A4000 not recognising RAM

[edd_jedi]

Bloody typical - I finally get round to fitting a nice 80GB IDE HD, and now I've put it all together my A4000 is only recognising 500k of Chip RAM and no Fast RAM (it has 2/16MB.)

I have tried removing the Fast RAM but it still only shows 500k of Chip as you can see in the attached photo.

Any idea what could be causing this?

[alenppc]

Memory traces corroded by leaked battery acid?

[fitzsteve]

I would guess as alenppc says battery damage to traces has nuked the Fast Ram, you only have 500k Chip Ram left as the rest was used to load Workbench on account of no Fast Ram.

Suggest you get the Motherboard looked at by either Amigakit or one of the resident guru's here or at Amibay.

I highly recommend recapping at the same time.

[edd_jedi]

Did cross my mind but it looks OK to me but it's obviously hard to tell without taking the MB out. It was fine last time I used it at Christmas, I should have checked before disassembling it this time.

I was wondering if anyone knew of anything else that can 'wipe out' the RAM, like a short or dislodged daughter board or something.

[edd_jedi]

Something that may also be worth mentioning - there's a chance it has literally just happened as when I put it all back together the first thing I did was launch a game (Oscar AGA) and that ran, which it won't now with no Fast RAM. But it did crash half way through the Oscar intro and since haven't been able to see any RAM.

[fitzsteve]

It's certainly worth stripping down to the bare motherboard and checking everything over and cleaning with IPA the simm sockets/daughter board slots. Whilst you are at it if the Buster is socketed remove and clean that too.

What's the history of the A4000, any previous leakage? If not cleaned up properly it will continue to corrode a way the tracks so whilst stored the damage might have been accumulating sadly

[alenppc]

Take the motherboard out, check the traces with a multimeter, also get a magnifying glass and inspect the bridgette (the NCR chip close to the simm slots), make sure you did not bend any pins by accident.

[cpiac64]

i have same problem with a3640 defect

can you test with another cpu?

[edd_jedi]

Interesting - no I only have the 030 card at the moment. Have had to give up today, hopefully can have a better look at it at the weekend.

[tnt23]

Could as well be those angled 72-pin SIMM sockets, they often loose the ability to hold modules in place. I wonder why you've got only 512M of Chip RAM though.

[Turran]

Because loading his workbench is probably eating up 1.5MB =)

[edd_jedi]

Here's a couple of close up photos of the topside of the motherboard. As you can see there was some minor battery leakage before I removed it, but I don't think it looks too bad. The RAM sockets all seem very clean to me. Interested to know what others think.

[hese]

The traces underneath the SIMM sockets do not look good.
Nor does the U177, U975, U976 area but that's another matter.

[edd_jedi]

Yeah there's a small amount of fuzz on the legs of the three chips you mention, I've seen far worse though. I can't see anything wrong with the RAM sockets, can you be more specific please? I have now taken the motherboard out and the underside is perfect.

[hese]

You can see that the traces between the SIMM banks 3 and 2 near the battery are corroded due to battery acid and some of them may be broken.
Do you have a multimeter so you could test if the traces are okay?

[Loedown]

That board is going to need extensive repair. The chip marked as F245 above where the battery used to be is showing signs of corrosion which means it has probably eaten out several traces.

Someone will have to remove all the simm sockets and clean under them or check every pin manually for continuity. You may as well get it recapped at the same time either using aluminium capacitors or ceramics and you will also need to extensively clean around U976 etc.

Many of the vias towards the left of the battery are showing signs of corrosion too.