Exidy Sorcerer II schematics?

[Pete Turnbull]

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
ROM Section
I/O and UART
Interfaces
Cassette Interface
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 
LS74.

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 
48K fitted.

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
						Network Manager
						University of York