Be careful, that's a hot chassis. One side of the powerline directly connected to the amplifier circuits, without any isolation, except maybe a capacitor. No power transformer. Looks like you have a bench isolation transformer. You can get an isolation transformer to wire into the amp at
www.tubesandmore.com their P-TN-51X for about $22
The 50EH5 can produce about 1 watt. I'd replace the capacitors, those ceramic cylinder caps are just wax paper inside, which get leaky.