If memory serves me right, those Galaxy amps run either the M2057 tubes or 8908's, both are quite rare. Looks like that particular model runs the M2057's. Honestly, I wouldn't even mess with it, those tubes are quite pricey, provided you can even locate a set these days. Run one of the MaCo 200's instead, much easier to retube those.
Just my .02 worth.
~Cheers~
Just my .02 worth.
~Cheers~