OK, I'll give you my personal DIY tech tips:
1. Inspect the power transformer for the secured loose wires. You can assume that these wires if swapped with existing connected will reconnect to 220V operation. If there are no visible secured wires than probably conversion is only possible by swapping the power transformer. Very less-likely the voltage transformation happens on the DC side of the preamp circuit.
2. The measured voltage across these above mentioned wires usually near 2x lower when 110V is at the input. for this you need to measure the voltage across the existing wires and compare them vs. the disconnected loose wires (once again the voltage should be approximately 2x lower).
3. For this you'll need to carefully disconnect existing wires(make sure to remember the connection places!) and start measuring an output voltages between the terminals (chassis to wire) and filling out the 'data sheet' containing all possible information about the wire you're testing: color, voltage, location.
4. Match the measured voltages and 'map' the conversion diagram.
I had PH3 phonostage and rewired it for 220V before I shipped it to Europe and charged buyer extra $120 for barely 20 min of effort. I believe that LS-3b might have the same strategy of rewireing.
Some unit might have jumpers and serial connectors that just need to be 'slided' onto the different set of terminals...
Let me know what do you see arround power supply
