I generally do not bother to drain the caps to remove the chassis. But if I am going to do any work on a tube amp I will do it after I get the chassis out. Just do not stick your hands onto the circuit board or hold onto any exposed connections. Lay the amp down on the floor with the bottom closest to you. You can remove the power tubes and rectifiers if you have not done so. If you have never had all of the power tubes removed before, take a picture of the amp with the tubes installed so than when you go to put them back in, you do not mix up power tubes with rectifier tubes meaning where do they get installed. (easy thing to remember, the rectifiers install in the two sockets closest to the power cord). After the chassis is out, nothing plugged into the amp, to discharge, I will just switch the standby switch as if I was going to play through the amp. Let that go for at least one hour. At that point I will measure for any residual stored voltage across the main capacitors using a multimeter. Best if the leads have alligator clips so you do not have to use both hands to hold probes against wires. Clip the negative lead to the chassis, confirm it has good contact to chassis ground, you can do a resistance test first, meter on ohms, take the + terminal and touch a jack or even the ground pin on the socket for the power cord. Not sure if all Roadsters came with a removable power cord. If not, you can confirm with the round pin on the power plug. Set the multimeter to read dc voltage and connect the positive lead to the positive side of one of the supply caps. Note that the two 220uF caps are connected in series. May as well check both + leads on the large blue caps. If you measure any voltage, let it sit for longer. When the meter reads 0 volts or a few millivolts you are good. Before you get your hands into the wiring, you can probe around at some of the plate pins on the preamp tubes as they are accessible inside on the preamp board. On the 12AX7 sockets, the plates are pin 1 and pin 6. leave the negative lead connected to the same spot on the chassis. What is the chance the bleed resistors are open? it can happen, if it does, there will be high voltage potential that will require a different method to discharge. If you never did any of this before or are not familiar with electronic parts or tube amps in general, the chances of you getting zapped and falling over dead due to cardiac arrest are 1 in 3. Don't worry, you will only feel it once if it happens. Play it safe, may be cheaper to have it serviced.
The only pots that run on the back side are the reverb controls, slave out, and effects send. The effects send has a center point detent that you can feel when rotating. The others are just basic potentiometers.
