Charles Gutman  wrote:
> My 128 is not getting power through the expansion port. No game
> cartridges work, Ramlink won't power up (Just had it fully
> tested and it works perfectly).
> Also the 128 powers and loads and runs perfectly from the
> serial port.

So 5V power is available to all of the other 5VDC outputs on
other ports of the C128?

> I did a reference check and found that the 5vdc output to
> the port are located at pin 2 and pin 3 respectively. Thus,
> would it be considered "safe"  to run jumpers from the User
> port and from the cassette port to pins2and 3 of the expansion
> port to power it up so I can run my carts?

The reference I have for the C64 Expansion Port (AKA User Port),
which I think is the same as the C128's, shows that pin 2 is the
only 5VDC connection. Pin 3 is an active low input for the reset
signal. That means it is held high at 5V, but only so that it can
be shorted out on purpose in order for a device to tell the
computer to reset. It would not work for power because it will
not be designed to supply significant current.

If both pin 2 and pin 3 are not at 5V, this likely means that the
expansion port connector has broken, or the C128 circuit board has
broken near the connector. This has severed some of the connections
between the port and the computer. Power could be connected directly
to pin 2 from the cassette port without risk, however as more than
one pin is known to be damaged, it is likely that there will be
broken connections on data lines as well; to fix these will require
repair of the circuit board or connector inside the computer.

Pin 3 should not be brought high via a wire. It is only commonly used
by reset switches on cartridges and leaving it in its disconnected
state will not affect operation of the user port. Connecting it to
direct 5VDC is not likely to cause damage, but damage is possible
if the input goes to a Standard TTL type chip inside the computer.

If only pin 2 is not at 5VDC, then the failure may be due to a
burnt-out track on the circuit board caused by plugging in a faulty
cartridge, or otherwise shorting out the power at the port. Power
could be restored directly from another of the computer's 5VDC
outputs, however care should be taken that the offending cartridge
or action which caused the failure is not repeated, because this
could cause more severe damage than in the first occourance.

If your diagnosis of a lack of power to pins 2 and 3 is based
solely on the failure of the port to function, rather than actual
voltage measurements, I recommend you perform direct measurements
before taking any action.

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