Amiga 2000, red screen at startup

[NisseN]

Hi everyone!

A few days ago I booted up my Amiga 2000 (rev 4.1) for the first time in 10 years. The first minutes everything was just fine, the normal Workbench-screen, I loaded a game without problems. Then I turned the machine off to connect the RF adaptor. After that the machine didn't boot again. The PSU was dead. I replaced it with a PSU from a working PC, according to this guide: http://wordpress.hertell.nu/?p=282. With the new PSU I get a red screen two seconds, after that green screen (sometimes yellow). The power LED blinks 10 short 1 long.

Since I also had a battery leakage, I removed the battery and cleaned the area. I noticed some blue-ish corrosion on some of the pins on the 68000 so I removed it and cleaned the pins. After that I still have the two seconds red screen, but the power led is not flashing anymore, and the green screen is gone with scrambled video output.

When I measure the voltage from the orange 12 V wire at the connector at the motherboard, I get 12,4 V. Voltage from the other wires is normal (5,0 V, -5,0 V, -11,99 V).

Any ideas where to start troubleshooting?

Thanks a lot!

Nils

[Franchute13]

Hi.
I had the same problem with my Amiga 2000 that I bought second-hand.
http://eab.abime.net/showthread.php?t=76813
It may be that the clock chip is going badly, you may have clues that are cut off. You have to control the area affected by the battery.
Successes

[NisseN]

Impressive work with your Amiga 2000!

There is some deep corrosion at the blue arrow. I was worried that the line between 1 and 2 was cut off at the spot of corrosion. But resistance is 0 ohm between 1 and 2 so I guess there is connection? Should I try to connect a wire between 1 and 2?

The battery leakage may have caused the problems. But another possibility is that components on the motherboard was fried when the old PSU died. What is most likely? I don't think the voltage from the PSU is an issue since 12,4V is within the tolerance in the ATX standard (+- 5% is accepted on the 12V rail).

[NisseN]

Just a clearification of the errors:

1. When the old PSU died, the Amiga was completely dead, just a small ticking sound from the fan.
2. After changing PSU and clean up of battery area: Power LED blink 10 short 1 long, 2 seconds red screen at startup, after that green screen (sometimes yellow)
3. After cleaning pins and socket of 68000 CPU: 2 seconds red screen at startup, after that scrambled video (white background with some kind of horizontal lines). No blinking power LED.

[dalek]

I'd pop out Agnus and Kickstart from their sockets, clean and reseat. Also check continuity of the 68000 pins on the bottom right to make sure there are no completely coroded traces under the socket. There doesn't seem to be much damage but if the legs were blue it's possible the traces under the socket are broken.

[NisseN]

Originally Posted by dalek

I'd pop out Agnus and Kickstart from their sockets, clean and reseat. Also check continuity of the 68000 pins on the bottom right to make sure there are no completely coroded traces under the socket. There doesn't seem to be much damage but if the legs were blue it's possible the traces under the socket are broken.

The pins looked like this before cleaning:


The area under the socket looks ok, no corrosion as far I can see with my eyes. I've also been thinking about reseating the Agnus. But I must wait until I get an extractor tool.

How do I check the trace under the negative pole of the battery? Its a blue dot with really deap corrosion. I cleaned this area with a toothbrush. Maybe I wiped away material that worsened the conductivity? I measure zero Ohms between 1 and 2 in the picture in my previous post. Does zero ohms means the trace is ok or do I have to measure in another way?

[dalek]

Agnus you can remove by pushing it from the back of the board through the holes with a pair of blunt instuments (like chopsticks, back of pencils). In some ways this method is easier than the proper puller as the chip can get quite stuck in that socket due to years of oxidisation.

I wouldn't worry about the battery area too much at this stage until it's booting. The negative of the battery goes to ground (and e.g. the negative side of cap C811 on the left). Those points you marked 1 and 2 are part of the ground plane and if they beep then that's all fine.

0 ohms means continuity so connected directly.

[Rob_MyAmigaShop]

Hi NisseN,

I would try and measure continuity between most of the connections around the bottom of the cpu area. Especially around the area at the bottom of the red resistor pack, RP900.

Maybe a trace has gotten broken from the battery leakage...?

If the corrosion got under the CPU socket, you may have to replace the socket.

But check continuity to see if most of the connections down there are working or not first.

[NisseN]

Thanks dalek and Rob MyAmigaShop for replying!

There is corrosion in the socket, does this mean it could be corrosion inside the traces even if no corrosion is visible on the surface of the motherboard?

I will try to check the traces and reseat the Agnus.

[NisseN]

Btw, is it good or bad that the green screen disappeared (replaced with hortizontal lines on whitegray background) after reseating the 68000?

[NisseN]

A few minutes after power on, I can feel with my finger tips a slight temperature increase in the 68000, Paula, Denise and Agnus. Seems normal to me. But the Gary chip is cold. Is this normal?

[kipper2k]

Hi,

Red screen is a good indicator of a bad ROM. If the old power supply took it out then it is toast, if you have another 16bit rom, try that or even try the rom from the a2000 in an a500 (rev 5 or higher) or a600

[Rob_MyAmigaShop]

I'm not an expert on this. But, yeh, I would say that cpu socket needs to come out asap. And replaced with a new one. In my experience its hard to clean that and get all the leakage out of the socket. If any leakage is left in the socket it'll keep corroding over time. So best just to replace it with a new one.

Here is a youtube video that may be helpful:
[ Show youtube player ]

[NisseN]

Originally Posted by kipper2k

Hi,

Red screen is a good indicator of a bad ROM. If the old power supply took it out then it is toast, if you have another 16bit rom, try that or even try the rom from the a2000 in an a500 (rev 5 or higher) or a600

I've ordered a new kickstart ROM (v 1.3 to be as much original as possible ), and also looking for a working OCS Amiga 500 for testing the other chips.

[NisseN]

Originally Posted by Rob_MyAmigaShop

I'm not an expert on this. But, yeh, I would say that cpu socket needs to come out asap. And replaced with a new one. In my experience its hard to clean that and get all the leakage out of the socket. If any leakage is left in the socket it'll keep corroding over time. So best just to replace it with a new one.

Here is a youtube video that may be helpful:
[ Show youtube player ]

I am worried about the CPU area because the behaviour changed when I reseated the 68000 (continous light on power led instead of flashing, scrambled video output instead of green/yellow screen). But for now I'll wait for the new kickstart ROM. I want to try things step by step. It was a mistake to change the PSU, remove the battery and clean at the same time. Because now I don't now if the problems are PSU related or leakage related.

This is what video output looks like after initial red screen:

[dalek]

Based on the socket photo, either way you should replace the CPU socket and check all traces under it

[Rob_MyAmigaShop]

Just guessing here, but the behavior change could be the cpu pins connection to the socket. While your waiting, you could at least check the continuity between the pins down there. That should tell you alot about the area. You could also try cleaning the socket for now to see if you can get a better connection on the cpu. Then replace the socket as soon as you can. I would guess that the first 7 pins on the right are having problems with a good connection to the cpu pins. But really, check the continuity of the pins in that area. Would be interesting to see what you find... :-)

[Rob_MyAmigaShop]

Some more info from some of my experiences with screen colors are, not sure what the RED screen might be telling you in this case (ROM?), but the green maybe the agnus chip seating in the socket, try pressing down on it to make sure its in good (had this happen just the other day) and the yellow screen might be the cpu exception. Probably the corrosion interfering with the cpu connection to the socket. Anyways, hope that helps some more. :-)

[NisseN]

Now I've checked the 8 bottom right traces of the socket. The back of the motherboard looks very good and I get perfect beeps from the multimeter. Is this kind of checking enough, or do I have to make more detailed tests to make sure the traces are ok?

[NisseN]

New proceedings... After cleaning CPU socket and pins with a needle I get a stable red screen at startup. Before it was red only two seconds. I feel a little bit more comfortable with this error than the green screen, yellow screen, scrambled video output I had before.