Welcome aboard.

These are the random jottings of Andy Collins, a Fifty-something bloke who still thinks a blog or website is a good idea.

Here you will find small nuggets of information about Hovercraft, retro-computing and other stuff that amuses me or appeals to my sense of wonder.

Recent posts

In the last post about the Nascom-1 I showed a photo of the screen whilst it was running some test software. At first glance it looks good (don’t be put off by the fact that the top line is very different to the bottom, that’s due to the way the screen is mapped). If you … Continue reading Nascom-1. Back on the workbench – Part 2.

It’s been a long time since I tried to fix my Nascom-1. In fact is was my Retrochallenge project for October last year. A little while ago I got the offer of some help with this underrated (outside the UK) marvel and with the PDT-11/150 awaiting new drive belts and a new floppy disk, I … Continue reading Nascom-1. Back on the workbench – Part 1.

So the belts I fitted in the previous post got the drives spinning but the only floppy disk I had wouldn’t read. The retro computing community is a wonderful thing and a quick post in the vcfed forums got me two offers of help from members keen to try and get the old thing up … Continue reading DEC PDT-11/150 – Part 8. Try new media.

I ordered a pair of 590mm belts from http://www.beltingonline.com/ and  they arrived very quickly. The original belts were 588mm so 590mm should be fine. However, they are too small and don’t fit. How can a belt that is 2mm bigger than the original be too small? The answer is in the detail or more specifically … Continue reading DEC PDT-11/150 – Part 7. The disk drive belts.

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

In the last post I had found a faulty RAM chip on the disk controller board and ordered a replacement from a supplier on ebay. Well, the part arrived Today and one fitting, the error lights on the disk controller went out… For a while. I can confidently say that we are past the RAM … Continue reading DEC PDT-11/150 – Part 5. The new disk controller RAM arrived.

I have been running some tests and learning a lot about this little machine and its ways. It has two layers of self-test. The first is a mandatory Power On Self Test (POST). The second layer is an optional interactive test made available by setting switch 4 on the main DIP switch block and activated … Continue reading DEC PDT-11/150 – Part 4. Self tests and the drive controller

I was preparing to share with you all my efforts driving the ODT with PDP11GUI. I have been using it to assemble Marco-11 assembler code and squirt it across to the PDT’s ODT. The problem is that when I came to fire up the machine to do a bit more and maybe take some screenshots … Continue reading DEC PDT-11/150 – Part 3. Healing hands.

In the last post I described the PDT-11/150 a little bit and the state of play. It was showing signs of life but not talking to me. It turns out the cable wasn’t right. Switch to a new cable, fire up GtkTerm and we’re on the right lines. What we have here is the ODT … Continue reading DEC PDT-11/150 – Part 2.

DEC PDT-11/150

22nd May 2018

This is an unusual one. The PDT-11/150 is one of a series of “smart terminals” based on the PDP-11/03’s LSI-11 chip set and so is basically a little PDP-11 atop a pair of massive 8″ disk drives. It came to me from a friend who presides over a massive collection but is still, like the … Continue reading DEC PDT-11/150

A short step from where you are.