Replacement GS PowerSupply – Complete :-)

October 22, 2009

Well today I completed my first electronics project :). I initially was going to just mount the regulator to the case, but someone at work suggested i use a bit of strip board as well as use relevant connector (floppy type in this case). All works. Apart from the 240Volts I got yesterday lol, it was a pretty successful little project. Photos below.

After old power supply was stripped out

New Power supply mounted including Regulator
Used existing mount point to provide a secure fixing then plastic mounts for the rest.

Used existing mounting point to mount the strip board with L7905CV regulator

Circuit diagram for the negative regulator (make sure Capacitor + is to ground)

Circuit Diagram for the MeanWell PT65B PSU

L7905CV -5 Regulator


Meanwell PT-65B

September 17, 2009

The new PSU has turned up. Need to look at getting connectors sorted out….

New Power connectors (KK series in the 3.96mm pitch) have now turned up from RS, just waiting on the Crimps (now here).

  • 6 way locking housing stock no. 173-3105
  • 3 way locking housing stock no. 173-3076
  • Crimp terminals – 22-28 Awg Stock no. 245-4718

More? GS Replacement PSU

September 16, 2009

As you can tell I have just started “blogging” today. The main reason i put this together was to have a place people might be able to get information on projects I am working on and if it helps them then it was worth it. It also gives me a record and something more to do that is Apple IIGS related yippie 🙂

My latest project is to replace the insides of ageing GS PSUs with a modern equivalent. Why you might ask? Well it all goes back to having things original. My main GS happily works with a Mini ATX and external power pack. Its great as all the heat generated by the PSU is not internal to the GS. This is perfect for day to day use…well once a week use :P.

I have a couple of older GS machines (and also my newly acquired ROM03…but it has a 110v psu another reason for this project) that have PSUs that struggle when under load..so i wanted to use them as my guinea pig.

After some posting on the comp.sys.apple2 i was pointed into the direction of a Meanwell PT-65B open frame switching PSU (It has been used to replace a Vulcan PSU with some minor modification to component placement). Though this should fit inside an existing PSU casing it only outputs +5/+12/-12 the -5 is missing and you need to use a negative regulator to produce a -5 for the GS.

The GS connector has :-

  • Pin 7 -5 Volts 0.25 Amps
  • Pin 6 -12 Volts 0.25 Amps
  • Pin 5 +12 Volts 1.0 Amps
  • Pin 4 +5 Volts 4.0 Amps
  • Pin 3 Not Used
  • Pin 2 GND
  • Pin 1 GND

I am hoping to have this completed over the next month or so but suspect there will be some challanges around actual placement and fixing inside the old PSU case etc and also that i will need help from friends who are more clued up around electronics as well as the Apple II community 🙂

Today I ordered my PT-65B and also picked up the following from Maplins

  • Negative L7905CV Regulator to provide -5V from -12v
  • Radial-lead style tantalum Capacitor 35v 2.2uF to be used with the Regulator
  • TO220 Insulator and Bush so i can isolate the Regulator from the PSU case which i will attach it too.