Webster Spectrum PDP-11/73

  PDP-11

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.

The Spectrum is mounted in a half-height rack that also houses a Cipher tape drive.

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

I haven’t done much with this system so far, other than initial investigations.

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.

The MFM drive is a Priam Model 519 (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.

I haven’t yet tried powering up the tape drive.

On the back panel there are 4 SLU ports (4 x DB25F) as well as 8 x RS232 MUX ports.

Here is the dialog that scrolls past on the system console on power-up:

MFBoot V2.2.6

LSI11/73  FPU 1024Kb  Parity

 Devices -
DY: (Offline)
 Devices -
MS: (Offline)
 Devices -
DU: (Offline)

Testing Memory   - OK



    Bootstrap Menu

    DU:   CSR = 172150   Offline
    DM:   CSR = 177440   Non-Existent
    DL:   CSR = 174400   Non-Existent
    RK:   CSR = 177404   Non-Existent
    DY:   CSR = 177170   Offline
    DX:   CSR = 177170   Non-Existent
    SF:   CSR = 174210   Non-Existent
    SC:   CSR = 177340   Offline
    MS:   CSR = 172522   Offline
    MT:   CSR = 172522   Non-Existent
    B1:   CSR = 171000   Non-Existent
    B3:   CSR = 173000   Online, Max Unit No. = 0
    B4:   CSR = 174000   Non-Existent


Enter Device as Dxn(@Optional CSR)

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.

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.

Photos

Here are some photos of the system:

Next steps

I might try some of the following:

  • Boot from a TU58 emulator
  • Boot from the floppy drive using an RX02 disk
  • Attempt to initialise the MFM hard drive
  • Install a known good MFM hard drive

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