Just what the title asks....
- Can I use 7.5VDC @ 1.0A on 6V @ 2.0A device?
Anyone know the answer?
No. The supply would not be able to provide enough current and would likely overheat.
Watts = volts X amps. One supplies 7.5 watts the other 12 watts.
Reinforcing the previous answer: No.
Looking at this from a voltage rather than power standpoint the answer is either "No" or "Maybe, but you shouldn't".
It depends on what kind of power converter is in the device you are trying to power and whether it has a hard limit of 6V or supports a voltage range. The current is only relevant to how "well" your device deals with not getting enough power.
If your device only takes 6-6.5V then using a 7.5V supply could well destroy the circuitry in the device and make it unusable.
If your device has a well specced power converter inside then you may be okay to use it but the device may not be getting the full amount of power necessary to, say, charge batteries at full power or even power up if it needs more current.
Working out how we'll specced the power converter in your device is is not really our job, that's your manufacturers job and they likely chose that power supply for a reason.
You may or may not damage your device, but either way you're not using the right power supply for the job.