Exidy Sorcerer II schematics?
pete at dunnington.plus.com
Mon Mar 1 15:52:52 CST 2010
On 01/03/2010 20:47, Bill Sudbrink wrote:
> The original Sorcerer manual has a page explicitly devoted to 110/60 to
> 220/50 modifications. Mods are required for both the PS and the video
> circuits. If there is a similar page for the II, that would be really
> useful (as Thomas the Tank Engine says).
The 110V / 220V mod is all you need to take care of the power; the
50/60Hz mods are purely for the video. Actually I (and many others)
found the modification for 50Hz wasn't bad on a Mk.II but rather less
than perfect on a Mk.I, and there are some variations.
The schematics in the Sorcerer 2 Technical Manual are:
Master Timing for Exidy Standard Video
Sorcerer Video Interface 30 lines 64 characters
Sorcerer Central Processing Unit
Sorcerer Dynamic RAM Section
I/O and UART
Sorcerer II Power Schematic
Expansion Chassis Motherboard
The Master Timing is the one you'd want in order to understand the
50/60Hz change. Logically, the Power Schematic would be the one for
110V/220V, but it doesn't actually show the transformer primary.
On a Mark II, the 50/60Hz is set by one section of a DIP switch at
location 11A. Section 1 of that is on for 50HZ and off for 60Hz. When
on, it grounds the /SEL inputs on a pair of LS157 muxes which are part
of the feedback in a set of counters made from a couple of LS161s and an
The other parts of that switch control whether you have 3 rows of DRAM
(on) or 2 (off), 16Kx1 RAMs or 4Kx1, and 2 rows or 1 row.
From the manual:
"For 110V, the power supply transformer primary windings are
connected in parallel; to convert to 220V, disconnect them and
wire in series. Do this by cutting the black-yellow and black-red
wires at the line filter, and soldering them together."
On mine, they're neatly soldered together inside some sleeving.
If you look carefully at the line filter mounted to the left of the
transformer, you'll see that one terminal has a black-green wire going
to the transformer, and that's the one that the black-red wire should
connect to for 110V. The other terminal has a plain black wire, and
that's where the black-yellow wire should connect for 110V.
While you have the lid off, and are looking around thre anyway, check
the big filter cap next to the transformer, and a somewhat smaller
(usually blue) one on the PCB near the regulator heatsinks. These are
two common points of failure on these machines. Another common problem
is the 0.156" Molex connector on the main board, which can get very hot
and start to go high resistance. If it looks brown, clean the contacts
and perhaps replace the shell.
Incidentally, there's a timing problem evident with some DRAMs, and
there's a modification to fix it. The symptom is that a machine with
48K of DRAM only appears to have 32K, or at worst, doesn't boot with all
Another thing to be aware of is the serial port problem -- the original
Sorcerers had a logic mis-design that meant that the RS232 line was held
in the wrong state when idling. There's a software "fix" that doesn't
work nearly as well as the authors claim, but a hardware fix is fairly
easy. You /don't/ need any fix on a Mk.II and trying to make one will
actually stop RS232 working.
Have you got any software for yours? I've got a couple of things as
MP3s, one or two old tapes that I'll investigate "one day", a few binary
files saved to disk (I used to "save" down the RS232 line to a tape
emulator on another machine, and load back the same way), and dumps of
the WP PAC ROMs. I don't have the WP PAC manual; I do have the Dev PAC
manual but haven't been able to find a dump of the ROMs for it (which is
annoying, as I used to write Z80 code using the Dev PAC, decades ago).
Pete Peter Turnbull
University of York
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