Amiga 1200D Indivision-AGA MKII Installation

Connecting the Indivision

Introduction

This post is a step-by-step tutorial for installation of the IndivisionAGA MKII hardware into an Amiga 1200 Desktop machine.  The target Amiga already has a FastATA fitted and there are some extra (easy) steps that will be necessary in order to allow these two peripherals to be fitted together in the machine at the same time.  This tutorial will also cover these steps.

MyAmiga1200D
My Amiga 1200 Desktop

What you will need

In order to complete a working installation of the IndivisionAGA MKII you will require the following:

  1. An Amiga 1200 Desktop (or towered – the steps will be similar) Computer.
  2. An IndivisionAGA MKII peripheral from AmigaKit.
  3. A phillips-head screwdriver for removal of the A1200D enclosure.
  4. A couple of 40-way DIL sockets (See Note 1)
  5. A hot-melt glue gun.
  6. A piece of thin plastic or other suitable (strong) insulating material approximately 75mmx60mm (See Note 1)
  7. An anti-static wrist strap with associated electrical earth connection.

*NOTE 1: These items are only required if you intend to install the IndivisionAGA with a FastATA.

Preparations

Step 1: Remove A1200 top enclosure

In order to complete this procedure you are going to need to take the cover off your Amiga.  If you are unfamiliar with this kind of task then I can offer you the following advice:

Amiga computers were born to be modified.  You are almost committing a crime if you don’t modify it.  Modifying your Amiga comes with the territory, and should form part of the enjoyment you get out of using the machine.  As long as you’re able to be careful, and take things slowly (thinking each stage through as you go along) you shouldn’t encounter any major difficulties.
That said, I do feel obligated to point out that damage to your Amiga is possible if you mess something up.  If you’re already convinced that hardware modification is not your strong point then I would advise you to seek the assistance of a trained technician.  AmigaKit is one company who can offer these kinds of services, and I would highly recommend them to you.

Step 2: Prepare work surface

First, prepare your work top.  My Amiga is a Commodore edition in pristine condition so I like to avoid scratches and scuffs.  If you feel the same then you’re going to want to put something soft down on your work top to prevent cosmetic damage to your machine when you work on it.  The ideal solution would be an anti-static bench mat, but if you don’t have one of these (I didn’t either) then any soft material that does not tend to generate any static should work.  I used an old towel.
Position your Amiga as shown below and then release all of the enclosure screws.

Release screws
Release screws

Once you have released all of the securing screws, carefully turn your Amiga back over and then remove the top cover.  Be careful because it is still tethered to the Amiga motherboard via the power/hard-drive LED wiring.  You should be able to flip the top cover over as shown below:

RemoveCover
Remove the top cover

Step 3: Remove the keyboard

The next step is to remove the keyboard.  The keyboard is connected to the Amiga motherboard via a green flat flex-foil cable.  Care must be taken to ensure that the mating connector clasp is released before you try to pull this flat cable out.  In order to release the clasp, pull the top collar upwards on each side until it releases its hold on the flat cable.

Note that the clasp does not fully remove.  It releases its hold on the flat cable and then sits in a released position on the connector housing.  Do not try to remove the clasp from its housing because you will break it!

When the clasp is released it’ll look like the photo below:

 

Clasp Released
Clasp Released

Once the clasp is released the flat cable should pull free without resistance.  If you feel any resistance then you have not fully released the clasp.
With the cable pulled free you can lift the entire keyboard from its retaining points and set it to one side.

Keyboard Removed
Keyboard Removed

Step4: Remove FastATA

If you have a FastATA fitted then you will need to remove it in order to allow fitting of the IndivisionAGA.  If you don’t have a FastATA then you can skip this stage.

TIP
In my experience the FastATA Gayle connection is not to be tampered with.  Once it has been connected, and it has settled in place, then the less it is disturbed the better.  For this reason I would recommend leaving the Gayle connection alone – you can separate it from the FastATA motherboard by removing the IDC connector.  This will leave you with just the FastATA motherboard to remove from the A1200 ROM sockets.

You need to take great care when removing the FastATA from the A1200 ROM sockets.  The risks, if you’re not careful, are as follows:

  • Bending or snapping pins on the FastATA if it is released suddenly at an angle.
  • Damaging the FastATA PCB if it is levered against without care.
  • Damaging the A1200 motherboard if a sharp instrument is used to lever the FastATA from the ROM sockets.

 

FastATA removed
FastATA removed

With these potential hazards in mind, use a flat instrument (preferably plastic but I was able to use a flat screwdriver with great care) to gently prise the FastATA from the ROM sockets.  Work on all four corners of the FastATA a little bit at a time, exercising patience.  The retention force of the ROM sockets will initially be very strong because the FastATA will have settled in its connection.  Eventually, after some perseverance and patience, you will be able to release this connection and pull the FastATA free.

 

Step5: Removing the floppy drive

Remove Floppy Drive
Remove Floppy Drive

In order to route the IndivisionAGA graphics cable it is better to remove the internal floppy drive.  This item is easily removed by releasing its retaining screws and disconnecting the power and data cables.  Please exercise care when removing the data cable as if it is pulled away at an angle you will bend pins.

Installing the hardware

Step 1: Fitting the IndivisionAGA

The IndivisionAGA main board connects over the top of the Lisa chip.  Make sure you connect it with the orientation shown in the photo below!
When making the connection, press with equal force on the top of the PLCC socket so that it engages Lisa with the minimum angle possible.  It will be necessary to press quite hard in order to complete the connection fully.

Don’t use any tools to force the IndivisionAGA onto Lisa! Use only your hands.

Connecting the Indivision
Connecting the Indivision

After you’ve fitted the Indivision to Lisa then you will need to route the graphics cable.  Methods are varied but there is unfortunately no ‘perfect’ solution for this as of yet.  My preferred ‘solution’ was to route the cable underneath the floppy drive (hence why I asked you to remove it) and then out of the rear expansion slot next to the mouse port.  I left the DVI connector dangling out of this small access panel, but I secured it later by using the monitor cable fasteners.  Not an ideal solution by any means, but it works.

Step 2: Fitting the ‘riser’ ROM sockets

40 way DIL socket
40 way DIL socket (round pin)

If you are installing the Indivision with a FastATA, or you plan to use a FastATA in the future, then you will need to fit ‘riser’ sockets into the ROM locations so that the FastATA board will fit over the top of the Indivision.  To do this you will need to fit one pair of 40-way DIL sockets into the existing ROM sockets.  The best type of DIL sockets to buy are the ’round pin’ type as shown in my photo.  You should be able to obtain these from AmigaKit, or you can get them direct from an electronics supplier such as Farnell, e.g. order code 1103855.  Note that the ROM sockets fitted into the A1200 motherboard are 42-pin

riser sockets fitted
Riser sockets fitted

but the front two pins are not used.  Therefore you will need to fit your riser sockets so that they sit flush with the back of the A1200 motherboard sockets as shown in the following photo.  Note that some Amiga users report that they prefer to fit two pairs of riser sockets so that the FastATA is hoisted up further, providing even more clearance.  If you order four 40-way DIL sockets then you are free to experiment with this but my experience is that one set of riser sockets provides just enough clearance whilst also ensuring that the Fast ATA does not foul against the keyboard.

Step 3: Preparing the FastATA (insulating) for re-fitting

The FastATA motherboard is mostly through-hole construction, which means that the component connections protrude through to the bottom side of the board.  These protrusions are quite lengthy and as such there is a risk of short-circuit to the Indivision PCB.  In order to guard against short-circuits it is important to insulate the two boards in some acceptable manner.

FastATA insulation
FastATA Insulation Plate

In my experience I was able to find a piece of strong, thin plastic from an old ring-binder that I trimmed to size.  I then fitted it to the bottom-side of the FastATA using two spots of hot-melt glue.  Hot-melt glue is a good solution because it is easily removed at a later time should the need arise.  Remember that the glue is not there to hold the FastATA board together – it only needs to keep your piece of insulation in place!
I think it goes without saying that the chosen insulation material must be non-conductive.  Plastic is a good choice for this reason.

Step 4: Refitting the FastATA

Once you have settled on a suitable method of insulating the bottom-side of the FastATA from the Indivision you are ready to fit the FastATA back into the ROM socket risers.  Be very careful to ensure that all the pins on the FastATA line up with your riser socket receptacles.  Your FastATA will now entirely fill the ROM sockets because you fitted 40-way sockets into the existing 42-way sockets that are fitted to the A1200 motherboard.  Once you have fitted the FastATA back into the ROM sockets you need to press firmly all around it to ensure a solid connection.  If you end up with a dodgy ROM connection then you will experience all sorts of problems reading/writing to your storage devices so the connection needs to be very secure.

Step 4a: Tie down the Fast ATA?

Some Amiga users prefer to tie-wrap their FastATA motherboards in place to secure it from coming loose after fitting.  I have had mixed experiences with this method and I have not found it to be necessary in a desktop machine, provided of course that your machine is not subjected to transportation.  A modified desktop A1200 is rarely a portable one.
The problem I’ve found with tie-wrapping the FastATA is that it doesn’t quite hold the board down in a manner that is guaranteed to prevent the board from working loose.  In fact, I have had experience of the tie-wraps themselves forcing the FastATA to retreat from its ROM sockets.

The ideal solution to this common problem would be to do some surgery on the A1200 motherboard, removing the existing ‘flat’ type ROM sockets and fitting the ’round’ type (like the ones you’ve used as risers) instead.  This would provide a much stronger connection both electrically and mechanically.  Unfortunately this is not a task for the amateur Amiga tinkerer because it can be very difficult to remove through-hole components from a multi-layer PCB like the A1200 motherboard.  Still, it is possible and a good technician would be able to do it for you if you think it’s necessary.

In my case I found that I was able to complete this work without replacing the A1200 ROM sockets and without tie-wrapping the FastATA in place.

Note that you should strictly limit the number of mating cycles you subject the standard A1200 ROM sockets to.  In practice this means that any time you dismantle your A1200 in the future you should always disconnect the FastATA from the riser sockets, leaving the riser sockets fitted to the A1200 motherboard.  This is because your riser sockets are round-pin and the standard A1200 motherboard sockets are square-pin.  A consequence of fitting a round peg into a square hole is that the connection quality is reduced, and the number of reliable mating cycles is once or twice at maximum before the connection will cease to be mechanically or electrically sound.  If you compromise the standard A1200 ROM socket connection quality then you may be forced to have the ROM sockets replaced (if so use round pin types as described earlier!) so the best advice I can give you is connect the riser sockets once, then never touch them again.

Step 5: Refitting the floppy drive and keyboard

We’re almost done! The floppy drive goes back in the same way that it came out.  Be careful when re-fitting the data cable because it’s all too-easy to miss a set of pins if you are complacent.
Once the floppy drive is re-fitted you can re-fit the keyboard.  Make sure that the mating connector clasp collar is released before you try re-connecting the flex-foil.  If the collar is released then there should not be any resistance when you try to mate the flex-foil to the connector.  Grap the flex-foil with one hand so that it is held in a fully-home position inside the mating connector, and then with your other hand press the clasp collar back down into place.

Step 6: Testing your installation

Murphy’s law says that if you put the cover back on before testing your installation then your work is guaranteed to be a failure.  For some reason as yet unexplained by science, you have to humour Murphy by testing it before putting the covers back on.  If you don’t believe me, try fitting the cover back first and you’ll see what I mean!

First Test
First Test

In any case, testing first is a good idea.  If there is any unexpected behaviour or problems then you are in a much better position to see what’s going on, and react appropriately, if you have the covers off.
If, for example, you have unwittingly created a short-circuit condition of some kind then you will often see, hear or smell evidence of this if your senses are able to be trained on the gubbins of your equipment.  Reacting to these kinds of issues quickly will save your Amiga.  Blissful ignorance of them (like when the cover is fitted) could damage your equipment beyond repair.  Please take my advice!
If all goes to plan then you should see an Individual Computers logo appear on your monitor within 2-3 seconds of switching on your Amiga.  If, after this, your Amiga boots into Workbench then you will also have confirmed that your FastATA is still working.  If you don’t see the logo, or your Amiga doesn’t boot (or both!) then you will almost certainly have some kind of connection problem.  Go back through your work, checking and re-checking all of the connections and making certain that all the socketted connections are seated firmly in place.

Step 7: Closing

After all is confirmed working Murphy will let you fit the covers back on and all will be well.

I hope you have found this tutorial to be of use.  Please feel free to write a comment.  Constructive criticism is also very welcome – I am an electronics engineer by trade but I certainly do not pretend to know it all!

If you have problems with your installation I may be able to offer some advice.  In that case I would prefer you to comment so that the advice is then available to others, but I also welcome email – please see the ‘contact’ section of my website.

Enjoy, and happy modding!

Finished
Finished

 

 

Hardware Hacking the IOMEGA StorCenter ix2-200

Introduction

The StorCenter ix2-200 is a RAID network drive supplied by iomega.  I have used the 2TB version for about two years now to keep secure (backed up) copies of my precious data.  Any data I write to the device is mirrored on its paired 2TB drive inside the unit, so one drive can fail and I’ll still keep my data.

Recently I’ve had cause for complaint with this unit’s default network setup routine.  When you switch the device on it goes through a boot-routine which involves setting up the network address and subnet.  If possible it does this via dhcp so if you’ve got it connected to your router it’ll be assigned an appropriate IP and will be instantly visible on the network.
The problems start when, for whatever reason, the device is not able to obtain network settings via dhcp.  In that case it assigns itself an address in the range 169.254.x.x with subnet 255.255.0.0.  In that case the network drive could end up with one of 65536 possible IP addresses in that range.  How is one supposed to know what IP address it’s assigned itself?

Hardware Hacking

Location of JP1 on ix2-200
Location of JP1 on ix2-200

I had two choices.  Set my computer to scan all of the 65536 possible IP addresses until it finds an active one.  Or, take the unit apart and see what hardware hacking can be done.  The former is probably quicker, but the latter is more fun.  Hence, this hardware hacking blog was born.

With the unit apart, I found a conspicuous looking pin header called JP1.  A few pokes around with my ‘scope revealed what looked like microprocessor level (3.3V) RS232 comms on one of the pins.

 

Completing the hack…

RS232 data on pin (2)
RS232 data on pin (2)

The next task was to try and see if I could view these signals on a PC.  The main problem here is the fact that the data output is 3.3V logic levels (basically it’s the raw output from a microprocessor) and the RS232 input to a PC is +/-12V standard RS232 logic levels.  It’s easily solved though, you just need to get yourself an RS232 level-shifter chip such as a MAX3232 and rig-up a circuit as per my schematic shown below, and then connect it to JP1 (as shown on the schematic) according to the pinout in the photo.

Schematic

JP1_2

 

 

 

 

I only had an SMT version of the MAX3232 part in my junk bin so I soldered it onto some proto-board with the 0.1uF capacitors tacked on top and then I wired it up to JP1 as shown in the photo below.

My hacked on level shifter IC to interface with the PC
My hacked on level shifter IC to interface with the PC

Viewing the data on the PC.

In order to view the data on a PC you simply need to put everything back together, connect the ends of your cables to a DB9 connector as shown in the schematic, and then connect the DB9 connector to your PC’s serial port via a standard 9-way serial cable.  Then fire up a terminal (I recommend PuTTY) and enter the following settings:

PuTTYConfig
PuTTY Terminal Settings

 

 

 

 

 

 

 

 

 

 

 

Once you’ve entered in the settings, select connect, and power on the NAS.  If all goes well some boot-time debug data should start spitting out on the terminal.  Something like that shown below:

Debug data coming through over the terminal
Debug data coming through over the terminal

After 2-3 minutes you should be presented with a login prompt.  If you want to gain root access to the NAS over your PC terminal simply log in with the following credentials:

USER: root
PASS: soho

Gaining root access via the terminal
Gaining root access via the terminal

Sweet!

That’s it – you’re in with root privileges. You can now enter the standard Linux commands and change whatever you wish.  My main reason for going to all this trouble (apart from enjoying hardware hacking) was to find out the boot-time network settings it was assigning itself.  Once I knew those I was able to gain access via the standard PC based web interface and change the settings to suit my home network.

I hope you enjoyed! Here is a quick video of the entire boot process and logging in:

Sinclair ZX Spectrum Composite Video Modification

Introduction

The Sinclair ZX range of computers were among the first affordable computers and kick-started the UK’s home computer revolution in the 1980s.  These machines relied on consumer television equipment for their display output and, as such, they featured an RF modulated output so that users could simply “tune-in” to them on their television sets.

Modern TVs use digital tuners and thus are no longer compatible with the analogue output of the Sinclair ZX computers.  However, most TVs – even the most modern models – still feature composite video inputs and it turns out that it’s very easy indeed to modify the video output on these computers to be compatible with a TV composite video input.  As well as providing compatibility with modern television sets, this modification also improves the computer’s video output quality.  This post will detail the procedure for modification of the Sinclair ZX Spectrum Computer, but it should be fairly similar on other Sinclair models of that era.

As shown in the basic block-diagram below, the basic principle of video generation and display for the ZX Spectrum Computer is as follows:

  • Generate composite video output from memory map
  • Add chrominance (colour)
  • Generate UHF with RF modulator
  • Send down cable to TV
  • Recover composite video with TV UHF demodulator
  • Display
Video display block diagram

As can be seen, the modulation/demodulation process is actually quite wasteful because we start with composite video, modulate it at the Spectrum video output, and then we just de-modulate it at the TV end to get composite video again! This was convenient at the time the computer was designed because it allowed users to display the computer output on standard analogue tuner TVs, but with most modern TVs featuring composite video inputs it’s pointless – we can just cut the mod/de-mod process out and connect standard composite video out straight from the Spectrum Computer directly to the TV composite inputs!

Completing the modification

The modification is very straightforward.  All you need to do is disconnect and remove the RF modulator, and then connect the machine’s composite video compatible output directly to the RCA connector via a decoupling capacitor.  Here is the process broken down into stages:

1: Remove the front cover

Cover Removed

To remove the front cover, release the 5 screws on the bottom of the machine.  The front cover will then lift away, but BE CAREFUL of the keyboard flat cables – you will need to disconnect these before you can lift the front cover all the way off.  They can be a little bit tight but with care they will simply pull out.  After this you should be able to remove the front cover completely.  The item we are going to remove is the RF Modulator unit which is enclosed inside a metal screening can at the top left-hand side of the unit, shown in the photo to the left.

 

2: Remove the RF Modulator top screening plate

Screening Can Removed
Remove Screening Can

Next you will need to remove the top plate from the RF Modulator screening can.  It simply prises off – a flat blade screwdriver will help you.  Be careful not to slip and cut yourself though!

With the Screening can removed you will be able to see the RF modulator circuit inside.  We are going to remove this circuit board completely in the next steps.

3: Disconnect the Modulator 5V supply & composite video feed

Remove Cables

The RF Modulator has two connection cables from the main PCB, as shown in the photo.  One is a 5V power supply and the other is a composite video feed.  These need to be de-soldered from the main PCB.  The easiest way to do it is to heat the joint from the top side of the board and then, with soldering iron still applied to the joint, carefully pull the cable through the joint with a pair of pliers.  Be careful when you do this as there is a danger of flicking up molten solder – unless you wear glasses then basic eye protection should be worn.

 

4: Disconnect UHF feed resistor from RCA Connector

Disconnect Resistor

Now you need to disconnect the feed resistor from the RCA connector shown in the photograph.  You can either desolder it or just snip it off with a good pair of wire snips.  The choice is yours!  If you’re going to snip it off then make your cut close to the RCA connector itself – this way you can save the RF modulator circuit complete and it will be easy to reinstall in the future in the unlikely event that you decide to put it back.

5: Remove the RF module from the Main PCB

Desolder & remove the RF Module

Now it is time to remove the RF module completely.  To do this you will first need to remove the Main PCB from the bottom casing.  This is very easy to do – there is just one screw securing the Main PCB to the bottom casing so release it and the Main PCB will come away easily.
After this you need to desolder the RF module anchor points which are shown in the photograph.  It can be a little tricky to desolder these because they are connected to a huge ground plane which – in conjunction with the screening can itself – tends to sink the heat of your iron away from the solder joint itself.  If you have an adjustable temperature on your iron you will want to turn it up to full for this particular job.  It is quite difficult to completely free the joints of solder so you will probably find that the removal process is a case of heating the joint and carefully prising the module free a little bit each side at a time.

6: Remove RF Modulator PCB

Remove the modulator PCB

With the RF module removed it is time to remove the modulator PCB.  This is very easy – there are four anchor points as shown in the photograph.  Desolder these and the PCB will come free.  You will then be left with an empty screening can which you’ll want to solder back in to the board so that you can re-use the RCA cable.

 

7: Fit decoupling capacitor

Fit decoupling capacitor

With the empty screening can fitted back onto the PCB as shown in the photograph you’re ready to fit a decoupling capacitor between the machine’s composite video connection point and the RCA connector.  All you need for this is a 100uF 10V capacitor.  I used a 16V part because it’s all I had in my parts bin – it works fine.  At these kinds of capacitances you’re probably going to be using a polarised part (most likely an electrolytic like the one I’ve used).  In that case connect the positive end of the component to the RCA connector and the negative end to the main PCB.  On an electrolytic capacitor like the one shown, the negative lead is designated by a marking on the component body itself.

.

NOTE: The decoupling capacitor isn’t really that essential.  It may improve picture quality for certain models of television set – it depends how the composite video input circuitry works – but on other models you probably wouldn’t notice any difference.  If you don’t have a suitable component around you and you can’t be bothered to order one then you can just try connecting a cable straight from the composite video point on the Main PCB directly to the RCA connector itself.  It should work.

8: Test

Time to test it! Don’t bother putting it all back together just yet – connect up the power and  connect the RCA connector to your TV composite video input using a standard RCA cable.  If all is well (and it should be) you will see a nice clean video output!

9: Enjoy!

I hope you enjoyed this simple modification.  If you try this mod yourself then I welcome comments – please feel free to join the discussion! I will leave you with a video I made of the modification that I made it while I was still on a voyage of discovery with it myself – you may still find it useful.

10: Links

Here are some links to other good sources of information on modding your Spectrum:

http://mrpjevans.com/2013/04/how-to-zx-spectrum-composite-video/

http://samsmods.blogspot.co.uk/2011/10/zx-spectrum-48k-composite-video-mod.html

http://www.jammarcade.net/zx-spectrum-composite-video-mod/

http://womblesretrorepairshack.blogspot.co.uk/2008/11/zx-spectrum-composite-video-mod.html

VIDEO: