Re: IIc internal power supply

[dempson@actrix.gen.nz (David Empson)]

ron clarke <user@clarke-ron.karoo.co.uk> wrote:

> Does anyone have the pin out of the internal IIc power supply.

It is called the "internal power converter" in Apple's documentation.

Which pinout?

The external connector (DIN-7) is numbered like this:

         V
      7     1
     6       2
      5     3
         4

Pins 2 and 3 are signal ground.  Pin 4 is shield ground.  Pins 5 and 6
are the power input.  Pins 1 and 7 are not connected.

The motherboard connector for the power converter is rather large: a
44-pin conector, according to the circuit diagram.  It is probably a
ribbon cable header.

All of the odd numbered pins are ground.  The even pins are: GND
(twice), -12V (twice), NC, "FFF", +12FIN (five times), GND (twice), +5V
(four times), +12V (three times), GND (twice).

The "FFF" signal goes to the power switch on the back of the case, which
switches between the input supply rail (after some signal conditioning)
and ground.

I'm not sure what the difference is between "+12V" and "+12FIN".  It
looks like the latter is used to drive an LM311 in the video circuitry,
but I can't see it anywhere else.  Perhaps it is a fine-tuned version of
+12V.

> I now it has 15 volts in. Prussumably it has +12 +5 0 -5 -12 but waht are
> these rated at?

Here are the full specifications from the IIc technical reference.

Input voltage:               +9 to +20 VDC (nominally +15 V)

Maximum power consumption:   25 W

Supply voltages:             +5V   +/- 5%
                             +12V  +/- 10%
                             -12V  +/- 10%

Maximum supply currents:     +5V   1.5 A
                             +12V  0.6 A continuous
                                   0.9 A intermittent
                                   1.5 A surge (for < 100 ms)
                             -12V  100 mA
                            (-5V   50 mA)

Maximum case temperature:    60 C  (140 F)

The converter doesn't actually have a -5V rail.  A limited -5V supply is
derived from the -12V rail using a 7905 regulator on the motherboard.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P O Box 27-103, Wellington, New Zealand