3 Jun
2011
3 Jun
'11
7:26 a.m.
Pete Turnbull wrote:
I got the 4.5A from the microPDP-11 Systems
Maintenance Guide, which
happened to be the nearest to hand when I wrote that. It might not be
correct; it does seem a lot even for such an old drive. I've just
looked hrough some other manuals
I believe that I actually measured the current
at one point. It was initially 2.5 Amp on the
12 volt, then about 1 Amp after that.
Incidentally, that Maintenance Guide is the same
manual which (on page
8-14) tells how to set the drive select jumpers for DU0: and DU1: in a
BA23. Although it also says (on page 5-6) only to install one RD52 in
a BA23 :-)
Whenever I use 2 hard drives on a BA23 for
more than about 1 hour, I always use an additional
PC power supply just for the hard drives.
As for an RD5n or RD3n on an RQDXn, the BA23
circuits fully support 2 hard drives with a 6 button
front panel. In my experience, it is the 12 volt current
that is the problem. Just be sure to use DS3 for
drive 0 and DS4 for drive 1.
However, in
any case, from my point of view,
it is far better to use an additional PC power
supply (for just the hard drives) when there
are two hard drives used in a BA23 box.
This take the load off the internal power supply.
I don't bother doing that, but... And if you
want to use an RX50 and a TK70
as well, then you would almost certainly exceed
the 7 Amp available on the 12 volt internal
power supply. As I mentioned, always use
the internal power supply for the TK50 / TK70.
Whereas I leave the RX50 outside the BA23
box if there is no TK70, with a TK70 I usually
place the RX50 and TK70 inside the BA23
box and the 2 hard drives outside the BA23
box.
...my 11/83 has two RD drives in the BA23 running off the internal
supply, and (when I got it) had an external RX50 which had its own PSU.