Summary of A PDP 11 BY ANY OTHER NAME: HEATHKIT H11 TEARDOWN AND REPAIR
Lee Adamson explores a Heathkit H11A, an LSI-11 based on the DEC PDP-11 architecture. The article details a teardown revealing cards on a DEC QBus backplane and highlights the machine's extensive software library. A key repair involved fixing a power supply where a diode was improperly attached, ensuring the system could start up successfully despite its vintage nature.
Parts used in the Heathkit H11A:
- Heathkit H11A
- DEC QBus
- CPU board from DEC
- Heathkit assembled boards
- Power supply
- Diode
[Lee Adamson] is no stranger to classic computers. He recently picked up a Heathkit H11A which, as you might remember, is actually a PDP-11 from DEC. Well, technically, it is an LSI-11 but still. Like a proper LSI-11, the computer uses the DEC QBus. Unlike a lot of computers of its day, the H11 didn’t have a lot of switches and lights, but it did have an amazing software library for its day.
[Lee] takes us through a tour of all the different cards inside the thing. It is amazing when you think of today’s laptop motherboards that pack way more into a much smaller space. He also had to fix the power supply.
We are looking forward to seeing more videos on this computer. We miss the days that your computer broke down into multiple boards plugged into a backplane. Even though the computer is a Heathkit, the CPU board came from DEC assembled. However, Heathkit had its own boards that you did build along with things like power supplies.
The power supply needed some care, as you might expect. A diode wasn’t attached properly but it wasn’t clear if it had been damaged in transit or if it had never been installed correctly. Replacing it put the power supply right and now he’s ready to see if the thing will start up.
There are plenty of ways to emulate a PDP-11 on things like Arduinos. If you want to see what assembly language looked like on this machine, there’s a tutorial.
Source: A PDP 11 BY ANY OTHER NAME: HEATHKIT H11 TEARDOWN AND REPAIR
- What is the Heathkit H11A?
It is an LSI-11 computer based on the DEC PDP-11 architecture. - Does the H11 use a standard bus?
Yes, it uses the DEC QBus like a proper LSI-11. - How many switches and lights did the H11 have?
Unlike many computers of its day, it did not have a lot of switches and lights. - Who assembled the CPU board?
The CPU board came from DEC assembled, while Heathkit provided other boards. - What issue was found with the power supply?
A diode was not attached properly, though it was unclear if it was damaged or never installed correctly. - How was the power supply fixed?
Replacing the diode put the power supply right so the computer could start up. - Can you emulate a PDP-11 on modern hardware?
Yes, there are plenty of ways to emulate a PDP-11 on things like Arduinos. - Where can I see what assembly language looked like on this machine?
There is a tutorial available that shows what assembly language looked like on this machine.
