Way back in 2020 I reviewed the 1501 Power Monitor for Commodore 64 and VIC-20 computers, built by a guy in Australia. Now he’s produced another product that works with your disk drive PSUs too called the Commodore 64 FDD Power Monitor.
Whilst the original device was designed to monitor the power output of C64 and VIC-20 PSUs this one is designed to check the output of 1541-II and 1581 PSUs instead.
The attractive box is finished in a suitable Commodore beige colour with black side panels. It’s 12cm wide, 14cm tall and 3.5cm deep.
Power Monitor Top View
It features two large LED displays on the top panel of the box, each measuring 5cm wide and 3cm tall, along with a very professional looking Commodore 1501 badge. (Confusingly the same model number he gave to the original C64 device).
Commodore 1501 Badge
The bottom of the box has a neat little ‘FDD II Power Monitor’ label displaying the unit’s serial number on it along with a reminder that it was made down under.
FDD II Label
This time around there’s only one port to be found on the device, a four pin DIN socket for attaching the output of a Commodore disk drive PSU. This is only to be used for testing and not continuous monitoring.
Power Socket
As is the way, I saw the two screws in the base and couldn’t resist taking a look inside.
Opening up the box
There’s not a huge amount to see but I did notice the ‘©1982 commodore intl’ text on the PCB silkscreen which I thought was a nice touch.
The 1501 PCB
The top of the box is attached to bottom by a few wires that run from the rear of the LED displays to the PCB so I had to be careful not to dislodge them.
LED Panels (rear)
Testing it out
With the visual inspection complete I decided to give it a go and test the output of my 1541-II’s PSU.
The device couldn’t be any simpler to use, just plug the PSU into the socket on the side of the device and power it on.
Voltage readings
I observed a 5V line reading of 5.21V and a 12V reading of 12.7V. According to Commodore’s engineering schematics for these drives they require nominal outputs of 5VDC ± 5% @ 1.0A and 12VDC ± 5% @ 0.5A. That means the tolerance is 4.75VDC – 5.25VDC and 11.4VDC – 12.6VDC.
My PSU is getting close to the upper limit for the 5V line and is just over it for the 12V line. However those figures are measuring the output of the PSU when it isn’t under load so I’d expect those voltages to drop and be within tolerance levels when in use. Still, it’s definitely something I will need to keep an eye on in future as I certainly don’t want to fry one of my drives!
Conclusion
This is another terrific little device and incredibly useful if you are nursing one or more geriatric Commodore floppy drives through their senior years. I mean, sure, you could test your PSUs with a multimeter but you’d have to consult the pin-outs each time (unless you have a great memory) and who is going to bother doing that? Furthermore, there’s also the risk of shorting out a couple of pins if you don’t have steady hands and/or 20/20 vision. This device on the other hand offers a convenient and simple way to test Commodore FDD PSUs and it looks great whilst doing it too.
If you’d like to get hold of your own FDD Power Monitor then head on over to eBay and grab one from user bluebolt12’s store. At the time of writing they’re around $54 (AUS) which is about £29 or $39 (US) plus postage. You can also pick up the original C64 Power Monitor or even pocket sized versions of each whilst you are there too!
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