After finishing repairing my RV8 for the God knows how many th time, I can tell you that the posts I've read are barking up the wrong tree. The problem is not electronic with these units, it's mechanical and relates to the poor quality connectors Lexicon used in the units. The ribbon connectors for instance are not terminated at all, and simply press into the slots on the board. Over time tarnishing results in higher resistance and they need to be pulled cleaned and reinserted. Similar with the plastic ones as well which are just the usual computer types and I'm not sure they're designed for 10+ years use without maintenance.
The ones which seem to be most important, and which I go for first are the molex from the SMPS (both ends of this need cleaned) power into the SMPS, and don't forget these connectors are locked with a plastic clip. The black power ones to the amps got a clean this time, and also the long ribbon cable which attaches to the top circuit board which always appears to cause the most issues.
Do not pull all these connectors off at once ! There are a lot of them and you can easily get them mixed up. Also there are connectors which are difficult to access so again don't pull them off unless you know you can get the things back in place again. Once you are familiar with reinserting these it's fairly simple, so pick an easily accessible one to practice on first.
Use a switch cleaner to help remove any tarnish and it's even better if it's a cleaner with lube which will stop it happening as quickly. Alas once these things begin to tarnish it's like a car beginning to rust. Everything should work fine for maybe a couple of years, but you will have to revisit it and do it all again - I can't see a way around this unless you fancy replacing wiring looms connectors and ribbon cables.
Mine would either fail to reach standby constantly cycling with all three LEDs on the front lit, occasionally it would get through the start up and then drop out again, and other times it would frustratingly work for 10 minutes and then fail! After the service above, it's just run playing loud for two hours without any glitch, fingers crossed I'll not have to pull it apart again for another couple of years !