[Texasrocker]

The front ends of the 41-250 & 41-280 sets using the XXL / 7A4 tubes can sometimes ( most times) be intermittent because of dirty loctal tube pins. Clean ( scrape) all the individual loctal tube pins shiny clean with a exacto knife blade. Do the same with the other loctal type tubes pins in the set. Work all them in and out of the sockets a few times for good sockets contacts. Lube all the tube pins with WD-40 from a Q-tip. Spray WD-40 in the old sockets as well. Let dry, remove excess lube. The old band switches in these sets are highly problematic also. Flush them several times with Deoxit, carefully work the switch back and forth using deoxit, then relube switch contacts and wafers with WD-40. Check the old candohm resistor going to ground from the filter caps also to make sure the resistors built in are still good.