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Hi folks, First, I wanted to thank each of you for your help, suggestions, and resources. The schematics and manuals were very valuable. Next, I wanted to share my final findings and resulting fix. The underlying issue was a completely faulty photointerrupter. It ended up that both the IR LED...

I scoped both the LED and phototransistor. Both never changed value whether or not a disk was blocking the sensor. Measuring the diode: Red wire: 1.26V, Black wire: ground Measuring the phototransistor: Yellow wire: 5V, White wire: ground The diode's input voltage seems awfully low to run it...

It is a pity, would make things easier but my drive seems like it's an earlier revision since it does not have as much integration as fritzeflink's. Here are pictures of my M4851.

Thanks for the replies, everyone. I just wanted to follow-up that I did some hardware swapping to eliminate the computer, floppy controller, and floppy cable. I pulled the drive from the Leading Edge MP-1673L that the drive came in and inserted it into a Gateway PII system that supports 360K...

Hey folks, I have a Mitsubishi M4851 360K drive that reads disks without any issues, but it refuses to write to any. All of the disks I have tested do have the notch in them to allow the drive to write and are 360k formatted. I managed to find a manual online for the drive and browsed through...

Hey folks, I finally got around to running more tests on my terminal and keyboard. Here are my results. After testing the keyboard extensively, I can rule it out. There are no issues with any of the ICs on the keyboard, the 8048 is fully functional - I even programmed an 8748 with the keyboard...

Yeah, I don't have a lot of membrane keyboard experience except for a handful of 90's keyboards and they usually have a sheet of plastic taped to the back of the trace membrane - making it easy to repair breaks; so I was surprised and concerned with how to repair any extensive breaks since...

Hey folks, I'm glad to see that this subject is getting some attention. Here is my experience as I have also recently acquired one of these terminals from ebay. Opening the keyboard is straightforward but once the assembly is removed from the case, the keyswitches are apparently ultrasonicly...