The bug in HP16c DEC view in the HP16c mode of HP15c Collectors' Edition

The HP15c Collector's Edition has a hidden, non-supported HP16c mode. To get to it, you need to switch it off, press G+ENTER, and switch it on: you get to a 3-item menu. Here you press 4, and you get to another menu. The 15 and 15.2 are two HP15c versions, the second with double memory (up to 196 registers); the third is the hidden HP16c mode.

(isn't nice to have another calculator included?)

However, with the original firmware, while you can enter a number in any base, it does not display properly some numbers in DEC format.

It is easily seen like this:

Press [DEC] to select Decimal mode

Try to enter the number 11111

Pressing 1 repeatedly, the display changes as follows:

1 -> 11 -> 105 -> 1111 -> 11111

And indeed when showing 105 and you change to HEX (or octal or binary) you will see that the actual value is correct, it is only displayed incorrectly.

Entering continuous 2’s, we get:

2 -> 22 -> 216 -> 2216 -> 22216

This renders this mode nearly unusable.

However, the newest firmware (0A0Ah) fixes this behavior (aside for providing backup and restore facility). You just need a POGO cable and follow the instructions here:

https://hpcalcs.com/download/