Missing RAM = source of all evil?

Hi guys,

Mega-newbie to the forum, but not a newbie to the Amiga, have owned a A500+ since '91 I think. Such happy times, so many swears shouted at my slightly older sister during the heat of gameplay battle..

Anyhoo, I come bearing a problem I was hoping you could help me with: I've just picked up an A500 motherboard since the family's aforementioned A500+ appears to have various problems I don't quite have the time to sort out. I'm using the disk drive, keyboard, RF modulator and power supply from the 500+ with the 500 (I'm pretty sure they're compatible?) but it just ain't werkin' right.

When the 500 is fired up, the screen goes from static to black so it's obviously actually working, the powerlight comes on but stays on, no flashing. I know all of the aforementioned peripherals worked fine with the 500+, it just had a problem with the custom chips I think.

Upon further inspection of the 500, a few of the RAM chip positions have been socketed, and one of them is WITHOUT A CHIP! U17, to be exact.

Long story short, is this chip essential to start-up and, indeed, the A500 to function properly? I've found a few sources of the chip needed (KM41256-15), but would prefer not to piddle six quid up the wall if I don't need to.

I can appreciate this is suuuch a newb question, I do apologise.. but at least it'll be an easy one!

'Gards,
-Doog

[Loedown]

I used to have an A500 with a socket on one of the ram chips, did this so I could test ram chips in my Miggy.

Bottom line is you need that chip.

[Toni Wilen]

Non-working Chip RAM should normally cause green screen at boot.

[rkauer]

Can you please show us a picture of your board? And tell us which REVISION it is?

On A500 rev5 there is no U17, on rev6 the U17 is one of main chip RAM (not a spare space).

More information is necessary.

[Zetr0]

Hiyas Doog,

welcome to EAB, theres lots of retrolicious mischief to get up to around here, so hopefully when you A500 woes are fixed you can take part in some of the fun going on around here.


A500
Now as my good friend rkauer points out only the Rev6a A500 has the U17 - without it as Toni points out the screen would be green under Kickstart 1.3.

So we have a bit of a problem in ascertaining the real fault - so when you get some time - can you take some pictures of the motherboard for us =) (the higher the resolution the better)


A500+
These are awesome machines in a lot of ways - however one of their biggest draw backs is the onboard battery - these things leak and will eat copper tracks like crazy.

If I could suggest that you open up the A500+ - remove the battery with tin-snips or wire cutters. then douse the area with spirit vinigar - give it a few moments to neutralize the alkaline from the battery and then clean with pre-diluted car-screen wash or any non-smear -non-residue -water based cleaner - (i used a dishwasher on 50c no dry cycle) once done - place the motherboard in a warm airing cupboard - on its side - for atleast 24 hours =)

Its quite likely the battery leak has done some damage to the motherboard as well so if you could take pictures of the A500+ we can help you with this also.


=)