Power Computing PC702 external floppy disk drive question

[MR*Atari*]

hi all

 

i have the above external floppy drive, this is the one with the blitz interface on the rear

 

anyway i'm asking anyone who has one of these if they can look at their power supply

 

the PSU is 5 volts (NOT 12v like most) but i want to know the MA (milliamps) as i need to get a replacement

 

i've tried a standard one of those generic/universal types 300ma 3.6va and it's not enough

 

also can anyone tell me how to measure MA (milliamps)

[tetrode kink]

I don't know anything about the hardware you're asking about, but I'll tackle the measurement question.

 

In most circuits, the easiest way to measure current is to measure the voltage across a resistor in the circuit and do a little math - Voltage divided by Resistance equals Current.

 

Unfortunately, measuring current in a power supply circuit in this way would involve inserting a low-ohm resistor in series with the circuit being powered, which would modify the power usage of the circuit, which would make readings inaccurate. Therefore, when measuring current in a power circuit, resistance is futile. Sorry, couldn't "resist!" Sorry, I'll stop now.

 

So, you'll have to do it the old-fashioned way; break the circuit in a place where the power supply feeds the powered circuit, and connect your meter to the broken connection.

 

If there is a fuse between the power supply and the powered device, that's a good place; just remove the fuse and connect your meter's wires to each side of the fuse connection.

 

If there is a connector between the power supply and the powered device, unplug the connector and use your meter to make the connection instead. Otherwise you'll have to find a wire to cut and insert your meter's wires to temporarily re-make the connection.

 

Once you shoehorn your meter into the circuit, just set it to measure A (or mA) and fire up the power. And pray.

 

-tet

[A.J. Franzman]

One thing novices should train themselves to do, is after taking a current measurement, IMMEDIATELY return the meter's probes and switch setting to the voltage measuring configuration (unless you have one of those fancy fully-automatic meters). Otherwise it's a very common mistake to grab the meter without checking it, and place the probes across a voltage source. Doing so while it's configured for current measurement will instantly either blow the meter's internal fuse, or destroy the meter (or, if you're unlucky, both!)