Not sure when the series 2 was released but the easiest way to tell the difference is the modes. The Series 1 was 4 modes; Clean, Pushed, Vintage, Modern. Series 2 has the addition of Raw. One the back Series 1 was straight up 6L6, Series 2 added a bias select for EL34 operation if desired.
There was a channel switching latency on the series 1 I think they corrected in on Series 2. Never heard of these amps popping like the Roadster though.
+1 on changing the tubes out. I ran JJ 6L6's in the power section and GT silver series in the preamp. One of the best tube combos I've used in any amp to date. Instead of cutting it into a head (unless your tired of lugging the 70lbs combo) pick a Rectifer 2x12, you can fins them for about $350 used. I loved the combo of the Black Shadow with the 2 V30's.
Great amp, should never have sold it.