Notices by root42 (root42@chaos.social), page 3

I got a hint that the 74LS74 flip flop divides the clock twice. First to 2MHz then to 1Mhz. But both outputs look misshapen and measure at 4MHz.

Out with the old, in with the new.

Oh wow. Suddenly we have 2Mhz and 1MHz signals!

We have life! The machine boots!

Next step is now to reactivate the power supply. I removed the mains filter and rewired all the connections using fresh solder and WAGO clips. I also cleaned the power cord. Afterwards I tested that GND is connected to all metal parts of the case, N and L have good continuity and low resistance and that the power switch works and properly opens and closes. I think this should be safe to turn on!

The voltage without load looks good. I think it's safe to reinstall the mainboard and power it up. If it comes online, we can attach the drive mechanisms and cross our fingers! How are your bets?

The board is in, and first power on test is successful.

Drive unit 0 is attached and motor is spinning when closing the latch.

Sadly, we still have issues. The HEADER command does nothing at all. Drive doesn't even go into error mode. No spinning and no head movement. Error channel lists error 10, no error string. That error isn't document in the manual...

The DIRECTORY command does move the heads and spins the disk, but ends in an error LED lighting up. Error status in BASIC is still 10 / empty.

Well, if you plug the IEEE-488 plug all the way in, things suddenly start to work! @8bitgames 's Hibernated works, and PETSCII Robots, too!
I think this was a resounding success! From literal trash to treasure. I still have to do something about the rust on the top cover, as well as perhaps replacing the regulators with @elosha's low noise switching regulators, to protect the mainboard from future overvoltage events, and make it run much cooler. But at the start I never thought to get this far!

Drive 1 has some startup issues. Drive 0 seems fine though. I think either the motor or one of the bearings is still gummed up. After a few tries it starts working just fine. I mean, come one! If you spent the last thirty years in a damp basement you would need a couple of minutes to get up to speed right?
I can HEAR how it is turning too slow!

After lubricating drive 1 and adjusting its speed using the potentiometer on the analog board, it is running reasonably well.
Next up: replacing the voltage regulators with ultra low noise switching ones. The old ones are fine but the cases have a bit of corrosion and they produce much more heat than the new ones. The new regulators also have protection should something go haywire.

Removing the regulators requires careful drilling of the rivets. Cost saving at its best.

One of the 7812s took a pad with it. However on the top side it’s merely structural. The pad on the bottom side is still there.

With the heatsink removed we can see that the top pads are not connected.

The M4 screws look like they are a bit large, but I think they will do nicely to hold the regulators in place.

But I won't give up quite yet. If the motors work, and if the head is good (it measures fine), maybe we can restore this thing and/or use the mechanism on the other drive. This will require partial disassembly of the mechanism and lots of scrubbing, oiling and lubrication.

Oh yeah: If anyone in my bubble has either a Micropolis or MPI 100 track per inch mechanism in good condition: feel free to contact me!

And there we go again! Laary 3 is on. Never played this one either! From the get go it already seems a bit more polished and seems to have more of a musical score, which is nice

#retrogaming #commodore #amiga #sierraonline #larrylaffer