been using the machine every day, in on-off mode for 80-90 minutes per day on average. The battery life of 4 new AA NiMH batteries (2300 mAh as claimed by the manufacturer) is over 30 hours, which means recharging is due every 3 weeks. The HP-35S under this use pattern eats 2 coin cells in about 1 month.
With the batteries installed and cover on, the calculator is exactly 390 g:
Retro look-and-feel of the original is preserved:
Admittedly, the letters are a bit of a screw-up. I used a white-out marker and hand-writing. To fix it, I have ordered letter stickers.
The SD card fits natively between two "fake slot" covers. Note that the original calculator used two right-most covers for the expansion slots and the other two served decorative purpose. I just expanded the "fake slots" with Dremel.
With the card in, all looks pretty native:
How, the sacred question "So, how much memory does this thing have?" the answer is "Just under 8 gigabytes!"
The quick usability remarks after 1 month of extensive usage:
* Keyboard quality - excellent, better than the original and about par with HP-35S.
* Screen readability - good, better than the original and far superior to the HP-35S non-backlit LCD.
* Battery life - comparable to the original (if modern NiMH are used), but because of the Instant-ON, the Resurrect does not need to be on for long periods of time, which saves a lot of battery time.
* Program entering and editing functionality: comparable to HP-35S. Additional screen lines help.
* Original functions of MK-52 badly missed: none so far. Tried many historical programs from A.Schelest and other books, always was able to reproduce results.
* Functions badly missed from HP-35S: One-Key Solvers, Hyperbolcs, One-Key Stats, Numerical Integration, Unit converters, Physics Constants.
* Portability: 390 g against 184 g of HP-35S. MK-52 is exactly 1 3/4 inch longer and 1/8 inch thicker. Some little price to pay for being "Retro".
The next picture is without photo light to show the relative screen brightness/contrast under normal usage conditions.