Amiga 500 issues.

[runholen]

Hi. I reccently bought a used amiga 500. The seller claimed it was working fine when he tested it, but alas, it dit not
when i received it.
Main problem:
When I turn on the amiga after not having tried it for a while, it usually boots fine into kickstart. However, after some
time, usually 10-30 seconds, the video image becomes disturbed, usually suddenly displaying a white screen with blinking,
black diagonally aligned stripes that are moving from left to right. (See attached avatar image). When turning the amiga
off and on again (after waiting some seconds), I then very often get a green screen (signifying ram problems) but not
allways. And when the amiga has been turned off for a good while, it almost always boots ok to kickstart, before the video
trouble kicks in after a little while. I have tried opening the amiga and pressing down on chips etc, with no result. Have
anyone had the same trouble, or know what the trouble might be? On the positive side, the seller actually also included
another defect A500 main board, for spare components, so if it is just replacing a certain chip or something, I can mabe
try that from the other main board.
Secondary problem:
I haven't managed to load a single disk from the internal disk drive yet. Often I just got read/write errors, sometimes it
managed to load a little bit before errors occured. I understand that over 20 year old diskettes may be hard to read, but
I expected to be able to maybe read at least a few. After reading some threads, I decied to try to clean the read heads on
the drive, so I unplugged it and opened it and tried applying alcohol with at q-tip to the heads and then cleaning it with
the other side of the q-tip. Unfotunately, the only alcohol I had available was some hand disinfectant, and now the drive
is worse off than before, just going back to the kickstart image after trying to load a diskette.
An external diskette drive actually was included, but I don't think I can boot from this. Is it possible to open this up
and replace the internal disk drive with the external without too much work? I am also thinking of maybe investing in a
disk drive simulator, but I cannot do this before the rest of the amiga is working ok (see main problem).

[Lurch]

I'd try re-seating all the chips, most likely one is not sitting right.

You could start by pushing each chip to make sure they're inserted okay.

Is it a 500 or a 500 plus? If it's a plus it could be the onboard battery causing problems, I'd remove it. Once removed you can clean the area with lemon juice, but make sure to remove all lemon juice after you finished and make sure it's dry.

The lemon juice stops the battery acid from doing further damage.

The other thing to check is if it's got an expansion card that too has a battery onboard, same deal remove it and clean it.

As for the floppy drive you can try cleaning it with cleaning alcohol and a cotton bud but most likely the drive might be out of a alignment.

This is a good article

http://www.techrepublic.com/article/quick-steps-to-service-a-broken-floppy-drive/1055927

If not Amigakit sell new drives...

http://amigakit.leamancomputing.com/catalog/product_info.php?products_id=106

Although Floppy drives are a real pain, so I've switched to an HxC2001 floppy emulator

http://hxc2001.free.fr/floppy_drive_emulator/

[Lurch]

You can open up the external drive and use that, although it may not align properly with the button on the side.

But give it a try.

[runholen]

It should be a plain 500 with only half a meg of ram, and
I don't think there are any expansion cards.  I will try replacing the drive with the external one, but not before the graphical problems are solved. I tried pushing the chips. Is there a special one i should concentrate on or maybe replace? Anyone else with similar video problems?

You can open up the external drive and use that, although it may not align properly with the button on the side.

But give it a try.

[GadgetUK]

Sounds like RAM fault to me - not the easiest thing to fix, involves desoldering RAM chips, adding sockets and replacing any faulty chips.

Could also be PSU, you should rule that out.  Or loose fitting Agnus.

[amiman99]

Why not just return it, there can be multiple problems with it, you may spent a lot of time fixing the Amiga instead of enjoying it. Unless the machine is rescued and you really wanted to fix it.