Hi Warren, Thanks for responding - thats good news. Do you have any more detailed technical information than the ... Yeah, wunnerful... I suppose it's great for current products if you have the HP service tools, and you can still get board replacements. Not a cheap way to repair, but perhaps when a customer pays $10,000 for a scope, he doesn't mind paying for whole boards (I'd guess they wern't all that cheap). Be nice to have some real service information for the times when board level repair is needed however ... Thanks for the info. I checked the supplied, they look pretty good and are within tolerance for DC voltages, I couldn't find a spec in the service manual for the ripple - Here's what I measured, some of them are beyond a single digit mV reading. Supply Spec.(V) Measured(V) Ripple(mV) ------------------------------------------------ 15 14.25 15.75 15.12 15.8 12 11.4 12.6 12.19 5.7 5 4.75 5.25 4.99 2.8 -2.4 -2.16 -2.64 -2.52 4.9 -5.2 -5.2 -5.7 -5.41 13.0 -12 -11.4 -12.6 -12.02 3.7 While I was measuring the power, the scope started to work correctly again - probably only after about 5-10 mins of power-on, where yesterday I let it sit for several hours... The readings did not change significantly from when it was not working to when it was working. Voltage and ripple were about the same in both cases. When it's not working, it triggers constantly on all sources - setting the trigger range all the way to the top doesn't stop it from triggering, however setting it to large negative values will usually stop triggering. At this point, applying a signal can make it trigger, however the trigger points appear to have no correlation to the input signal. When it starts working, it's not a gradual shift - it just "suddenly" starts responding to normal trigger levels. It doesn't seem to me like a symptom of a slight change in power supply ripple... I'm thinking that something in oscillating that shouldn't be ... with no input source the trigger should be at a constant level, presenting no edges - the fact that I can set the range over such a large area suggests that there is a fairly big waveform "somewhere" along the way. Problem is the analog board is a big board with several large chips that I don't have any information on - I can see that the external trigger goes to it's own and somewhat simpler area of the board, so I will probably begin by trying to follow that through, but I imagine I will have quite a ways to go since the problem is deep enough in that it affects all trigger sources (except the digital analyzer trigger - that seems to always work, but I'd guess it doesn't come into the mix until some time after all the analog stuff has turned digital)... having some information on signal paths would be very useful ... anything you can provide would be MOST appreciated. Regards, and thanks again. Dave -- dave06a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Collector of vintage computing equipment: http://www.classiccmp.org/dunfield/index.html