Alot of that comes with time and experience, but there are some things to look for that can help to point out a bad joint. If the solder connection looks very dull and crystalized, that is usually a good sign. Big blobs of solder can also cause problems. Another thing to do is to get a magnifiying glass and check out connections for a "halo" effect, where the wire or component lead looks like there is a small ring between it and the solder. On those pedals the most common places for joints to go bad are on the pots and where the wire/pots join the board, the power connector and 9v battery wires, input and output jacks and of course the pedal switch. Hope that helps somewhat.I'm handy with a soldering iron, if anyone has an idea on how to troubleshoot any cold solder joints or what to look for, let me know.
I think the new price for Holy Grails is a little ridiculous. They can be had used for well below $100. Often with the adapter. They tend to suffer from sloppy solder work at the connectors. But that's easy to fix.Good point.. have you seen any EH Holy Grails coming back with complaints or know if the store has had a lot of them returned? I just really don't want to be out 100+$ on a pedal that sounds great for a week and then becomes a noisy can of hiss.