Sano 50 WRT - convert 8417 to 6550

[KRKozBassman]

I want to convert my Sano 50 WRT from 8417's to 6550 mainly because 8417's are scarce and I already have 6550's. One of the two 8417's was replaced by the previous owner with a 6L6 and I want to drop in a pair of 6550's instead. I am a 35 year electronics veteran, but haven't worked with tubes or circuits in this detail for 25 years! From what I see by the tube specs and the amp schematic it looks like it should work - it works now with the mismatched 8417/6L6, but I want it better/reliable if that's even possible. I am not worried about watts or perfection, I just want to make it reliable so I can sell it without feeling like I am ripping anyone off. In case it's possible or easier I do also have an extra 6L6 to use so it would be 2 6L6's but the tube data doesn't look as compatible as the 6550.

[Leo_Gnardo]

I've run across these Sanos with 8417 output tubes, very rattley, and replaced them with modern 6L6GC. Didn't have to make any circuit changes, the self biasing resistor settled the 6L's into a comfortable bias current, the amp turned out 25 watts at clip and customer very satisfied. I've also seen Sano with KT77 (original Gold Lion Genelex) also very worn out, replaced those with EL34 after making sure pins 1 & 8 were tied together, and that worked out fine too.

Also, despite the figure "50" in the amp's designation, neither this nor hundreds of other similarly named amps produce the power level suggested by their titles, so don't worry about chasing every last watt you think is supposed to be there.

[KRKozBassman]

Thanks, I'll give it a try this weekend.