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--- Kevin Andres <kandres(a)epssecurity.com> wrote: That's one possibility, but typically only if it's in the zero page area. One way to test that is to swap out the zero page RAM with a higher page and see if the problem persists. If the machine comes up with less RAM for BASIC, that's probably what the problem is. OTOH, those sockets are really crappy. It's possible that removing and reinserting the RAM will make a difference. Just pressing down on the socketed parts to reseat them can revive a "dead" PET. On a couple of later units, I've had to resort to removing sockets and replacing them with machined-pin ones. No chips were faulty, but there was intermittent contact causing all sorts of flaky behavior. Using a test instrument (pulse stretcher/logic probe, oscilloscope, etc.) to monitor the reset line is another thing to check. IIRC, they use a 555 timer to generate the reset pulse (common in the mid-70s) and I've seen those circuits fail for a variety of reasons. You can also build a NOP generator (use a second CPU chip) by bending the appropriate data bus leads up and hardwiring the databus to the NOP instruction (0xEA?) - You can then use a logic analyzer to monitor the address bus for stuck bits and the select lines on the MSI chips to see that they respond at the appropriate times. A buddy of mine had one of those when we were kids. He built his into a robot chassis (his second - the first was run by a Quest Elf with 256 bytes of RAM). Fun little guys, as I recall. RL02s. Not rare, but that means that you have the drive controller, either an RL11 or RLV11, probably (unless it's a PDP-8/a, in which case it's an RL8A controller, but that's less likely). There are plenty of people who could help you with that one if you provide a description of what you have. Welcome and good luck, -ethan __________________________________________________ Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com