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Old 15 May 2013, 16:25   #1
Abelardator2
 
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Yellow Screen Amiga 500 with +512kb

Hello,
Someone can help me?, I have an Amiga 500 and connect a few days ago, I got the problem that when turn the computer screen is yellow with LEDs flash until reset and thus makes a loop.
Remove the 512kb RAM expansion and now all correct, the computer works fine. I acquired another 512kb RAM thinking that was the problem and kept going the same with the new. I tried both RAM's in another Amiga 500 and yellow screen appear again.
Can anyone help? Thanks ....

Sorry for my english
 
Old 15 May 2013, 16:52   #2
kipper2k
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Quote:
Originally Posted by Abelardator2 View Post
Hello,
Someone can help me?, I have an Amiga 500 and connect a few days ago, I got the problem that when turn the computer screen is yellow with LEDs flash until reset and thus makes a loop.
Remove the 512kb RAM expansion and now all correct, the computer works fine. I acquired another 512kb RAM thinking that was the problem and kept going the same with the new. I tried both RAM's in another Amiga 500 and yellow screen appear again.
Can anyone help? Thanks ....

Sorry for my english

Hi,

Yellow screen indicates that there are CPU lines not connected. Use a plastic scouring pad to clean the contacts on the A500 board (or an pencil eraser). The contacts are likely oxidized and not giving a good connection.

However i am puzzled by what you say... you say both boards give yellow screen in one computer and also another computer, so i am not sure if something is being lost in translation.

Try the cleaning and see if that works
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Old 15 May 2013, 17:41   #3
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Originally Posted by kipper2k View Post
However i am puzzled by what you say... you say both boards give yellow screen in one computer and also another computer, so i am not sure if something is being lost in translation.

Try the cleaning and see if that works

If now both computers do not work with the RAM. Normally the screen is yellow, but sometimes white or green.
The connectors for the RAM are very clean....
 
Old 15 May 2013, 18:22   #4
kipper2k
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Originally Posted by Abelardator2 View Post
If now both computers do not work with the RAM. Normally the screen is yellow, but sometimes white or green.
The connectors for the RAM are very clean....

The fact you are getting different colours means that there is definately connectivity issues, white is a normal boot colour, green indicates Ram (or ram access) error. If you are happy that the connectors on the Amigas themselves are good then you may just be unlucky enough to have 2 bad expansion boards. If you know someone close who has a good board, borrow it and try it to see if it works in yours.
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Old 15 May 2013, 18:26   #5
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read here part titled "diagnostic test":
http://en.wikipedia.org/wiki/Kickstart_(Amiga))


long times ago, i had known on A500:
Light green - CIA problem[5]

because i had connected a external home made drive (electric short circuit)
=>only found solution to replace one of CIA chip

your must be:
Yellow - Mostly a bad CPU (no trap routine) or a bad Zorro expansion card.[4] CPU exception error before the "guru meditation" trapping software was enabled.[3]

Last edited by CFOU!; 15 May 2013 at 22:51.
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Old 15 May 2013, 20:59   #6
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I connected a megadrive pad that is almost supported, almost because the pinout is almost equal, but not button 3, pressing it on the pad that gives ground to +5 Amiga signal and that something could happen.

CIA is Agnus chip? it is possible to replace?is in a socket?

Thanks....
 
Old 15 May 2013, 21:28   #7
kipper2k
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Originally Posted by Abelardator2 View Post
I connected a megadrive pad that is almost supported, almost because the pinout is almost equal, but not button 3, pressing it on the pad that gives ground to +5 Amiga signal and that something could happen.

CIA is Agnus chip? it is possible to replace?is in a socket?

Thanks....
there are 2 cia chips. odd and even, part # is 8520 (written on chips).you can actually swap them and sometimes be able to boot the A500. I dont think the CIA chips are bad, but its worth a try. Sometimes symptoms don't actually reveal the true suspect
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Old 15 May 2013, 21:30   #8
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snapshot of the motherboard with labeled CIA chips, original snapshot is here.

if you want to swap them, ensure they have the original orientation. do not rotate them.
with a tiny screewdriver - protected with some tape - you can lift them , in tiny steps - left, right, left ... . try not to scratch the motherboard

edit: one more advice: never plugin/disconnect things from your amiga, until power off
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Old 15 May 2013, 21:47   #9
Toni Wilen
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Yellow = bad CPU does not make any sense. CPU needs to work because it is the CPU that writes yellow color value to Denise's color0 register! (It seems many believe error colors are magic and can appear without working chips or cpu..)

Lots of ROM instructions (hundreds) have to be executed correctly (which includes "green screen" chip ram test) before yellow screen exception can work.

Green screen: First 256 bytes (or it was 1024) bytes of chip ram don't work. Possible reasons: agnus chip bus problem, ram chips damaged, CIA overlay pin not working (controls if ROM is in place of chip ram after reset, OCS/ECS only)

Yellow screen: I think usual problem is trapdoor/fast ram being damaged (or connection problem between rams and CPU), system crashes when first structures are allocated from fast ram (including supervisor stack). Trapdoor RAM detection routine is quite simple and won't detect all kinds of problems.

Blue: Does not exist, at least in any normal KS ROM.
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Old 15 May 2013, 22:34   #10
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I see...
The computer works properly without the memory expansion. In two different computers the error is the same with both embedded memories. I think the most logical thing is that both memories are damaged. Do not believe?
Thanks for taking your time to answer.
 
Old 16 May 2013, 14:30   #11
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bad memory probably,what card is it?

have you got a picture of the cards?


maybe even partly bad gary or bi directional buffers.
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Old 16 May 2013, 20:15   #12
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Are two cards.




High resolution photo: http://img94.imageshack.us/img94/377...0516190358.jpg
 
Old 16 May 2013, 20:31   #13
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the one on the right has got battery damage.(may of leaked under the sockets)

the one on the left used to have a switch where that jumper is,can you put the jumper on the other two links above.(its basicly in the off position,yes i know it says on but thats for a toggle switch)

i have both of these cards by the way.

Last edited by roy bates; 16 May 2013 at 20:37.
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Old 16 May 2013, 20:47   #14
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I remove the battery long time ago, but the card will work fine without it. Also change the jumpers, but it did not work.
I purchased a new ram card here in Spain, I hope to receive it soon and try it.
Thanks....
 
Old 16 May 2013, 20:53   #15
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which one works?
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Old 16 May 2013, 21:37   #16
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I not yet received the new card. But this working well, it is assumed ....
 
Old 17 May 2013, 04:03   #17
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On the board with the 4 ram chips, move them up one slot...

i.e. chip 1 to socket 2, 2 > 3, 3 > 4 and 4 > 1. then retry it

If the memchip in the low area of memory is bad then this may at least allow the Amiga to boot
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Old 19 May 2013, 17:29   #18
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Originally Posted by kipper2k View Post
On the board with the 4 ram chips, move them up one slot...

i.e. chip 1 to socket 2, 2 > 3, 3 > 4 and 4 > 1. then retry it

If the memchip in the low area of memory is bad then this may at least allow the Amiga to boot
Hi, I tried this but it did not work.
I got another memory and this works perfectly. I had two bad memory.
Here the new memory:



Is should remove the battery? I do not need. I can prevent leaks?

Thanks....
 
Old 19 May 2013, 17:40   #19
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That's a Lithium cell which does not normally cause much trouble. However, if its voltage is 0V, you might as well replace it if you want your RTC to work.
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Old 25 June 2013, 22:25   #20
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I am new to the Forum so apologies but I have the card on the left of the picture with 16 chips on it, could someone please tell me what this card is, I have bought another amiga for my collection and this came with it, many thanks
 
 


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