HP-67 Reads cards but does not write

[Trevor Gale]

One further (surprising) advance: after trying a few things with my mates' HP-67 as well, it turns out that the entire pack of cards (new) that I have been using are far, far less reliable than another new pack I have just tried.

So now, my HP-67 that originally read but did not write, is now back to writing perfectly well all the time but will not read - not even cards that have been check-read by my mates' HP-67 and my own HP-97.

I am really at a loss, the first time I have ever been at a loss wuth these card readers...