Exidy Sorcerer II with S-100 Expansion Unit

[DutchAcorn]

Just had to get this: an Exidy Sorcerer II with some nice expansions:

An S-100 expansion unit:

Vista S-100 floppy interface and two 48TPI full-hight single sided floppy drives:

A hacked-up EPROM cassette, converted to a RAM and IO module

And a Basic Pac.

Status:
- The Sorcerer itself works and the RAM module seems to work (it reports a higher top when inserted).
- One of the drives works.
- The Basic Pac has two dead roms (of the four).
- The S-100 unit: I don't know yet if that works.
- The other floppy unit I suspected that the PSU was faulty so I attached a known good PSU. Resulting in a smoking PCB One or two 74 chips seem fried.

About the floppy drive: I am looking for the address to call from the monitor to access the drive. I'm sure I saw it somewhere but I can't find it now...

I'll update the thread if I can report progress...

Thanks!

[DutchAcorn]

...About the floppy drive: I am looking for the address to call from the monitor to access the drive. I'm sure I saw it somewhere but I can't find it now...

Found it: its D900. So the disk system is fired up by issuing the command "GO D900" from the monitor. The few disks I tried so far worked. It is fun to see Pirate Adventure run on the Sorcerer:

DIL 14 sockets and a 74LS20 + 74LS74 are on order to see if those bring back life to the disk drive...

[DutchAcorn]

The disc drive is not playing along yet.

I am also having trouble getting the Basic Pac to work. Two of the original roms are faulty. I have tried to replace them with 2716 EPROMs I got from ebay:

2716.jpg (17.93 KiB) Viewed 3220 times

They program and verify fine, but if I try them in the basic pac I get corrupted values:

The pinout of the EPROM and the original masked ROM is not identical:

So I bend out pins 21 and 20 and connected 21 to 24 (VCC) and 20 to 18 (chip select). If I read the data sheet correctly that should get it in the correct read mode:

But to no avail. The access speed, according to the data sheets, is 350ns for both the original and the EPROM. Any suggestions are very much appreciated. Also if anyone as working 2716 EPROMs to share...

Of course, it is not unlikely that the eBay seller sells EPROMS that are almost, but not quite ST 2716-1 chips.

Edit: pin 20 needs to be connected to 0V (as is default on the ROM cart), not to 18.

[DutchAcorn]

Some progress. I got some other 2716 EPROMs, old ones (SGS 2716-1F1). These also verify on the programmer and give corrupted data when accessed in the Sorcerer's BASIC Pac, but once I heat them up with a hair dryer they shape up and work fine!

So what does this tell me? Do I need yet other 2716's? Slower ones?

[DutchAcorn]

Ok, BASIC pac is fixed. For some reason the ROM pac does not like some EPROMs as much as others. In the end I found 2 in the 10 EPROMs I have that work (different types).

As Tezza mentiones on his site pin 21 of the EPROM needs to be connected to 5V. I choose not to alter the ROM pac PCB but make the modification directly on the EPROMs and bend pins 21 out.

On this ROM pac a toggle switch mod was made that can used to switch off the ROM pac so you don't need to remove it if you want to boot to the monitor instead of BASIC.

Next: the faulty disc drive.

[jonb]

Oh yes, Paul, I have one of those (with a faulty disk drive).

It's a Liveport FDM 180 and it contains a boot ROM, so is connected to the bus at the back of the Sorcerer. The problem is that I cannot see all of the boot code, probably because some chip is bad on the drive or the connections are dodgy. I think I have captured the drive ROM contents though. I discussed it on this thread: http://www.stardot.org.uk/forums/viewto ... 45&t=13868 .

[DutchAcorn]

Oh yes, Paul, I have one of those (with a faulty disk drive).

It's a Liveport FDM 180 and it contains a boot ROM, so is connected to the bus at the back of the Sorcerer. The problem is that I cannot see all of the boot code, probably because some chip is bad on the drive or the connections are dodgy. I think I have captured the drive ROM contents though. I discussed it on this thread: http://www.stardot.org.uk/forums/viewto ... 45&t=13868 .

In your case the interface and the drive logic are integrated? That makes it somewhat harder to diagnose and fix. In my setup the FDC is on an S-100 card in the S-100 expansion unit. It works fine with a different drive. So I know the problem is with the disk drive.

Of course the fact that one of the 74 logic chips on the drive started smoking was also a bit of a giveaway.

[DutchAcorn]

The read logic of the disk drive has failed. I tracked down the probable cause of the fault: the 15uF capacitor in the picture had shorted, taking out the inductor next to it. The inductor no longer conducts.

So now I'm looking for replacements. I am not at all familiar with inductors, but I think this is a 150uH inductor and that the capacitor is a 15uF tantalum capacitor. I have searched RS Components for replacements, but axial is an issue and the original inductor is only 1.4 Ohms so it must take a lot of current (over 1 amp).

The circuit diagram is not much help; it is a bad copy and hard to read:

Any advise about the replacement? Can I just get any other inductor and a tantalum capacitor in a different package?

[jonb]

Paul, I replaced a tantalum cap with an equivalent on a Superbrain and it worked fine (but for smoothing a power rail feeding the SRAM so probably not critical). Not sure about the inductor.

The Liveport floppy drive has two cards inside it linked by a fat ribbon cable. It is either a functional split (one is the interface & boot code, the other is the FDD controller) or a physical requirement given the shape of the enclosure and the way they are mounted. As there is no FDC present and it is hard sectored, it is possible that the former applies, but the way they are sized suggests the latter...

"Interface" card. The 2 small chips with white labels contain the 256 bytes of boot code.

"FDC card". Exactly the same size as the interface card, so I am not entirely sure it is merely the FDC.

[Pernod]

Vista S-100 floppy interface and two 48TPI full-hight single sided floppy drives:

I'm currently working on Sorcerer emulation and the Vista controller is a rarity. Can you post photos of the S-100 controller card and have you dumped the bootstrap ROM for it?

[DutchAcorn]

Vista S-100 floppy interface and two 48TPI full-hight single sided floppy drives:

I'm currently working on Sorcerer emulation and the Vista controller is a rarity. Can you post photos of the S-100 controller card and have you dumped the bootstrap ROM for it?

Sorry, I no longer have the Sorcerer / vista drives. I scaled down significantly on my retro computer stuff and the Sorcerer has a large footprint…