The mosfet is likely P-channel that needs the gate driving negative in respect of the source voltage to activate, so it's 'OFF' state is with the gate at the same potential as the source with a pullup resistor - it's probably driven from a tiny NPN bipolar transistor to pull the gate to ground via a 10k resistor or so. I wouldn't worry about that so much (it'll probably be activated by the FPGA once all the other preliminary startup tests complete)...
As for the shutdown I don't know if that is expected behaviour or not, but I think it could be worth a second try, I've certainly tested things without other stuff attached on the UJF - typically results in other errors though, not a shutdown.
Stupid question, is there a separate power switch at the front like on the UJF that needs to be on - I've had the UJF come on with main power, only to shut down a short time later because the front power switch was in the off position (it's a 'soft' power control)..
I have not been able to find another switch on the front. That said, on the keypad, there is a "Enter" button that lights up in blue when the machine is turned on. That continued to be blue after the power seemed to shut down and screen turned off.
(And I think it is Pchannel based on part number)
Have you ever had PCB's need replacement? One of the things that continues to worry me, is do PCB's tend to just fail sometimes and simply need to be replaced without there being an external cause. I would love to hook up everything and power it up but concerned if a component external to the PCB on one of the connectors may be shorted, etc. and cause a repeat board failure. It does appear that my station 4 PCB certainly had some issue based on the new one at least powering up. Just trying to think if there are other preventive steps I can take before trying again just incase. The boards being hefty priced and long lead times being the reason.
2 additional questions:
- During the boot up, does the machine go thru any steps such as trying to move carriage, pump inks, circulation pumps, etc. ? If it does do some kind of startup routine, then trying to think which items I can try to manually check first to make sure they don't have shorts, or spin freely, etc. This machine had been sitting unused for many months before it they powered up to sell and I was told thats when this error occurred. Not being the original owner, I have limited knowledge of its history. Wondering if the lines, valves, pumps, heads etc. could be clogged, and if the machine tries to run those during startup if that could have caused a failure to the PCB / PCB's
- And is there a way to save/ store the parameters from the machine main board when I can't fully boot up? Just incase I mess up something and need to replace the mainboard I would need to restore parameters.
Thank you again!
