PDP-11/10 repair started

Noel Chiappa jnc at mercury.lcs.mit.edu
Sun Oct 4 21:00:39 CDT 2015

    > From: Tony Duell

    > There are at least 2 versions of the 11/10 CPU boards. The later one,
    > which I thought was the 11/10S, has soldered wire links to disable the
    > arbiter ... I think another link disables the built-in console port.
    > And didn't it use a crystal rather than RC clock for the built-in
    > serial console port? 

It would be good to know exactly how many there are! I think there are at
least three, because:

There are two sets of 11/05 (let's not bother with the 05-10 distinction, I
think that's just the artwork on the front panel) prints on-line,


and "1105S_Schem":


Both of them show the exact same board revs:

  M7260 Rev C (drawing: date 1-22-73, rev N)
  M7261 Rec F (drawing: date 9-5-73, rev U)

However, I don't think they show the W1 jumper to disable the onboard serial
line, etc (I spent quite a while looking for it in these prints, after hearing
of its existence :-); and they definitely show an RC circuit, and not a
crystal, as the baud rate generator.

So, the board set with those features (jumper + crystal) must be a later set
than the ones shown in those two on-line sets of prints. (One of which is
marked "11/05S", just to be confusing - I didn't check to see if that rev of
the cards has a jumper to allow another machine to be bus master.)

However, I have a set of hardcopy 11/05 prints, and they show an even earlier

  M7260 Rev B (drawing: date 4-07-72 rev H)
  M7261 Rev C (drawing: date 3-19-72 rev J)

On this rev of the M7260, the UART chip is down near the contact fingers, and
'horizontal', not up near the Berg connector to the console, and 'vertical'.
The M7261 is also quite distinct; there's a big gap on the center left of the
card (full of traces). Just to thicken the plot a bit more, I have an M7261
that looks like that, and it is marked "M7261E" in the etch!

So that's '3 versions' at least of the 11/05:

- The latest (jumpers and crystal)
- The middle (in the on-line prints)
- The early (in the hardcopy prints I have)

I say '3' because it's possible there are only early and late versions of
each card, and the '3 versions' I listed are actually 3 different mixes of
old/new cards.

    > The original and later boards seem to have the same numbers.

Indeed; there's nothing on the handles, etc to indicate that they are
totally different boards (except for that "M7261E" in the etch.

Any chance you can find a print set that shows the later cards, with the
jumpers, crystal, etc?


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