PET 2001 oddity

I dug the 2001 out of the cupboard the other day - it's reorganise time, try to get *even more* stuff into exactly the same amount of space as less (but still lots of) stuff occupied. It never works, but it does give me an excellent excuse to have a play around with some of them. Unfortunately, the PET seems to have developed an odd fault: It won't take a BASIC program, and some keywords seem to be knackered... It reports 7167 bytes free, as per spec. But if I type: 10 REM blah or 10 ?"HELLO" it hangs. If I load a program from tape, it does one of two things: a) Loads but won't run, typing LIST produces something like this: 10 2 READY. b) It loads & hangs immediately after the READY. prompt comes up. I tried to put together a FOR loop (the idea being I could use it to display chunks of memory at a time, e.g. FORI=0TO10:?I;:NEXT Instead, the machine goes into an infinte loop displaying zero on a new line each time (it's ignored the I variable, and the semicolon after the PRINT command. If I replace NEXT with NEXTI, it fails reporting NEXT without FOR. So.... I figure the BASIC ROM has become slightly corrupted, OR I've got a flakey memory chip which reads OK but doesn't write properly. The question is, how to find out? 1) Can the BASIC ROM be swapped with one from, say, a 3032 or 4016? In fact, which one IS the BASIC ROM? 2) If it's a dodgy memory chip, what's the best way of isolating it? I have an oscilloscope, but nada skill in this sort of thing. 3) If, as my money is on, it's the BASIC ROM, can it be replaced with an EPROM - if so, there's a whole gamut of additional questions to follow.... Thanks in advance! -- Cheers, Ade. Be where it's at, B-Racing! http://b-racing.com