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Old 16 March 2017, 22:25   #1
Forest_Penguin
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Question A500 green screen

I bought an A500 about a month ago and when I power it on It displays a green screen (chip ram problem). Upon inspection the board looks pristine, none of the caps are leaking or bulging, all the resistors look immaculate and the battery isn't leaking. I then proceeded to reseat and (with alcohol and a Q-tip) clean all the socketed chips including Agnus and to no avail. I also checked if any of the chips were getting hot but they were all fine. Is there anything I can do apart from replacing the chips one by one because at that point I think I would prefer to just buy a working one of of ebay.

Here are some pics of the motherboard: http://imgur.com/a/NxDnp
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Old 16 March 2017, 23:05   #2
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I recommend getting DiagROM if you have the means... www.diagrom.com

It will most likely let you diagnose even with a bad ram chip.

S.
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Old 17 March 2017, 09:10   #3
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Some people say they buy one of those DIP DRAMs (TMS44c256) and piggy back it on top one of the old ones to detect which one might be bad.

diagROM is awesome, but a programmer might cost you nearly as much as a new board

Edit: I saw some boards with battery acid near the trapdoor header that actually began to eat the traces on the mobo, but yours looks clean.
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Old 17 March 2017, 12:35   #4
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Perhaps someone can send FP a preloaded ROM for the cost of the ROM. Where are you based?


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Old 18 March 2017, 15:12   #5
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I recommend getting DiagROM if you have the means... www.diagrom.com

It will most likely let you diagnose even with a bad ram chip.

S.
I only have blank DD and HD 3.5" floppies. Can I use either of these?
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Old 18 March 2017, 15:13   #6
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Perhaps someone can send FP a preloaded ROM for the cost of the ROM. Where are you based?


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I'm in the netherlands, do you mean a rom chip with diagrom on it to replace the kickstart rom?
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Old 18 March 2017, 17:17   #7
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Yep, that's what the DiagROM is. It can be used to tell what part of the chip RAM system is damaged, making diagnosing the issue much quicker.
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Old 18 March 2017, 17:19   #8
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I'm in the netherlands, do you mean a rom chip with diagrom on it to replace the kickstart rom?
Yes. I've used it twice on my channel to identify which bit of ram was broken. Think the ROMs are dead cheap. 27c400 then find someone nearby with a programmer.
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Old 18 March 2017, 18:04   #9
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Yes. I've used it twice on my channel to identify which bit of ram was broken. Think the ROMs are dead cheap. 27c400 then find someone nearby with a programmer.
Won't a floppy work? Do I need to do it with a rom chip?
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Old 18 March 2017, 18:09   #10
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No.

You cant load a floppy disk when the operating system cant see RAM! There is nowhere to read the floppy disk to. You need DiagROM or to get lucky changing chips.
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Old 18 March 2017, 18:21   #11
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On the DiagROM site the author states if you want a programmed ROM he will send you one. You just have to contact him and ask.
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Old 18 March 2017, 18:23   #12
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On the DiagROM site the author states if you want a programmed ROM he will send you one. You just have to contact him and ask.
Yup. John will do that. Or you can find a local person with a programmer if you are in a hurry... because i happen to know John is away for the next few days.
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Old 18 March 2017, 19:03   #13
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Yup. John will do that. Or you can find a local person with a programmer if you are in a hurry... because i happen to know John is away for the next few days.
I'll contact John, thanks a lot for your help.
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Old 24 March 2017, 22:07   #14
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Yeah. I can program roms for fee of eprom + shipping.. no problem. just ping me..
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Old 26 March 2017, 09:20   #15
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if i remember rightly, isn't a green screen a resident virus in memory that a cold boot would fix?
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Old 26 March 2017, 09:22   #16
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As he clearly states when he powers it up.. nahh. green screen is chipmemissues..
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Old 26 March 2017, 10:46   #17
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As he clearly states when he powers it up.. nahh. green screen is chipmemissues..
Agreed. Green screen is chipmem.
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Old 18 April 2017, 17:37   #18
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Agreed. Green screen is chipmem.
Thank you all very much for the replies, and thank you chucky for offering to send me a rom, I contacted John from diagrom and he sent me a pre-loaded rom but my amiga would still not work, instead of showing a green screen it flashed green and red for about twenty seconds and then showed a static purple screen. When I took the memory expansion out it still flashed red and green but after twenty seconds it would switch between a black and a green screen about twice a second. I contacted john and he said the following:

"That means you have issues with ALL of your chipmem. so I guess if you have 512k memory in and when the screen is purple and you move your mouse screen will flicker in several colors.
as the machine cannot allocate any chipmem, it is not able to show anything on screen except simple colorchanges. BUT it you connect a PC or another Amiga via nullmodem and serialcable at 9600BPS you will get serial output telling what type of error you have on the memory (you can then calculate what bits are wrong and from that decide if it is a chipissue/datapath issue etc..) and with fastmem attached it will start in fastmem and you need the serialoutput to get the menu.
clearly you have issues with fastmem that you need to figure out."

Not wanting to bother him with any more questions I came here. I can get my hands on a null modem if this is the correct item: https://www.cardwriter.nl/null-modem...rce=googlebase
and I have plenty of PCs with serial ports but I have no idea how to configure a setup like John describes.

I would greatly appreciate any help I can get!
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Old 18 April 2017, 17:44   #19
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You need that cable and a 9pin -> 25 pin adapter for serialport (as the Amiga serialport is 25 pin)

I usually use PuTTY on my windowsmachine ( http://www.chiark.greenend.org.uk/~s...ty/latest.html )
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Old 18 April 2017, 17:53   #20
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Yep, that's a null modem cable, but you need a 25-pin connector on one end for it to fit the Amiga. Alternatively, building one yourself is pretty trivial and the 9 and 25-pin connectors are very common.

To read the output, all you need some sort of terminal software on the computer you connect to. On older versions of Windows, HyperTerminal is included and can be used for this - just set the COM port, 9600 baud and (presumably) no handshaking and it should work fine, the terminal window will then display any characters it receives.

HyperTerminal isn't included with newer versions of Windows, so something like Termite or Putty can be downloaded and used instead.

If you have a couple of computers with serial ports, try setting them up to talk to each other so that you know you have it working - set them both up with terminals, type into one terminal window and the text should appear in the other.

Edit: Ah, there's the man himself beating me to it
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