How do I test an adjustable voltage regulator in my guitar preamp?

[rosssurf]

I have an Egnater ie4 guitar preamp that recently died on me and wont power up. I have emailed Bruce at Egnater amplification and he says most likely it is the Voltage regulator or the bridge rectifier. I did manage to find info online as to how to check the bridge rectifier and that seems fine.
Can anyone tell me how to test my adjustable voltage regulator?

[Amp Kat]

Not seeing where that is adjustable or what it's running as it's low voltage high current (maybe heaters) but usually since the collector is metal you can put the MM black lead on ground and touch the top of the regulator and it will show voltage. On another view there is nothing more easier than changing a LM350 TO-3 style regulator. Simply remove the two screws and plop the new one in and see if it works. They cost around $5 max.