A600 with green screen

naujoks · 28 July 2022, 17:20

I have an A600 which boots to a green screen.
Apparently it's a RAM error.
I already re-capped the mainboard (and PSU) and did a visual check on solder connections, but couldn't find a problem. I'm still measureing out continuity between the RAM chips and AGNUS.
Is the next step swapping RAM chips? Is there a chance that if I remove a faulty RAM chip that the machine starts booting? Is there a way of finding out which RAM chip of the two might be the faulty one?
Are there alternative makes to the HM514260JP8 chips that I have on the board? What are they called?

naujoks · 28 July 2022, 17:22

PS: Both RAM chips are cold to the touch during operation of the computer. I checked the voltages and they're fine.

Leon Besson · 28 July 2022, 19:16

Have you checked the traces for damage/corrosion?

naujoks · 28 July 2022, 19:17

Yes, generally the board is in very good condition.
There was a bit of leakage from caps in the top left corner, but I think I cleaned most of it when I replaced the caps.

Leon Besson · 28 July 2022, 19:36

Quote:

Originally Posted by naujoks

Yes, generally the board is in very good condition.
There was a bit of leakage from caps in the top left corner, but I think I cleaned most of it when I replaced the caps.

Only reason I suggest it, is because I had a green screen issue on a A1200 and it was due to the traces between the CPU and Chip RAM.

naujoks · 28 July 2022, 19:54

I thought the RAM is connected to AGNUS, and not the CPU?

Leon Besson · 28 July 2022, 20:13

Worth having a look here Bromigo!

https://www.amigapcb.org/

Matt_H · 28 July 2022, 22:44

I had a 4000 that was giving me a green screen due to a faulty 3640. In other words, the whole "green screen = chip RAM problem" is a bit of an over-simplification and the fault can be within any number of areas.

MrClump · 29 July 2022, 00:08

The 600 will run with only U16 populated, so you could get lucky and remove U17 and find that’s the issue.

Saying that, I would isolate every other possible cause before you start ripping the RAM off the board. Getting them back on again is non-trivial as the ICs are so close together, I’ve only previously managed it with solder paste and hot air.

Have you tried Diagrom? If you aren’t able to get a display the serial output can tell you a lot.

Vypr · 29 July 2022, 01:20

Check the traces around C612. I had a board where C612 leaked and damaged the traces, specifically around R152E and R152F. Of course I didn't find this out till after I had replaced both RAM chips.

28 July 2022, 17:20	#1
naujoks Registered User Join Date: Jul 2022 Location: Berlin Posts: 26	A600 with green screen I have an A600 which boots to a green screen. Apparently it's a RAM error. I already re-capped the mainboard (and PSU) and did a visual check on solder connections, but couldn't find a problem. I'm still measureing out continuity between the RAM chips and AGNUS. Is the next step swapping RAM chips? Is there a chance that if I remove a faulty RAM chip that the machine starts booting? Is there a way of finding out which RAM chip of the two might be the faulty one? Are there alternative makes to the HM514260JP8 chips that I have on the board? What are they called?

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28 July 2022, 17:22	#2
naujoks Registered User Join Date: Jul 2022 Location: Berlin Posts: 26	PS: Both RAM chips are cold to the touch during operation of the computer. I checked the voltages and they're fine.

28 July 2022, 19:16	#3
Leon Besson Banned Join Date: Feb 2022 Location: Anywhere and everywhere I have a contract Posts: 822	Have you checked the traces for damage/corrosion?

28 July 2022, 19:17	#4
naujoks Registered User Join Date: Jul 2022 Location: Berlin Posts: 26	Yes, generally the board is in very good condition. There was a bit of leakage from caps in the top left corner, but I think I cleaned most of it when I replaced the caps.

28 July 2022, 19:54	#6
naujoks Registered User Join Date: Jul 2022 Location: Berlin Posts: 26	I thought the RAM is connected to AGNUS, and not the CPU?

28 July 2022, 20:13	#7
Leon Besson Banned Join Date: Feb 2022 Location: Anywhere and everywhere I have a contract Posts: 822	Worth having a look here Bromigo! https://www.amigapcb.org/

28 July 2022, 22:44	#8
Matt_H Registered User Join Date: Jul 2008 Location: Boston, MA Posts: 948	I had a 4000 that was giving me a green screen due to a faulty 3640. In other words, the whole "green screen = chip RAM problem" is a bit of an over-simplification and the fault can be within any number of areas.

29 July 2022, 00:08	#9
MrClump Registered User Join Date: Aug 2020 Location: Torquay Posts: 166	The 600 will run with only U16 populated, so you could get lucky and remove U17 and find that’s the issue. Saying that, I would isolate every other possible cause before you start ripping the RAM off the board. Getting them back on again is non-trivial as the ICs are so close together, I’ve only previously managed it with solder paste and hot air. Have you tried Diagrom? If you aren’t able to get a display the serial output can tell you a lot.

29 July 2022, 01:20	#10
Vypr Registered User Join Date: Dec 2016 Location: East Kilbride, Scotland Posts: 452	Check the traces around C612. I had a board where C612 leaked and damaged the traces, specifically around R152E and R152F. Of course I didn't find this out till after I had replaced both RAM chips.

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