Peter, does your Hand Controller (HC) display come up on boot?
Is the LED (below the menu) active?
Does the menu button work?
Did you try the "REV" buttons?
Have you just replaced the EPROM? I read somewhere that someone did this and they had to put to slew mode back to visual via RS232 for the system to restore...don't know why.
Is your cable to the HC ok?
You mentioned RS232. Gemini1's are particular about what or how much +5V is drawn from the system (PCB) and plugging in/out RS232, Auto-guider ports can shut-down the HC. Maybe remove them (all other devices) and try a re-boot. My Gemini BT was originally designed to use Gemini +5V but I found that sometimes plugging it in/out would cause the hand controller to go blank....aka a +5V line shut down.
Sorry lots of questions and you have probably already tried most...
Originally Posted by Marke
Does it have an internal battery ? if so could need replacing
..Nah..if backup batt dead you just get SRAM re-set on boot. The system will run with a dead Backup batt but lose settings and time when shut down.
Possibly a bad PTC Fuse F2...though more than likely a HC issue.
A correction to the above and edit:
Gemini +5 volt regulator (U19) actually produces +5.4V and goes to 3 places. Two of these are thru Diodes D10 & D11 which drop this voltage to ~+5V and run the system ...aka CPU ect.
The +5.4V goes to the HC (pretty much by itself I think) and this feeds the HC thru J1 (DB15) +5.4V DC which powers the LED (I spoke above about, the HC LED) and display etc. The HC also gets +5V (from Gemini fuse F2) feed to it thru pin 1 of J1.
All this tells me if the LED (and probably display) are dead then you have lost +5.4V. If you have the display ok and the buttons do not work you have lost +5V via F2.
So try do the fault finding I mentioned with all points!.....and get back and I can make a rabid wayward assumption with no basis at all