On Wednesday, April 27, 2016 at 4:37:21 PM UTC-7, Computer Nerd Kev wrote:
> 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.
> 
> -- 
> __          __
> #_ < |\| |< _#


 Wow! A lot to take in. The serial port works perfectly, so it may very well be
that the cass and User Port may also be damaged as well as the exp. port.
Doubtful it is the power section as the computer works on the I/O port. So the
problem lies in the 
exp, user, and cassette lines someplace probably.

 Thanks to you and to everyone else that is pitching in  to fix this mess.


 Charles

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