Playing with HP2640B

is there a dif between 40 a and 40 b with the firmware/loader/etc? Ed# In a message dated 11/15/2017 12:48:24 P.M. US Mountain Standard Tim, cctalk at classiccmp.org writes: I have been working on a HP 2640B terminal. It was mostly about fixing the "screen mold" problem and cleaning up the liquids that had been seeping out The small coaxial wire that connects the 4.9152 MHz clock signal form the power supply (never seen a crystal controlled SMPSU before!) to the backplane was broken off, but after fixing that the terminal worked fine. Just needed some adjustment to the brightness. With the correct terminfo installed it worked quite well as a serial terminal to a Linux box. Then I tried the short 8008 programs that Christian Corti pointed to http://computermuseum.informatik.uni-stuttgart.de/dev_en/hp2644/diag.html and ftp://computermuseum.informatik.uni-stuttgart.de/hp/hp2644 I tried both a couple of times. The terminal enter the LOADER mode but just hangs completely at the end. I tried different baudrates but no difference. The selftest STATUS line tell me 40<802 which should indicate that there are 4k memory in the terminal. However there should be 5k since there is one 4k board and one combined control store and 1 k RAM board. Maybe there is a fault in the 1k SRAM? The terminal doesn't complain though. Regardless, the programs listed either starts at adress 30000 or 36000 which should then be within the available space. The question is, should these program work for the HP2640B as well? It has a 8008 but my guess is that the firmware is different from the 2644. What is the joint experience regarding this? Has anyone ran these small programs above on a HP2640B? The HP 2640B firmware consists of four EA 4900 ROM chips which annoyingly are not anything like normal EPROMs. So dumping will need special considerations. Has anyone dumped the HP 2640B firmware already? I didn't find it on bitsavers. /Mattis