I’ve decided to sell of a few PDP-8’s as the hoard is getting rather large at the moment and so I’m prepared to part with the following:

• PDP-8/M, 8KW core, M8655 serial UART, very clean machine in working order
• PDP-8/E, 4KW core, M8650 UART, requires a full rebuild
• PDP-8/A, 16KW core, extended memory, serial, paper tape drive and controller (non DEC). Very clean and in working order
• RX8E + RX01 drives
• PC8E + PC04 paper tape
• DECmate III
• WP78 (aka a VT78)

Email offers to toby@pdp11.co.uk . Machines are located in UK

This table details locations of cards on a PDP-8/L backplane. I’ve put it together to aid in working out what is missing from my 8/L. I believe it to be accurate but you are encouraged to double check!

Optional data break interface
Optional memory parity
Optional power fail
Optional high speed reader and/or punch

The following documentation is available as PDFs for the PDP-8/E (source Bitsavers)

	DEC-8E-HMM3A-C-D_MaintVol3.pdf	04-Jul-2002 02:11	26M	-
	DEC-8E-HR1C-D_8eMaint_Feb73.pdf	14-Oct-2003 23:39	13M	-
	DEC-8E-OCASA-B-D_CAPS8_UG.pdf	03-Jul-2003 01:14	9.6M	-
	PDP-8E_ECO_LOG_Dec74.pdf	31-Dec-2008 21:36	41M	-
	PDP-8E_IPB_Feb74.pdf	21-Nov-2007 19:01	826K	Illustrated parts breakdown
	PDP8E_MaintCourseHandouts.pdf	-

Here are a collection of You Tube videos featuring PDP-8s playing music:

A rather nice new arrival for my collection is a PDP-8/E. The machine is in 3 H960 racks and has a pair of RK05 drives and a pair of Magtape drives (with pertec interfaces).  The 8/E has an expansion box giving a total of 40 slots. The machine has 12KWof memory, 3 x serial ports and a posibus interface. Alas there were no disk packs with the RK05s although I do have one 16 sector pack (unique to PDP-8s)

The machine was owned by a local company who had it in the basement of their country house and they were the owners from new. Removal required us to get the machine up a very steep and narrow staircase and so we had to dismantle the machine considerably in order to get it out. Careful notes and pictures were taken to aid in reassembly.

The machine is going to get pride of place in my office alongside my PDP-11/70 and PDP-8/Ms.

My second PDP-8/M is just about back in the land of the living. I followed largely the same process as with the restoration of my first 8/M. Luckily this examples case wasn’t corroded and so I didn’t bother respraying and left it in original condition.

The main sticking point with getting this machine back was a failed +5V and +15V rail on the PSU. Being no expert on PSUs and having been mildly ‘warning’ zapped by it when I decided to see if anything obvious was failed, I had a hunt for a company to perform the repair.

I opted for Electronic Repair Centre Limited after some internet searches. I was very impressed with their service, which was fast and very well priced. I thoroughly recommend them to anyone looking to get a power supply repaired.

After getting the PSU back, I reassembled the machine and with a bit of CPU board swapping (3 of the originals turned out to be failed), I now have a mostly working machine. The one gotcha I currently have is that on entering the DEC accumulator counting test, the accumulator counts at full bore and cannot be seen neatly increasing on the console. My suspicion is that the line time clock might be the cause of this.

The investigation continues…

[Show as slideshow]

Here are a list of my spare OMNIBUS cards:

G104 MM8E 4K Memory sense/inhibit
G227 MM8E Memory X/Y drivers
H212 MM8EJ 8K Memory stack
M837 KM8E Extended Memory and Time Share Control
M8300 KK8E Major registers (x4)
M8310 KK8E Major register control (x4)
M8319 KL8A PDP-8/A 4 channel serial I/O
M8320 KK8E Bus loads (x6)
M8321 TM8E Magtape output control module
M8322 TM8E Magtape control and data break module
M8323 TM8E Magtape transport status and control module
M8327 TM8E Magtape register module
M8330 KK8E Timing board (x6)
M8335 VT8E
M8336 VT8E Video Display Clock and Frequency Divider
M8337 VT8E Video Display Line Buffer Module
M8340 KE8E Extended arithmetic element
M8341 KE8E Extended arithmetic element
M8342 LP8E Centronics printer control (replaces M8329) (x2)
M8357 RX8E RX01/RX02 interface
M840 PC8E High speed paper tape reader/punch (x2)
M8416 KT8AA PDP8A Memory Management (hex wide)
M8417 MSC8DJ PDP8A 128K MOS Memory (hex wide)
M842 XY8E X/Y Plotter Control (x2)
M8433 RL8A Disk controller for RL01/02 (hex wide)
M847 MI8EP Hardware Bootstrap Loader for RX01/RX02
M848 KP8E Power fail and auto-restart (x3)
M849 KK8E RFI shield (x4)
M860 DK8EP Programmable Real Time Clock
M865 . Console Teletype Control (current loop only)
M8653 KL8M Modem Control, used with KL8* to provide data ready stuff
M8655 KL8JA Terminal Control (UART based substitute for M8650) (x3)
M868 TD8E DECtape Control (x2)
M880 MR8E H241 daughter board. Labelled MAINDEC-08-DHMRA-A
M935 OMNIBUS bridge (joins two adjacent backplane segments) (x4)