[Arran]

Thanks Ron. I ment to say 250 vs. 280 but forgot. The reason I was asking this was that I have a 280 I've been working on which won't put out any sound and recently acquired a 250 which does work. In comparing the 2 I found two spots where the capacitors are installed differently so I made the 280 like the 250 but no change in my problem. O well I'll just keep plugging away and hopefully I'll find the answer.

Check for an open power output transformer, the result will be no "B" voltage on the plate of one or both of the power output tubes, you can use an ohmmeter to check the primary or a voltmeter to check for missing voltage.
Regards
Arran