YES, an open idle current adjust pot will cause excessive current in the output stage, as explained.
My procedure:
1. With power OFF, clean the pots with DeOxit, and work them back and forth several times.
2. Check with ohmmeter, that the resistance varies smoothly as you rotate it with no open spots. A good analog ohmmeter actually is better for this than a digital. Note that most bias adjust controls are actually connected not as potentiometers, but as RHEOSTATS. Once you have checked it, LEAVE AT THE MINIMUM BIAS CURRENT POSITION which in most is the minimum resistance (normally zero ohms).
3. Power up with VariAC and monitor the current the unit is drawing.
4. While carefully watching the current draw, slowly increase the bias current by turning the pot. When it starts to rise, STOP and back off to the original idling current. Repeat for the other channel(s).
5. Now you are "in the ballpark" but on the SAFE side. Follow the manufacturer's instructions from here in. If you have a distortion analyzer you can monitor the crossover distortion on an oscilloscope. Verify that it is GONE at the manufacturer's specified idle current, on a 1kHz sinewave at about 1/2 watt output. If not, you will need to research whether that is CORRECT (in which case you have a bad-sounding amplifier by design) or if something else is wrong.
The distortion analyzer and oscilloscope are not necessary; in most cases a properly fixed-up amp will be fine at the manufacturer's specified idle current. But I consider the ability to vary the line voltage and monitor current draw to be indispensable when working on amplifiers. If you are using a dim bulb tester you are out of luck. A VariAC costs what, fifty bucks or so? And a device to monitor the current draw can be built up from a meter and a shunt resistor. Or you can BUY one. The ones intended for test bench use are pretty expensive but the Kill-A-Watt®, normally used to monitor current draw by appliances and such, works fine and costs about $30.