Of course the first thing to do is to repeat the resistance checks before applying power.
Presumably, some other change in wiring occurred during the change of capacitor - perhaps another component was damaged, or another solder connection was broken, or a wire was bent to where it touched something it shouldn't.
The one clue we have at this point is that the 620 ohm 2 watt resistor was overheated. That suggests the 1000uF capacitor was installed correctly - if not, the resistor would be OK and the cap would have blown out!
Since the circuit worked before, we can speculate that only one new problem occurred. The only way to get an excess current through the 620 ohm 2W resistor is if it goes through the tube. That would happen if the tube lost bias, so check the resistance from the grid (pin B1 on the tube socket) to the negative end of the new capacitor and the 620 ohm resistor - I think that's terminal 32. It should read 250K ohms. A bad connection of the 249K resistor at T12 could have happened; inspect Terminal 34 at the other end and the 220 ohm grid stopper from terminal 34 to B1.
If that does not turn up anything, remove the tubes before testing it again, to confirm that the current is going through the tube. Then insert the A tube in the B socket (leave A empty) to see if a known good tube works properly on the B side. THat will give us more information. You can monitor the voltage across the new capacitor (and the 620 ohm 2 W resistor) with a voltmeter while it warms up; that voltage should go to 17 volts as the tube heats up. If it goes much higher then there is a problem - shut it down before you get more smoke. Always use clip leads to test voltages during startup so you ave a free hand to switch the power off if there's a problem. Your other hand is in your pocket, right?
