Logic Analysers

Evening folks, I have two so-called Logic Analysers, both cheap Chinese clones of other more expensive units that hook up to the host via USB2 and stream readings direct to software, in one case the open source Sigrok and in the other genuine Saleae Logic. I'm getting different and inconsistent readings out of both of them whilst sampling at 25MHz which should be more than enough for this 6MHz Executel I'm working on. Both of them are good for spotting dead or stuck outputs but I still can't get a good set of readings from eg all points on a single address line. Tonight I replaced all four ROM sockets and ROM chips, tested each individual line for resistance (0.5 ohms on all apart from an occasional 0.4 and 0.6) but still get ghost readings. Is it me or the cheap clones? Whilst looking for better quality units I came across a couple of 'proper' HP/Agilent analysers, a 1663A 34 channel and 1661A 102 channel which seem complete apart from the chip leg grabbers. Am I right to assume some of you might have experience of these beasts? Forums seem to mostly think the streaming USB units aren't worth anything for more than a few channels but I'm still a relative beginner to all of this. I really need to watch all 16 lines of an address bus and externally clock it as Tony has suggested. Any insights appreciated! -- Adrian/Witchy Binary Dinosaurs creator/curator Www.binarydinosaurs.co.uk - the UK's biggest private home computer collection?