[Tubester]

Thanks for the replies. It's not the really the hum that I am after. Just trying to understand why only the shortwave band part of the osciallator is different from oem schematic. Most of the wiring looks original, although there was evidence of some newer (50-60's) capping. OBTW, mine has only 5 bakelite blocks, so it appears to be a later production unit. Was hoping someone with a 610B could weigh in and comment on my oscillator wiring comparted to theirs. Will eventually change the oscillator wiring to oem schematic and see what happens. Then, will tackle replacing the speaker cone. Is does work but has been heavily repaired. Does anyone know a good source for the cone? Looks to be about 5-1/2" od x 1" deep. Thanks