Absolutely sure. If you draw too much current from the 100V transformer output then you run the risk of burning up the output windings. They were fused at 3/8 amps. Based on this rating, I cannot imagine they can output much more than one amp without damage.
If you are using an inefficient linear type supply to provide power to the pin2dmd then the 3-5A load will burn your windings. But, linear supplies are not common any longer.
If you are using a switching type supply and you measured 3 to 5 amps at the pindmd then you are probably drawing less than 3-5 amps from the 100VAC source. With a 5V, 5A load then you are sourcing 25 watts. Assuming an 80% or better efficiency then you are drawing 25/.8 or about 32 watts from the source. With a 100VAC source then the current load would be about 0.31 amps.
It all depends on what power supply you are using. Who's power supply are you using?