Posts: 4,027
Threads: 172
Joined: Aug 2005
Hi;
I'd guess your HP42S is set to TRACE mode, but the annunciator would go off by itself after printing. Have you placed an HP82240A or B in front of it to "see" if there's anything actually being sent to the printer?
Also, have you considered a memory clearing (Memory Lost) procedure? I mean, if you don't have it filled with long programs or important data (all data and programs are iomportant, but if they can be keyed back in, then it's a matter of having the time and pacience...), a clearing procedure may restore original condition. The HP42S has no external access to a hardware reset, but the [EXIT]/[SIGMA+]/[XEQ] should be enough. If not, short circuiting the battery terminals (remove batteries first) for five to ten seconds would also be fine. Of course, if you want to give it a try. This is just a guess, I'm not sure if the memory clearing will also solve the problem. BUT if it doesn't, I also cannot think of anything else but IC terminals with external short circuit (any sort of durt) or a faulty IC.
I wish I could help more.
Luiz (Brazil)