Re: Microdigital TK2000-II PSU

[mjmahon@aol.com (Michael J. Mahon)]

Richard Kilpatrick wrote:

>On 3/8/04 12:15 pm, in article BD35324F.8007%delorean@NOSPAMbtconnect.com,
>"Richard Kilpatrick" <delorean@NOSPAMbtconnect.com> wrote:
>
>> Does anyone reading have one of these Brazilian Apple II 'clones'? I've got
>> one, but I'm unsure about the PSU wiring. It lurks in an an Atari 1200XL
>> case and has a similar DIN connector, but opening it up reveals a -12, +12,
>> +12, +5v PSU connection - however only the -12v and +12v (black and blue
>> respectively) are obvious, there are also red and orange wires with a brown
>> for ground. I think that the red will be +5v, and the orange the other
>+12v,
>> but I have no way of knowing this and would rather not blow the computer up
>> right away ;)
>
>Just for more information - tracing the wires and checking with a meter for
>continuity between the solder point marked with a voltage, and the suspected
>wire, has lead me to this conclusion:
>
>DIN plug:
>
>  7   6
>3   8   1
> 5     4
>    2
>1. +5V (orange)
>2. Ground
>3. +12v (red)
>4. -12V (black)
>5. +12V (red, siamesed with 3)
>6. +5V (orange, siamesed with 1)
>7. +12v (blue)
>8. No connection
>Shield - no connection, but present.
>
>Ideally I'd like to be able to double check this before I plug anything in

I'm a bit suspicious of your identifications.  The provision of three +12
lines and only two +5 lines is strange, since the +5 current is usually
higher than the +12.  And there is no -12v!  Real Apples need -12, and
if a negative supply is omitted, it is usually -5, since it can be easily
produced by regulating down from -12.

I suspect that pin 7 is actually -12v, but this should be carefully circuit-
traced.  Perhaps there is a short between +12 and -12...?

Another possibility is that pin 7 is a "sense" wire, used to provide
feedback to the external power supply for better regulation--but I doubt
it.

A good way to proceed is to check continuity from the peripheral slot
connector(s) to the power wires.  All the voltages are present on the
slot connector.

-michael

Check out parallel computing for 8-bit Apples on my
Home page:  http://members.aol.com/MJMahon/