It was 1989 when Applied Engineering first made their Vulcan hard drive solution for the Apple IIGS, Apple //e and Apple II Plus computers. Now, 31 years on you can have that impossible to find circuit diagram and PCB overlay you’ve been waiting for to repair your aging power supply…
by Mark Cummings
This project came about as I had a need to repair a Vulcan power supply that I got many years ago. At the time I wasn’t able to trace the fault because it kept blowing fuses immediately. I had done a partial circuit diagram and replaced a few parts previously but didn’t have the time to fully trace it out due to time constraints so I retired it to the shelf. (More on that in a separate article.)
Vulcan IIGS 40MB Hard Drive with
integrated power supply and fan
Recently with more time up my sleeve, and with assistance from a fellow Australian Apple II Mail list member, Craig Bradley, who graciously sent me his prized Vulcan collection I decided to get a usable circuit diagram done even if I wasn’t able to repair my own drive. Using Craig’s Vulcan drives and my own, I was also able to compile a list of variants for inclusion in the diagrams. As it turns out there was two different PCBs layouts between the three I had available and they were different enough that I decided to create two PCB overlays, a single circuit diagram and single parts list.
Circuit Diagram created with Protel Schematic application
DC voltages reaching 330V is reached on the main filter capacitors.
I really enjoyed reverse engineering this power supply as I knew it could help me trace the fault in my own Vulcan power supply, and hopefully I would be the first to make it available for others too. Maybe it’s not too late for those who have held onto their broken Vulcan PSUs in the hope that one day…
In the famous words of Mr. Spock...
‘Live Long and Prosper…’
MC
Several parts were hidden under the main SMPS transformer and were impossible to access. Removing the transformer was necessary to meter out its internal windings as well as reveal all the hidden parts. Desoldering all 21 pins (including extra windings protruding from the top of the transformer) was like extracting a sharks teeth.
Top View inside a VULCAN Hard Drive for an Apple IIGS.
Note how tightly packed the parts are compared to other Apple II power supplies.
A VULCAN //e PCB showing high density of parts.
Note how some parts are hidden from view
A VULCAN IIGS PCB with transformer and other parts removed for access
PCB Overlays for the earlier model #4289 PCB, created with Protel Autotrax
PCB Overlays for later models #4589 and #8950 PCBs
Parts List with additional information
