The Philips P2000C is a luggable CP/M machine from 1982/3 and comes from the generic P2000 range of machines which in typical Philips style aren't compatible with each other - see further down this timeline for the P2000T I got last year. It weighs 15kg and is lugged around using the industrial-like strap which handily clips into the metal frame of the case and also holds the keyboard in place. No danger of THAT becoming brittle with age!

Everyone who writes about these machines simply says they're 'twin Z80' but that's a much simplified overview. Every other luggable of the day simply had a direct video feed to the built-in CRT, but the P2000C was different. Instead of a video feed it had an actual terminal inside the case which was fed data via an RS232 feed from the main board. This terminal had its own Z80/RAM/ROM/serial as well as an external video feed (that comes in handy later).

The main board has a 4Mhz Z80 and 64K RAM which I was happy to see WASN'T made up of 4116 DRAMs which meant there was an excellent chance the machine would just work. There was also a 120 pin slot between the PSU and CRT module which could contain a card called 'CoPower' which had an 8088 and 512K of RAM to allow the P2000C to run MS-DOS 2.11. Much like the CPT8520 I have that will run CP/M, there's a 'helper' disk that you boot first, then swap to the MS-DOS disk and boot that. While not in DOS mode the extra RAM is available for CP/M to use as a RAM disk. Handy.

Tim, the previous owner, said he heard a pop when he turned it on so he quickly turned it off again. No smoke, so I've no idea what that pop was.

First job - dismantle! This was an easy job. Some screws and gentle persuasion got the all-encompassing case off, then 4 screws to undo the front panel, 6 more screws to undo the strengthening bar running the entire width of the machine, then 2 more to get the PSU out. There's no branding on it but the layout is classic ASTEC and sure enough, one smokebomb had been removed with some force and the other 0.01uF smaller RIFA was still there ready to burst. New filter caps were fitted after cleaning the up the spooge from the exploded one.

No reason not to just go for a power up so I did. Floppy activity told me the machine was booting but the CRT remained dark. Checked for voltages and the 12V for the screen was present so the issue was elsewhere. Thankfully Philips provide you with schematics for everything EXCEPT the Mitsubishi NT-1200XU CRT module (why not a Philips one?) so if there was an issue with the controller board I was a bit hosed.

Tracing the wiring I could see that everything depended on the 12V and video feeds so I grabbed the user manual which had the pinouts of the external video socket, put the scope on the composite video/horizontal/vertical sync pins and could see a proper video feed. I could also see the h&v sync at the internal monitor, but no video. Hm. I quickly made up a cable and hooked up a little composite CRT to the external socket and got a screen of a happily booted machine so that was a relief!

Why no video at the internal CRT though? Looking at the schematics there are two signals called OUT0 and OUT1 which define the two video feeds - one internal (OUT0) and the external OUT1. These are pushed through a 74LS399 multiplexer with a clock signal to generate VID0 (internal) and VID1. These are then fed through a pair of 7407 hex buffer/driver/level shifters and resistors then head off to their respective destinations. With a scope I could see all signals were present and correct, so the fault was in the path to the internal CRT.

Following the wiring looms it was obvious that the only component in the way was the brightness control. This is a simple variable potentiometer which contains a resistance (470 ohms in this case) and a wiper which runs around the resistor rail creating a variable output. I pulled it out and tested it - it has 3 pins. Top to bottom (or 1 and 3) should show the value of the resistor and I could see 430 ohms. Close enough. Measuring top to middle (or 1 to 2) should show a reading that varies as the pot is turned. I got nothing.

Dismantled the pot and as you can see from the pic there's no wiper - it's broken off. The weird thing is I couldn't find it in the case so who knows where that went. Since the voltage passing through is the video feed I just bridged top and bottom with a piece of wire and the CRT came to life 😁 Found a replacement part for £4 on ebay.

So! Out of all of that the only things that needed to be swapped were the mains filter caps in the PSU and a potentiometer. Happy machine!

Cheers to Pete for the heads up on this auction!