{"id":3632,"date":"2019-10-06T09:55:27","date_gmt":"2019-10-06T09:55:27","guid":{"rendered":"http:\/\/avitech.com.au\/?p=3632"},"modified":"2019-10-06T20:37:57","modified_gmt":"2019-10-06T20:37:57","slug":"webster-spectrum-pdp-11-73","status":"publish","type":"post","link":"https:\/\/avitech.com.au\/?p=3632","title":{"rendered":"Webster Spectrum PDP-11\/73"},"content":{"rendered":"

\"\"<\/a>This is a PDP-11\/73 in a Webster Spectrum enclosure. The 11\/73 board (M8192) appears to be the only genuine DEC board in the backplane.<\/p>\n

The Spectrum is mounted in a half-height rack that also houses a Cipher tape drive.<\/p>\n

The Cipher tape drive is a Model F880640-90-1025U, with Option E and 1600 BPI (according to the nameplate).<\/p>\n

I haven’t done much with this system so far, other than initial investigations.<\/p>\n

The system comes up with a boot menu and attempts to read from the floppy drive. I haven’t tried putting a floppy disk in it yet. <\/p>\n

The MFM drive is a Priam Model 519<\/a> (1224 cylinders, 15 heads, 17 sectors\/track, 160MB) spins up, but the boot software doesn’t seem to be able to boot from that drive.<\/p>\n

I haven’t yet tried powering up the tape drive.<\/p>\n

On the back panel there are 4 SLU ports (4 x DB25F) as well as 8 x RS232 MUX ports.<\/p>\n

Here is the dialog that scrolls past on the system console on power-up:<\/p>\n

\r\nMFBoot V2.2.6\r\n\r\nLSI11\/73  FPU 1024Kb  Parity\r\n\r\n Devices -\r\nDY: (Offline)\r\n Devices -\r\nMS: (Offline)\r\n Devices -\r\nDU: (Offline)\r\n\r\nTesting Memory   - OK\r\n\r\n\r\n\r\n    Bootstrap Menu\r\n\r\n    DU:   CSR = 172150   Offline\r\n    DM:   CSR = 177440   Non-Existent\r\n    DL:   CSR = 174400   Non-Existent\r\n    RK:   CSR = 177404   Non-Existent\r\n    DY:   CSR = 177170   Offline\r\n    DX:   CSR = 177170   Non-Existent\r\n    SF:   CSR = 174210   Non-Existent\r\n    SC:   CSR = 177340   Offline\r\n    MS:   CSR = 172522   Offline\r\n    MT:   CSR = 172522   Non-Existent\r\n    B1:   CSR = 171000   Non-Existent\r\n    B3:   CSR = 173000   Online, Max Unit No. = 0\r\n    B4:   CSR = 174000   Non-Existent\r\n\r\n\r\nEnter Device as Dxn(@Optional CSR)\r\n<\/pre>\n
I have tried entering “DU0” at the prompt, but it does not boot the MFM hard drive.  It gives the error message “Bank logic bad, ECO131?”.  It doesn’t respond to any keypress beyond that prompt.<\/p>\n
After being powered up for about 10 minutes, there was the familiar popping noise followed by a significant stream of blue smoke being ejected from the front of the chassis.  The computer still powers up fine though, so it was very likely the usual X1 RIFA capacitors that let go.<\/p>\n
Photos<\/h4>\n
Here are some photos of the system:<\/p>\n