PDP 8/e, RK8E Weirdness

system. Yes, I totally agree that the RK8E is a weird beast. It is definitely not the easiest thing to troubleshoot. several "bad" sitting at all test. And I checked the +5V supply today, both with a DVM and an Oscilloscope to look for ripple or noise. The +5 was running at +4.776 V, and there was virtually no ripple or noise on the line. I checked it on all of the +5V bus lines and it was consistent. So, is +4.776V "good enough", or do I need to tweak the +5 supply up a little bit? This was with everything plugged into the Omnibus: CPU, EAE, PC8E, RX8E, 2x4K Core Sets, 16K Solid State Board, RK8E, 2xM8650's (Serial), MemExt/Timeshare, Front Panel and Bus Loads it... The test itself is a crazy piece of code. I've actually typed the whole thing in from the source listing PDF, so that I can "instrument" the code by putting in various typeouts and such as the tests go along. I've also run the RK8E Drive Control & Instruction Test (DHRKBG). It runs great until it does the part where it does "WRITE ALL" commands to format the pack, and then does "READ" commands to verify, and it fails partway through that, just as the RKLFMT (formatter) fails. The reason it gets part way through the RKLFMT verify and the verification pass in the RK8E Drive Control & Instruction test is that the write (format) part puts the upper bit of the disk address in word 0, and the lower 12-bits of the disk address in word 1 of each sector. Since the first word of each sector is '0000' for most of the pack, it verifies OK there. It's when it changes to '0001' that is when the verification fails. I didn't have much more time today other than to do the power supply testing, and, just on a hunch, I moved the RK8E boardset to a couple of different locations in the Omnibus, and it didn't make any difference. Of course, if anyone has any other ideas, I'm all ears. Thanks, Rick Bensene