Amiga 500 White screen

[AdelaideAmiga]

Hi All,

I recently got hold of an Amiga 500 and have been using it on and off.  The other day I pulled it out to demonstrate it to a couple of guests we had over for boxing day and right while we were having a go at the old lemmings classic the screen started resembling a scrambled picture and eventually froze.  When I rebooted the system, instead of going to the usual "workbench" screen that it does it just went to a white flickering type screen with no workbench logo or anything.  It still continues to do this and does not load any software now.  

I was just wondering if anyone here on this forum has any suggestions as to what the issue may be.  The only thing i've been thinking of doing is taking the back cover off and making sure all the chips are in proper place and maybe giving the board a 'blow' using an air compressor.  

Looking forward to hearing from anyone.

Kind regards,
George

[ElPolloDiabl]

Do you have a 512k card? Take that out first and check if it boots. Otherwise it may be the CPU has failed or something in that area. Take off the cover and check that area.

[ElPolloDiabl]

P.S. Unplug the power first. Don't touch the chips or motherboard without earthing yourself first. Touching the metal RF shield for a few seconds is usually enough.
When you take off the cover there will probably be the RF shield the keyboard connector.

[dougal]

If its a 500 it could be a leaky battery in the ram expansion

If its a 500 Plus it could be the onboard battery has leaked

Check socketed chips

Check power supply

[AdelaideAmiga]

Thank you everyone so far for your responses.

@ElPolloDiabl I believe there is a memory expansion on the Amiga system.  What I have realised though is that I will need some special star shaped screwdriver to get the cover off to check everything.

@dougal Is this expansion that you mention the one located under the cover that you open on the underside of the unit?

Happy new year,

George

[ElPolloDiabl]

Use a flathead screwdriver to gently release the underside bay.That is where the 512k expansion is.
The other screws are probably torx screws. A phillips head screwdriver was good enough for them in the old days.

[AmmoJammo]

If you'd like, I'm happy to have a look at it for you, assuming pulling the memory expansion doesn't help.

Where abouts are you located?

[AdelaideAmiga]

@ElPolloDiabl Yes it appears that those screws are torx screws.  Will try the Phillips head on them and see if they come loose.  Was just concerned before that this may wear the thread on them.

@AmmoJammo Thank you for offering your assistance.  If you are attending the event on the 19th of this Month then perhaps that might be a convenient time to look at the machine ?

[AdelaideAmiga]

Today I pulled the memory expansion out and tested the machine.  Works fine without the expansion!  Workbench screen boots up etc.

Following the instructions on removing the battery (see http://awesome.commodore.me/about/pgarcia/amiga-500-new-owners-first-steps/#comment-17381)  I cleaned the memory expansion board and replaced it.  The battery unfortunately was leaking but it appears that the board itself has only a bit of staining but no noticeable damage.  When the expansion board was inserted back in the same white flickering screen occurred with no workbench screen.  

Given that the issue appears to be with the memory expansion, is it likely then that one of the chips is kaput on there?

[ElPolloDiabl]

The chips are probably fine. It's the tracks that get cut. Someone could repair it if it is worthwhile.

[AmmoJammo]

I'm happy to have a look at the memory expansion

Post some pics of it on here first?

[AdelaideAmiga]

@ElPolloDiabl  Can the tracks get cut via the battery acid?  

@AmmoJammo  Here are the pics of the expansion unit.

[dougal]

Well, at least you know the problem is with the expansion.

It doesn't look badly damaged. You could try the following:

Check the condition of the pins on the ram expansion bay (on the Amiga) for any green corrosion. If so you may need to clean them.
[Its possible that the acid from the battery ran from the tracks through to the pins, in bad cases it can even travel to the motherboard itself.]

Check the ram expansion with a digital multimeter for continuity - You will need to check around the area that got damaged / corrosion from point to point. If there are any breaks in the tracks you will need to repair them. Bridging them or whatever.

512K ram expansions are cheap, so if you cant fix it its no big deal but i'm pretty sure its fixable.

[AmmoJammo]

@ElPolloDiabl  Can the tracks get cut via the battery acid?  

@AmmoJammo  Here are the pics of the expansion unit.

Yes, it seems I did offer to have a look at it for you :lol:

Let me know if you still need a hand!

[AdelaideAmiga]

@AmmoJammo

- Yes I remember, it was around the time we were having our January event

The machine works fine now apart from a slight issue with the keyboard that locks up occasionally.  

Kind regards,