IT pro turned amateur

[robjordan]

My dad brought home an Exidy Sorceror in 1978 or 79, when I was 15 years old. I learned to program on that machine, later moving to BBC Micro. It was my number one hobby, but I never had a thought of making it a career until I was almost through university. Finally it dawned on me I could make a living doing what I loved. In a 35 year career I was a software developer, network specialist, technical and enterprise architect, consultant, lecturer. I had plenty of fun, but as I moved up the ladder had fewer and fewer opportunities to just play with computers, and I missed it.

I'm now fully retired, and seem to have returned to that early enthusiasm. Lately I've been learning something about electronics - which is new to me. Following I guess a typical hobbyist path of Arduino, microcontrollers, small circuit design. I still have that Sorceror. I tried firing it up a while ago and it hummed but didn't display anything. I have an ambition to see it working again. It's quite daunting and I'd love to have access to a community who might be able to help me with that task.

I'm in the UK.
Rob

 

[GeoffB17]

Hello,

Lacking a response from someone familiar with this machine, I'd suggest that it might help your cause to supply some extra information.

Firstly, it's not clear from your comments as to if it's the actual computer that's not working, or the monitor unit that should be attached (and is the connection between the two verified).

Secondly, I understand that there are different options for the ES, and you don't say how yours should start up, from ROM, or from cartridge, or if you've got a floppy drive for CP/M use?

Geoff

 

[Dwight Elvey]

We can walk you though trouble shooting the hardware.
We'd need information on what test equipment you have?
We don't know which machine you have. You can find some documentation at http://www.bitsavers.org/pdf/exidy/ .
It would be useful to know which hardware you have?
Dwight

 

[robjordan]

Hi Geoff, Dwight,

Thanks for the replies. I only meant this post as a personal intro as I'd just joined the site. I'm not yet quite geared up to start the debug and will start a new thread in a more appropriate area when I'm set to go.

The machine is the first edition Sorceror, with 32K and Basic ROMpac. Cassette interface only, no discs. As I mentioned, we had the S-100 chassis but it hasn't survived. I currently only have a multimeter and a cheap logic analyser, but I'm planning to get an oscilloscope for this and to progress my other learning projects. The simple, quick test I did a while ago was just to plug the composite output into the AV port of a monitor and power on... there was no display. No smoke, no obvious overheating. So I know there are a wide range of problems that might account for that. Dwight, thanks for the link to that document store, that looks really useful. I'm gathering together relevant info before I embark on this.

Will pop up again in another forum in due course.
Rob

 

[daver2]

First of all Rob (as this is your first post) welcome to VCFED.

Yep, let us know what machine you have and what test equipment you have access to. A decent multimeter is a must. I have both an analogue and a digital one. They are generally used for different things. An oscilloscope is also useful. If you haven’t got one of these, they can be acquired these days quite cheaply. The cheapest ones are limiting for the frequencies we are talking about on a Z80 ES.

Can you understand electronic schematics would also be a bit of useful information.

Also, how are your soldering/desoldering skills if you have to replace some components? Perhaps get a bit of practice in with some cheap components from eBay!

Just note that you will be moderated for the first few posts. This is designed to keep spam off the board, and it works very well. Just be patient...

Dave

 

[Dwight Elvey]

Hi Geoff, Dwight,

Thanks for the replies. I only meant this post as a personal intro as I'd just joined the site. I'm not yet quite geared up to start the debug and will start a new thread in a more appropriate area when I'm set to go.

The machine is the first edition Sorceror, with 32K and Basic ROMpac. Cassette interface only, no discs. As I mentioned, we had the S-100 chassis but it hasn't survived. I currently only have a multimeter and a cheap logic analyser, but I'm planning to get an oscilloscope for this and to progress my other learning projects. The simple, quick test I did a while ago was just to plug the composite output into the AV port of a monitor and power on... there was no display. No smoke, no obvious overheating. So I know there are a wide range of problems that might account for that. Dwight, thanks for the link to that document store, that looks really useful. I'm gathering together relevant info before I embark on this.

Will pop up again in another forum in due course.
Rob

Get at least a 50MHz sample rate scope if digital. There are lots of good used 100MHz analog scopes available. Do look for one with delayed sweep.
Dwight

 

[daver2]

Rob,

I assume you have looked at the treasure trove of documents that Dwight pointed you at (http://www.bitsavers.org/pdf/exidy/)?

As you have already powered it up and tested to see if it lets the black smoke out - and it doesn't...

The first thing to do is to identify exactly what you have got - and identify the correct schematics for the beast. Either look for part numbers on the board and do it yourself (and point us at what you have found) or post some high-res photographs somewhere that we can get to for us to look at.

The fault finding procedure for most computers is generally exactly the same. There is no 'magic' formula!

Check the power supplies, then look for the presence (or absence) of clocks, then look for some of the control signals to the microprocessor (a Z80 in your case) not being correct. For example, is the Z80 being held in a permanent reset? Is something generating a permanent interrupt that is confusing the Z80 microprocessor etc.

The power supply checks can (initially) be done with a cheap and cheerful multimeter. It will not tell us everything (i.e. it wont tell us if there is too much ripple or noise coming from the voltage regulators) but it will tell us if one of the dc regulators is completely dead or not generating the correct voltage...

What logic analyser have you got? That could turn out to be a useful piece of test equipment!

We're here to help you. Don't be too daunted - many people have got their old treasured machines working with virtually zero knowledge to start with and minimal test equipment - so you are not alone in this venture! I am quite certain we can provide the help you need. However, we just need to do things methodically...

Dave

 

[robjordan]

A quick update from me about the Sorcerer. Thanks for all your contributions! The excellent news is that the machine is basically working! One small issue I'm aware of (described later) but it's not a show-stopper.

I put up an album of photos here. Some have text descriptions explaining the content.

I haven't consciously done anything to repair it... I opened it up, gave it a very light clean, removed and reseated circuit boards, checked supply voltages, which are +4.8, -5.2, +11.5; apparently close enough to +/-5 and +12. Oh I also removed the giant 8000uF capacitor and tested it for leakage and it seemed fine (30uA leakage after 5 minutes, dropping to 20uA shortly after). Maybe these interventions helped in some way, but I suspect my prior test a couple of years ago was flawed. That time I just plugged the composite output into a TV, and saw no output. This time I connected it via a handy SCART-to-HDMI converter to a PC monitor, and right away it booted to the Exidy Monitor.

The only defect I'm aware of is that the BASIC ROM Pac isn't working (screen fills with alternating 0/9 pattern). I suspect I'll need to replace one or more of the PROMs with a new EPROM. Terry Stewart has comprehensively documented the process he went through to repair a failed ROM Pac.

I've also downloaded Tezza's amazing software trove and I'm exploring it. Loading via the tape interface is very troublesome, especially at 1200 baud, but I have succeeded occasionally. The oscilloscope I bought to help with the expected fault-finding has been handy for tuning audio levels and I'm sure it will be well-used in future. The experience has given me the ambition to implement some way of loading software over an electrical, rather than audio, interface, i.e. serial or parallel. I saw someone had connected a Teensy microcontroller with SD card directly to the Sorcerer UART. It's a great idea and one I'd like to follow up on. With that in mind I wrote a Python script that can demodulate the tones from WAV files and save the program in a binary format.

Thanks for all the documents you have alerted me to. It does seem the Sorcerer was, and is, an exceptionally well-documented, and well-engineered system. Another document that I found very useful and quite readable (maybe familiar to some of you): Steve Ciarcia's 'Build Your Own Z80 Computer'. The whole content is on Google Books.

Having fun! Thanks.
Rob

 

[daver2]

Repairing faults like that are the best!

Over on the NASCOM google group Neil has developed a solid state replacement for the cassette player to load software. Sounds like a similar thing as you mention...

I am also working on a PIO connected SD-CARD interface for the NASCOM using an SD-CARD breakout board with a 5V to 3.3 Volt regulator and voltage converters built-in.

Fortunately, we have the sources for PolyDOS available so we can modify and reassemble the disk drive interface software to suite our own requirements. I am sure there would be a similar way to add a unit on to the Exidy, but you will have to explore that avenue yourself.

If you can get a few more posts under your belt (>10) then your posts should stop being moderated.

I look forward to further progress on your Exidy...

Dave

 

[dutchacorn]

Welcome Rob, and thanks for sharing your findings. Tezza’s software library is one of a kind. One thing to note is that the 1200 baud versions are really suitable only for the MAME Sorcerer emulator. Actually I am surprised to hear you managed to load one of them. On a real Sorcerer you can use the 300 baud versions. They should load reliably.

The monitor defaults to 1200 baud. To set it to 300 baud you need to enter
SE T=1
in the monitor.
Of course you can then switch back to 1200 baud (SE T=0) and save the program for future re-loads.

The Exidy Sorcerer is quite uncommon and as a result has a modest active community.

The BBC Micro however has a very active community also still developing new hardware and software projects. Have a look at the Stardot forum for more info.

 

[robjordan]

Thanks dutchacorn for your comments. You may be right, perhaps the file I loaded was at 300 baud, I can't remember for certain. As I mentioned, I'm turning my attention to a digital interface to the UART, similar to what ClausB built with Teensy. I posted just this afternoon on a Sorcerer thread, a few more details about the Python script I wrote to demodulate the WAV files to a binary format. I also posted the script to Github in case you are interested.

 

[exidyboy]

Welcome Rob, and thanks for sharing your findings. Tezza’s software library is one of a kind. One thing to note is that the 1200 baud versions are really suitable only for the MAME Sorcerer emulator. Actually I am surprised to hear you managed to load one of them. On a real Sorcerer you can use the 300 baud versions. They should load reliably.

I don't concur with that view. All the software I have contributed to Tezza's site has been saved out of a real Sorcerer and painstakingly tested to ensure that it will load back into a real machine at 1200 baud. Tezza's original rationale for setting up the site was because real machines couldn't load a lot of the files circulating on the Internet for use in MAME - and this was actually leading people to conclude there was a problem with their Sorcerer.

Getting to the bottom of tape loading issues is on my very long list of things to do and I now have on long-term loan an MSO so might be able to make some progress in that area. In particular a project for someone would be to evaluate what all the many official Exidy and unofficial mods to the cassette interface actually do and which are meaningful for vintage machines today.

I have much better luck playing WAVs from my Mac into my Sorcerer than I do from a PC and a recent discovery is that pulling the bass down ever so slightly makes a massive difference to the reliability of loading.

 

[robjordan]

I don't concur with that view. All the software I have contributed to Tezza's site has been saved out of a real Sorcerer and painstakingly tested to ensure that it will load back into a real machine at 1200 baud. Tezza's original rationale for setting up the site was because real machines couldn't load a lot of the files circulating on the Internet for use in MAME - and this was actually leading people to conclude there was a problem with their Sorcerer.

Getting to the bottom of tape loading issues is on my very long list of things to do and I now have on long-term loan an MSO so might be able to make some progress in that area. In particular a project for someone would be to evaluate what all the many official Exidy and unofficial mods to the cassette interface actually do and which are meaningful for vintage machines today.
.

Thanks that's a useful observation about the WAV files. I'm motivated to explore the factors that make tape loading reliable or not, so I'd like to collaborate on that task. I have a DSO now, which helps. For me (as you've seen and commented on a separate thread) I think my noisy power supply is a significant factor.

 

[dutchacorn]

I don't concur with that view. All the software I have contributed to Tezza's site has been saved out of a real Sorcerer and painstakingly tested to ensure that it will load back into a real machine at 1200 baud. Tezza's original rationale for setting up the site was because real machines couldn't load a lot of the files circulating on the Internet for use in MAME - and this was actually leading people to conclude there was a problem with their Sorcerer.

Getting to the bottom of tape loading issues is on my very long list of things to do and I now have on long-term loan an MSO so might be able to make some progress in that area. In particular a project for someone would be to evaluate what all the many official Exidy and unofficial mods to the cassette interface actually do and which are meaningful for vintage machines today.

I have much better luck playing WAVs from my Mac into my Sorcerer than I do from a PC and a recent discovery is that pulling the bass down ever so slightly makes a massive difference to the reliability of loading.

Thanks for that, I was actually under the assumption that all of the 1200 baud files were saved from an emulator. Tezza confirms that most are. In my experience WAVs created @ 1200 baud from MAME cannot be loaded into a real Sorcerer. But I have not dived into what causes the issue.


All the WAVs that I sent to Tezza were 300 baud only (saved from an original Sorcerer). I assume that the 1200 baud versions of those were created by Tezza using MAME.

 

[exidyboy]

Thanks for that, I was actually under the assumption that all of the 1200 baud files were saved from an emulator. Tezza confirms that most are. In my experience WAVs created @ 1200 baud from MAME cannot be loaded into a real Sorcerer. But I have not dived into what causes the issue.

I've spent a lot of time thinking the technical and political issues. For the former I think the issue is that MAME creates what one MAME developer describes as "naive square waves" and these look nothing like what a real machine creates. The tapetool2 application lets you convert between square, sine and indeed arbitrary wave shapes which can be handy to make them palatable to real hardware.
It can take half-a-day to preserve a single software title 'properly' and test it and not everyone has the space to have a Sorcerer permanently set up.

However if you are re-saving files like I do it is easy to mess up in the intrinsic metadata in the tape header.
Now software is also starting to appear as WAVs that created from .COM files which have already lost information from the tape header when they were converted 'back-in-the-day'. This data gets replaced with semi-arbitrary values for the file type byte for example that you see when you issue a LOad or FIles command.

 

[robjordan]

Haha, we just turned up this photo. Christmas Morning 1980 I think, me in pyjamas ready to play my new Galaxians game. Strangely, reading the manual first!! Same Sorcerer that's on my bench now.

 

[exidyboy]

Haha, we just turned up this photo. Christmas Morning 1980 I think, me in pyjamas ready to play my new Galaxians game. Strangely, reading the manual first!! Same Sorcerer that's on my bench now.
View attachment 63322

Great photo! Images of people using computers in their homes in the 80s are very rare. Are you sure its Galaxians? That looks like a Quality Software manual on brown paper.

 

[robjordan]

Great photo! Images of people using computers in their homes in the 80s are very rare. Are you sure its Galaxians? That looks like a Quality Software manual on brown paper.

Well Galaxians is how I recall it, but memories are fallible. It's great that you recognise the Quality Software manual. What was their software portfolio? I'm sure we bought a Space Invaders-type game, but also perhaps a version of Adventure. Would that perhaps be QS? It's more plausible that there would be written documentation for Adventure I suppose.

 

[exidyboy]

Well Galaxians is how I recall it, but memories are fallible. It's great that you recognise the Quality Software manual. What was their software portfolio? I'm sure we bought a Space Invaders-type game, but also perhaps a version of Adventure. Would that perhaps be QS? It's more plausible that there would be written documentation for Adventure I suppose.

Martin Sevior wrote a version of Galaxians published by System Software and it was one of the most well received games for the Sorcerer - so you may well own it or have played it. Their manuals tend to be printed on glossy white stock. A lot of the Sorcerer software that has been preserved to date is available on Tezza's site, often with manuals, so it might be possible to work out which document you are holding from the layout. I can see you also have an early version of the Software Internals manual on your desk. There were 3 versions of Space Invaders for the Sorcerer I believe including one by QS. I'm not sure I have seen a catalogue from QS but pricelists from their distributors might give a sense of their portfolio at a given point in time.

 

[boraxman]

My dad brought home an Exidy Sorceror in 1978 or 79, when I was 15 years old. I learned to program on that machine, later moving to BBC Micro. It was my number one hobby, but I never had a thought of making it a career until I was almost through university. Finally it dawned on me I could make a living doing what I loved. In a 35 year career I was a software developer, network specialist, technical and enterprise architect, consultant, lecturer. I had plenty of fun, but as I moved up the ladder had fewer and fewer opportunities to just play with computers, and I missed it.

I'm now fully retired, and seem to have returned to that early enthusiasm. Lately I've been learning something about electronics - which is new to me. Following I guess a typical hobbyist path of Arduino, microcontrollers, small circuit design. I still have that Sorceror. I tried firing it up a while ago and it hummed but didn't display anything. I have an ambition to see it working again. It's quite daunting and I'd love to have access to a community who might be able to help me with that task.

I'm in the UK.
Rob

I'm starting to learn about electronics, largely due wanting to try to get older computers working, but also radio's etc.