Replacement power for 14.4k HST
After proving my HST worked in my previous post with an ATX power supply, I went looking for triple-output power adapters (5 VDC, 12 VDC, -12 VDC). I finally found something that works, an ELPAC WM113TT AC-DC power adapter along with a new female DIN 5 connector.
21-Jul-2025: update to the update below, may have found an original power adapter on eBay
There were a few power supply ideas on eBay, the first I found was the Mean Well RT-65B for about $21-$27. This would have worked, but it’s only in a metal cage with exposed contacts so I’d need to get a case for it. It’s also well over powered on the 5 and 12 volt outputs at 5 A and 2.8 A, respectively.
Then I started searching around on Digikey under “AC DC Desktop Wall Power Adapters”, and found matches under output “5 VDC, 12 VDC, -12 VDC” with DIN 5 connectors. Maybe I’d get lucky and USR used an COTS product. Here’s where I found the WM113 series of power adapters from Inventus Power. They were all marked as obsolete, but figured they’d show up on eBay if they were. The DIN plug was the wrong gender, but I was ready to chop it off and solder on a new DIN connector if that’s what it took.
I ran across somebody selling ELPAC WM113TT power adapters for $15-$20, still had the triple output and a DIN 5 connector. I found a datasheet for the WM113 or the WM113TT with the DIN output pinout, what I was looking at had exactly the same voltages on the pins I needed (or so I remember) and thought this was almost perfect if there was a way to swap genders.
DIN 5 female-female coupler, wound up not using
On Amazon I found a DIN 5 female-female coupler, and thought this would be perfect if the power supply had the right pinout. I got these before I got the power supply, cut off part of the plastic and found it fit into the back of the Courier HST just fine.
However when I finally got the Elpac WM113TT, it did not work as I expected when I plugged it in.
Elpac WM113TT pinout
The pinout I had was completely different than the datasheet I had saw, so I had to put on a new DIN connector. Above on the right shows what I used on the new DIN female connector.
Completed power setup
Hooked it all up and it worked perfectly! The WM113TT is basically a literal brick of a power supply. For only providing < 1 A on each of the outputs, the thing is nearly 5″ long and weighs a couple of pounds. At least the input and output cables are long so it can be placed out of the way.
21-Jul-2025: I think this eBay auction (archive.org) is likely the original AC adapter for this particular HST. The photos are a goldmine, it has the pinout and voltages written right there on the back of the unit! It’s a US Robotics branded “Multi Products Intl'” model WA512750/27, female DIN-5 connector, input voltage of 120 V, output voltages of +5 VDC at 750mA, +12 VDC at 200 mA, -12 VDC at 200mA. This is the same pinout I came up with (sans common), nice to see it verified. At $90 that’s a very expensive power adapter, but there it is. There’s a “1889” stamped into the black plastic case, I’m wondering if this is a 18th week / 1989 date code which would line up when the HST came out.
