Some questions in order to cure an A4000.

[arkpandora]

Hi,

I am currently jumping from one failing Amiga to another, hoping to bring it one of them to life without a technical intervention that would be beyond my competence.

The current one is an Amiga 4000 Desktop which used to belong to the same seller that sold me the A3000 I describe in another thread.  When I power it on, it only shows a black screen, while the power led either stays half-bright, or flashes for a few seconds before a reset that loops the process.  Sometimes (every minute or so), you hear a single click from the floppy drive.  I am of course unable to reach the startup screen.  The keyboard is responding : the power led answers the manual resets, and the Caps Lock key is operational.  I tested the computer without any Zorro card or hard drive : just with two different floppy drives successively.  I also removed the Fast Ram, removed then replaced the Chip RAM module, without success.

In order to identify the problem, I ask myself (and the Amiga.org community at the same time) a few questions.  At the moment I don't find any precise answer for them.

1. Can an A4000 work with without Fast RAM (only Chip RAM) ?  If so, can you confirm no jumper has to be changed ?

2. How do I know if a bare RAM module of the right dimensions, memory and speed will be suitable as Chip RAM ?

3. Can I use as Chip RAM a 4 Mb or 8 Mb RAM module (assuming the computer will only use 2 Mb) ?

4. Can an A4000 work without a hard drive (only a floppy drive) ?

5. Can you confirm that no hardware change (cable or jumper for example) is required in order to use a low density floppy drive instead of a high density drive as the only internal floppy drive ?

6. Without the IDE and floppy cables, what should the A4000's behaviour be at the switching on ?

Any answer to these questions is very welcome !

[Tahoe]

1. Can an A4000 work with without Fast RAM (only Chip RAM) ?  If so, can you confirm no jumper has to be changed ?

No problems, no setting jumpers; should work just fine.

2. How do I know if a bare RAM module of the right dimensions, memory and speed will be suitable as Chip RAM ?

Any double-sided FPM (preferably not EDO) module should work. I have used 8MB SIMM's as chipram without any glitch

3. Can I use as Chip RAM a 4 Mb or 8 Mb RAM module (assuming the computer will only use 2 Mb) ?

Yes, you can. Although the Amiga is picky, not any module will work. Single sided SIMM's will only work as 1MB chip, double sided should work as 2MB.

4. Can an A4000 work without a hard drive (only a floppy drive) ?

Sure, no problems.

5. Can you confirm that no hardware change (cable or jumper for example) is required in order to use a low density floppy drive instead of a high density drive as the only internal floppy drive ?

Confirmed. Jumpers need only be set if you use a HD and DD floppy at the same time.

6. Without the IDE and floppy cables, what should the A4000's behaviour be at the switching on ?

Bring up a purple Kickstart screen asking you to insert a floppy.

[arkpandora]

Thank you very much for your answer !

OK, my PC says that "FPM" means "Fantastic Plastic Machine", but I find out it is "Fast Page Mode".  How do I distinguish a FPM from a non-FPM module ?

I see there's a stain on the motherboard, that shades tracks.  Until now I have never cleaned a motherboard, so I have to add another question.  One would recommend isopropyl alcohol.  Being not more a chemist than an electronics specialist, can somebody tell me what this alcohol's specificity is for that use ?  Here I have denatured alcohol, whose exact nature I don't know : would it be convenient too, that is useful for such a cleaning and not agressive (if alcohol may be) towards the motherboard ?

Thank you again.

[marcfrick2112]

Arkpandora: I am no expert, but almost positive denatured
is NOT recommened. Isopropyl alcohol probably wouldn't hurt
anything, you would have dry the mobo out thoroughly after.
However, professionals actually take out all chips, and soak
the entire motherboard in a mildly caustic liquid (think acid)
to clean them. (A guy here in the US did this to one of my 4000's)

Did you check the battery on the motherboard for leaking?

Hopefully, some other A.org members can help further...

[A4000_Mad]

 8-)

Providing none of them are faulty you should only need 3 things connected to an A4000 motherboard to successfully get the purple insert disk prompt:-

1. PSU

2. chip RAM

3. CPU card


SOME JUMPER NOTES:-

J351 closed.......   enable 2nd internal floppy 880K as DF1:

J351 open.......   no 2nd floppy or 1.76MB floppy as DF1:

J352 set to EXT and leads removed from the internal floppy.............. An external floppy drive on the rear socket labelled FLOPPY becomes and external DF0: :-)

[Lemmink]

Having no floppy and / or HD connected it will take some time for the kickstart screen to show up. Could be up to a minute. With just the floppy it will still be about20 seconds or so.

One thing on the ChipRAM: 4 MB Modules will be recognised as 1 MB, 8 MB modules will be recognised as 2 MB. However this should require the 2MB / 8 MB ChipRAM jumper to be changed to 8 MB. (Won`t give you more then 2 MB but will help recogniseing modules with a capacity other then 1 or 2 MB)

[countzero]

You also need a working CPU card for a A4000 to function. If you have a A3640, these are quite notorious for leaky caps due to production error. Check that you have a working CPU board with another A3000 or A4000. Also check you have the clock jumpers set correctly.

[TjLaZer]

However this should require the 2MB / 8 MB ChipRAM jumper to be changed to 8 MB.

I am a little purplexed by this comment.  I doubt this will help as I heard this jumper is not even enabled on the MB.  Can Dave Haynie now chime in with his infamous quote?

[zipper]

 (2/8 MB test:)
 :pint:  Where's the free sex?