Repairing a Radius 16 Accelerator (Plus)

[360alaska]

Hello all,

I just want to share my experience regarding a newly acquired Mac Plus. It was flup-flup-fluping when I bought it and to my surprise it had the Radius 16 accelerator! I uninstalled the Radius 16 and discovered that the Mac worked fine without it. After troubleshooting, I discovered that the +12v was being shorted to ground by the accelerator and after further troubleshooting I discovered that the 150uf capacitor was shorted and the rectifier diode (!N5822) was also shorted. After replacing these components the accelerator is working...See pictures...





View attachment 5320

 

[uniserver]

hey that is a pretty sweet upgrade,  what all does that bad boy give you?

 

[360alaska]

16mhz 68020, this card has an fpu installed...The question mark at boot flashes at double the speed!

 

[miniMOJOman]

nice! the radiusware image is available to download and install the extensions

 

[360alaska]

Yeah, I got the software, but as a downside, this accelerator will only run up to system 7.0. But it's still pretty cool...

 

[CelGen]

What a flimsy power supply. Can't even blow up a shorted tant.

 

[360alaska]

It looks like this card takes 12v from the mac and regulates it's own 5v...

 

[Trash80toHP_Mini]

Actually, the card and drivers should support 7.1 for the SE version, have you tried that with the Plus. version yet? I'm loving that airflow redirecting cooling baffle, is there any chance you could do a scan of it for me?

 

[CharlieFrown]

omg these cards are so rare, lucky you! congrats.

 

[360alaska]

Adding more photos of the accelerator as requested by a forum member:

 

[lucaseverini]

Thank you for the photos.
I think I got it.

Accordingly with page 10 of analog board schematics at http://home.earthlink.net/~gamba2/images/plus_analog.PDF



the yellow wire connects to +12V (pin 10) while the violet one connects to ground (pin 7).

On the 4-pin plug in the accelerator board the order of the wires starting from the outside is violet, yellow, black, red.
Violet and yellow go to the main analog plug of Mac mainboard, red and black go the fan.
Does it makes sense to you?

 

[360alaska]

That’s correct!

 

[Trash80toHP_Mini]

I forgot all about the baffle pic! Never took note the fan installation. If you've still got the goodies out, could you scan the baffle and both sides of the bracket, all with a ruler for scaling?

Looks like a great cooling mod in general for Compact convection affliction correction.

edit: interesting hack to be had there for my Drexel/Plus/MicroMac Performer combo. does the fan blow straight up at the flyback? Do you feel an increased airflow exiting the vent above it?

 

[jlindsay26]

I picked up one of these recently does anyone have access to installation instructions. Specifically trying to figure out where the spring on the video board connect too. Thanks