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Published Tuesday, May 8, 2012 at 7:10 PM

PDP-11/35 Restoration, Part 4: The System Modules Come Out

Big day today, restoration wise. I extended the 11/35 out on its rails until they locked, and flipped it up so I could get access to the underside. Like the top cover, the bottom cover of the 11/35 is missing - I assume ATARI got rid of it years before they scrapped the system. But the system modules (as the backplanes are called) seem to be relatively unscathed. The pins show signs of oxidation, but no severe corrosion. Electrical connections are probably OK, but I'll need to verify by tracing, once I've washed out the backplane slots thoroughly. Not tonight, however. For now, all I've done is remove the system modules and set them aside for future cleaning and testing.

Figure 1: All three system modules. From left to right: DD11-A, MM11-S, and KD11-A.
Figure 2: Closeup of the DD11-A. So much wire wrap!

The other task was to completely disassemble and remove the front panel, starting with the metal (aluminum?) bezel, then the plastic overlay, then the KY11 board. The switches are in excellent shape, both mechanically and cosmetically, and the KY11 PCB looks OK. I have high hopes that this machine may yet ride again.

Figure 3: KY11 Front Panel without face
Figure 4: KY11, removed from the chassis

I also took my first peek inside the power supply. It's spotty with oxidation here and there, but otherwise looks in very good shape. I will pull it out just as soon as I figure out how, so I can inspect it and test it on the bench. Time to buy a Variac!