So I dug an old Ultra 30 out that I've had sitting in the loft for about a decade and surprisingly it actually booted up and I got a serial console.
Unsurprisingly the nvram was dead. So I tried the dremel and coin cell fix and thought I'd done an ok job.
However, now when I boot up the serial is garbled as if I've got the wrong settings. I tried the same as I had initially, and tried multiple other baud rates too, but still nothing.
Have I fried something with the nvram upgrade?
One thing I have noticed is the power LED on the front no longer comes on. It was illuminating straight away previously.
(serial is the only option too, no monitor or keyboard available)
This comment worries me. So the behaviour of the system has changed since the dremel job. Can you measure the battery voltage? Is it correct? If not, is there a short-circuit across the battery now?
What serial terminal/serial emulator are you using? Are you using the correct cable? Do you have the service manual?
Using minicom, and serial was working until after the first boot with the modded nvram. Unfortunately I didn't save the output from that boot.
Cell voltage was 3v, and I checked numerous times from various sources to make sure I had the correct polarity for it.
And yeah, I've found all the manuals for it.
It's weird, I boot it up and I get output from the serial, so it's definitely trying to output something to the console. It's just unreadable, as if I have the baud rate wrong, but I've tried every common one from 300 to 115200. Not sure what options it might use for serial settings. I've also tried serial a and b.