A2000 Rev. 6.3 - black screen

Eamoe · 06 August 2020, 14:13

Hi everyone,

I've recently put my hands back into my long-neglected A2000 build. Completely recapped motherboard and PSU (original). Added a PWM-controlled fan with custom-made control box to spin the fan at desired speed, installed an SD-Card hard disk controller.

I had just managed to intialize the system and was able to boot into WB a few times, was overjoyed, but suddenly the computer froze, started giving me color screens on boot (randomly red, green, purple, grey, name any possible color code), and then nothing, just black except for a blip on the 1084 monitor at power on, but now even that is gone, it's really completely dead.

What I've done so far:

tested every chip on an A500 motherboard, they are all fine (except BUSTER which the A500 does not use, but apparently it "only" deals with the Zorro bus anyway)
tested every socket lead for continuity (one probe on the seated chip leg, the other on the socket led protuding under the board), every single socket contact is fine
measured voltages from PSU under load, all correct (5V @ 5.18V, 12V at 11.75V)
pulled my modern fan out to see if it wreaked havoc with current requirements or something, to no avail

Observations:

power LED steadily on
chips (CPU, AGNUS, ROM) get lukewarm
I hadn't unscrewed the motherboard from the case in a long time, and when I did to look for visible problems, I found a literal bug stuck underneath it in the DENISE region — I first thought "there you are", but removing it + cleaning that region did nothing

Out of despair I've ordered a crystal from Amigastore.eu and I'm still waiting for that. Also I haven't yet checked for continuity between chips.

But if anyone has another suggestion, I'll be happy to take it!

Eamoe · 06 August 2020, 16:49

Okay I've checked continuity between CPU and KS and it is dodgy. Did get a couple additional red screens. I'll replace the sockets.

Is it correct course of action to test resistance of resistor arrays while on the board? And are there other kinds, apart from series-(two by two) and bussed-to-a-common-pin types? Because I go around the board checking them and, while some make perfect sense, some are sometimes mildly inconsistent, sometimes completely out of whack, or sometimes have just the one pin out of spec.... Weird.

06 August 2020, 14:13	#1
Eamoe Stunt Car Racer Vet Join Date: Mar 2006 Location: Vevey/Switzerland Age: 43 Posts: 145	A2000 Rev. 6.3 - black screen Hi everyone, I've recently put my hands back into my long-neglected A2000 build. Completely recapped motherboard and PSU (original). Added a PWM-controlled fan with custom-made control box to spin the fan at desired speed, installed an SD-Card hard disk controller. I had just managed to intialize the system and was able to boot into WB a few times, was overjoyed, but suddenly the computer froze, started giving me color screens on boot (randomly red, green, purple, grey, name any possible color code), and then nothing, just black except for a blip on the 1084 monitor at power on, but now even that is gone, it's really completely dead. What I've done so far: tested every chip on an A500 motherboard, they are all fine (except BUSTER which the A500 does not use, but apparently it "only" deals with the Zorro bus anyway) tested every socket lead for continuity (one probe on the seated chip leg, the other on the socket led protuding under the board), every single socket contact is fine measured voltages from PSU under load, all correct (5V @ 5.18V, 12V at 11.75V) pulled my modern fan out to see if it wreaked havoc with current requirements or something, to no avail Observations: power LED steadily on chips (CPU, AGNUS, ROM) get lukewarm I hadn't unscrewed the motherboard from the case in a long time, and when I did to look for visible problems, I found a literal bug stuck underneath it in the DENISE region — I first thought "there you are", but removing it + cleaning that region did nothing Out of despair I've ordered a crystal from Amigastore.eu and I'm still waiting for that. Also I haven't yet checked for continuity between chips. But if anyone has another suggestion, I'll be happy to take it! Last edited by Eamoe; 06 August 2020 at 14:21.

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06 August 2020, 16:49	#2
Eamoe Stunt Car Racer Vet Join Date: Mar 2006 Location: Vevey/Switzerland Age: 43 Posts: 145	Okay I've checked continuity between CPU and KS and it is dodgy. Did get a couple additional red screens. I'll replace the sockets. Is it correct course of action to test resistance of resistor arrays while on the board? And are there other kinds, apart from series-(two by two) and bussed-to-a-common-pin types? Because I go around the board checking them and, while some make perfect sense, some are sometimes mildly inconsistent, sometimes completely out of whack, or sometimes have just the one pin out of spec.... Weird.

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