DEC PDT-11/150 – Part 6. Looking at the disk drives.

I am now at the point where the disk controller is passing the RAM test but is hitting another fatal error. The Manual says there is a problem seeking to track 0 and I should replace the defective drive.

That’s more than a little harsh and frankly isn’t an option.

Take a look inside.

When I unscrew the rear cover on the bottom disk drive I am greeted with this image..

It seems unlikely that someone packed a spare drive belt 😉

There is nothing so obvious looking in to the top drive but on removing the drive I get a similar story.

This is the top drive bay with the drive removed.

You can clearly see that both drive belts have fallen off their respective pulleys.

So what has happened is that the belt have lost their condition over the thirty or so years that they’ve been on the drives and just don’t grip any more.

What to do next?

As you can imagine, new belts from DEC are not an option, so I need to improvise a little.

Snipping through one of the belts and measuring gives a length of 588mm and so a diameter of 558/pi which equals 188mm.

Record deck belts are available around that diameter and I have one on order but the suggestions on-line say they aren’t a good option as they tend to be stretchy.

I have also found a flat industrial belt at 590mm length and so I’ve ordered a couple of those.

I’ll let you know how I got on.



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