I have a syrah. I believe the schematics on the Suprateks have changed over the years, in some cases quite a bit so getting one's hands on a schematic may not be enough.
Winsound, in some cases the hum may be to some type of tube resonance - I've had this happen on mine, but is easily resolved by just tapping the tubes with my finter nail and I find such a hum immediately goes away - just though I'd mention, in case your issue is the same one.
Winsound, in some cases the hum may be to some type of tube resonance - I've had this happen on mine, but is easily resolved by just tapping the tubes with my finter nail and I find such a hum immediately goes away - just though I'd mention, in case your issue is the same one.