re: [midatlanticretro] PDP-11/20
- OK/mental note taken.
-------- Original Message --------
> From: "David Gesswein" <djg@...>slightly
> Sent: Monday, May 27, 2013 11:40 AM
> To: email@example.com
> Subject: [midatlanticretro] PDP-11/20
> Posting this so next person who looks at the 11/20 will know its state.
> I did a little testing on it on the last day. I checked the voltages
> on the paddle boards and 5V was slightly less than 4.8 and -15 was
> over -15. I didn't find the right document or section looking at what Icould
> find with my laptop to know what the other voltages on the little powerDeposit
> paddle boards should be.
> The load address switch lit up the address the switches were set to.
> set the data lights to the switches set. Reading the address backreturned
> all zeros. I didn't know what address the core was at. I tried addresszero
> and addresses like 0x8000, 0xf000. Some of the upper addresses strangeconsecutive
> things happened when I read such as the address jumping to non
> addresses or run light coming on. The low addresses didn't do this.wasn't
> Looking in through the side the first couple of cards were being pressed
> by the foam. The foam was stiff but the amount they were pressed in
> that far. The later cards didn't seem to be pressed at all. I didn't seeremoved.
> anything obvious indicating the foam caused the problem but it was
> Yahoo! Groups Links
- --- In firstname.lastname@example.org, David Gesswein <djg@...> wrote:
> Looking in through the side the first couple of cards were being pressedI looked over David's shoulder at the work he reported and got similar impressions. I was concerned that the "foam" - actually more like rubber anti-static matting which is heavier - was so unyielding, that it pushed some of the one-width cards sideways out of position or contact. The two-width and four-width cards can't be pushed "sideways" in that fashion. I believe I suggested removing that material; I saw it was removed in any case.
> by the foam. The foam was stiff but the amount they were pressed in wasn't
> that far. The later cards didn't seem to be pressed at all. I didn't see
> anything obvious indicating the foam caused the problem but it was removed.
The 11/20 is challenging in that the front panel is upside-down relative to the cards. Thus if the 11/20 is mounted for use, the cards hang "under" the backplane. It may be that *soft* foam is needed (not necessarily antistatic) to hold the cards in place. More DEC-11 experienced people can address this.