[Drake] L75; What went KERPOW??

[Dave Edwards]

Have not heard much from the Drake list lately...Anyway, wonder if anyone can suggest a likely culprit in the innards of my L75 amp?  I was having a chat on 20 CW. The amp suddenly made a beep sound (like a warning buzzer...what the heck could that have been??) and then a "ker Crack!" sound. 
I hit the standby switch and finished the QSO without the amp. 
Later, I turned the amp back on and it seems to be working fine. But, there is that yummy smell of burnt bakelite in the air. 
So, when I get the chance I will pull it out of there and pop the lid to see what is going on. Can anyone suggest what could have gone south, and yet allow the amp to keep on working? 
Just now it keys down at 320 mils and 2500 volts. The output about 650 watts.
Any thoughts would be helpful. 
If you are interested, I will post my findings here after I "dive in" !
Thanks all;
...Dave